Light Snow Possible Tomorrow/Tonight

Mostly cloudy skies are expected to dominate tonight with a chance of light snow later in the night.  Accumulations before 7 AM will be less than half an inch if there are any at all, with any snow being both powdery in texture and very light overall.  Low temperatures get into the mid 20s at the coast and low 20s inland.  It previously looked like steadier snow could be a threat overnight, but short-range guidance shows very few accumulations should be expected.

Winter Weather Advisories were in effect for Westchester County and coastal New Haven and Fairfield County calling for 1-4 inches of snow. They were overdone, and they were recently pulled, as Premium clients were told earlier this evening was likely.

Snow appears most likely to fall in bursts, with one burst of light snow expected to move from west to east from 12 AM through 4 AM (bringing up to half an inch of snow) and another burst moving through tomorrow morning from 7 AM to 12 AM.  Snow should not even get moderate in intensity, but could briefly cover roadways and make them a little slippery. Overall, though, this should be nothing more than scattered snow showers with briefly steadier banding at times.

Storm Recap And Tuesday Night/Wednesday Snow Threat

The below is part of a recent Premium forecast that was sent to clients outlining potential impacts to schools and travel in the next 48 hours.  To get these updates emailed to you upon release and view the latest forecast school impacts, subscribe here.  Otherwise, the Free content is below:

RECAP OF TODAY: The storm today turned out to have a few surprises after all. In one of the largest failures of short-range HRRR/RAP guidance, banding was not properly forecast across much of Fairfield County, where actually some of the highest snowfall accumulations were seen which came as a surprise.  Snow also continued slightly longer than expected, with one moderate band even continuing into the evening as seen here.  The result was a very impressive snowfall gradient across the county, where anywhere from 2 to 5 inches of snow was observed just in that one county.  This was the exact range instead forecast for New Haven County, where this banding was shown being set up by the majority of mesoscale guidance.  The below snowfall accumulations are the latest as of 7:30 PM:

   3 SSE BROOKFIELD       4.0   500 PM  2/08  TRAINED SPOTTER
   WESTPORT               4.0   600 PM  2/08  PUBLIC
   DANBURY                4.0   300 PM  2/08  SOCIAL MEDIA
   NEW CANAAN             3.8   500 PM  2/08  CT DOT
   BRIDGEPORT AIRPORT     3.5   700 PM  2/08  COOP
   FAIRFIELD              3.0   509 PM  2/08  PUBLIC
   WILTON                 3.0   500 PM  2/08  PUBLIC
   GREENWICH              3.0   215 PM  2/08  PUBLIC
   DARIEN                 2.0   300 PM  2/08  CT DOT

We see that New Fairfield and Brookfield actually topped off the Fairfield County accumulations, though there was a report of 6 inches at New Milford that we saw on social media.  The official Bridgeport accumulation was only 3.5 inches, which seems a little low compared to radar estimates but still was above our final 1-3 inch forecast; I should have stick with the 2-4 inch forecast I had most of yesterday before short-range guidance made it seem like that larger band would set up across New Haven County.  Fairfield County is where the forecast went most wrong, as schools ended up dismissing early despite a plethora of guidance indicating that regular closures would be better.  Across Greenwich/Stamford this still would have been the right call, but further north and east the snow continued longer, potentially making the early dismissal the correct call in a very marginal scenario.

What was more puzzling was that New Haven County did not see accumulations that were all that impressive and that there was a wide range of disagreement in these numbers.  The Fairfield County numbers should have instead gone here, as the Fairfield County band sapped the energy from the band that was supposed to form over New Haven County and enhance their snowfall accumulations.

   SOUTHBURY              2.5   500 PM  2/08  CT DOT
   MILFORD                2.3   500 PM  2/08  CT DOT
   WATERBURY              2.3   500 PM  2/08  CT DOT
   NEW HAVEN              2.0   500 PM  2/08  CT DOT
   BRANFORD               2.0   422 PM  2/08  SOCIAL MEDIA
   BEACON FALLS           1.8   500 PM  2/08  CT DOT
   MERIDEN                1.0   300 PM  2/08  CT DOT
   2 ENE MERIDEN          1.0   536 PM  2/08  TRAINED SPOTTER

The Meriden forecast of only an inch looks very suspect when looking at radar, as do a number of New Haven forecasts.  It was a significant surprise that Southbury saw the highest accumulations in the county, as almost every model was consistent with this region seeing the most snow.  In fact, the National Weather Service upgraded to the region to see 6+ inches of snow in a Winter Storm Warning.  I was not as confident with that and kept them in the 2-5 inch range, which generally looked to have worked out better, but still these lower numbers are a bit of a shock.  I expect the final numbers will still come in a bit higher regardless, but here the storm was really not that bad and some of the school closures may not have been necessary.

Finally, the Westchester County forecast worked out almost perfectly, as seen below.

   ARMONK                 2.7   145 PM  2/08  PUBLIC
   HARRISON               2.0   413 PM  2/08  SOCIAL MEDIA
   HASTINGS-ON-HUDSON     1.0   330 PM  2/08  PUBLIC

That band in Fairfield County didn’t quite get to this county, and so instead the forecast worked just as models and I had expected.  We generally saw 1-3 inches of snow, and most schools here did not dismiss early, instead opting to cancel after school activities as snow died down by 2 or 3 PM.  It was the enhanced banding over Fairfield County that increased snowfall amounts there and decreased them over New Haven County, but that did not impact the western extent of the snowfall in Westchester County where there were almost no surprises.

After a number of good performances from the HRRR model, this one was a relatively sizable failure, as was also the case with the RAP which was for awhile showing widespread amounts of 4-6 inches across New Haven County.  There was some banding shown across Fairfield County, but it was not shown being that impressive.  Instead, we ended up with some surprise snowfall.

TONIGHT: As was shown on the radar above, a moderate burst of snowfall is moving through the state now, and another half inch to maybe an inch of snowfall can be expected through about midnight tonight.  The HRRR here only shows about half an inch moving through 9 AM tomorrow, with most falling before midnight.  In fact, after midnight it is increasingly looking like we clear out and we could be relatively sunny come tomorrow morning.

TOMORROW NIGHT/WEDNESDAY: Later tomorrow into tomorrow night and Wednesday is when the next chance of snow arrives, and it may be the last substantial one for the week.  A weak low pressure center/Clipper will move to our south, and with it will be an accompanying enhance area of snow.  It will be a very small area of snow, but could pack a punch with snowfall rates up to an inch per hour.  Model guidance varies on exactly where we should expect this to track.   The 18z HD NAM shows that it may hit the region Wednesday morning, per this forecast radar image at 4 AM here.  The SREFs for the same time are much less convinced, as seen here, instead favoring the storm sliding to the south.  The 18z GFS similarly keeps all moderate snow over New Jersey and just gives us flurries overnight Tuesday night here.  And at 6 AM on Wednesday, the NMM shows a glancing blow while the ARW misses us entirely here.  The RGEM is a little more amplified, showing the potential for up to an inch of snow through 7 AM here.  A slight jog to the north on most of this guidance and we see a quick enough burst of snow to cause some impacts.

More on this Tuesday night/Wednesday snow threat will be available in the coming day, as well as a brief update on the weekend severe cold which could bring wind chills down below 0 across virtually all of the SWCT/NY region Saturday night.


Snow Winds Down Through 3 PM

The strongest band of snow has set up from Greenwich up to Danbury over the past hour, where we have seen snowfall rates up to a half inch per hour.  This band is expected to gradually deteriorate over the next hour or two, and was actually well forecast by the short-range HRRR model.  Total accumulations of up to 3 inches are possible under that band.

Snow will remain light and fluffy in consistency through the day today.  Gusty winds to 30 mph or so will allow it to blow around and weakly drift, which also means roads will stay snow-covered (though not quite as icy).

The forecast remains for 1-3 inches of snow across Westchester and Fairfield Counties and 2-5 inches across New Haven County through 8 PM tonight.  Short-range guidance continues to indicate that about 2 inches of snow from 11 AM onwards can be expected for the region, though slightly less may be possible in western Westchester County where the backside should move through even quicker.

The worst travel conditions should continue from now through about 2 or 3 PM.  After 3 PM we should see snow really die down as conditions improve from there.  Given only 2-3 inches of snow being widespread, however, conditions at no point are really all that bad.  Travel should improve into the evening, though light to moderate snow could continue in eastern New Haven County where conditions will be the worst.

Schools appear to have made their final decisions, and it looks like almost every district in Fairfield County has opted to dismiss early.  Given the timing of the storm, this does not appear to be the correct decision, but again with the light nature of the storm it should not be too large a deal.  Still, short-range guidance continues to show snow intensity greatly falling off between 2 and 3 PM while some of the heaviest banding will be lingering from 12 to 1 PM, meaning that visibility will be more reduced when students are leaving schools.

For schools that do not dismiss early, expect all after school activities to be canceled as snow showers linger through the evening, not winding down until at least 7/8 PM.

Snow accumulations across Fairfield and Westchester County into the overnight hours past 3 PM will be minimal.  Generally less than half an inch is expected.  New Haven County could see up to an inch or so.

Monday Forecast Has Only Minor Revisions

Models continue to home in on the final scenario tomorrow.  The first flakes across the region are likely to by flying sometime between 5 and 7 AM, but coastal areas should not see snow accumulate until 7 or 8 AM, with inland areas potentially not even seeing steady snow until 9/10 AM.  The precipitation shield is looking less impressive, but at least somewhat steady snow should continue through at least 2 PM.  Scattered snow showers will still continue through the evening.

The snow will still be slightly more light and fluffy than in past storms, but slightly warmer trends at the surface have me believing that ratios will be closer to 11:1 or 12:1 than the 15:1 that it previously looked like, especially at the coast.  Snow will start relatively wet but will become more powdery through the storm.  Temperatures at the coast may not drop below freezing until around 7/8 AM, so the first snow flakes may initially struggle to stick across coastal New Haven County.  This could keep travel conditions from deteriorating until at least 8 or 9 AM along I-95.

The forecast is now for 1-3 inches of snow across Westchester County, 2-4 inches across Fairfield County and 2-5 inches across New Haven County through 8 PM tomorrow.  This remains a high confidence forecast as models have come into strong agreement with this range.  The gradient will still go from northwest to southeast, with northwest Westchester County likely to only see 1-2 inches but southeast New Haven County likely to see around 5 inches of snow.  Around 2 inches of snow is expected in northern Fairfield County but near the Bridgeport area closer to 3 inches is expected.  Isolated 4 inch amounts on the New Haven County border are possible, though looking less likely.  At no time should snow be heavy, but briefly moderate snow is possible late morning into early afternoon.

Generally, it looks like most of the snow should fall through 2/3 PM, with about an additional inch falling between then and 7/8 PM.  This means that worst travel impacts are still expected to be between 9 AM and 2 PM.  Even at their worst they should not be too bad as snow is never heavy, but roads could be slick with a couple inches of snow falling that will be difficult to melt due to the colder temperatures.

Yet Another Post-Super Bowl Snow

The below forecast outlines expected snowfall accumulations and impacts through tomorrow evening.  The post goes through accumulations, timing, and a couple model scenarios.  To view our more detailed analysis, including travel impacts and forecasts for school closures, along with additional weather model analysis, be sure to try a Premium subscription here.  All school closure forecast updates will be directly emailed to subscribers throughout the upcoming few days of storm threats.  Otherwise, please enjoy the Free forecast below.  An update will be posted this evening should conditions dictate:

PRECIPITATION TYPE/TIMING: One thing is for sure with this storm; it is all going to be snow.  Every model shows temperatures falling as the precipitation begins into the mid/upper 20s across the region with colder temperatures aloft as well.  This indicates snow could be relatively fluffy and we could see ratios in the 12:1 to even 15:1 ratio instead of the standard 10:1 ratio.  As for timing, that is lower confidence.  Most models show a chance of snow arriving by 6 or 7 AM.  Some have it beginning in New Haven County, which is possible if the storm is further east as it takes time for light bands of snow tomorrow morning to rotate back west into the region.  Other models show a slightly more direct hit with snow beginning as early as 3 or 4 AM across the region, but the general consensus is that snow does not really begin to fall at a rate to even coat the ground until 6 AM at the earliest.  From there, steadiest snow can be expected between 8 AM and 2 PM, when steady light snow should continue to awhile.  Then, the precipitation shield gradually breaks down through the afternoon, as we can expect scattered on and off snow showers to continue into Monday evening.  A chance of light snow showers could even continue into overnight Monday night, but any briefly moderate snow showers should die down before that.  Minor snowfall accumulations will be possible Monday night and again into Tuesday, however, with additional updates on that coming in the next day.

ACCUMULATIONS: Across the region anywhere from a dusting to 5 inches of snow remains possible.  As was the case with the last storm, once again it looks like New Haven County will see the worst impacts and Westchester County should see the least impacts.  This leads to a forecast where Westchester County sees 1-3 inches of snow through Monday evening, while New Haven County is instead expected to see 2-4 inches of snow through that timeframe.  Fairfield County is the true battle zone, as northern portions of the County could see only an inch or so but southeastern portions could see up to 4 inches.  For now, I continue to favor the solutions where total accumulations in Fairfield County stay broadly below 3 inches, so the forecast is still for 1-3 inches of snowfall in Fairfield County as well, but there is a chance that I may need to boost both the Fairfield and New Haven County forecasts by about an inch if there is even a slight jog west in model output (or a couple of the more amplified models verify).  That has been a trend this winter, though a couple other pieces of model guidance that had been performing well indicate it is actually less likely that we see more than 2-3 inches widespread, so there’s definitely some confusion.  Up to another inch or so of snow is possible Monday night from lingering snow showers, though that will be more of a focus later tonight into tomorrow once I figure out the exact track of this upcoming storm, as how the lingering energy interacts with the region will be impacted by how this first storm tracks.

BRIEF TRVEL NOTE: This all creates a very tricky impact analysis because it is a non-trivial amount of snow falling across the region, but at no point do snowfall rates look to exceed .5 inches per hour, and even then that is the maximum rate for an hour or two during the middle of the day.  Overall, this storm looks relatively manageable.  The less intense snowfall rates makes it seem like road crews should be able to keep up through the day, but surface temperatures in the mid to upper 20s means that snow should easily be able to stick to roads, even treated ones, and that they could accordingly be a little slick through the day.  This makes for an increasingly hard judgement call as to exactly how bad conditions will get on roadways, so I do emphasize using as much caution as necessary if traveling tomorrow.

BRIEF MODEL NOTES: I want to dive into some of the model scenarios.  To start, as I typically like to do, I want to show the latest SREF model probabilities for snowfall.  Here we see the snowfall probabilities on them through 4 PM tomorrow.  New Haven County sees about an 80% chance of an inch of snow, while Fairfield County sees about a 50% chance and Westchester County sees about a 35% chance.  Note that this is based off a 10:1 ratio, and given the colder temperatures I expect ratios of closer to 12:1 or 15:1, so that should raise the probabilities slightly, though with so little snowfall it will not make that significant a difference.  To the right of that we see only New Haven County is shown having any chance of reaching 4 inches of snow, and even there it is around a 10% chance.  The SREFs have been performing relatively well this winter, and this output certainly seems to be downplaying the impact potential tomorrow across the SWCT/NY region.

Next we have the HD NAM, which is one of the more aggressive models.  However, even the HD NAM only has very light snow showers struggling to overcome dry air at 7 AM tomorrow, as seen here.  Finally by 10 AM we see relatively steady light to briefly moderate snow move in, as seen here.  But that breaks down and moves out by 2 PM here as the precipitation shield falls apart.   Through 4 PM the model shows 1-2 inches of snow in Westchester County, 2-3 inches of snow across Fairfield County, and 3-5 inches of snow across New Haven County, seen here.

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