Storm Center

The 1st stage of our storm is just about complete. However… we have about 3 or 4 more stages of this storm to push through. This weak and disorganized system is going to bring a lot of uncertainty with it. So lets break this system into pieces to discuss.

Stage 1 (2am – 2pm) :

The radar loop shows how the first area of moderate to heavy snow is pushing mostly southeast of our area. Areas south of I-84 did get in on some of the heavier snow, and we have seen reports of 1 to 3 inches of snow in parts of Rockland, Westchester, and Putnam counties. But the remainder of the region has anywhere from a dusting to an inch after Stage 1.  This is going to give the impression of a completely busted forecast.  The forecast of 3 to 7 inches is no where near being verified for 75% of the region, mainly anyone north of I-84.  This was not entirely unexpected… although guidance did originally suggest this batch of snow pushed a bit further north before moving out.

Stage 2 (2pm – 8pm)

This is the futurecast radar of the storm from 1pm to 8pm.  You can see the area of moderate snow pushing out to sea in the first frame at 1pm.  Then as we go through the next 2 or 3 hours, the guidance believes an area of light to moderate snow will fill in on radar across northeast PA and into the Hudson Valley.  This is due to considerable upward motion (vertical velocity) in the mid levels of the atmosphere.

The yellows and oranges indicate fairly good upward motion in the atmosphere, which could cause snow to develop and enhance, even though the radar looks quiet now.  If this is correct… despite the radar indicating that the snow is just about over… we should see the radar begin filling in, and spreading into the Hudson Valley through the afternoon hours.  For this reason, we anticipate periods of light to moderate snow through the afternoon, and into the early evening hours.  Accumulations over this time are likely to be a dusting to an inch or so… maybe an inch and a half in a few spots.

Stage 3 (8pm Thu – 8am Fri)

This futurecast simulation from 8pm tonight to 8am on Friday shows repeated periods of on and off light to moderate snow.  The lift in the atmosphere associated with the coastal low pressure appears to be enough to generate repeated areas of steady snow, that will accumulate slowly… but steadily through Thursday night and into Friday morning.  Here is the snowfall map associated with this 12 hour period of time…

This map is projected that for every 1 inch of liquid, we would see 10 inches of snow.  Actual snowfall ratios could be closer to 12 to 16 inches of snow for every 1 inch of liquid.  Here’s a visual representation of how the snow ratios could set up.

So the overnight snow amounts could be closer to 1.5 inches, possibly even 2 inches in the Hudson Valley.  A very minor difference… but could make a difference when compiled into the total storm.

Stage 4 (8am to 7pm Friday) :

You see that during the daylight hours on Friday (from 8am to 7pm), that the snow continues to fall around the Hudson Valley.  It may taper off at times, and fall steadily at others… but the snow is clearly in our region through the day on Friday, per the computer guidance.  Once again, these snowfall rates are not very impressive.  Here are the projected snowfall amounts from 8am to 7pm on Friday…

So once again… another 12 hour period of time, where another 1 to 2 inches of snow can fall.  These snow rates are not overly impressive, but the potential for an extended period of time, with persistent and consistent light to moderate snows.  This could add up over time… and by the time all is said and done, not counting what has fallen so far… here is the projected additional snow… after 1pm Thursday…

So in conclusion… when we eliminate the snow from this morning, that clipped the lower Hudson Valley and was focused south of the region… you can see that the guidance still believes that additional areas of persistent light to moderate snow will develop and fall in the Hudson Valley.  An additional 3 to 6 inches of snow is possible… mostly in the mid Hudson Valley.  The Catskills and upper HV may see slightly less snow… but even there, an additional 2 to 3 inches of snow is likely.

Could this be wrong?  Absolutely!  Any time there is a weak storm system, with an expectation that snow will develop right over top of us, and possibly continue for such an extended period of time… it’s entirely possible that the computer model is wrong about the development of light to moderate snow.  It is equally plausible, that the model does not show enough snow, that the upward motion that is expected is more significant… and the moderate snow becomes heavy at times.  These type of scenarios are very difficult to pinpoint… so we will trust that the model is properly projecting the atmospheric dynamics that will cause snow to develop and enhance over the Hudson Valley for the next 36 hours.

So in conclusion…. “No… this storm is not over.” … and at least for now, this storm is not a bust.  Be sure to anticipate a snowy, and slick Thursday afternoon and evening.  A snowy Thursday overnight… as well as a snowy Friday morning and afternoon, before things finally begin tapering off Friday night.  More updates as necessary.

Hot on the heels of a Monday night storm that brought a wintry mix to the Hudson Valley, comes another snow threat.  A relatively weak system developing in the southeast, will push into the Mid-Atlantic on Thursday.  This will spread snow northeast, into the Hudson Valley.

Timing:
– 2am to 9am : Scattered Light snow showers possible
– 9am to 1pm : Steady snow develops from SW to NE
– 1pm to 6am Fri : Periods of light to moderate snow expected
– 6am to 3pm Fri : Periods of light snow, gradually tapering off

Impact/Conditions:
– Long duration snow event
– Periods of light to moderate snow
– Winds not an issue
– Temps in the 20s, snow accumulates on all surfaces
– Snow covered & icy roads likely

Snow Accumulations:
– Entire Hudson Valley Region : 3 to 7 inches (locally 8″+)

Additional Discussion to follow separately.

A weak storm system developing in the southeast will spread northeastward on Thursday.  As it does, it will likely spread snow into the Hudson Valley.  The details of how this event will unfold are a bit unclear, but hopefully will resolve themselves on Wednesday.  But for now, the potential exists for a moderate snowfall across the region.

Timing:
– 7am to 1pm : Light snow likely developing from SW to NE
– 1pm to 6pm : Snow becomes steadier and widespread
– 6pm to 6am Fri : Periods of snow expected
– 6am to 6pm Fri : Periods of light snow possible/likely

Impact/Conditions:
– Potential long duration snow event
– Periods of light to moderate snow
– Winds not an issue
– Temps in the 20s, snow accumulates on all surfaces
– Snow covered & icy roads likely

Snow Accumulations:
– Catskills & Upper HV (Zone 1,2,N3,N4) : 2 to 6 inches
– Mid & Lower Hudson Valley (Zone S3,S4,5-9) : 4 to 8 inches (locally up to 10″)

— Discussion —

A storm system developing in the southeast will move northeast early Thursday, into the Mid Atlantic states.  As it does, there are some questions about the manner in which the storm develops.  The storm track will follow the northern edge of the offshore ridge.  But how the energy consolidates is a bit less certain.  Here is a futurecast radar from 1am Thursday through 7am Friday, that shows a storm that looks a bit disorganized at times through its progression.

Futurecast Radar : 1am Thu – 1am Fri

The snow tries several times to push into the Hudson Valley on Thursday, before making a successful push northward late in the day on Thursday.  How exactly this storm progresses could have significant implications for accumulations in the Hudson Valley.  From the wide view perspective, it seems like 2 separate pieces of energy.  From the 500mb level, it looks like the energy gets stretched from Louisiana to eastern Maine.  This elongated look to the energy may give us an extended period of snow.

As a result, we’ll have to monitor the progression and development of the storm on Wednesday, before we issue the final snowfall forecast.  The potential for a long duration event, with an geographically extended system, leaves a lot of room for error in the preliminary forecast.  The probability our final forecast will differ from our preliminary forecast, is quite high.  If we had to list our confidence level on the accumulations, it would be Low to Moderate confidence.  There are a lot of ways the details could change on how this storm unfolds.  Please check back late on Wednesday afternoon, to see if we have any new data to share.  The “Final Snowfall Forecast” will be issued before 9pm on Wednesday.

In the midst of a very active wintry weather pattern, Mother Nature has the ability to throw curve balls and sneak up on you.  Tuesday is very likely one of those times.

Timing:
– 3am to 7am : Light to moderate snow develops
– 7am to 1pm : Snow… locally heavy at times
– 1pm to 4pm : Snow tapers off

Impact/Conditions:
– Light to moderate snow Tuesday morning
– Snow rates over 1″ per hour possible in some locations
– Very cold temperatures = Light fluffy, high ratio snow
– Snow covered and icy roads likely
– School delays/cancellations expected
– Light winds expected, minimal blowing and drifting
– Both AM and PM commutes significantly affected

Snow Accumulation:
– Upper HV & Northern Catskills (Northern half of Zone 1,2,3,4) : 2 to 6 inches
– Catskills & Mid Hudson Valley (Southern 1,2,3,4) : 4 to 8 inches
– Southern Catskills & Lower Hudson Valley (Zones 5,6,7,8) : 4 to 8 inches
– Extreme Lower HV (SW corner of 8 & Zone 9) : 2 to 6 inches

-DISCUSSION-

The snow starts before sunrise in most of the Hudson Valley, and continues until early or mid afternoon.  Snow could fall heavy at times around the Hudson Valley and Catskills.  Road conditions will become snow covered and icy, with temps holding in the low to mid 20s all day.  Travel will be quite hazardous.  The good news, is that winds won’t be much of a factor on Tuesday.  The area of heaviest snow with this system is rather narrow… and runs from just south of Albany, to just north of NYC.  Normally, we would have considerable hesitation with the snowfall forecast, but the computer guidance has been extraordinarily consistent with the position of the heaviest snows.  The Hudson Valley has been in the ‘bullseye’ on just about every run, of every computer model… for the last 36 hours.  So we feel very confident, that the heaviest snows with this small system… will be in our area.

The 4 to 8 inches is likely going to catch some people off guard, because other forecasts are calling for 2 to 4… or 3 to 5 inches of snow.  But allow us to make the case for the 4 to 8 inch snow forecast.  Temperatures on Tuesday will be very cold, temps in the Hudson Valley will be in the low to mid 20s during the snow event.

Forecast Temperatures at 10am Tuesday

In addition, the atmosphere is very cold.  When the 850mb (cloud level) temperatures are between -5°C and -8°C, that is the ideal range for snowflake production.  It will create a light and fluffy powdery snow flake, that does not compact when it reaches the ground

When conditions are this cold, we can get what is known as a ‘high ratio’ snow.  That means more ‘bang for your buck’ in terms of snow accumulations, given the same amount of moisture.  Under standard conditions, for every 1 inch of liquid moisture, you can get 10 inches of snow.  However, when the air is colder, the snow becomes more powdery, and fluffy in consistency.  This allows the snow to accumulate without compressing or packing down as it does.  The result, is you can get accumulation ratios that are 12″ of snow or 15″ of snow, for every 1″ of liquid.  Conditions on Tuesday, are likely to be roughly 15 inches of snow, for every 1 inch of liquid.

Now, it is a bit hard to tell from this map, because cities are not marked… but the Hudson Valley is roughly around 14 or 16 inches of snow, for every 1 inch of liquid moisture.  This will give us a fluffy powder, which will accumulate at a faster rate than a snow like was seen on Sunday.  So the next question is how much moisture is available for the Hudson Valley.  Here is the NAM model, which is roughly the average… and thus a good representative… of all the computer model data available.

This gets us anywhere from about .4 to .5 inches of liquid on average, across the Hudson Valley.  The areas of blue, represent locations where over half an inch of liquid is projected.  There will be pockets of heavier precipitation with heavier bands of snow that develop.  So if we take Poughkeepsie’s 0.48″ of liquid equivalent… and multiply that by the 15 to 1 snow ratio… that gives us 7.2 inches of snow in Poughkeepsie.  Areas that see 0.40″ of liquid, would see 6 inches of snow.  Even areas that see 0.35″ of liquid, would see 5.25 inches of snow.

On this map, any location in purple, is at least 6 inches of snow.  That is a rather large area of 6 inches of snow projected for most of Dutchess, Ulster, Sullivan, and even northern Orange county.  The 4″ line, extends all the way down to southern Orange County and northern Westchester County on this particular map.

For this reason… we feel fairly comfortable with a widespread 4 to 8 inches of snow for the center of the region.  The northern and southern most counties, could see a little less, and so the 2 to 6 inch range… which accounts for the slight “wobble” in the area of heaviest moisture.

We’ll see how it plays out…

Well… this will be interesting, one way or another.  At this hour, 12 hours before the storm, we still have conflicting data.  So here’s the forecast, and lets talk briefly about it…

Timing :
– 7am to 11am : Snow begins from south to north
– 10am to 2pm : Steady snow, possibly heavy at times
– 2pm to 6pm : Snow tapers from west to east

Impacts :
– Quick system, fast mover, 6 to 8 hours in any location
– Snow rates around mid day could be up to 1″ per hour
– Cold, snow accumulates on all surfaces
– Considerable uncertainty regarding intensity and strength of system

Snowfall Forecast:
– Lower Hudson Valley : 2 to 5 inches
– Remainder of Hudson Valley : 1 to 3 inches

*Notes : Low confidence forecast.

— Discussion —

An extremely irritating storm to forecast, due to the wild swings in the computer model data, taking us for a ride that’s as nauseating as the worst rollercoaster you can imagine.  Six days ago this was projected to be a major snowstorm, almost as big as the storm from Monday.  That got everyone’s attention, and then the storm faded into the computer model abyss by mid week.  So we spent a day or two explaining to everyone that the major snowstorm that social media was buzzing about, was all but surely not going to happen.  Then slowly over 24 hours, computer guidance visited the local “lost and found” and located the storm once again… bringing it back along the east coast.  The new version of the storm looked to be able to drop 3 to 6, possibly 4 to 8 inches of snow.  Then, no sooner do we post the ‘preliminary forecast’… then the models begin shifting the storm further offshore.  This threatens to turn the storm back into a 1 to 3 inch event.

That brings us to our current snowfall forecast.  Due to limited moisture, and a fast moving system, snowfall totals of 2 to 3 inches seem likely, with possibly only an inch or two in the northern Hudson Valley.

This solution is the result of slightly less energy in the southern branch jet stream.  The storm is a little weaker as a result, a little further off shore, and has a little less moisture.  This is what we’ve seen trend on most of the guidance over the past 24 hours… a weaker, lower impact storm.  A general 1 to 3 inches, possibly 4 inches in a few spots.  As a result, we lowered our forecast for Sunday.

But we could see a scenario where this system has just a bit more energy in the southern jet… as the storm begins to develop, a little extra convective energy could transition to a stronger, more amplified jet stream.  This would bring the storm an additional 25 to 50 miles closer to the coast.  This would also deepen the storm quicker, providing more moisture to the Hudson Valley.  The end result… would look like this…

Both of these solutions shown here… are from computer model data that has come out in the last 6 hours (as of this post).  The NAM image shown here, is the extreme solution.  This is what would happen if everything comes together at the last second.  Instead of widespread 1 to 3 inches, it would be widespread 3 to 5 inches, with some localized totals of 6″ possible.  It’s also possible that we see a less intense version of the NAM, with slightly lower moisture amounts.  It really is a ‘nowcasting’ situation.  Nowcasting is when we stop looking at just computer model data, and start comparing prior computer data, to actual conditions… to see if the computer models are ‘verifying’.  If the computer models we based the forecast on turn out to be correct when compared to actual conditions… then we know we have the right idea.  But if we compare the computer model from 12 hours ago, and see that the actual conditions are noticeably different… then we know the models are either overstating, or underestimating the storm.  Then we can adapt, and pass the new information to you.  It can help you better temper your expectations for how the storm is going to unfold… even if you get the information only a few hours before it happens.  Information is power… and in this case, power could help keep you safe.  So we’ll see how it plays out.

We’ll be posting on Facebook on Sunday, and unlike the previous storm, we will be posting the updates here as well.  That was something we failed to do during the previous storm, and apologize for anyone who does not use Facebook.  We really feel like the general 2 to 3 inch amounts, with a localized 4″ total… are the most likely result on Sunday.  But lets see how it turns out.  Stay safe… and enjoy the light to moderate snow event on Sunday.

Seemingly hot on the heels of our storm 5 days ago… we’re tracking another storm for Sunday.  This storm is a particularly difficult system to forecast, as it is developing as it approaches the east coast.  The atmosphere dynamics trying to steer it up the coast are not very strong, so there is considerable uncertainty with the details of the forecast.

Timing :
– 5am to 9am : Snow begins from south to north
– 9am to 2pm : Steady snow, possibly heavy at times
– 2pm to 6pm : Snow tapers from west to east

Impacts :
– Quick system, fast mover, 6 to 8 hours in any location
– Snow rates around mid day could be up to 1″ per hour
– Cold, snow accumulates on all surfaces
– Considerable uncertainty regarding intensity and strength of system

Snowfall Forecast:
– Entire Hudson Valley : 2 to 6 inches

*Notes : likely to get a better handle on track and strength of system on Saturday, we may have to adjust snow totals up or down just a bit for final forecast Saturday PM

Discussion

This storm system at first look 5 or 6 days ago, was projected to be a major snowstorm for the region.  Then early/mid week… the models lost it entirely, sending it harmlessly out to sea.  Then 48 hours ago, the models detected a bit more energy in the southern jet, and this system has come back into play for the weekend.  The big question however, is just how strong is that southern branch energy?
– Is it going to help the system deepen quickly, and track right along the coast? … or…
– Is the energy flatter, keeping the system weaker and further off shore?

If the answer is the first… we could have a potent little storm system in the Hudson Valley.  One capable of dropping snowfall rates of 1″ per hour for several hours in the middle of the day.  The stronger storm would track closer to the coast and then out to sea by sunset.  By the time it tapers off… the snowfall in the northeast could look like this:

Stronger Solution : Closer to the coast = higher snowfall amounts

However, the computer guidance has been fluctuating from a stronger solution, to a weaker solution, as the models try to get a handle on the energy in the southern branch of the jet stream.  The difference in the atmospheric energy is small, but the end results are noticeable.  The slightly weaker solution means the low pressure doesn’t deepen as much.  If the storm doesn’t deepen as much, it won’t be pulled as far up the coast.  If it doesn’t come as close to the coast, the precipitation amounts in the Hudson Valley will be less… and as a result, snowfall totals will be less.

Weaker Solution : Further from the coast = lower snow totals

Unfortunately, we’ve seen next to no consistency in the guidance.  It’s been like a roller coaster, going up, then down… then back up… then down again.  The very latest guidance, is the image you see above.  The system is weaker, and pulls out to sea faster.  As a result, the northern edge of the snow is stunted, and begins to push east as it gets over the Hudson Valley.  Areas south of I-84 would see 3 to 5 inches, and the rest of us would likely see 2 to 4 inches roughly.

Does this mean we’ll only see 2 or 3 inches?  Possibly.  But we always look for the trend when forecasting, and right now we’re not seeing one.  That should change on Saturday, as the energy comes out of the Rockies, and dives into the Tennessee Valley.  So for that reason, we should be able to post our Final Snowfall Forecast by early evening on Saturday (roughly 12 hours before the start).  If the trend for a weaker storm continues, expect a downward adjustment in the snow totals.

We’ll see what the data holds on Saturday.