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.

Snow To Continue Through Evening

Premium subscribers have been made aware of recent forecasts for the upcoming storm and have had access to forecast school implications.  Below is the latest version of the freely available forecast:

First, as you can clearly see here, light snow is overspreading the region, with more along the coast thus far than inland.  Snow will become more widespread through the coming hours, as it started slightly earlier than most model guidance had expected but is in line with my updated timings yesterday afternoon.  It now looks like the heaviest snow could be moving in as soon as 4 PM and will continue through around midnight tonight, but I don’t see much more snow falling after midnight.

Sadly, the majority of weather model guidance is actually down at this time, so I can not access the HD ARW/NMM/NAM or RAP/HRRR extreme short-range guidance.  The majority of NCEP servers look to have somehow been hit hard and taken offline.  Accordingly, I don’t have a lot of weather guidance to share with you.  You can see from 1 to 4 PM the NAM has steady snow continuing across the region here before picking up a little more through 7 PM here.  Light snow then sticks around through about 1 AM here, with the model printing out accumulations of 6-7 inches widespread across the region.  It has trended significantly colder, showing only Westchester County turning over to freezing rain with SWCT remaining snow throughout, which is more in line with what I was expecting as the trend this winter is for storms to push further southeast as they approach.  Most models don’t show any freezing rain into Westchester County, and though we could briefly see a mix even into SWCT I doubt it will be sustained and really cut into accumulations.  You can see that the RGEM, which I have found most reliable this year, shows here widespread accumulations in the 4-5 inch range across most of SWCT with isolated amounts approaching 6 inches, in line with the forecast.  So I really think that snowfall amounts will end up in the narrow 4-6 inch range with maybe even a little more than 6 inches in spots, but that if there is any mixing with freezing rain, likely in southern Westchester County, that is where we could see accumulations limited to the 3-4 inch range.  Overall, the range of 3-6 inches of snow remains widespread as these models continue to support it.

Dangerous Travel Expected Tonight Into Sunday Morning

Premium subscribers have been receiving reports on the upcoming storm, but a freely released version of the forecast is also available below:

Snow has started on time slowly across the region but then picking up in intensity.  It will continue through approximately 10 or 11 PM, at which point coastal areas will start mixing with freezing rain.  Between 10 PM and 12 AM the coastal plain turns from snow to freezing rain and then to plain rain, while inland areas begin turning to freezing rain around 12 AM and could take until 1 AM or even a little later to turn over to plain rain.  Plain rain then continues through between 3 and 6 AM before moving out of the region, with clearing during the day on Sunday.  Thus, this timing looks to spare the region some of the worst impacts by having the most dangerous travel late Saturday night, where roads could easily be avoidable with proper planning.  There is fairly strong agreement among the weather models as well that we start all snow before gradually turning to freezing rain at the coast, rapidly spreading inland and then going over to all rain for a few hours before winding down.

As for accumulations, the National Weather Service has issued Winter Weather Advisories calling for 2-5 inches of snow across the region, right in line with what I was expecting.  However, I am becoming skeptical that the changeover hits inland areas before 10 PM, and thus was considering upping inland accumulations.  I believe that coastal areas still see 2-5 inches of snow (likely much closer to the 5 inch range, but a quicker turnover could melt some down to make it closer 2 inches) while inland areas I have decided to also keep in the 2-5 inch range.  I think only an extra half hour or hour of moderate precipitation falling as snow inland will not be enough to boost accumulations by more than  an inch more than the coast, and thus will keep them in the same range, especially as some models show slightly more liquid at the coast than inland.  As for ice, there is fairly strong model agreement in at least an hour or two of icing across the region which has me concerned.  Especially with the strong snow pack keeping the surface cold, at least some ice accumulations appear likely.  I generally expect .05-.15 inches of ice across the region.  I’d be surprised to see more than .15 inches of ice as the surface does warm fairly quickly once upper levels of the atmosphere warms, but I do expect to see at least ice from this system.  Then, after all this, we will likely see around a quarter to a third of an inch of plain rain falling into the snowpack.

The main concern I have is for road impacts between 5 PM and midnight.  That is when roads look to generally be in the worst shape across the region.  Extremely low temperatures tonight could keep surface temperatures below freezing slightly longer than air temperatures, meaning that ice could also last a little longer than some are expecting. This means in coastal areas, I’m expecting worst road conditions in the 8 PM to 11 PM timeframe with roads improving through the night as we turn over to plain rain, and inland I expect worst road conditions from 8 PM until 1 AM.

Snow Squalls Possible Tonight

Snow squalls will be moving through this evening into the overnight hours with accumulations anywhere from a coating to an inch expected.  However, I’m favoring the coatings more than I am the two inches. Essentially, accumulations in Westchester are looking unlikely, with the models agreeing on a general coating in Fairfield County and maybe up to an inch in New Haven County.  Even New Haven could see little to no accumulations.  Any accumulations over an inch look to be confined to far eastern Connecticut, where they could see up to 2 inches of snow.  It generally dries out after midnight with only scattered light snow showers that do not look to accumulate.  Thus, little to no impacts are expected.

Light Snow To Fall Early Tuesday

A strengthening disturbance will track far to our south tonight into tomorrow morning, bringing with it some light snow to the region.  The latest version of the forecast has been freely released below:

This southern jog in the storm track has taken us out of the moderate snow and means we are now expected only to see a coating to 2 inches of snow.  Amounts generally of a coating to an inch are expected up by Interstate 84, with amounts as high as two inches to maybe even a little more in spots are expected down by the coast.

You can see on the latest HRRR here that by 6 AM we will be looking at widespread light snow across the region.  It will be a very light, high ratio snow that will instantly stick to everything.  This will make roads a little slippery, even though accumulations will not be all that significant.  Light snow showers start now as soon as midnight or 1 AM before picking up in intensity gradually through around 7 AM, mainly at the coast.  The latest NAM here shows the moderate snow at the coast continuing through around 9 AM and then dying down into around 11 AM.  Light snow showers could stick around in New Haven County as late as noon or 1 PM but should move out pretty quickly, so roads will be improving quickly into the evening.  Worst road conditions from this can be expected from 7 to 10 AM or so.  However, roads will not be too bad from the light, airy snow.

There are no other major storm threats we are tracking, but this weekend there is a threat of at least some additional wintry weather, so please stay tuned.