Thursday, 11:55 a.m.
Fall officially ends Saturday with the winter solstice at 12:11 p.m. EST. From there, we're into the depths of winter, with average daily temperatures still falling another 2 to 3 degrees before reaching rock bottom in about a month. The days will start getting longer this weekend, but the effect of the higher sun angle really won't be noticed until we get into early February.
The storm this weekend coming out of the southern Plains and across the Mississippi Valley will pull together at least three seasons of weather - spring, fall and winter - as it darts for the Great Lakes Sunday. On the western flank of the storm, it will snow, with some of the snow being laid down from north-central Oklahoma through central and eastern Kansas, then across northwestern Iowa and southeastern Iowa into Wisconsin, as well as northern and western portions of Michigan. There can also be some snow at times into the start of the weekend across extreme northeastern New York state, northernmost sections of Vermont and New Hampshire and northern Maine, but even in these places it is very likely to warm up and rain at some point Sunday and Sunday night.
That may be it as far as the as the wintry aspects of the storm are concerned. Here's the broad look at the storm and its potential impacts, noting that some areas will, by default, overlap:
The other season that has not been mentioned is spring, which many associated with severe weather and flooding. There should be some of that associated with the storm. Let's first assess the severe weather threat. Given the depth of the trough, the amount of time there will be ahead of the storm for southerly winds to blow and transport tropical air northward into the southern Plains, the lower Mississippi Valley and the Deep South, there will be ample moisture lying in wait to be overturned by the approach of the trough and the deepening surface storm.
If you follow the 12z Dec. 19 GFS model, it is hinting rather strongly at severe weather from parts of Texas and even southeastern Oklahoma all the way to the Ohio Valley with its convective looking blobs on the QPF charts. Hail and damaging winds seem to be the highest severe weather risks at this point, and I'm sure we'll have more detailed severe weather analysis here at AccuWeather.com in the next 48 hours before the event unfolds before our very eyes.
If these convective 'blobs' turn out to be reasonably accurate, not only will there be severe weather, but heavy rains is likely to fall and cause flooding issues. There's still snow on the ground in the Ohio Valley over to parts of the mid-Atlantic and southern New England. There may not be by the time the storm is over weather by Monday morning. Look at the 12z GFS total precipitation forecast through Monday morning:
Compare that to the NAM forecast through Sunday evening:
Clearly the threat zone stretches from Oklahoma and maybe northeastern Texas through Arkansas, central and southern Missouri and western Tennessee up through the entire Ohio Valley into southeastern Lower Peninsula of Michigan. It is also likely to encompass portions of Pennsylvania, portion of upstate New York and central and northern New England.
Oh, and the temperatures being forecast for the next few days in the warm sector? Nothing short of remarkable for the latter third of December! Highs will be much more reminiscent of late September which, as of last check average temperatures still in the 60s and 70s!
Fall, winter, spring. Three seasons, one storm.
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