11 PM UPDATE: 65% Early Dismissal Tuesday

This will be the final update of the night on the site, so I wanted to take a little more time than in some of the other updates to outline exactly what I am now expecting with this storm and what the major differences between models are that I am still watching.  First, I’m going to outline yet another increase in the percent chance of early dismissals tomorrow.

I am confident now that snowfall will begin between 11 AM and 1 PM, with most areas seeing snow falling heavy enough to cover the ground by around noon.  I expect we will see a half inch by 2 PM, and an inch by around 3:30 PM, with heavy snow bands beginning to move in by 4 PM.  Because of this timing and the much safer road conditions that will be present before 12 PM, I expect that most districts will just bite the bullet and dismiss early, especially as the day will still count regardless.  Some districts are still in midterms currently, and that could affect a few decisions, but overall I believe that conditions will be present to warrant Early Dismissals across all of Fairfield County, and thus I have raised the percent chance yet again to 65%.  This will be updated yet again in the morning, likely at the 5 AM brief update as reports begin to come in, along with a 9 or 10 AM update that will be released right before districts have to make the decision on whether to dismiss early or not.  I expect most districts will know ahead of time by tomorrow morning that they will be releasing early, so I will be up at 5 AM to report on which districts announce ahead of time and which wait until the last minute.  I am not sure that every district will dismiss, as some districts, including Westport, Fairfield, Norwalk, and Greenwich, have shown that they do not often dismiss early, and my forecast is not saying every district is guaranteed to release early.  Instead, it is saying those that normally release early in marginal conditions will do so, and some of those that do not normally release early in these conditions will also do so.  There is a chance that all districts dismiss early, especially as forecast confidence and publicity of the storm increase, but I am not sure how likely that is.  Either way, keep checking back on here and on Twitter for the latest regarding Early Dismissals from districts across Southwestern Connecticut.

I also wanted to take some time in this blog post to analyze some new trends that I am seeing with the storm.  Though confidence has grown regarding when the snow starts (around the same time I have expected since publishing the original forecast), confidence remains very low on exactly when the snow ends.  We have two camps of weather models, the NAM and RGEM, which have the heaviest snow between 4 PM and 10 PM with snow winding down by 1 or 2 AM across the region, and the SREFS, GFS, and other global models, which have the heaviest snow mainly from 5 or 6 PM until 3 or 4 AM.  I am tempted currently to lean towards the NAM/RGEM, as they handled the last storm of this nature much better than the SREFs or the GFS did.  This means that I still expect around half an inch of liquid for the coast and around a third of an inch inland, resulting in anywhere from 5-10 inches at the coast and 4-8 inches of snow inland.  If it turns out the GFS and SREFs are correct I will end up bumping up amounts at the last minute, especially at the coast, but these storms are tricky and I got burned on the last one by having the banding set up further to our south keeping me wary of bumping up amounts.  Ratios will be decent but winds will keep them from reaching 20:1 at the coast, and so half an inch of liquid with ratios of 14:1-16:1 results in 7-8 inches of snow, solidly in the expected range.  Even with basic ratios of 10:1 the coast will still see 5 inches of snow, on the low end of the forecast but still in it.  This makes me very confident that all of Southwestern Connecticut should meet my forecasted amounts, the bust potential is instead on the higher end of the forecast.  As I have said all day and will continue to outline, there is around a 20% chance that mesoscale banding sets up across Southwestern Connecticut resulting in enhanced snowfall totals of up to a foot or more.  These bands cannot be forecasted with confidence until a few hours before, meaning I will have to watch the storm very closely tomorrow.  The GFS and the SREFs have so much more snow than the NAM/RGEM because they set up the banding across the area and have the low pressure a little more northwest, meaning that SWCT would see some of the heaviest snow from the storm.  The low pressure track is not one that climatology would argue gives us the best banding, and thus I am ignoring their band placement and instead going with the NAM and RGEM which have the mesoscale banding across Long Island.  This is the most likely scenario, and if it is the case it will result in a very tight gradient with a lot of snow at the immediate coast and significantly less snow up north by Interstate 84.  If there are major changes in these high definition models overnight then I will be updating the forecast, but I have increasing confidence that these models are getting a decent handle on the storm.

As for what this could mean for Wednesday, it means that there could be delays instead of snow days as snow would end between 2 and 3 AM.  However, the models still show up to 6-8 inches of snow in areas, and that volume of snow is still difficult to move in just a few hours.  Even in these scenarios I’d lean towards snow days but the chances of delays are still very real.  Should the GFS/SREFs verify then there is no doubt that every school district in Fairfield County would close.  I’ll have more details on this tomorrow, but I am certain no district will open on time Wednesday, it is just a matter of whether they open at all.

So that’s what I am looking at right now.  There is a chance (given brand new RAP guidance) that up to an inch and a half of snow could be possible by 3 PM, and maybe even 2 inches by 4 PM, meaning that an Early Dismissal call could make even more sense for Southwestern Connecticut.  This means there is a very real chance that the percentage will continue to rise tomorrow.  However, that would just be the start, with the heaviest snow still expected between 4 PM and 1 AM.  Accumulation forecasts remain on tracks, as do forecasted impacts.  It is recommended that everyone be off the roads by 2 or 3 PM if at all possible, as by 4 PM I expect roads to be extremely treacherous as visibilities rapidly drop.  Most roads will not be safe until late Wednesday morning or early Wednesday afternoon, so prepare to stay home and enjoy the storm for a little amount of time.  I’ll continue updating on the entire process, and I’ll have brand new information and updated forecasts tomorrow morning, so make sure to check back in!

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