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In what’s turning out to be quite an interesting winter across the entire US this season. We’ve had a blizzard in the Northeast, record low pressures in the Upper Midwest, a blizzard there too, one of the coldest Decembers on record in spots, snow in Vegas, graupel in Phoenix, and snow in many of the foothill and desert communities north of Los Angeles, record rainfall and snow in California, flooding in the Northwest, record brutal cold and snow in Europe, and on, and on. And that may have just been the appetizer.
What’s coming over the next 1-3 weeks is nothing short of awesome to watch unfolding on the weather maps. Over the next 10-15 days there will be some of the coldest air of the season draining into the Central part of the country and possibly into the Southern and Eastern parts as well, at least 2-3 *chances* at storms in the Northeast/Mid-Atlantic, the potential for the Southeast as well, and possibly even a winter storm deep into Texas. All *possibilities* in this pattern.
The image I posted (click it or any other image to enlarge) is a map from Allan Huffman’s model site (http://raleighwx.americanwx.com/models), which illustrates the European ensemble mean 850 mb temperature anomaly over the period 6-10 days from now. Basically, just an average of how much warmer (yellow) or colder (blue/purple) than normal this model is predicting over the period 6-10 days from now. And notice how almost the entire US (except Maine) is in the below normal range. Keep in mind, 850 mb temperatures are just temperature about 5,000′ above sea level. Translate this down to the ground and under clear skies and/or calm winds…that is cold, even for January, even for these areas. Also keep in mind that these temperature anomalies are in degrees C, not F, so 23F colder than normal aloft could be 30-40+ degrees colder than normal at times on the surface. And I’m not posting it, but the 11-15 day forecast looks equally as cold, if not even colder.
Does it get any better? One of the main drivers (probably the easiest to explain, but certainly not the only driver) is the Arctic Oscillation, or a measure of atmospheric blocking in the Arctic region. High pressure can set up there aloft, and it basically displaces the cold air that’s supposed to be there and dumps it southbound into the US, Europe, etc. The AO tanked in December and really has not recovered, and it seems to be reinforced this month. This happened last winter and helped make it one of the colder winters in recent years for the Southeast and parts of the Central US. This looks as impressive as anything that was seen last winter or this past December. Coupled with things we’re seeing elsewhere, this adds up to what looks to be a long-duration and impressive period of cold in the US. The biggest question is whether or not the extreme cold can spread south and east far enough to impact larger population areas. But for the Northern Rockies and Northern Plains, this looks awful.
So what about snow? This will be the more challenging forecast to make. The map to the left is the GFS forecast for this coming Saturday. Last night’s European model absolutely bombed areas from Baltimore northeast into Boston with extremely heavy snow. Today’s GFS tries to do something similar, displaced further north a bit and behaving differently. This is the first of several threats. I’m not on board with this being a major storm at this point, but a weakish “clipper” type system with a widespread light snow, isolated pockets of heavy snow (potentially a squall line type of scenario with embedded thunder as it moves through NY/PA and New England). Right now there’s a low risk of this being a big system for most of PA/NJ and south, and a medium risk for New England. Stay tuned.
The more important storm comes early to middle next week. The image to the right shows the GFS forecast for next Wednesday evening. Depending on how things play out over the next week, this one could be the one that presents a major threat to the I-95 corridor again. There are threats beyond that, but primarily for Texas and the Deep South….in other words, it may be “too cold to snow,” as they say.
I’m going to be non-committal on any of these threats at this time, but if you live in the Northeast or Mid-Atlantic, keep an eye on this Friday-Saturday and next Tuesday-Thursday, and load up on cold weather essentials…when us as meteorologists start saying that the winter weather is interesting, that’s usually not a good sign. I will keep you posted however.