7 PM Update: 60% Inland Delay, 10% Inland Closure, 35% Coastal Delay

The first winter storm that could bring school-related impacts is upon us.  Above is the latest breakdown I have in terms of potential school delays (with even a slight chance of a closure for towns quite far inland).  Basically, the further from the coast you are, the better chance you have of a more significant school impact.  This is because the main impacts from this storm come tomorrow morning are going to be caused by ice and freezing rain, which is purely dependent upon surface temperature, and the warmer ocean waters will help warm coastal towns first before the warmer air bleeds in further north.  I have seen many of these types of storms move through the area, and typically a model average is the best scenario as no one model measures surface temperatures perfectly.  I’ll explain what all this means below.

As of right now, we have light scattered snow showers breaking out across the area.  This won’t become more steady until around midnight.  We will have a few hours of snow before sleet mixes in gradually from south to north from maybe 2-4 AM.  Freezing rain will also mix in gradually from 3-5 AM, until by around 4 AM on the coast and 5 AM inland we have a mix of snow, freezing rain, and sleet falling from the sky.  Temperatures will be right around freezing at the coast and just below freezing inland at 5 AM, allowing for icing to continue.  Before that mixture with sleet, anywhere from a coating to 2 inches of snow is possible with locally 3 inches possible inland, but once sleet and freezing rain mix in it will stop all snow accumulations and pack the snow down.  In terms of freezing rain accumulations, at the coast just a coating of ice is most likely with inland CT getting maybe up to a tenth of an inch of ice.  Thus at 5 AM a coating to 2 inches of snow will be on the ground and freezing rain will likely be the predominant precipitation type across Southwestern Connecticut.

Between 5 AM and 7 AM the coast will gradually rise above freezing, and all freezing rain will change to plain rain.  This leads to a very close call regarding schools.  Typically, when ice is involved, as it is with this storm, districts tend to be more conservative with their decisions.  Ice is the most dangerous form of precipitation, after all.  However, at no point will precipitation be heavy overnight tonight, it will just generally be light.  No significant ice accumulations will accrue, and if temperatures rise above freezing by 6 AM across a town by 7 or 8 AM roads should be safe enough to drive on.  I find it more likely than not that coastal towns either completely or close to completely rise above freezing by 6 or 7 AM tomorrow morning, thus alleviating ice concerns and potentially avoiding a delayed opening.  If there is even a degree or two colder trend among the short range models that I am looking at currently (including the RAP and HRRR) then this percentage could be raised a large amount quite quickly, as just a few degrees will be that difference between freezing rain and rain.  Thus anyone on the coast should still monitor this closely as it could affect schools tomorrow.

Further inland, it is likely that the changeover from freezing rain to plain rain happens more in a time frame from 7 AM to 9 AM depending on how far inland you are.  Towns like Weston/Wilton likely will see it between 7 AM and 8 AM whereas Danbury may not see it until closer to 9 AM.  It’s similar to the coast in that once temperatures rise above freezing almost all ice concerns will be alleviated and roads will become safe, but before that there could be significant ice concerns, especially with black ice.  Because it appears road conditions will not be safe until at least 7 or 8 AM inland, I am now predicting that inland towns in Southwestern Connecticut will have a delayed opening.  This forecast is not very likely to be redacted unless there was a sweeping change in model consensus and current surface observations.  The cold air has been winning out, and it will likely still be around early Monday morning.  It is important to note with this percentage that the further inland you are the higher the percent chance that you are delayed/close is.  The chance that there are any closures remains quite low, though a few models have freezing rain linger quite inland until close to 10 AM, which could complicate decisions on whether to open at all.  However, those are among the coldest weather models and most precipitation from that batch looks to move through by 9 or 10, meaning that conditions should begin clearing by then if not earlier.  Thus chances of schools closing are not likely, though chances of schools delaying inland continue to look increasingly likely.

So this is a brief summary of where these percentages are coming from and what they mean.  As always, throughout the evening there will be updates to these percentages as more data comes in.  Most updates will generally look to be brief, though if there are any major forecast changes a blog close to this length or potentially even longer could be posted.  Regardless, make sure to stay tuned as snow, sleet, freezing rain, and rain all approach Southwestern Connecticut!

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>