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February: Does a Change in Months Mean a Change in Weather?

Matt Ross @ 1:00 AM

We have just ended one of the most variable winter months in recent memory in terms of a switch from warm to cold. In fact, January was just a more dramatic rendition of December. Years from now if we just look at the surface stats we will see two months that averaged slightly above normal. However, this certainly is an instance where the quantitative does not reconcile nicely with the qualitative. If we look back at December, we see that like January there also was a mid-month switch from warm to cold. December 1st through December 13th averaged 5.7 degrees above normal, while December 14th through December 28th averaged 4.9 degrees below normal.

This cold period was "highlighted" by our coldest December day since 1989 on the 20th following a powerful cold front that brought us our first taste of snow, a dusting for most and a bit more to our South and East. Some of you may remember the rumbles of thunder that preceded the switch from rain to snow. Then came January.

Forecast: In the short term, today and Wednesday look sunny and seasonable with highs nearing 40 degrees today and perhaps the low 40's on Wednesday. With the sun out, we should see some significant melting of this past weekend's snow during the day with some refreeze at night. Also, it appears that Super Bowl Sunday looks dry and seasonably mild with any precipitation holding off until Monday, and highs in the mid 40's. But first we must get through Thursday and Friday. See Bottom.

January 1st through 15th averaged a staggering 11.9 degrees above normal, punctuated by five days that exceeded 60 degrees including January 13th when it hit 71. The following 15 days averaged an also very impressive 8.7 degrees below normal including many nighttime lows in the teens and several snow events. The pattern of December and January with respect to these mid-month switches clearly invites the question of whether it will repeat in February. I think that it will, but to a lesser extent than we experienced in January. It is natural for these rubber band type swings to occur, and thus after our cold and snowy end of January, the pattern should relax a bit and reload before a possible colder and snowier ending to the month. But, even as we rebound to seasonable temperatures in the low and mid 40's during the day and possibly even a bit milder next week, we still will face occasional threats. It is the heart of winter after all. The first one comes Thursday into Friday as discussed in more detail below.

Possible late week system: There is a system over the gulf states while at the same time there is a somewhat rare system in the Atlantic Ocean. The Ocean system may retrograde and affect New England toward the end of the week. What happens with that system will help determine what happens with the Gulf system. Right now there is great model divergence over what occurs. One solution brings the Ocean system into New England and suppresses the Gulf system to our South and keeps us dry(see depiction below). While another model keeps the Ocean low out to sea and allows the Gulf moisture to come our way. While it is too early to say with confidence, I favor the latter solution which will give us precipitation on Thursday into Friday. Because there is no solid source of cold air, precipitation types will be greatly dependent on the strength and track of the system. A more Westerly track will keep us mostly rain, while a more Easterly track with a stronger coastal component would allow for more wet snow possible, particularly in the far North and West suburbs and Mountains. Stay tuned.

The 1/31 18z GFS which shows the result of the Ocean low suppressing the Gulf system and leaving us in between and dry.

The author is photographed up top as a 10 year old enjoying the aftermath of the Blizzard of 1983 in his Thundertube. Could we see a repeat this month?

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