March Madness: In Like a Lion, Out Like A Lamb (?)

This blog post is going to briefly focus on a storm threat I am watching very closely from Sunday night through early Wednesday morning of next week.  It is very early, and I don’t usually post this early, but with a strong model consensus on the storm set-up and on some timing aspects I wanted to give everyone advanced warning of what to expect and how the forecast may change over the next few days.

First, there will be gusty winds and scattered snow showers/squalls tomorrow as an arctic front moves through the region.  No accumulations are expected though visibility could be temporarily reduced and roads made briefly more slippery in some of the squalls, so do drive with some extra caution.  Nothing too serious.  There could also be some snow flurries Saturday afternoon into the evening as another system moves by the area, but again no accumulations are expected.

The main focus will be next week.  There are two storm threats, one in the Monday/Tuesday time frame and one in the Thursday/Friday time frame.  As the one in the Thursday/Friday time frame is over a week away, I won’t get into any more detail than to say that we are tracking a potential storm then.  It could miss and bring the area absolutely nothing, or there could be an impactful snow storm, but it’s just too far away for anything other than a mention of a threat.  However, it is the storm in the Monday/Tuesday time frame that is coming into a range where we can begin to work out some of the details, and I plan on going over exactly what we know and what we do not.

Precipitation will break out at some point on Sunday, likely Sunday late afternoon but more likely Sunday evening.  At first, it will be very light with scattered light snow showers, but as time goes on and Sunday evening turns into night and eventually Monday morning, snow will become more steady and likely be moderate by morning.  This is where models begin to diverge and we deal with multiple different solutions.  I’ll take a step back here to explain the overall pattern: a frontal boundary is moving through the area tomorrow, and another Saturday night or Sunday morning.  The frontal boundary this weekend will stall to our south, and along it will form a convergence zone, along which multiple waves of low pressure will ride, making this such a long-duration event.  Each low pressure center will bring with it a burst of snow.  Models all agree on the set-up of this convergence-zone and on the timing of some of the low pressure centers, but they differ on how many, and as you go past Monday morning there get to be some fairly divergent model solutions.

Anyways, back to the real conditions I am looking at: we have the first main low pressure center moving through on Monday.  The ECMWF weather model, historically one of the best, says that this is the main low pressure center, and actually breaks down the convergence zone on Monday, meaning that we have heavy precipitation on Monday but everything is over by Tuesday morning.  The ECMWF is also the warmest model, showing snow through Monday morning turning to sleet and freezing rain before turning back to snow.  And that is a potential, I see a scenario in which we do not see all snow but instead snow turning to a sleet/freezing rain mix and then back to all snow.  One thing I don’t really see is an extended period of just plain rain, as I think temperatures at the surface generally remain below freezing through Wednesday morning, except maybe at the immediate coast.  What this means is likely an extended time frame of impacts depending on the exact scenario.  The GFS and CMC weather models seem to agree on an all-snow scenario where we have one burst of snow on Monday and another on Tuesday morning.  A few weather model solutions also show a third, weaker wave keeping snow showers going until Wednesday morning, with the GEFS ensembles generally supporting the GFS but being a little warmer, and other ensemble members showing a general snow event with maybe some sleet and freezing rain.  And for those of you that don’t know what all those acronyms mean, I’ll break that down in the next section.

My current thinking is that we get snow starting later on Sunday, steadier Monday morning, maybe mixing with sleet/freezing rain during the day but ending as all snow if it does mix at all, and then another round of snow into Tuesday morning as a second low pressure center moves along this convergence zone.  It is too early to talk accumulations, but we aren’t looking at crazy accumulations here.  My best guess would be anywhere in the 6-10 inch amount for storm totals across all of Southwestern Connecticut, but it could be less if sleet/freezing rain mix in more, maybe a little bit more if the storm strengthens rapidly or there is a third event.  That amount isn’t an official forecast as I think it is too early for that, it is just a general ballpark.  My best guess is that if we DO get that second wave, snow winds down Tuesday morning.  I don’t see the scenario where snow continues through Tuesday and into Wednesday morning playing out, and in fact models appear to be trending more towards a mainly Monday event.  This means that in terms of school impacts, I am looking at Monday being the day most likely to be impacted by wintry weather, with some impacts possible on Tuesday.  Until we work out details and confidence increases with the storm I won’t go into more detail with regards to school than that, but definitely stay tuned for additional information on how this storm is projected to impact schools, as I think there is a very good chance that there are widespread school impacts of some sort across Southwestern Connecticut next week.

That’s really what I’m looking at, snow starting Sunday evening and continuing through Monday, maybe mixing with sleet/freezing rain, before ending as all snow Monday overnight or Tuesday morning with a second burst of snow possible.  This remains a highly thread-the-needle type event with low pressure systems moving along a stalled frontal boundary, and models historically have a hard time picking up on exact thermal profiles and front placement in this exam, so it is likely that there will be numerous tweaks to come along with the additional details I’ll be hashing out over the next few days.  Make sure to keep it here for the latest breakdown of winter weather and potential school impacts across Southwestern Connecticut!


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