As we are currently in the midst of a January thaw, many people are looking ahead to find out when this thaw will end and when snow chances will begin. Some rumors had been spreading about a snowfall event on Wednesday/Thursday, and again around Saturday, but both of these threats appear unlikely to produce much in the way of snow. It is not until next week and beyond when we expect the pattern to become more favorable for snow.
Taking look at the threat, or lack-there-of, for Wednesday into Thursday, the main problems stem from a progressive pattern and one that is still in flux.
Today’s 12z European model shows an unfavorable look for a snowstorm on Wednesday night with a very progressive pattern. Image credit goes to the WSI Model Lab.
The above image is the 500mb pattern and vorticity that is forecast by the European model for Wednesday night. There is a large area of vorticity in the southeast states, but notice how it is very elongated and not consolidated. Also notice how there is another disturbance right on its heels in the Northern Plains and Midwest. This leads to shortwave ridging in the Ohio and Tennessee Valley, which penetrates the trough and forces it to be very narrow and progressive. Also working against the potential for a bigger system is the lack Atlantic blocking to help the pattern to buckle. Instead, the entire country has a NW to SE axis to the heights, instead of a more meridional north to south flow. Thus, there is no room for the trough to grow and amplify. So this disturbance slides out to sea, and does not impact the area. There may not be any precipitation at all in the Wednesday night into Thursday time period.
The same general theme holds true for the threat on Saturday.
Today’s 12z European Model valid for Friday night shows a slightly improved pattern for snowfall, but still not one that ultimately supports a snow event. Image credit goes to the WSI Model Lab.
Moving forward to Friday night, we can notice a few important features. First of all, there is still a strong PNA ridge out west, which promotes a tough in the East, and could theoretically favor snowstorm chances. That being said, the Atlantic and Arctic blocking are still nowhere to be found, so the trough cannot buckle. It’s still a progressive pattern — one with a NW to SE height orientation throughout most of the country, which leaves no room for major trough amplification. We have a trough in the East, but once again, the vorticity is relatively disjointed and the trough is being pushed eastward. There is another disturbance right on its heels again in Minnesota, which forces weak shortwave ridging in Illinois, further preventing major amplification of any trough. By the time the trough is finally able to amplify and consolidate, it is already out to sea, with maybe a few passing snow showers. Eastern New England could potentially receive a couple of inches of snow, however.
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