HALF-TIME UPDATE: 65% SNOW DAY

It seems to have worked well that the weather evening data lull coincided with the first half of the Super Bowl.  Not too much new to report here, and I believe the National Weather Service is currently handling the storm tomorrow very well.  The storm continues to look like it will start around 6 AM for the region, but again snow will be moderate to heavy by 8 AM and that really steady snow will continue through 12 PM.  Snow will then wind down through 2 or 3 PM, with lingering snow showers possibly lasting a little bit longer.  In fact, there is very strong model agreement regarding the timing of the storm.  That’s what is set, and I’ll break down more why even with perfect timing I still think there is a chance a few districts open tomorrow (though I believe all should close).

In terms of amounts, the going forecast is still set at 3-6 inches by the coast and 2-5 inches for anywhere north of the Merritt.  Now, recent weather models (RAP and HRRR) continue to show extreme amounts of moisture, and if they were to verify we could be talking about 6-10 inches of snow across the area.  What is most interesting is there is NO other model support for such extreme scenarios, they are even more extreme than the 12z ECMWF was.  I am not ready to up forecasts to this level, and the NWS is not quite ready either.  I’m going to piggyback off of a little of what was in their forecast discussion when they discuss how very warm surface temperatures today along with cooling boundary layer temperatures at the beginning of the storm will hamper snow from beginning to accumulate, and will also make snow much more dense.  This will result in lower ratio snow, it could be as low as 8:1 or 9:1.  Basically, the marginal cold air will have the opposite effect that the very cold air has had in past snow storms and instead of making the snow light and fluffy it will be heavy and dense.  This also means that it will be harder for snow to stick on the roads.  So even though snow starts around 6 AM, it will likely not be until 8 AM or so that it sticks on the roads.  Hypothetically, that would mean there is a period of time with some moderate snow at the onset but road conditions which are not too bad.  This is specifically why the snow day forecast is not in the 80 or 90% range, because there is a chance that road conditions are not too bad for the first couple hours of the storm.  I still recommend schools closing because road conditions will be deteriorating through that time period and this would be quite the gamble to open schools.  Snow being just a little heavier or it just being a few degrees colder would mean that the snow would have no problem sticking on roads, and road conditions would be very dangerous even by 7 AM.  I don’t think the afternoon commute will be THAT dangerous after 3 or 4 PM, but again road conditions will still not be great with temperatures below or around freezing any anywhere from 2-6 inches on the ground.  Because of marginal temperatures road conditions could vary greatly in different regions depending on where the temperature is 30 vs. 33 degrees, but in general I think that travel tomorrow will be dangerous, especially between 8 AM and 12 PM because there will be very heavy snow falling.

Weather models continue to show that convection with this storm is very strong and there is an abundance of Gulf of Mexico moisture that this storm is tapping into.  That is why even though the snow will be very wet, it could still pile up.  It will be so heavy the NWS admits even isolated power outages are possible.  Winds won’t be an issue, but really heavy snow could hypothetically bring down a few power lines.

This storm is looking to be more extreme than I expected even a mere 12 hours, as there is that abundant moisture.  I’m still not ready to upgrade from 3-6 inches, but I’d say the chance I need to is closer to 30% or 35% than it was to 20% the last time I wrote.  I will of course continue watching this very closely and reporting based off of what the HRRR, RAP, and other short range/mesoscale guidance continues to show.  With amounts potentially increasing further and the National Weather Service even contemplating issuing Winter Storm Warnings in areas (per their latest discussion), it is very likely that all of Southwestern Connecticut will get the day off from school tomorrow.

CONCLUSION: So the timing is locked, most of the impacts as well, but it all comes down to accumulation and how intense snowfall is during the height of the storm that will determine whether the forecast verifies or not.  I think the RAP and HRRR may be overdone and over-amplified (they often are later in their range), but I am becoming more and more convinced that someone could see half a foot of snow with this storm, and isolated areas could get even more.  If this trend continues and some other 0z model guidance coming out in the next hour or two shows it, and/or the National Weather Service upgrades areas to Winter Storm Warnings, snow days would virtually be a guarantee.  For now, they just remain very likely, as I struggle to see how a school could safely open tomorrow given the very heavy snow that will be ongoing by 8.  I’ll continue to update on Twitter through the evening, and the next update will come at around 10 PM.  I would be surprised if the snow day chance didn’t continue to rise through then, as confidence only continues to increase that heavy snow is coming to the region, and even though these are not memorable accumulations or anything they will cause many problems tomorrow.  Stay tuned.

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