Monday Discussion : Watching Wednesday

We’ll have a quiet but chilly start to our work week across the Hudson Valley.  Lots of sunshine and temperatures generally in the 30s to near 40° for a high on Monday.  After a chilly night Monday night with lows in the low 20s across the valley (upper teens in the Catskills)… Tuesday will see a cold start, before temperatures moderate into the low and mid 40s during the afternoon for highs.

That allows us to talk about Wednesday, which is really the only thing on everyone’s mind anyway.  We have another upper level low pressure diving into the central US, it will continue to roll eastward, into the Ohio Valley late on Tuesday.  At the same time, we’ll see a wave of low pressure develop along the front side of the upper level trough.  Where that coastal low pressure goes, will have a major impact on our weather for Wednesday…

As of Monday morning, we’ve got considerable disagreement on the track that the coastal low pressure will take.  There IS agreement on the development of this low pressure system, almost all data has it developing near the coast of VA and North Carolina.  The uncertainty is what happens next.

Track #1
The GFS and NAM models develop the coastal storm, and immediately have it hug the coast.  The storm tracks right along the coastline, and moves northward, before jumping northeast and heading toward Cape Cod.  This track is likely the result of the upper low pressure system off to our west influencing the track.  The rotation around the upper level low, likely pulls the coastal low pressure in toward the shore.  This also aids in the rapid development of the storm, and generates substantial lift.  If track #1 is correct, it would be a substantial storm for the Hudson Valley.

Track #2
The European and Canadian Models develop the low pressure, and immediately try to jump the storm out into the ocean, before gradually hooking it back toward the New England coastline.  This track would spare the Hudson Valley almost any real impacts.  We might see some light snow develop along the front edge of the trough, as the low pressure is forming… but then the substantial snow would be pulled out to sea, and off to our east… possibly impacting Long Island and NYC.

Which is right?
That’s the challenge we have ahead of us, is to figure out which track is the right one.  Right now, we have track #1 more likely, at about 65% chance to occur.  We really would like to see the European model come around to our idea, that would help boost our confidence a bit.  But the reason track #1 seems to make sense, is that the upper level low should influence the track of the coastal storm.

The upper level low pressure is deepening as it pushes eastward… in fact the GFS has the low closing off as it reaches the coast… a sign of a strong upper level low pressure.  As it deepens, the trough should begin to tilt negative, and with a negatively tilted trough, the storm should tuck in tightly along the coast… not push out to sea.  We’ll have to keep a close eye on the track, and see if this plays out the way we think.

If everything comes together the way we think it might… this could be our weather map Wednesday afternoon…

Notice that the NAM model is picking up on the dramatic lift that may be possible in the Hudson Valley.  The purple shading is indicative of snowfall rates well over 1″ per hour.  If track #1 is correct, then we’re in for a very snowy Wednesday afternoon across the Hudson Valley.  Snowfall amounts would likely near or exceed 6 inches in most locations, with someone possibly reaching double digits in terms of snowfall amounts.

Winds?
There are obviously concerns about strong winds, with portions of the Hudson Valley still without power today.  As it looks right now, the sustained winds should be less than what we saw on Friday for certain.  We could still have a few gusts that pack a punch, up over 30mph… but the strength and frequency of the strong wind gusts should be noticeably less than what we saw on Friday.

Now, we want to be clear… people should take this storm seriously.  The point we are trying to make, is that there is a difference between the size and scope of this storm, and the size and scope of the previous storm.  It is worth mentioning however, that due to the fact that this will likely be a heavy wet snow, with the gusty winds that we do anticipate with a developing nor’easter… that additional power outages will be a concern.

But let’s nail down the track first… and then once we know whether this storm will come up the coast, then we can worry about the wind and the potential for power outages.  Have a great Monday afternoon, we’ll have more updates tonight.

Winter Storm Recap : One For The Record Books 3/2/18

A very rare, and very damaging storm took aim on the Hudson Valley on Friday.  The impacts were wide ranging, and depending on what part of the Hudson Valley you live in, your experience was dramatically different.  Some of us saw a heavy rain for the majority of the storm, only picking up a slushy coating on the grass late in the afternoon on Friday.  Some of us were on the line between rain and wet snow, and spent the entire day switching back and forth from heavy rain to heavy wet snow… accumulating several inches in the process.  And then there were those of us who saw a heavy wet snow fall from sunrise to sunset on Friday… picking up anywhere from 1 to 3 feet of wet snow, and likely losing power due to trees and power lines snapping under the weight of the wet snow.

We’re going to focus on the meteorological aspects of this storm in this post.  We’re not going to get too far into the damage and power outages.  We have covered those already extensively on Facebook, and you can find a link to one of the discussions right here: Top 5 Most Damaging Storm for Central Hudson.  The damage was incredible, and worthy of it’s own discussion.  If you have time, check out this photo documentary from our good friends at Central Hudson, as they worked to restore power on Saturday.  Some of the pictures are breathtaking.
Central Hudson Storm Restoration Work.

Lastly, a point of clarification… we’re about to talk about this storm from a meteorological standpoint.  We may use descriptions of awe and wonder.  As snow lovers, we may make the storm sound ‘awesome’.  We want to be clear, that in no way are we minimalizing the hardship many people are facing as a result of lost power and damaged property.

So let’s get down to business.  We’ll begin the recap with 3 images:
– Our final snowfall forecast with our mid storm modification
– The snowfall history map
– Snowfall reports via the National Weather Service

Take a good look at that snowfall history map, you likely won’t ever see another one like it.  A literal bulls eye of rain, within a sea of heavy wet snow.  As snow lovers, Alex and I feel punched in the gut by looking at his map.  I live in the SW edge of the ‘snow hole’, and he lives in the NE edge of the ‘snow hole’.  Widespread 6 to 12 inches of wet snow… and nearly nothing at all for many in central Ulster and Northern Orange counties.

Interesting Spotter Reports
The reports out of Ulster are telling… because typically, if you underachieve in an event, or don’t get any snow… a trained spotter simply won’t call the report in.  But 2 people, one in Kerhonkson and one in Saugerties, were so irritated by this storm, that they reported the 0.1″ to the National Weather Service.  If more trained spotters had done that, the ‘snow history map’ would have been more accurate than it was.  To be honest, we believe the map shows too much snow in the ‘snow hole’.  In Pine Bush, I got 0.1″ as well, just a slushy coating on grass.  But it suggests I got 1 to 2 inches.  But aside from splitting hairs, this map paints an incredible picture.

So What Happened??
How on earth does something like this happen?  Is it magic?  Climate Change?  Do the Snow Gods just hate Bill & Alex?  While we believe the answer is actually the 3rd choice… that the snow Gods hate us… there actually is a scientific explanation.  The explanation is quite complex, but let’s walk through it step by step.

Dynamic Cooling: So remember, we were in the 50s on Thursday, and we needed to cool temperatures dramatically just to get to a place where it could snow on Friday.  The mechanism that did this, was called “Dynamic Cooling”.

This was the “vertical velocity” map we posted on Thursday.  It shows the upper level low pressure marked with the “L”.  The bright colors represent intense upward motion, or “lift” in the atmosphere.  The upper level low pressure generated very strong upward motion over the Hudson Valley.  This caused the air to rise very rapidly, which in turn caused the air to cool dramatically.  As the air cooled, it condensed, and rain began to fall heavily.  As the heavy rain fell, it pulled that cooled air back down to the surface.  As this process repeated over time, eventually the column of air was cooled enough so that SNOW was falling instead of rain.  This process is known as ‘dynamic cooling’.  Ultimately, this storm created its own cold air… which is pretty intense meteorological stuff by itself.  But then things got even more complex.

While forecasting, Alex and I began to see the models suggesting it would rain in parts of the Hudson Valley.  With the tremendous dynamic cooling we were expecting, and the heavy precipitation, this didn’t make sense.  Once cold enough to snow, we thought it should continue to snow heavily, at least until the snow eased up later in the day.  This complex riddle resulted in an hour and a half phone call between me and Alex, because we needed to talk about what the heck was going on.  To Alex’s credit… he called it.  He told me over the phone that he thought the model was detecting downsloping winds off the Berkshire Mountains.

What are downsloping winds, and why would it cause rain in the central Hudson Valley?

The winds around a nor’easter originate out of the northeast for the Hudson Valley.  So as the winds rotate around the storm, they blow through Massachusetts, and over the Berkshire Mountains.  As they do that, the air rises and cools over the Berkshires.  This part of the process is called upsloping, and results in higher snowfall amounts and colder temperatures in the Berkshires.

But as the air continues out of the Berkshires, and moves down into the Hudson Valley, the air sinks and drops in elevation.  When air sinks, the opposite happens… the air warms considerably, and dries out.  The result is quite amazing.  Temperatures were falling due to the dynamic cooling process.  At our HVW Station in Hurley, NY… check out these temperatures, and see if you can notice when the downslope effects started to be felt:
12am: 38.3°… 1am: 36.3°… 2am: 34.8°…(skip a few hours)…  6am: 34.7°… 7am: 37.8°… 8am: 38.4°… 9am: 38.1°

So the dynamic cooling had begun to take effect, and it was resulting in a change over to sleet and wet snow… but once the downsloping effect kicked in, it negated the effect of the dynamic cooling, and made it too warm to snow over a portion of the viewing area.

The map above is a bit of a crude demonstration of the location of the Berkshire Mountains, factoring in the northeast wind, and the net impact area.  Now, you might wonder why the ‘rip off’ zone or ‘snow hole’ is many miles away from the Berkshires.  The reason, is because the elevation remains rather high with the Taconics, and elevation doesn’t decrease with the Hudson Valley until you get much closer to the river.  So the downsloping effect doesn’t really kick in until you get closer to the river.

From a forecasting perspective it’s frustrating… because like I mentioned, Alex called it in our conversation.  And we then discussed it repeatedly, in both posts and live streams, as a possible wildcard.  But we hesitated to nail down a specific area, because it was not something we had seen before… at least not to this magnitude.  But now, having experienced it, we know that it can happen.  Pretty wild stuff.

Blockbuster Wet Snow

So now that we’ve highlighted the meteorological phenomenon that caused a large area in the middle of the region to get do little snow, let’s show the snow map once more, and soak in those incredible snowfall totals…

AMAZING snow totals.  Ignoring the previously discussed snow hole, and we had widespread 6 to 12 inch amounts across the  Hudson Valley.  As you went up in elevation across Dutchess and Columbia counties, you even broke 12 inches.  Unfortunately, we also saw wind gusts reports in the 30 and 40mph ranges.  When we forecasted 6 to 12 inches of wet snow, along with those wind gusts… we were concerned that power outages would become a widespread problem.  We hope that power gets restored ASAP, as it’s really tough this time of year to not have power.

Then there’s the Catskills… woo doggy… the Catskills.  Just take look at Greene county.  28 inches for Hunter, 26 inches for Windham, and similar high numbers of 1 to 3 feet across the Catskills.

This storm was truly dynamic, and when you stack it up against other historical storms… you see just how unique and significant it was.

Saturday Outlook : Blustery Winds Continue

On Saturday, we’ll begin to process what was truly a historic storm for the Hudson Valley on Friday.  If not so much in terms of impact (and there was a lot of impact)… then at least in terms of the meteorological nature of the storm.  We cannot recall a storm where it poured rain all day in southern Ulster county, while it thumped snow all day in much of Dutchess, Orange, Putnam and Rockland counties.

There will be numerous different statistics and graphics that we begin pulling together on Saturday, as the data all roll in.  So we’ll be pretty busy on Saturday as well.  We’ll try to get the snowfall totals to you first, and then we’ll worry about the other jaw dropping statistics… and there will be several.

Winds of Change

The big weather story over the next several days will be the winds.  Saturday we’ll begin to see clouds mix with sunshine, as our coastal bomb of a storm gradually drifts out to sea.  The winds wrapping around that system as it meanders away, will be quite strong.

Northeast winds 10 to 15mph, will gust over 30mph at times, as the storm continues to deepen off shore.  This could be a problem for those of us who saw upwards of 10 to 15 inches of wet snow on Friday.  If the winds continue to batter the trees and power lines that are coated with several inches of wet snow… at best, it will make the work of our local utility crews that much more difficult… and at worst, it could cause additional power outages.  Something to be aware of on Saturday… as the cleanup across the eastern half of the Hudson Valley continues.

That’s not to diminish what happened across the western half of the Hudson Valley, where parts of Orange county, Rockland County, Sullivan and Greene counties were plastered with wet snow.  But Ulster County (in general) is going to be one of the more phenomenal stories.  The bulk of the county saw less than an inch… with many places seeing 0.1″ or 0.0″ of snow.  We are still compiling the snowfall data, so ‘officially’ we don’t have the numbers… but what we’re seeing is effectively a giant snow hole right in the center of the Hudson Valley.

As a personal anecdote, it’s almost impossible for me to believe that parts of Dutchess county saw 12 to 15 inches of snow, and that Monroe (roughly 15 miles to my south) pulled in 12 inches.  All while I received a whopping 0.1″ of snow… yes I had a slushy coating late in the day on Friday, after many inches of rain had fallen.  Or that Alex, located roughly 20 to 30 miles to my northeast, also saw 0.1″ of snow… and that roughly 5 to 10 miles to his east, Rhinebeck had 6 inches of snow.  It’s truly wild stuff.

So we’ll continue to pull together the data on Saturday, and share it with you as soon as we can.  Bundle up, and be safe on Saturday… have a great day!

Wild Winter Storm Discussion : 2pm Update

A complex and diverse storm continues to hammer the Hudson Valley at this hour, with a wide range of weather conditions. 
Eastern half of Ulster/N. Orange/SE Sullivan:
The central part of the Hudson Valley is seeing light to moderate rain, mix with wet snow and sleet.  Temps are in the mid 30s, and winds are howling out of the north/northeast.  Some mixing of wet snow is occurring, but accumulations are negligible.  This storm continues to be a bust in this area, with mostly a windswept rain falling.
 
Remainder of Hudson Valley:
Dutchess, Columbia, Putnam, S. Orange, Rockland… you guys continue to get hammered, with moderate to heavy wet snow.  Viewer accumulations continue to come in generally on the order of 4 to 8 inches, but some local reports up to 10″ are coming in.  Unfortunately when the powerful NE wind gusting over 35 and 40mph is factored in, the weight of the heavy wet snow coating the trees & power lines are leading to power outages only increasing in number.  Road conditions vary greatly as well, with elevation playing a role as well.  As one of our First Responder viewers asked us to say, “If you don’t have to be out on the roads, stay home.”  Conditions in these areas will continue to vary greatly over short distances… with another 2 to 4 inches of wet snow possible on average.
 
Catskills: Delaware, Sullivan, Greene & NW Ulster:
Holy Moly… you guys are getting plastered.  Reports of 10 to 20 inches already having fallen, with another 6 to 10 inches being possible before it ends.  Widespread power outages are being reported, with blizzard conditions due to wind gusts over 35mph.  This is a major event in those areas, and travel is STRONGLY discouraged.  Don’t go out unless it’s an emergency, the travel conditions are very dangerous.
 
This storm continues to defy expectations across the entire region.  Parts of the area are seeing conditions that were forecasted, while other parts are only seeing wet snow mix in at this hour.  As the analysis will show once the storm is finished, there was no way to accurately predict all of the nuance this storm had to offer… but on the average, the forecast and discussion did a decent job preparing everyone for the potential snow and wind, as well as the potential for a busted forecast in parts of the area.  Hopefully everyone is remaining safe out there, and we greatly appreciate you tracking the storm along with us at HVW! 

Storm Update/Adjustments

Good Morning,

Now is a good time to make some course corrections to the forecast, we are at the magic hour where we know where the forecast has problems and where it doesn’t, so lets do a quick system check and adjustments to the ongoing forecast.

Previous Forecast vs Actual Observations:

  • Temps cooling through a process called dynamic cooling to allow snow to fall despite previously warm surface temps ( OCCURRING)
  • Snow falling heavy enough to overcome warm surfaces and create hazardous travel (OCCURRING) 
  • Gusty winds causing power outages (OCCURRING)
  • Very localized snowfall that depends on precipitation rates and elevation with widely varying conditions (OCCURRING) (In some cases, two miles)
  • Thunder accompanying heavier snowfall bands (REPORTED/OBSERVED)
  • Forecast for more snow across the region than rain (OCCURRING)
  • Downslope effect causing an area of less snowfall, with warming air (OCCURRING) and ultimately the reason for the next bullet point
  • Snowfall forecast (WILL NOT VERIFY IN ALL LOCATIONS)

Forward Looking Forecast and Adjustments:

This has been well communicated as being a very complex storm for the last several days, in multiple forecasts and live broadcasts we highlighted all of what can go wrong with this forecast and to say the least it was a lot. We stand behind our forecast and were the first forecaster calling for any snow in our region outside of the Catskills just 48 hours ago. With that said we strive for perfection and we aim to deliver you all a forecast that is as close to flawless as possible, we went into this knowing there would be issues and even addressed last night the time frame in which these issues would reveal themselves by so we could adjust, that is what we are doing now. We realize and ave already fielded some comments of disappoint that if the forecast wasn’t right in your backyard the rest doesn’t count. We understand that and always try to prepare everyone for the best and worst case scenarios in these type of storms and we apologize for the areas where it won’t be right, lets get to it..

A look at the current Hires models and a comparison to all of your observations along with a look at current radar we have been able to determine the area where the snowfall part of the forecast doest not look to verify, now this are may expand or could even shrink a bit, but as of this hour (8AM) this is the zone with the highest probability of missing the forecasted snowfall amounts, the area is marked with a black box and has been overlaid on our final forecast. Below this image is the projected snowfall as of the latest run of the hires model, you can compare the two and see that the areas being impacted by the downslope, match up with the radar and all of your observations and in addition to the lower snowfall amounts being projected by this model, in the remainder of the region our forecast continue to look solid (for now). For areas within the black box we can expect that snowfall totals here will likely not even eclipse 1-3″ and in some cases not more than a coating is possible.

As you can see the forecast covered the variables and will also may still verify across a large portion of the region but despite that we will still field comments like we have already seen that we hyped the snow totals for clicks or we are always wrong etc etc. The fact is, if you actually read, or actually listened to the forecasts, facebook posts, hour long live streams and countless amount of effort and thought that went into todays forecast that has been described by Meteorologists with 30 years experience as the most difficult they can remember, you would have known that all of these outcomes were possible. We take what we do extremely seriously and brought attention to what was only a rainstorm 48 hours ago, sorry for the misses that will occur but forecasting nature will always be a humbling job that we love to do.

Here are the current outages across the region as well, please remember our utility crews are out in these dangerous conditions and away from their families fighting to keep our lights on, this was always a possibility and these numbers will likely continue to build..

Check here for updates from out friends at Central Hudson: https://stormcentral.cenhud.com

Winter Storm Discussion : 4:30am Update

As this unpredictable, and dynamic winter storm unfolds… this is where we’ll have all the discussions the rest of the way.  Anyone who is looking for a comprehensive explanation of the setup for this storm, can please view the following thorough discussions

Final Winter Storm Forecast : Friday 3/2/18
Complex Winter Storm Discussion

4:30am Update

As of the 4am hour, we’re already seeing the changeover occur.  We have widespread reports from all over the Hudson Valley, that the dynamic cooling is having its impact.  Just look at how much of the Hudson Valley has transitioned to wet snow at this hour…

The line is effectively down to I-84 in Port Jervis, Middletown, Newburgh and east toward the Connecticut border.  And based on the computer model progression, this pattern will continue for several hours, as we head into the daylight hours across the Hudson Valley.

You will notice that the Hudson Valley is projected to transition between a cold rain and heavy wet snow for pretty much the entire day.  Most of us start the day as heavy wet snow… but it looks like the rain will arbitrarily mix in with the wet snow at times all across the region.

We continue to be very unsure about:

  • How much does the dynamic cooling effect hold across the Hudson Valley?  Will the moderate to heavy precipitation that is expected be enough to keep us as wet snow?  Or will we experience a mixing with rain?  This will have dramatic implications for snow totals… and thus snow totals are extremely likely to be tweaked or changed… and possibly busted, depending on how the storm unfolds
  • Shadow effect from downsloping?  This looks to be a concern with the dynamic cooling we anticipated.  It’s possible that the downslope effects from the NE winds off the Berkshire Mountains cause lower precipitation rates, and thus a change over back to rain.  We’ll have to monitor.

We’ll have updates through the day… as it’s going to be a LONG day.  We’ll see if all our forecasting and energy spent gets us on the right side of this forecast…. or if we stuck our necks out a bit too far.  Be safe on the roads this morning if you’re travelling… conditions will deteriorate rapidly.

Final Snowstorm Forecast : Friday 3/2/18

A powerful upper level low pressure system will interact with a rapidly deepening coastal storm on Friday.  The end result will be a wild variety of weather across the Hudson Valley.  The impacts from this storm could be quite significant across the region, as the combination of heavy, wet snow… and powerful wind gusts over 40mph, could cause down trees and power lines.

Timing:
– 8pm to 11pm Thursday: Rain develops from SW to NE
– 12am to 7am Friday: Rain mixes with & changes to wet snow from NW to SE
– 7am to 4pm Friday:  Snow falls heavy at times, whiteout conditions possible
– 6pm to 11pm Friday: Snow tapers off from west to east

Snow Accumulation:
– Catskills (Zone 1 & 2): 18 to 24 inches (locally 30″+ in highest elevations)
– Southern Catskills, Shawangunks, Hurley Highlands (zone 5 & 6): 8 to 16 inches (locally 20″)
– Majority of the Hudson Valley (Zone 3, 4, 7 & 8): 6 to 12 inches (locally 12″+ in higher elevations)
– Extreme Lower Hudson Valley (Zone 9): 2 to 6 inches (locally up to 8″ in higher elevations)

Discussion:

We’re going to go light on the discussion in this section, mainly because we’ve discussed so much in our afternoon discussion, which you can find at the following link:

AFTERNOON STORM DISCUSSION: EXTREMELY COMPLEX SYSTEM FOR FRIDAY

There are some items that we do want to highlight with this system:
– Dynamic Cooling
– Winds
– Elevation & Snow Accumulation

Dynamic Cooling
We’ve discussed the fact that this entire snow event hinges on one thing… and 1 thing only… dynamic cooling.

Our upper level low pressure will basically follow the track shown in the image above.  As it moves west to east, it will generate TREMENDOUS upward motion, and it will cause the air to rise.  As the air rises, it cools and condenses, and causes heavy precipitation rates.  We’ll need the upward motion to play out as shown above, to get the temperatures to drop as they’re projected overnight…

Look at how fast temps drop, and this is the key to getting the temperatures cold enough to support snow.  Most of the guidance, as well as weather history, suggests that the upper level low pressure will causes the temperatures to respond as indicated… which will allow a heavy, wet snow to fall.

Winds
If the wet snow falls as projected, we’re very concerned about the possibilities for power outages.  This storm will really ramp up offshore, and as the storm bombs out, the rapidly deepening storm will generate powerful winds out of the northeast.

With the heavy wet snow sticking to everything like paste… wind gusts over 35 or 40mph howling against tree branches loaded with wet snow… and we could see a fair number of downed trees and power lines.  As we highlighted earlier in the day, our friends at Central Hudson have provided us with links for everyone to stay informed on the situation, should conditions deteriorate on Friday.

Central Hudson: Storms & Outages
Central Hudson Storm Center

It’s probably not a bad idea to plan for the possibility that power could be lost for a time on Friday.  Something to consider, because if the heavy wet snow begins to fall… the powerful wind gusts could cause an extra dimension to this storm.

Elevation & Snow Accumulation

Finally, we want to make clear… that this storm sits on the head of a pin.  Meaning, that so many factors have very little wiggle room, and no margin for error.  We need to get tremendous cooling to take place, so that a heavy wet snow falls.  Once that happens, elevation still plays a roll.  Higher elevations tend to cool faster and to a greater extent.  The higher your elevation, the better the chance you see a heavy wet snow that accumulates considerably.

However… lower elevations CAN NOT be discounted.  A lot of people and forecasters are writing off the valley areas as too warm for snow.  Dynamic cooling can impact those areas the same as higher elevations, and we do believe that valley areas can see the snow thump.  It is worth stating, that lower elevations have a greater risk of seeing the forecast bust… i.e. the rain mixes in more than expected, and snow totals are lower… but while elevation plays a role, it’s not a deal breaker.  All of the Hudson Valley could see a significant event.

And with regard to the projected accumulations… we want to be clear, that there is a LOT of variability within each range.  We posted 6 to 12 inches for the Hudson Valley on average… but there will be some valley areas that see rain mix in, due to downsloping or elevation… and those areas could see 3 or 4 inches of wet snow.  Not far away, in a location that is higher in elevation and doesn’t have downsloping to contend with… it wouldn’t be shocking to see a report of 13 or 14 inches of wet snow.  The point is… don’t get too hung up on the accumulation forecast.  This is a dynamic storm, and the forecast will be dynamic as well.  We may yet have to tweak details as new information comes in.

Expect more updates as we get closer to the storm.  Thanks for reading, and continuing to support HVW.

Storm Discussion : Extremely Complex System for Friday

As of early afternoon, we have no formal changes to our preliminary forecast, which you can view here:
PRELIMINARY STORM FORECAST: 3/2/18

But we want to discuss just how complex and difficult this storm is going to be to forecast.  Very often, winter storms are complex and difficult to forecast… and then there is THIS storm.  So we want to highlight some of the complexities, and then discuss what some of the ‘wildcard’ factors could be on Friday… so you have a better handle on why this storm will be so difficult to forecast when it comes to the details.

For starters… it’s currently 57° in Poughkeepsie.  There are no arctic cold fronts heading this way, but our flow is now out of the northeast, so we’ll begin to chip away at that number.  But our northeasterly flow only gets us to the low 40s by midnight and the early morning hours.  We’ll see rain overspread the entire Hudson Valley between 6pm and midnight… and the storm will have a very mild feel to it.  No true sign that this will end up being a winter storm… and based on much of the traditional computer model data, no reason to think that a strong snowstorm may be on the way.

The Key: Upper Level Low Pressure

But it’s right about this point, where we’ll begin to see the storm show us signs of change.  A strong NE wind will continue to funnel cooler air into the Hudson Valley, but a deepening upper level low pressure system will pass by just to our south, and move out over the ocean.  As it does… we’ll see the intense upward motion within the upper level low pressure…

Upper level low pressures are notoriously unpredictable.  This feature is projected to have intense lift associated with it, and as air is forced upward… it cools and condenses.  The rapidly rising air causes intense precipitation rates.  That heavy precipitation is likely to fall as rain initially… but as the precipitation falls, it drags the colder air down to the surface with it.  As this process occurs over time… it constantly repeats itself:
(Air rapidly rises…. Air cools and condenses…. heavy precipitation develops…. cold air pulled back to surface…. and repeat)

This process is called “Dynamic cooling”… and it’s the critical feature in how we get the temperatures cold enough to support snow.  If we are in the low 40s at midnight across the Hudson Valley, we will need this dynamic cooling process to generate it’s own cold air… and make it cold enough to snow.  Here’s a map showing projected temperatures at 12am… and projected temps at 5pm…

Temps drop nearly 10 degrees in about 5 hours, due in large part to the dynamic cooling that is expected.  As the upper level low moves just to our southeast, the Hudson Valley is in prime position for dynamic cooling, brought about by the strength of the upper level low.

**Critical note** We cannot emphasize this enough… if this scenario is right, our forecast will be on target.  We are forecasting under the expectation that the dynamic cooling will be as significant as shown here.  If the upper level low pressure tracks differently, or isn’t as dynamic… it will mean less cooling, and dramatically lower snowfall amounts than what we’re discussing.

Massive Blocking = Long Duration Snow Event

One of the big factors in this storm being a significant snowstorm for the Hudson Valley, is a very negative NAO or North Atlantic Oscillation.  The NAO is a tool that meteorologists use to forecast weather patterns.  A negative NAO indicates that there is blocking in the atmosphere.  The ‘blocking’ prevents the storm from moving out to sea, and really extends the storm for the northeast.  This simulated radar paints a clear picture with regard to blocking.

Notice how at first, the storm is moving eastward, off the coast… and then it suddenly stops moving east.  Instead, it just sits and spins over the same places for hours and hours.  This is a 24 hour radar loop, and you’ll notice that the Hudson Valley is seeing snow for much of the time… which is a big factor in our forecast.  If it snows substantially for 12+ hours… the potential for us to get substantial snow accumulations is quite high.  But exactly where this storm stalls out, and exactly where the heaviest snow is at that time… are all vital pieces of the forecast puzzle.  If any of our assumptions or data is wrong… the forecast will also be wrong.

The Howling Winds

One of the not so enjoyable aspects of this system, will be the winds.  The heavy wet snow we are projecting, will not interact well with the anticipated wind gusts on Friday.

There is no sugar coating it… if these wind gusts are not overdone (and there is reason to believe they could be rather accurate)… then the heavy wet snow will coat trees and power lines, and the strong wind gusts will likely cause scattered power outages.  Our partner Central Hudson is already planning for a very busy couple of days.  They have provided us with a couple helpful links to obtain information:

Central Hudson Storm Center
Storms & Outages

The setup for power outages is similar in some ways to our February 2010 blizzard, which provided 1 to 2 feet of heavy wet snow, that stuck like a paste to everything.  So when the winds began to howl, it was a lot of extra weight to trees and power lines, and much of the Hudson Valley was without power for days.  We hope that this will not be like that storm… but we see signs of similarities.

Conclusion…

So as you can see… there are MANY factors that are going into this storm.  We didn’t even have time to list all the complicated wildcards in play.  Where the heaviest snow bands set up will be critical to the heaviest snow totals… but we’ll discuss the banding potential in a separate discussion, possibly in the final forecast.

Even if we get this right, and it’s a mostly wet snow event for the Hudson Valley… and we increase our snowfall forecast, we’ll still have parts of the Hudson Valley where the forecast ‘busts’.  That’s because as Alex mentioned… even within the Hudson Valley, we could see downsloping winds off the Berkshires negate the dynamic cooling in some parts of the central Hudson Valley.  It would mean parts of the valley seeing rain mix in, especially when the precipitation becomes lighter… and snowfall amounts be lesser in downslope areas.  So expect wildly different conditions across the area… depending on location and elevation.

Forecasting and communicating this storm effectively will be extraordinarily tough.  Alex and I will give you absolutely everything that we have… and we hope to keep you informed, and ahead of what will likely be the most significant storm of the winter… in terms of total impact on the region.  Once again… here is our preliminary thoughts on snowfall amounts… all signs point to us increasing these…

More updates as we continue to get closer to the storm… thanks for reading!

Preliminary Storm Forecast : Friday 3/2/18

Warm air is entrenched over the eastern half of the United States.  The Hudson Valley has been a solid 10° to 15° above average all week so far.  So that fact that we’re about to talk about discuss the likelihood for a snowstorm on Friday may seem a bit hard to believe.  But a dynamic upper level low pressure system will interact with rapidly intensifying nor’easter.  The timing will be crucial… but the expectation is that a sizeable snowstorm will impact the Hudson Valley on Friday.

Timing:
– 8pm to 11pm Thursday: Rain develops from SW to NE
– 12am to 7am Friday: Rain mixes with & changes to wet snow from NW to SE
– 7am to 4pm Friday:  Snow falls moderate to heavy at times
– 6pm to 11pm Friday: Snow tapers off from west to east

Snow Accumulation:
– Catskills (Zone 1 & 2): 10 to 18 inches
– Southern Catskills, Shawangunks, Hurley Highlands (zone 5 & 6): 6 to 12 inches
– Majority of the Hudson Valley (Zone 3, 4, 7 & 8): 4 to 8 inches
– Extreme Lower Hudson Valley (Zone 9): 2 to 5 inches

Discussion:

In the midst of a very warm pattern, we are going to witness the power of an upper low pressure system, as it single handedly tries to cool the region substantially enough to take temperatures in the mid 50s… and turn them into temperatures in the mid 30s in 24 hours.  There is no arctic cold front, no source of cold… Canadian air.  If it’s going to snow… and we believe that it will… it’s going to do so under the power of a strong area of upper level low pressure.

This map shows the upward motion in the atmosphere.  There is projected to be a very large area of strong to intense upward motion just to the north of the upper low.  As a result, we should see rapidly cooling air temperatures, and moderate to heavy precipitation.  The entire logic behind this storm being a snow maker for the Hudson Valley… is that the tremendous upward motion is THE ingredient that cools the air mass enough to support snow.

This shows the projection by the European model, for temperatures at cloud level (in degrees Celsius).  With the progression of the Upper Level Low pressure eastward Thursday night into Friday morning… you can see that the cloud level temperatures are projected to respond in kind.  At sunset on Thursday, cloud level temperatures are above freezing in the Hudson Valley (star)… but by sunrise on Friday, cloud level (850mb) temperatures are projected to be below freezing (white color).

If this scenario is correct… and we believe that the European & NAM model solutions have the right idea… by sunrise on Friday… a moderate to heavy snow is expected to be falling across the Hudson Valley.

Based on the factors we’ve laid out… this is what the weather map could look like Friday morning.  It would set the stage for a very snowy Friday across the Hudson Valley.

Important Notes

This is an extremely complex setup, and all the pieces of the puzzle need to come together just right, for us to see snow.  If any of the factors change… it could have major implications on the end result of our weather.  Here are a couple of extra items we want to highlight related to this storm and forecast…

… The track of the upper level low pressure is critical.  It needs to track just to our south, but not too far to our south.  This is how we’re going to get our cold air, and if the upper level low is too far away, the influence of cold air will not take hold.

… Temperatures are extremely marginal… meaning near or above freezing through the duration of this event.  That will mean variations in accumulations.  Snow could struggle to stick to paved surfaces, and even on grassy areas.  So travel conditions will vary across the region.

… The data we’re seeing remains VERY conflicted at this time.  The uncertainty level with this forecast is VERY HIGH.  We are talking about a very dynamic situation.  Upper level low pressures are notoriously difficult to forecast, only adding to the uncertainty level.

… There is a STRONG block over Greenland at this time.  That will prevent this storm (rain or snow) from exiting the area quickly.  The result will be the storm getting trapped just offshore on Friday, and for the Hudson Valley and Northeast US, it means an extended period of snow (or rain)… possibly leading to very high accumulations of snow in some places (especially the mountains like the Catskills).

BOMBOGENESIS!  This storm is projected to go from 1001mb at 7pm Thursday to 971mb at 7pm Friday night.  When a storm’s central pressure drops by more than 24mb in 24 hours… the storm is said to have “bombed out” or undergone Bombogenesis.  This is another indicator of just how dynamic and powerful this storm is.

… Thanks to Bombogenesis… we’ll have very strong winds.  We’re seeing indications that sustained winds between 10 and 15mph are possible, with frequent gusts over 30mph possible.  There is a high wind watch for Westchester County, and if this storm transitions to snow as the Euro and NAM models suggest… we could see Blizzard Watches posted, or blizzard conditions experienced in some parts of the area.

… Power Outages?  Sadly… when dealing with potential blizzard conditions, due to such strong wind gusts… power outages may become a concern.  Temperatures will be mild, barely getting to the point where snow can be supported by the atmosphere.  With temperatures relatively mild, we’ll be looking at a heavy, wet snow.  When we combine wet snow and wind gusts over 30mph… we could see elevated concerns about downed tree branches and power lines.

… And Finally…WE ARE EXTREME!!… we anticipate our forecast to ruffle a lot of feathers.  To our knowledge, nobody is forecasting anything close to the snowfall map we have issued.  The National Weather Service has Winter Storm Watches posted for the Catskills, but the valleys are not projected to see much if any snow by other outlets.  You don’t have to agree with our forecast… but we would appreciate criticism be constructive.  We’re not issuing this forecast lightly… we see considerable data that supports our ideas.  We are trying to get our viewers out ahead of what will likely be a rapidly developing situation on Thursday… as more data comes out.  We do not hype storms to cause panic and worry… this storm has dynamic elements that could lead to unusual and extreme weather.

So in conclusion… there are A LAUNDRY LIST of complex items surrounding this storm and it’s forecast.  Expect there to be substantial changes to our final forecast.  We could see a scenario where we have to increase the snowfall forecast for the entire Hudson Valley… and we could also envision a scenario where the snowfall forecast gets reduced substantially.  We will have updates through the day on Thursday, as more and more data becomes available.

Thank you for reading… and we greatly appreciate all of your support!

Wednesday Outlook : Beautiful Weather / Eyes on Friday

A fantastic Wednesday shaping up across the Hudson Valley.  We’ll see sunshine and blue skies mixing with some fair weather clouds at times.  Our flow will shift out of the southwest on Wednesday… allowing temperatures to climb into the mid and upper 50s across the region.

The focus of the day will be on Friday of course… as we continue to track a surface storm system that will move from the Chicago area and redevelop south of NYC and Long Island.  At the same time, an upper level low pressure system will intensify and track from Detroit to areas off the Mid Atlantic coast.   The exact track will be tough to iron out, as we have multiple weather features to gather data on.

It’s warm… VERY warm, across the Hudson Valley.  Without any real invasion of arctic air to speak of… it’s going to take the energy from the upper level low pressure to generate cold enough air to cause snow.  In the Catskills… that looks easy enough, with Winter Storm Watches already posted for the mountains of the viewing area.  But the big question we’re going to focus on today:  “Can we get the Upper Level Low Pressure to track just to our south, and cool the air enough in the valley, to turn the rain over to snow?”

We’ll have updates on this potential through the day.

Rainfall Recap : Last Weekend

We’ve had many people ask for a recap on the weekend’s rainfall totals.  The reports out of the northern half of the Hudson Valley were not very encouraging (Greene, Columbia, Ulster & Dutchess).  But we wanted to share the information with you.  The map below covers the 7 day period from Tuesday 2/20 thru Tuesday 2/27… which encompasses all of the rain (and wet snow), from Thursday through Sunday.  The totals listed, are just from Saturday and Sunday.  All data is from the National Weather Service…

 

Thank you for your continued support of HVW!