Tricky Tuesday: Burst of Snow Tuesday AM: 45% Snow Day (inland) 35% (coast)

This blog is going to break down all expected impacts from a 6-7 hour burst of snow moving through Southwestern Connecticut tomorrow.  First, I’ll start with a section on accumulation/timing/precipitation type, and then go into a brief section on school impacts.  The preliminary snow day percentages out for the area are above, and there is a good chance that they will continue to rise throughout the day as additional data comes in.  I won’t be breaking down on a district by district basis because so many schools are on break, but I’ll continue the divided forecasts between inland and coastal districts.

Snow looks to break out across all of Southwestern Connecticut generally between 5 and 7 AM tomorrow morning.  It will be generally light at first as overrunning precipitation reaching the area from the primary low pressure system, but by 8 AM we will begin to see precipitation pick up as a weak secondary low pressure system begins to set up across the region.  Heaviest snowfall looks to occur between 10 and 11 AM, with a period of snowfall rates of 1-2 inches per hour.  However, the secondary low pressure center forming near us will pull in warm air close to the surface, meaning that by noon I see coastal SWCT mixing with and turning over to rain.  Precipitation will then end between 1 and 2 PM across the region.

The overall accumulation forecast for the region is a general 2-5 inches of snow, though dividing it up I am expecting 2-3 inches of snow along the immediate coast and 3-5 inches further inland.  The result is that Winter Weather Advisories will be posted inland but I am not sure they will be posted at the coast as the National Weather Service has to be confident in widespread snowfall amounts of at least 3 inches, which I don’t see as a guarantee at this point.  It is possible, though, due to the complex nature of the storm precipitation shield.  Temperatures aloft at 850mb, in snow growth region, will remain below freezing throughout the storm, so all precipitation will fall as snow throughout the storm up in the atmosphere.  As it falls it hits warmer air by the surface and that is why we are dealing with the rain threat.  Even at the coast the heaviest precipitation through noon should be enough to pull down just the right amount of cold air to keep a very heavy, wet snow falling to the surface.  That is why I expect at least widespread amounts of 2 inches of snow at the coast, if not more.  However, once the heavier precipitation moves out by noon, I see the last couple hours of the storm generally as rain or as a rain/snow mix that does not add any additional accumulation.  Even a little further inland the storm could end as a rain/snow mix instead of just snow as the low pressure center pulls up that low-level warmer air.  The mixing at the coast is what will likely cap most areas at around 3 inches of snow, though areas across all of Southwestern Connecticut could see up to 5 inches.  Further inland, where there is no mixing, widespread amounts of 4 or more inches remain a very real possibility, and someone could get up to 6 inches out of the storm as there will be a period of very intense snowfall with rates of 1-2 inches per hour.  It just seems to be a trend with all storms this winter to have very intense snowfall rates.  So overall, that’s 2-5 inches across SWCT with mainly 2-3 inches at the coast and mainly 3-5 inches inland.

In terms of school impacts this results in a very difficult forecast.  With the storm ending between 1 and 2 PM, and rain mixing in at the coast by noon, I don’t expect the trip home from most schools to be especially treacherous, especially as surface temperatures across Southwestern Connecticut should be above freezing at that point.  It is the morning rush that will be the main impact.  First of all, delayed openings and early dismissals make absolutely no sense in this scenario.  Snow will be heavier at 9/10 AM than it would be at 7/8 AM, so a delayed opening would be only more dangerous.  Likewise, road conditions will likely be much worse between 11 AM and noon than they would between 2 and 3 PM when most schools would let out.  This leaves us with a decision between a full cancellation and opening for a full day.  As of right now, I lean towards the full day at the coast, but with a decent chance of a closure.  Inland, I likely would lean towards closures, but I need more confidence in the exact timing of the heaviest precipitation before I forecast them.  Heavy snow between 7-10 AM, even with minimal accumulations, may be enough to close schools, especially because so many districts are dealing with salt/sand shortages that keep them from pre-treating roadways.  Coastal areas, especially those further east, may be able to just beat the heaviest snow bursts or get kids to school right before road conditions really go downhill between 8 and 9 AM, and then if they keep them in school all day conditions should be much better by mid-afternoon.  Thus, there is a very real scenario in which schools can open tomorrow, which is why snow days are not yet forecasted, though I still expect chances to rise as more details on when this very heavy burst of snow comes roll in.

That’s really all I have for now with this storm.  It is a short duration event starting early tomorrow morning and ending by very early afternoon.  The ending will feature the heaviest precipitation, but that is when snow, at least at the coast, begins to mix with and maybe turn to rain.  While widespread amounts of 2-5 inches are still forecasted, generally expect 2-3 inch amounts at the coast and 3-5 inch amounts inland.  School closures are a very realistic possibility but I just do not have the confidence to forecast them yet, so as always make sure to stay tuned for the latest forecasts across all of Southwestern Connecticut.  The next update will come around 5 or 6 PM, so make sure to check back in for that as well.

Leave a Reply

Your email address will not be published. Required fields are marked *

You may use these HTML tags and attributes: <a href="" title=""> <abbr title=""> <acronym title=""> <b> <blockquote cite=""> <cite> <code> <del datetime=""> <em> <i> <q cite=""> <strike> <strong>