6 PM UPDATE: Early Dismissal 45%

6 PM update here and while there are no changes to the accumulations forecasts I have upped the chances of an Early Dismissal while also eliminating the chances of a snow day.  Given recent model trends, there is really no scenario where snow begins before 11 AM or 12 PM anywhere in Southwestern Connecticut, so there would be no reason for school districts to close for the day.  However, with snow still expected to start between 12 PM and 1 PM, and with Winter Storm Warnings for all of Southwestern Connecticut set to go into effect at 12 PM tomorrow, chances are increasing that schools will have to close early.  It is likely that most areas only see an inch of snow through 3 or 4 PM, but because of the cold air it will stick instantly and make roads treacherous.  Some districts may try and tough it out and close on time, as historically Westport and Fairfield are districts that do not like to call Early Dismissals, but I expect the majority of districts to close early and I think that may be the right call.

The thing with this decision tomorrow is that it is a very difficult call.  With only an inch or so of snow on the ground after when most schools would let out it may not mean that Early Dismissals are necessary.  But the right call will likely be to play it safe, which is what I expect many districts to do.  I just do not want to forecast widespread Early Dismissals until I am absolutely confident that it is the correct decision for districts, and at this time I am not confident in that.  Some weather models delay the start of the snow until 2 PM and don’t have steadier snow until 4 or 5 PM.  While these are outliers, in these scenarios schools could just cancel after school activities and have full days.  Many districts call Early Dismissals very easily as the day counts regardless, but there are a few stingy districts (as noted above) that only close early when it is absolutely necessary.  At this time, there is not enough model consensus for me to say that it is absolutely necessary for schools to close early, though I am leaning towards believing it is the right call.  I believe that by 10 PM or so tonight I will be able to say with better confidence whether schools should close early or not, and by tomorrow morning I will be able to lock in a decision without a doubt. 

As for the more technical side of things, the 18z GFS came in recently with a lot of moisture in a scenario that could give areas of SWCT up to a foot of snow.  As with the last snow storm, I think this model is overdone.  The 18z NAM came in showing around 4-6 inches of snow widespread across the region with even a little less inland.  I think this model is underdone.  And then we have the 18z RGEM, which I favor, going more with a 3-7 inches inland and 4-10 inches at the coast.  I think this model is closest to what is going on.  The reason the ranges are so big there is because the model has an extremely tight gradient, with twice as much liquid on the north shore of Long Island as there would be in Ridgefield, with only a third as much liquid along Interstate 84 as there is on most of Long Island.  This would mean that a difference of only 5 miles in inland could mean up to a couple inches of snow, and that is what I am worried about with this storm.  Other weather models do not have quite as sharp a gradient, but many are close, and if this is right then I may need to change my snowfall forecast just to account for the gradient between I-95, the Merritt Parkway, central Fairfield County, and I-84.  I’m not ready to do that just yet, but a sharp gradient could warrant such a change.

And then there are the 15z SREFs with their average snowfall of 13 inches at Bridgeport.  They have both too much liquid and too much moisture, leading me to discount them at this time.  Last storm (Jan 3) with a makeup like this they predicted far too much moisture and ratios that were too high, and I like to think I can avoid making the same mistake twice.  In fact, models are performing almost exactly like they did with the last storm, where inland areas saw generally 3-7 inches and the coast saw anywhere from 5-9 inches of snow.  This is one of the reasons I am confident in the forecast of 4-8 inches inland and 5-10 inches on the coast.  However, there will be higher ratios with this storm, so besides the lollipops from the last storm I expect many areas could see an additional inch or two from what they saw last time.  Again, there is still time for model trends, and a slight tick northwest of what that 18z RGEM showed could put coastal SWCT into that extreme snow on the north shore of Long Island.  This is a very dynamic event where a few miles will make a big difference, and that is why it is taking so much time to sift through all the model data.

With regards to schools on Wednesday, I don’t have any more clarity just yet.  End timing remains as unclear as ever, with somewhere in the range from 3-8 AM guaranteed and a 4-7 AM range most likely.  With accumulations and Public Works Departments determining whether schools open or close it is very hard to say whether delays or closures will be more prudent Wednesday.  I will have much more on that tomorrow as I follow the storm tomorrow, and I’ll have numerous other updates this evening as well detailing the Early Dismissal threat so make sure to stay tuned.

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