Accumulation Forecasts Raised For Today’s Snow

In an email just sent out to Premium subscribers I highlighted the risk for more snow than was forecast across the area and have accordingly raised accumulation forecasts.  The latest forecast is available below:

Light to moderate snow is breaking out right on time across the region.  It will start light initially, though over the next hour or two we could get a couple of moderate bursts.  From there it will still begin to pick up in intensity between 12 PM with steady moderate to briefly heavy snow until 4 PM, with lingering snow showers through 8 PM.  Models overnight showed a slightly higher threat for bursts of heavy snow any time between 11:30 AM and 4 PM, with eastern and coastal regions the focus.  High ratios may allow snow that does not seem particularly heavy to add up rather quickly.  Snow should end by 9-10 PM across the region as the storm pulls out, though a couple models show a couple snow showers across New Haven through around 11 PM.

A snowfall gradient is still expected, though it may not be quite as sharp as previously expected.  Snow to liquid ratios up to 20:1 continue to look possible with the storm moving through, which is why I am becoming increasingly concerned about moderate accumulations into Fairfild County.  Later in the storm winds will pick up a bit so we could see some dendrite shattering more so by the coast (depending on exact snow growth regions) that may bring ratios down a bit, but at least 15:1 ratios seem reasonable throughout the entire storm.

The forecast has been tweaked with more location specificity.  5-8 inches of snow is expected in southeastern and coastal New Haven County, with 4-7 inches of snow expected across inland New Haven County and coastal and inland Fairfield County.  Far inland Fairfield County (north of I-84) can expect to see 3-6 inches of snow, as can costal Westhchester County, while inland Westchester County will see 2-5 inches of snow.  In this way the gradient is best reflecter, but overnight guidance shows less intense banding and moderate snow extending further to the west, increasing confidence that some of higher accumulations across New Haven County will be possible in Fairfield County as well.  Recent short-range guidance has shown the possibility of widespread amounts even further west of 6-7 inches of snow, so a slight tweak higher may be needed as the storm develops, primarily because of just how light and fluffy the snow is going to be as it adds up quickly.

Moderate Snow Threat Tomorrow

A chance of snow has sprung up across the region tomorrow as the precipitation shield of a rapidly strengthening low pressure center will expand further west than previously expected.  Premium subscribers received a detailed update earlier in the day and will receive coverage of the storm through the next 24 hours, while below we have listed our latest forecast:

Light to moderate snow breaks out between 9 and 11 AM across the region tomorrow morning.  It will start light, but begin to pick up in intensity between 12 PM and remain steady and moderate through around 7 PM.  Intensity will generally be light but some moderate pockets of snow will be possible as it does remain relatively steady.  Between 8 and 11 PM snow should wind down across the region, ending entirely overnight tomorrow night.

A rather sharp snowfall gradient is expected across the region, which is keeping confidence below average for this snowfall event tomorrow.  Models have shifted rather dramatically in the past 24 hours ahead of this storm, and with such short-term volatility we can expect some surprises to continue into the day tomorrow.  Short-term guidance is some of the most aggressive, showing that eastern areas could see up to 6-8 inches of snow, while global models show amounts closer to 3 or 4 inches.  One of the more complex variables is how cold it will be and thus how light and fluffy the snow will be again.  Snow to liquid ratios up to 20:1 may again be possible with the storm moving through, so even though liquid amounts will be less than half an inch we could still have moderate accumulations.  Later in the storm winds will pick up a bit so we could see some dendrite shattering (depending on exact snow growth regions) that may bring ratios down a bit, but at least 15:1 ratios seem reasonable.

Accordingly, I see the potential for 4-7 inches of snow to fall across New Haven County.  2-5 inches of snow is likely across Fairfield County, with 1-3 inches of snow expected across Westchester County.  However, the gradient may be a bit more sharp, meaning we could go from 6-7+ inches of snow in southeastern New Haven County down to just 1 or 2 inches in inland Westchester County.  A model consensus shows around 4-5 inches of snow across coastal Fairfield County with 3 inches or so expected most inland areas.  This all is based off of the latest guidance out over the past 2 hours, though again a shift of 20 miles either way could bump up or drastically reduce accumulations through the day tomorrow, and models remain in a bit of flux playing catch-up with this storm so if this trend west remains sustained I may need to upgrade Fairfield and Westchester County accumulation forecasts slightly.

Models Back Off Snowfall Expectations Overnight

Our forecast for light snow has been updated.  The updated forecast is available below, having just been emailed out to Premium members.  To view the updated school delay chances, subscribe here.  Otherwise, the latest forecast is below:

Light snow showers begin to move in across the region over the next couple of hours.  Steadiest snow is then expected between 1 and 5 AM, moving from west to east.  Between 5 and 8 AM we rapidly clear out, with the entire region dry by 8 AM as the sun attempts to come out by late morning.  Only an hour or two of steady snow is really expected in any one location as the storm remains very unorganized.

Current snowfall estimates have been updated to a coating-2 inches regionwide.  No longer does it look like much more steady precipitation will occur at the coast, and most models backed off the more impressive liquid amounts they had been showing this morning.  Interestingly, the National Weather Service updated the coast to a Winter Weather Advisory this afternoon which was in line with our previous forecast, but recent updates indicate that this may be overdoing it as I would be surprised for anywhere to see more than 2 inches.  Amounts closest to two inches are likely across coastal New Haven County, with generally an inch or a bit less expected across Fairfield/coastal Westchester County and even less expected across inland Westchester County.  No longer is an inch a guarantee even in coastal areas as steady precipitation looks to have shifted just a bit south, lessening impacts.

Minimal travel impacts tomorrow morning are likely for the Friday morning commute.  Of course, snow will be light, so impacts will be minimal, but slippery travel looks most likely between 3 and 6 AM.  Snow will stick instantly on roadways with cold temperatures, and though it may not be too icy and snow will not be heavy it may be hard for any sand/salt to melt much of the snow, so we could see slushy/snow-covered roads into around 7 AM.  Temperatures struggle to rise above freezing, so some snow could linger on back roads later into the morning.  Accordingly, just be slow to take it slow tomorrow morning, especially if you are out before 6-7 AM, though with only an inch or so of this light snow it is unlikely to have too much of an impact.

Light Snow Likely Overnight; Highest Accumulations Near Coast

Below we share our official forecast for the light snow expected overnight into tomorrow morning.  Premium members have been receiving updates for the past 24 hours, and just received the updated percent chances of delays/snow days for schools across the SWCT/NY region.  They will receive additional updates through the day as to the chances of snow impacts, while any changes to the accumulation forecast will also be posted here.  To view the current chances of delays/closings and to receive all future changes by email, sign up here.  Otherwise, the latest forecast is attached below:

Partly cloudy skies early this afternoon become mostly cloudy by the evening as moisture approaches from the west.  Light snow showers between to move in betwen 9 PM and midnight tonight.  Steadiest snow is then expected between 1 and 5 AM (UPDATED), moving from west to east.  Between 6 and 9 AM we rapidly clear out, with the entire region dry by 9 AM as the sun attempts to come out by late morning.

Current snowfall estimates are for 1-3 inches of snow along coastal and inland regions and a coating-2 inches far inland around/north of I-84.  Model guidance is relatively consistent with the most steady snowfall occurring along coastal areas.  There remain some differences in guidance; short-range HRRR guidance shows only about a tenth of an inch of QPF, as do the short-range ARW/NMMM, but other guidance like the NAM and RAP show the potential for .15 to .2 inches of liquid by the coast which could easily become 3 inches of snow.  All snow will be quite light and fluffy, resulting in snowfall ratios of 1:15 to even 1:20 across the region.  Accordingly, even just .05 inches of liquid could become an inch of snow, which is why I am very confident that at least an inch of snow will fall along the coast.

Travel impacts tomorrow morning are likely for the Friday morning commute.  Of course, snow will be light, so impacts will be minimal, but slippery travel looks most likely between 3 and 7 AM.  Snow will stick instantly on roadways with cold temperatures, and though it may not be too icy and snow will not be heavy it may be hard for any sand/salt to melt much of the snow, so we could see slushy/snow-covered roads into around 7 or 8 AM.  Temperatures struggle to rise above freezing, so some snow could linger on back roads later into the morning.  Accordingly, just be slow to take it slow tomorrow morning, especially if you are out before 7 AM.

Tomorrow’s Storm Mostly Wet For Region

All week we have been updating Premium subscribers on a storm system moving through tomorrow.  We had been downplaying expectations as it had been clear that the setup was not conducive for significant snowfall accumulations, especially down at the coast, and recently weather modeling guidance has moved in that direction.  Today we issued an updated forecast for them, along with a travel impact highlight and forecast through the next 2 weeks as to when we could see the next major winter weather event.  To view the full forecast for the upcoming storm and to get email updates around all weather events, subscribe here.  Otherwise, below we have attached the summary of our forecast for tomorrow:

A rapidly strengthening storm system will move even closer to the region than expected tomorrow.  Model forecasts shifted a bit further northwest with the storm system and take slightly longer to develop the independent low pressure center that was supposed to lock in colder weather, so accordingly we are going to see more rain than any type of wintry precipitation across the region.  Light snow showers start between 7 and 10 AM across the region, quickly mixing with rain by 10 AM.  After 10 AM the entire region quickly turns over to heavy rain.  In the heaviest bursts of precipitation some wet snowflakes could mix in through the afternoon, but with temperatures in the upper 30s/lower 40s it will be very difficult for any snow to stick at all.  Rain lingers into the evening, potentially mixing with some snow on the back end as precipitation winds down by 9 PM.  We then dry out overnight with low temperatures in the low 30s/upper 20s.  As the storm rapidly strengthens to our northeast we should see gusty winds overnight with gusts into the low 30 mph range.

Accumulation forecasts are much more high confidence now as the entire storm is expected to be rain at the coast and even some inland regions.  Only far inland is there a threat for some wintry accumulations.  At coastal regions, a slushy coating is possible with the original round of snow showers before the rapid turn to rain.  Only on grassy surfaces will any coating be possible and just that seems unlikely; any coating will begin melting rapidly by 10 or 11 AM.  Inland further from the coast we could see a coating to 1 inch of snow in the first round through 10 or 11 AM, again mainly on grassy surfaces.  At the height of the storm, especially on the back end, some heavier banding of precipitation could see some snow reach the surface further inland, but recent models are showing even that be a bit unlikely.  Far inland, a coating to 2 inches is possible.  In the colder scenarios either at the front or back end of the storm we could have a quick thump of snow, but even far inland (north of I-84) almost all of the storm will be rain, limiting accumulations dramatically.