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Dangerous Travel Expected Friday Afternoon/Evening

Premium subscribers have been made aware of the threat for light to moderate snow accumulations tomorrow afternoon for the last few days.  Below is the relevant portion of the forecast detailing accumulations and timing of the storm as it moves into the region for tomorrow.  Should you be interested in the potential travel impacts or the chances of school impacts, you can purchase the detailed Premium forecast here or subscribe to receive email updates with every forecast change here.  If not, the relevant portions of the forecast are attached below:

The forecast accounts for all of the most recent model trends that have been explained to Premium members; more snow is expected at the coast and in western areas than inland areas, and as the NAM shows at 5 PM tomorrow here coastal areas won’t be much warmer, if at all, than inland areas.  Thus, fairly consistent ratios, except maybe in coastal Westchester County, can be expected across the entire region.  Similarly, western areas look to see more accumulations than eastern areas; Westchester County will see more liquid equivalent than New Haven County.  The GFS does not show that, but the RGEM shows that well here.  As such, New Haven County will host lower snowfall overall I expect than Westchester County.  This creates an interesting gradient for the revised snowfall accumulation forecast.  I am now calling for 1-3 inches of snow falling across all of New Haven County along with inland areas of Fairfield and Westchester Counties.  I am increasingly struggling to see how inland areas see enough precipitation to get over 3 inches of snow, especially with most if not all snow falling during the day and thus not having as impressive snowfall ratios (thinking 8 or 9:1 right now).  Coastal portions of Fairfield and Westchester Counties can still expect to see 2-4 inches of snow, but again this may be revised down to 1-3 inches this evening depending on model trends this evening.

Essentially, this storm is running into impressive confluence further north as the Clipper on Saturday moves into the region, and this cuts off moisture as the storm proceeds and causes it to slide further east, not coming quite as far north.  This was a concern I have had for some time, and though models seemed to be going against the idea yesterday, they have been trending back towards it today.  I don’t think they are completely done trending today, which is why I have cut accumulations so significantly inland/across New Haven County.  However, there is a chance that these southern trends continue even more and we are stuck looking at as little as 1-2 inches of snow across the entire region, or some regions being dropped to a coating-2 inches.  It is too early for me to do this with any confidence, but these storms later in March that just are not strong enough to bring heavy snow can very easily bust due to the more impressive sun angle and the tricky nature of determining the exact track.

With the accumulation forecast changing, the timing forecast has been slightly updated as well.  Snow still looks to start between 12 PM and 2 PM now across the entire region.  Heaviest snow can be expected between 2 and 6 PM, with snow winding down between 7 and 8 PM.  Very few models now have any precipitation falling after 7 or 8 PM, and road conditions should improve from there.  It may also take a little while for the snow to start accumulating, so although it starts falling around noon in western areas it could take until 1 or 2 PM to start sticking on non-grassy surfaces.  Still, temperatures below freezing and the threat of moderate snow means it is likely that snow eventually sticks to all surfaces, although it should be quite slushy.  Thus, this really is just a quick 6-8 hour burst of snow, quickly moving out of the region by Friday evening.

 

Wednesday Night/Thursday Forecast On Track

The school delay/closure forecast has been updated in a Premium forecast, which you can purchase here.  Parts of it have been freely released below as well:

The forecast remains generally the same.  4-7 inches of snow at the coast, 3-6 inches inland.  However, I am adding the forecast of 2-5 inches far inland, as I don’t see far inland getting more than 5 inches of snow.  Only the GFS model shows that potential, with the RGEM hinting at it as well, but I would be very surprised if anywhere far north of Interstate 84 saw more than 5 inches of snow.  The HRRR shows the radar looking like this at 9 AM tomorrow, and the wintry accumulations looking like this.  That’s already 4 inches of snow at the coast, 3 inches inland and 2 inches far inland.  That’s part of the region I differentiated far inland areas.  Still, with that snow falling at 9 AM at that rate, impacts will be similar across the entire region even if a couple more inches of snow is falling at the coast.

The RAP guidance is similar as well, showing at least half an inch of liquid falling at the coast after the turn to snow, which would indicate at least 5 inches of snow falling.  I am still a little worried about snow taking a little while to stick after the rain, but once the snow starts falling heavy enough that should not be much of a problem, especially as temperatures crash below freezing and any standing water turns to ice.  It is this timeframe past 10 AM that I am actually most interested in the weather models, as most models do not show much easing of snowfall by 9 AM, which is why I had previously upped the snowfall totals, especially at the coast.  Each run of the RAP continues to show more and more moisture for the area, and though .1-.2 inches of liquid looks to fall as rain, the rest looks to fall as snow, making me believe that we should not have much trouble falling into the forecast snowfall ranges.  Surface temperatures inland drop below freezing between 1 and 2 AM, and at the coast between 2 and 4 AM.  I expect the entire region to be below freezing by 4 AM with some of the heaviest snow falling between 4 and 6 AM helping to quickly ice over and cover in snow all roadways.  Thus, travel goes significantly downhill past the 4 AM timeframe, and will take awhile to improve as temperatures stay below freezing for awhile tomorrow.

 

Moderate Snow To Impact Morning Commute

Premium subscribers have been receiving consistent updates on the latest forecasts for the storm coming through tonight into tomorrow.  For the latest forecast update and for the school impact forecast, you can purchase the individual forecast here or subscribe here for all the content.  Part of the most recent forecast has been released below:

With the latest weather model guidance, I now feel confident enough to slightly upgrade total snowfall across the entire region.  The immediate coast I am now forecasting anywhere from 4-7 inches of snow.  Most models show accumulations right around 5 inches or so, but it looks like there is fairly strong model agreement at this point for 4 inches at the coast, and thus I feel confident forecasting that as a base now.  My one concern is that we stay rain slightly longer at the coast, and that makes it slightly harder for snow to stick.  Still, I think that 4 inches at the coast is a good minimum to have, and I see 3-6 inches of snow inland, with amounts closer to 3 inches far inland and any amounts approaching 6 inches occurring at the coast.  There is a chance that the forecast gets changed to just 3-6 inches region wide, or even upgraded to 4-7 inches region wide depending on the latest trends, but the 9 PM update will hold any such upgrade, as right now I still like having the coast with slightly more snowfall than inland areas.

The timing of this has changed slightly too.  Warmer air has been winning some battles aloft, and models indicate that the changeover may not occur down to the coast until as late as 2 or 3 AM.  Inland, it should occur as soon as midnight or 1 AM.  Still, precipitation is light at that point, but snow picks up by 5 AM, as seen on the HRRR here.  The model then shows light to moderate snow continuing through the morning.  The RAP model is in agreement as well.  The RAP at 7 AM shows steady snow continuing past 7 AM here.  And some models show steady snow continuing into the late morning, with snow showers maybe even remaining into the early afternoon.

With these slightly increased snowfall amounts, and with it looking like snow lasts longer into the morning, there is now an increased chance of school impacts and travel impacts lasting into the morning, which Premium subscribers have been briefed on.  First, travel impacts look to carry over through most of the morning.  Travel conditions do not go downhill in most areas until around 2 AM, but by 4 or 5 AM roads are getting bad, with worst travel conditions 5 AM through 9 AM most likely.  Snow should then taper off through the morning and into the early afternoon as road conditions improve into the evening.

The forecast remains quite variable, with a higher than normal bust potential due to the storm starting as rain and a huge range in weather model guidance remaining.  Please be sure to stay tuned for the latest.

 

Snow To Turn To Sleet/Freezing Rain, Then Rain

Premium subscribers have received updates on both the storm tonight and an official forecast for the Wednesday night and Thursday storm, which you can access by subscribing here.  However, a free portion of the forecast for the region has been issued below, with the free forecast for the Wednesday night/Thursday storm being released tomorrow:

Snow is now falling right on track across the region, and the general forecast as a whole remains the same for the evening with 1-3 inches of snow.  The HRRR supports the going forecast with a mix of sleet moving into western areas as early as 7:30 PM and overspreading the entire region by 8 or 8:30 PM.  This gives most areas only another 2-3 hours of snow, and as I don’t see snowfall rates intensifying to more than an inch per hour, I would be hard-pressed to see any snowfall accumulations over 3 or 4 inches.  The going forecast for 1-3 inches of snow thus holds, though isolated areas where the changeover holds off briefly when the heaviest precipitation moves in could see slightly more than 3 inches, so I’ll mention that isolated amounts to 4 inches are possible, especially if the sleet tries to significantly accumulate.  Most snow as indicated on radar looks to fall at around half an inch per hour, though at the tail end we could see snowfall rates of an inch per hour right before the changeover to sleet and then freezing rain.  Compaction should allow some of the snowfall accumulations to slightly shrink, which is the other region for these lower accumulations; measurements taken at the end of the storm should be slightly lower than those taken before the changeover to sleet as sleet compresses the snow together.

So I’ll run through what the HRRR shows.  The latest run is slightly colder, showing all snow continuing through 7 PM with rates of .5-1 inch per hour, as seen here.  By 8 PM, however, the entire region is over to sleet with some freezing rain working its way in, as seen here.  Freezing rain takes over by 9 PM and dominates through 11 PM with freezing drizzle continuing inland a little after as well, as seen here.  Then we warm and turn to plain rain overnight, but temperatures stay fairly close to freezing.  By 6 AM, the HRRR is quite impressive with warming, showing 40s trying to work their way into the region inland with the coast still in the upper 30s, as seen here.

Thus, travel between 7 and 11 PM tonight is most dangerous, but travel is already going downhill now with that heaviest snow trying to move in.  However, travel conditions improve through the night, and I expect minimal if any impacts remaining for the morning commute tomorrow.  Be sure to stay tuned for the latest.