forecasts

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.

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!

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!

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!

It’s starting to feel like the very beginning of spring.  Those days where the sun is bright, and the temperatures climb into the low 50s.  And you can start to feel spring in the air.  Days like yesterday, and today…

We’ve got lots of sunshine and blue skies for our Tuesday.  Our flow continues to be out of the west, reinforcing that mild air that is in place across the Hudson Valley.  Temperatures started out near or just below freezing across the area… signs of a hard frost and freeze in many places.  But the sun has melted the frost… and temps are on their way up.  Highs this afternoon should reach the mid 50s in many parts of the Hudson Valley… well above the average in the low 40s.  Hopefully you can get out and enjoy our early spring preview!

This fantastic weather will carry us through Wednesday, before some more clouds push into the area for Thursday.  That leads us to a very complex setup for Thursday night and Friday.

This continues to be the basic setup for our Friday.  However, this isn’t a ‘basic’ system… and we’re getting some new data that suggests that this storm may try to generate some snow.  So we’re going to be looking at this storm in depth through the day.  We’re going to try and have a comprehensive discussion on this system later today or tonight.

Winter… it seems, won’t go away without a fight.  Have a great Tuesday!

As we begin the final week of February, winter seems to have forgotten us.  We watched winter surge back in on the heels of the warmest February day on record… but just as quickly it exited the region over the weekend once again.  After several inches of rainfall over the weekend, we’re looking at things finally quieting down for the first half of the work week.

Clouds will mix with increasing amounts of sunshine as the day progresses on Monday.  Our flow is out of the west/northwest… but for snow lovers, the problem is that there is no cold air anywhere in the eastern 2/3 of North America.

So even with the NW flow to start the week, we’ll see temperatures about 5 to 10 degrees above average… with highs across the Hudson Valley pushing near 50°.  This trend will continue as we push into Tuesday and Wednesday as well.  So a warm finish to what has been a rather warm month of February.

Looking toward the end of the week, we’re tracking a major storm system developing.  All the ingredients for a major snowstorm are in place… except the cold air.  To torment snow lovers… we’ve had a terrible atmospheric pattern for weeks, and now the pattern breaks in our favor… but with absolutely no cold air to work with.  The result… looks like this…

As snow lovers… this is deflating.  But we can’t control the weather… we just diagnose and forecast it.  It looks like a strong coastal storm will stall out off the east coast, and eventually move southeast… out to sea.  That’s due to a monster block over Greenland, that will prevent the storm from exiting in it’s traditional pattern.

We’ll continue to track this storm as we push into the week.  Maybe we can find some cold air… or borrow some from our friends in Europe.  Ultimately, that’s where all the cold is… Europe.  The US maintains our relatively warm pattern… and we’ll see how long into March we can hold onto it.

Have a great start to your week!

As we begin our Sunday, we’re going to try and wrap up what’s been a very unsettled 4 day period.  No sooner did we have arguably the nicest February day on record (it surely was the warmest on record)… we ran into sleet and snow on Thursday, and haven’t been able to shake the unsettled weather since.

But looking at the radar loop as of 8am… you can immediately see, that we still have got a LOT of rain to get through today. This is a radar loop from roughly 6:30am to 8am of Pennsylvania and much of southern NY state (The Hudson Valley is in the top right of the graphic). There is a good batch of light to moderate rain over the Hudson Valley, and extending all the way up to Albany… there have even been some reports of sleet mixing in with the rain over the northern Hudson Valley.

But notice how much rain remains off to our west, and it’s pushing in our direction. So it looks like we’ll be saddled with the rain straight through lunch… before the rain tapers to scattered showers this afternoon. Temps aren’t looking too good either… as it seems we’ll be stuck in the mid 30s to low 40s for much of the day. So it will be a chilly, wet and raw morning across the region… with rain tapering off around mid day, and leaving us with some scattered afternoon showers, under mostly cloudy skies.

Grab your rain coat, and have a great Sunday!

 

It’s been a pretty wild week of weather.  We started with a snowstorm last Saturday in the midst of a mild pattern… and then ran back to back days of record breaking warmth on Tuesday and Wednesday… with Wednesday being the warmest February day on record.  Then Thursday rolled around… and much of the Hudson Valley went from mid 70s and sun… to mid 30s and snow, in 24 hours.

Lets take a look at our storm forecast, the storm history map, and the NWS reports…

Thursday’s event was expected to be focused on the northern half of the Hudson Valley, and that turned out to be the case.  In fact, when we looked for snow/sleet data for the southern half of the Hudson Valley, there were no reports at all for areas near/south of I-84.

The storm behaved well, at least in terms of what the forecast had outlined.  The system started off as widespread showers on Thursday morning, as the cold front began to filter the cold air into the region.  Rain mixed with sleet and quickly turned to snow in the northern Hudson Valley… but the abnormally warm air mass that was being pushed out of the area was so mild, that despite the rapid change to snow… the snow did not immediately accumulate in northern HV and Catskills.  Before too long, the surfaces cooled enough, and the snow began to accumulate.

For the Mid Hudson Valley, the rain showers held on a bit longer.  The forecast reflected a widespread slushy coating to an inch of accumulation, largely because the cold air would take a bit longer to push into the lower portions of the region… and it was a bit uncertain how long it would take for a transition to sleet in that area.  Eventually there was a transition to sleet and wet snow, and slushy coatings to half inch / inch amounts did occur.

The timing of the event for the evening commute was a big factor to the ‘storm’.  This was more of an area of precipitation that pushed overtop of some fresh cold air… than an actual storm system, but that’s focusing on the meteorology of the storm.  Impact wise, we were concerned that the expected burst of snow and sleet could cause some travel problems for the evening commute, and it seems like there were a few in the northern HV… while the southern HV remained just wet, with everything melting on contact.

Anytime you drop 40 degrees in 24 hours, and then have it snow or sleet in the process… it’s a pretty wild situation.  And despite the marginally low totals on Thursday… the event was a pretty wild one.  Thanks for all your support!

With warm SW winds helping temperatures climb into the mid and upper 40s across the Hudson Valley, the raw chill of the past few days has been lifted out of the valley.

However, a rather large batch of rain has formed over Pennsylvania, and it’s now entering the Hudson Valley as of mid day. This batch of rain is rather large, and will bring periods of rain showers to the entire Hudson Valley for much of the afternoon. The heaviest and steadiest showers should be focused from I-84 on north. Unfortunately, anyone with outdoor plans for our Saturday will need to factor this into their plans.

A quick return to winter across the Hudson Valley on Thursday, as we saw temperatures drop about 40° in 24 hours.  We’ll have a recap on the Thursday snow & sleet event tonight.

But today has started off cloudy and gray… with some areas of light drizzle and fog.  As we move into the afternoon, we’ll have some areas of light rain pushing into the Hudson Valley…

 

Temperatures will hold down in the low to mid 30s through much of the morning and early afternoon on Friday.  When the precipitation moves in, we should see it fall as scattered light rain showers.  It’s possible that we see some patchy areas of freezing drizzle in the sheltered valleys of the Catskills… but in general temps will be just above freezing.

The rain showers will continue through sunset… and then taper off after dark… and temperatures will likely climb near 40° overnight.  As we look to the weekend, a very unsettled weekend heading our way.  Clouds will be with us Saturday, and then some showers look to move in late in the day and at night on Saturday.  Then, it looks like we’ll have a period of rain Saturday night, lasting into Sunday morning.

So while the weekend won’t feature a total washout… there will be multiple periods of rain to contend with.  At least we’re not in a drought situation.  For a better timeline on the precipitation, check the Detailed HVW 5 Day Forecast.  We want to emphasize that Saturday during the day looks mainly dry… with scattered showers approaching near or after sunset.

TGIF everyone!