Cold air is spilling Southward behind a cold front into the central and southern Plains and Midwest this morning. The darker, solid yellow line on the above temperature map shows the location of the freezing line as of 6am CST. The temperature scale (in degrees F) is at the top left of the image.
This is just the leading edge of a very cold, arctic air that will invade portions of the country this weekend. The following images show the GFS computer model's forecast of the temperature near the surface at 12 hour intervals (roughly corresponding to the times of the high and low temperature each day) beginning 6pm CST today and ending 6am CST Monday.
Keep an eye on the darker purple shaded areas which correspond to temperatures in the single digits above zero (degrees F). The grey shaded areas within the purple show temperatures forecast to dip int the single digits to around 10 degrees below zero. The scale in degrees F is located at the right hand side of each image.
The first image is valid 6pm CST today:
...then 6am CST Saturday:
...6pm CST Saturday:
...6am CST Sunday:
...6pm CST Sunday:
...and finally at 6am CST on Monday, the 13th:
Note the punch of bitterly cold air across much of the northcentral Plains and upper Midwest early in the weekend, and across portions of New England late in the weekend.
There will also be an opportunity for a band of locally heavy snow from near or just North of the New York City area, on up into portions of mainly coastal Maine on Saturday. The image below shows the current HPC forecast of the likelihood for at least 4 inches of snow during the period 7am EST Saturday through 7am EST Sunday:
At least 4 inches of snow is likely within and near the red outlined area on the image, with lesser chances as you proceed into the green and blue outlined areas.
Another clipper will dive Southeast into the central and southern Rockies on Saturday night and Sunday, producing locally heavy snow across portions of mainly southwest and west-central Colorado and extreme northwest New Mexico:
This same system may also produce a swath of wintry precipitation across portions of Kansas and Oklahoma, into adjacent portions of Missouri and Arkansas on Sunday night. At the moment it appears that the precipitation will generally be light, but we'll need to keep an eye on this.
The overall pattern in the middle and upper atmosphere appears to be evolving into a much more active one as we head into mid and late February. I'll have more on that in a post later today...
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