Updated 01.14.21 @ 6:52p
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Updated 01.12.21 @ 8:08a
Finally we can breathe a sigh of relief as the seemingly unending low cloud deck erodes and gives way to increasing sunshine today. Along with a return of the sun will be a moderating trend in the temperature department. Expect highs in the low 40s today and mid 40s Wednesday and Thursday as a southwesterly flow develops ahead of Friday’s cold front.
The cold front, itself, will swing through central Indiana late Thursday night and early Friday morning. While we still think this will be a mostly dry FROPA (frontal passage), models are becoming more robust with a “bowling ball” of an upper level low pressure system over the weekend.
Note how the upper low becomes almost cut off from the primary steering flow for a time Saturday across the Great Lakes region. Additional “spokes of energy” (upper level disturbances) will pivot south of the primary cut off low across the Ohio Valley Friday night through Sunday afternoon. This will help lead to enhanced periods of snow and snow showers throughout the weekend.
We’re still not looking at heavy snowfall, but the rather persistent nature of light snow this weekend will accumulate to an inch or two for some communities along with a much colder air mass. After Friday evening, temperatures won’t make it above freezing again likely until Tuesday afternoon.
When we look at the bigger picture, this will likely go down as the first “jab” of more exciting weather to wrap up the month of January.
While still not overly cold (doesn’t have to be this time of year for wintry issues to arise), the pattern does look very, very active through the 2nd half of January and to open at least the 1st week of February. While the Greenland Block continues to mature, note the change in the Pacific. We may finally be able to get a negative EPO to develop to align with the negative AO and NAO.
If this does, indeed, transpire we should see a rather expansive snowpack get laid down across the country during the last week to 10 days of January. It would then be this time into early February to look for the possibility of more significant arctic air to spread out and cover more of the Lower 48 (after initially likely being bottled up in western Canada and the northern Rockies).
At the very least, times are becoming more interesting. It’ll be a fun ride through the rest of the month and to open February.
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The MJO is set to remain in the “null” phase through the end of the year.
This means we’ll continue to lean on the teleconnections to drive the pattern over the next few weeks.
For the most part, these teleconnection signals remain clustered in a manner that favors a predominantly chilly pattern to close out the year. (Not to say we won’t have a day or two thrown in with milder southwesterly winds).
The period where there’s greatest alignment for cold is centered on Christmas. Not surprisingly, we have an arctic blast dialed up for the big holiday (including highs that might not make it out of the 10s). Thereafter (from top to bottom), the AO remains negative, the EPO trends back to neutral to positive, the NAO trends neutral before heading back slightly negative, and the PNA goes back neutral.
Note the buckling of the jet and associated arctic air intrusion for Christmas.
With the negative AO and trending negative NAO, I’d look for another attempt of an eastern trough just prior or around the New Year.
While our short-term products will focus more on the Christmas storm, the current idea is for more of a progressive system (rain to snow with minimal accumulation Christmas Eve) preceding the arctic blast. We still expect wind chills to fall below zero Christmas morning.
Note the ensemble data continues to show a reflection of a trough across our neck of the woods as we close the year and open up 2021. One also has to like the positives over Canada (at least if you’re a fan of being on the playing field for the possibility of additional wintry events during this time). I’m also intrigued by the north Atlantic ridge as that can lead to eastern storminess and an overall “chaotic” pattern.
Further ahead, our updated Weekly products are bullish on warmth (relative to average) to open up January.
I would caution buying into the “torch” forecast off the long range data above. This is for a couple of reasons: the teleconnection phases and expected neutral MJO. Furthermore, what’s more likely here is that the modeling is either jumping on the warmth in Canada and “overwhelming” the Lower 48 with the warmth, or is way too warm in Canada. It’ll be mighty hard to pull off widespread warmth across the Lower 48 and Canada through the first couple weeks of the new year. The pattern should also continue to offer up a fairly active storm track to open up 2021.
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