5:30 PM UPDATE: 60% Snow Day

Snow days are officially forecasted for all of Southwestern Connecticut, snowfall totals are going to be increased in this update, and Winter Weather Advisories have been issued for the entire area since the last update.  There’s a lot to cover in this blog, and I’ll try and condense it as much as I can for you.  I’m going to start by analyzing the accumulation changes, how they came about, and any tweaks I have to the expected timing.  That’ll be followed by an analysis of exactly why snow days are now forecasted and what scenarios will close schools vs. what (increasingly unlikely) scenarios would allow schools to open tomorrow.

To begin, 18z weather models trended towards the international 12z guidance which showed additional moisture moving into the region for the storm tomorrow.  This is supported as well by short range guidance, such as the latest RAP.  I don’t like using the RAP this far out but it can often have a better handle on timing, and when the RAP and the NAM agree on short range timing along with other short range models I tend to put more stock in them.  It generally looks like snow will start from west to east now between 6 and 7 AM, and will be locally heavy by 8 AM.  I still believe the worst of the storm will be between 8 AM and 12 PM.  If I had to guess, already an inch will be on the ground by 8 AM with snowfall rates approaching an inch per hour over the next 4 hours.  Snow then winds down with another inch or so falling between 12 PM and 3 PM before snow moves on out.  Overall, I believe this results in anywhere from 4-6 inches for a lot of the area, though I also believe some of the models are slightly overdone with moisture in this fast-moving forecast.  Taking this all into account, I have updated the forecast to a widespread 3-6 inches of snow south of and around the Merritt Parkway with a widespread 2-5 inches of snow for areas north and removed from the Merritt Parkway.  This forecast takes into account almost all model solutions, and there remains an outside chance (20%) that amounts will need to be ticked up more to get even more in line with the latest ECMWF, but for reasons I am about to explain I don’t think it will be necessary.  With snow picking up in intensity by 7 or 8 AM I think it is likely that districts will have to close.  There is NO REASON to have delayed openings tomorrow, and there is NO REASON to have Early Dismissals.  Snow actually winds down after 12 or 1 PM, and conditions begin to improve in the afternoon.  Any schools that open should be open all day, but at this time I am advising that schools do not open.  Again, currently I am forecasting that there is a 60% chance that conditions will be present worthy of closing schools across Southwestern Connecticut and I only expect that number to continue increasing.

Why is the number for snow days not higher at this point?  It is because while models agree on a trend now, there has sometimes been a last minute shift southeast with low pressure centers that could cut down amounts a little.  There is a lot of variability in the range, a 3 inch snow storm has much less impact than a 5-6 inch snow storm, and if the lowest ends of the ranges are met some districts may be able to handle the snow and open schools.  If the higher ends of the ranges are met, I can say the chances of snow days would be on the 80-90% range.  Another thing to note is that temperatures at first could be above freezing before they drop in the storm.  Even around 6 or 7 AM temperatures, especially at the coast, could be in the mid 30s, meanings now would not immediately stick to roads and travel could not significantly go down hill until 8 or 9 AM.  In this scenario, getting kids to school would possibly be feasible, but I still believe that conditions won’t be good enough by 2 or 3 PM in the afternoon for it to be safe to bring them home.  There is a chance temperatures at the coast go back above freezing in the mid to late afternoon after the snow ends and road conditions improve, but I don’t think it is a gamble worth taking as if temperatures remain below freezing in the afternoon we could be dealing with ongoing icy, snowy, and slippery roads.  In summary, the 60% chance will likely continue to rise as the timing becomes even more certain, but it remains a marginal call for now only because there is that scenario with surface temperatures being slightly above freezing that could come into play.  I will continue falling surface temperatures trends this evening and that will greatly play into future snow day predictions.

As for the Wednesday and Saturday storms, I continue to follow the recent trends and I am very concerned for each.  Model trends continue to support an extended period of snow followed by an extended period of sleet/freezing rain before any plain rain would move in.  I believe that plain rain is more likely with the Wednesday storm than the Saturday/Sunday storm, and accordingly I think the third of these storms could have the worst impacts.  Still, the Saturday/Sunday storm is far enough a way that a lot of changes are still possible, and my focus now is mainly on the Monday storm because its impacts will be felt within 12 hours.

So, to summarize, snowfall forecast is now 3-6 inches for coastal SWCT and 2-5 inches inland where there will be less moisture.  I don’t expect a major gradient, especially because slightly colder surface temperatures inland will allow a little more snow to stick a little quicker, but for example Danbury will likely see significantly less moisture than Greenwich or Stamford.  Still, I think the 2-5 inches that Danbury sees will be enough to close schools, especially with their track record of closing easily.  If necessary, I will break down school closings by districts like I did last time, but I think this is much more of a general forecast with not as much variation district to district.  I’m now going to sit back and enjoy the Super Bowl while analyzing new data as it comes in, though I figure weather updates are not going to be the main focus of many during the game.  If necessary, I will post a brief update during half time, and I’ll have a new complete update following the game as well with updated snow day chances for tomorrow.  Make sure to keep it here for all of the latest on the incoming storm.

One response to “5:30 PM UPDATE: 60% Snow Day

  1. continued thanks for all the great info.

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