An unsettled week of weather is in store for the Mid-South. None of the storms moving through this week will be strong but precipitation is possible every day through the weekend, including the possibility for the earliest snow since 1993.
The current weather picture shows a negatively-tilted vort max over the central plains that does not have good upper-level support (located under the unfavorable left entrance region of jet streak) and is moving into a highly amplified ridge over the Midwest. Moisture will arrive in the Mid-South tonight into tomorrow as the southeasterly flow ahead of this system kicks in. Precipitation will be light and spotty with no more than a few tenths of an inch. Another vort max (seen in southern AZ Tuesday) will spin up another storm Wednesday that will track along the Gulf Coast. At the same time, note the intense Alberta Clipper in SW Canada associated with the very strong polar jet.
By Thursday, the Gulf Coast storm will be located over the Mid-Atlantic states and the Alberta Clipper will begin to dive southward into the Midwest. This clipper will lay down a swath of snow over the upper Midwest and produce a potent cold front that will sweep towards the Mid-South during the day on Friday with additional rainfall. The coldest air of the season will follow this front and will likely keep high temperatures for Saturday and Sunday near 40 degrees with windchills near freezing under mostly cloudy skies. With such a deep trough, the atmosphere will be cold enough for the first flakes of the season in places like Bowling Green as 850 mb temperatures will be around -6C and thicknesses should be around 530 dm. The best chance of any snow showers or flurries will be Saturday night as vort maxes rotate through the base of the trough; the lack of radiational heating at night should keep precipitation frozen. If at least a tenth of an inch of snow does fall, it would be the earliest snowfall since 1993 according to the Midwest Climate Center database (1993 for Bowling Green; its 1995 for Lexington)). NOTE: For those who love winter weather, the winter of 1993-94 and 1995-96 were both notable for extreme winter cold and heavy snowstorms in the Mid-South — just saying. Keep in mind however, that predicting even flurries this far out is fraught with peril as even a slight shift in the depth of the trough or the timing of vort maxes moving through the trough and even moisture availability could prevent snow. The big forecast point is that the temperatures this weekend will be colder than normal for even the middle of January (normal high on 11/15 = 58; normal high on 1/15 = 42; expected high 11/15 and 11/16 = 40-42).
Rainfall totals for the week should be in the 0.50-1.00 range with some places getting as much as 1.50 (SW KY). While it won’t be raining constantly during the week, this week will be remembered for a lack of sunshine and an overall raw feeling from the cold November rain (thank you Guns N Roses).
In the long range, the models show a brief warmup early next week before the next arctic blast arrives mid-week. The GFS shows that by even the following weekend, temperatures are still well-below normal. The Climate Prediction Center is in agreement that the GFS is correct as shown by its 6-10 day and 8-14 day outlooks. The key feature in the long range outlooks is the dry weather everywhere except the Great Lakes, where the lake-effect snow machines will be in full gear. The European model also agrees with the GFS in the long range although there is some disagreement among the GFS ensembles.