Forget the snow. Let's go for damaging wind. As the storm bombs out to our west, several ingredients for early season severe weather may come together over our region Wednesday evening. First, warm southerly flow will scour out cold air and bring in moist, relatively unstable air. At the same time, a low level jetstream will develop overhead, providing more moisture in addition to a source of strong winds for convection to bring to the surface. In addition, steep lapse rates may develop. Overall, there is a slight chance at some damaging wind gusts. Of course, severe weather in February very unusual. Throw in the bad timing (nighttime) and a possible cold layer near the ground, lowering instability, and this setup can go bad very quickly. We'll see. Heavy convective rains and some gusty winds are likely with the passage of the front though.
4:00PM Sunday 2/21/2016 Update:
We have ourselves a cutter. The first storm is too weak to do anything so we get rained on Tuesday. There might be a little wet snow at onset but it won't accumulate. The rain will get warmer into Wednesday and Tuesday as the second wave ramps up and begins to cut. For real now, congrats Chicago... And for us, next...
10:15PM Friday 2/19/2016 Update:
The Operational runs are still jumping all over the place. There is just too much energy moving around the next longwave trough next week. The ensembles look like a shotgun blast of solutions, from storms that cut over into Michigan to weak out to sea coastals. What we do know is that there are probably going to be two southern waves of energy along with a third northern stream piece of energy. If the southern energy phases with the northern energy, then we've got ourselves a cutter. Congrats Chicago. Otherwise, we want the first wave to be weaker than the second wave. In an ideal setup (for snow), the first wave would be weak and drag the trough a bit more eastwards while the second wave would be our storm. Our first wave (Tuesday/Wednesday) wont have cold air (unless you take the NAM solution... but it's the NAM... ) so its going to be rain. The second wave will have cold air building behind it. Sot its also a bit of a stretch but better. We want that storm to be stronger-but not strong enough to cut. Today, all the models backed off from a coastal storm so confidence has decreased again. All in all, the goalposts are between Michigan and the Atlantic. Snow is improbably but not impossible. And furthermore, hug the NAM and the Euro/CMC(Canadian) Ensembles.
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| Look at all the low centers over the Eastern US on the GFS Ensembles. Everywhere but the coast. All the cutters. |
10:15PM Thursday 2/18/2016 Update:
This far out in time, operational runs of computer models are more or less useless on their own. What we prefer to do is to use ensembles, which is basically when the model is run using initial conditions that are randomly varied from the observations. Then we look at the spread of the ensemble solutions as well as the ensemble mean. The idea is that although one run might give a wonky solution, a bunch of runs using slightly different conditions will give an idea of the possible solutions as well as forecast confidence. Although the operational Euro, GFS, and CMC models all give us storms, their solutions vary run to run, sometimes hitting us, and sometimes missing. However, their ensembles suggest that a favorable coastal track is the most likely solution right now although there is a cluster of ensembles on all three models that track the storm inland. This is due to the hostile Atlantic setup with the ridge over the West Atlantic mentioned before pushing strong storms inland.
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| GFS Ensemble Members. The mean shows a nice track but when looking at individual members, one can see that weaker storms track out to sea (Black circle) and stronger storms track inland (Blue circle) although the majority like the coastal storm. |
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| CMC Ensemble Members also agree to a coastal (teal circle) but there is a larger spread. Some members agree with the operational (red/pink tracks) with an inland track while most go off the coast or out to sea. |
The main issue is that we don't have cold air in place before the storm. It is pretty unusual for us to get a rain to snow scenario off of a coastal storm. Models bring in cold air with the storm at different rates with a high building in behind the storm. The Euro brings it in time for most of the precip to fall as snow. Surface temperatures are in the 32-34 range-barely cold enough for accumulating snow. The GFS keeps us too warm for snow other than the far NW. Right now it looks to be an elevation dependent event, with those to the NW above the fall line doing much better than the cities. If we get a stronger storm, it may drag in more cold air. A weak low is not going to cut it.
Original Text
This weekend, a storm will pass to our north, warming us up to near 60. Spring will be here for a couple of days. Boring spring weather. After that, it gets interesting again. There has been a signal on the computer models for a storm in the Feb 23-25 time period. Although the storm may start out as rain, there is a decent chance for snow on the back side of the storm. The general longwave pattern seems to be moderately supportive of the idea of a coastal storm. There is a steep upper level ridge (high pressure) over the western part of the US (+PNA), which helps to force the shortwaves to dig. However, there is an area of anomalously high pressure off Newfoundland, not unlike the past storm. Normally, we would like to have low pressure there to block high pressure from leaving Canada and to keep our storm from cutting inland. In order for this storm to work, we need to thread the needle, but it's a easier set to produce than this Monday's.
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| Euro Forecast for 7AM Weds 2/24/2016 For a snowstorm, you want blue (low pressure) to be in the circle, not red (high pressure) |
Computer models have show support for a storm but are at odds over how it evolves. The GFS and the Euro have different scenarios for this storm. The GFS has been quite erratic with storm evolution but generally favors a coastal or just inland track. It is slow to bring in cold air so we remain cool and wet. The Euro, on the other hand, brings cold air in more quickly but not enough to keep us all snow. The storm track is classic but surface temperatures are warm so we probably go as rain during the height of the storm, changing back to snow towards the end. Details at this point is moot point. The point is that there is a chance at a storm next week that is cold enough to bring snow. The Euro shows a favorable track with a nice source of cold air from a high to the north. The GFS is more jumpy and doesn't bring the cold air down as far south. The Euro is better. Therefore, hug the Euro until it drops the storm. Then hug whichever model gives us the most snow. Something to note: Days 11-15 on both the GFS and Euro Ensembles show all the teleconnections (+PNA/ -EPO (Western ridge), -AO/NAO (Blocking), 50/50 low, ect) lining up for that period. It's really quite a pretty look. Look out for that period too.
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