5:30 PM UPDATE: Snow Day Chance 95%

With colleges closing across the state and Somers Public Schools being the first to already close with the upcoming storm, the snow day chance has been raised to 95%.  Based on the severe icing and the heavy snow and sleet that will be seen tomorrow morning, I see no way that any schools will be able to open.  Even in the best-case scenario for coastal areas temperatures may rise above freezing by 9 AM, too late for roads to improve in time for delayed openings.  And there is only a 10-15% chance of that happening, as most towns, even at the coast, look to stay at or below freezing throughout most or all of the storm.  This blog post will go over a few updates to the timing, but other than that the main point of this update is that the forecast looks to be on track overall and that schools should be closing tonight due to the severity of the impacts felt by this storm.

The main timing impact is to change the estimated start of the snow to the 2-3 AM range as I don’t think snow will break out as early as 1 AM.  Not a huge difference.  I also think that sleet will take over now right around 7 AM along coastal CT according to all latest guidance.  Freezing rain could mix in by 8 AM or as late as 11 AM along the coast.  When freezing rain mixes in with the snow/sleet is actually currently the hardest part of this forecast, as it all depends on exactly how deep the warm layer is vs. how deep the cold layer is, and these are things that weather models have never handled too well.  The latest RAP shows a VERY deep warm layer, meaning freezing rain could be a problem earlier in the day.  This scenario is particularly dangerous because it means that the upper ranges of my ice forecast could be met, resulting in scattered power outages, downed limbs, and extremely treacherous roads.  Now the RAP also does not handle thermal profiles well, and I have noticed a pronounced warm bias, especially at the surface, towards the end of its range, so take it with a grain of salt.  Once the HRRR gets into better range that will be weighted very heavily in the forecast.  So far the HRRR looks colder aloft, which could be good as it may mean we escape the worst of the icing, but it isn’t totally in range yet so I can’t wait it too heavily either.  Overall, the period between 6 AM and 11 AM is going to be very turbulent with many different precipitation types across all parts of Southwestern Connecticut, and no one model is likely to nail it down exactly.

Other than that, the forecast published in the previous blog looks on track.  Still liking the forecast of a general 3-7 inches at the coast and 4-8 inches inland.  Again, the further you get from the coast, the higher in those ranges you should get, as the warm air aloft is moving almost directly south to north.  I’ve seen snowfall forecasts ranging all over the place, but I am confident in these numbers and I doubt they will change again throughout the storm.  I’ll have more details on timing, both here and on Twitter, once the RAP and HRRR get into better range and show exactly when each type of precipitation is expected.  By 9 or 10 PM tonight I feel I will have precipitation type timing down to the hour, so even though I am virtually certain schools will close tomorrow make sure to still keep it here for the latest details on this storm and the exact impacts that your communities will feel.

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