An increasingly active weather pattern is taking shape just in time for Christmas Eve and Christmas Day.
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One upper level disturbance tracking through the Four Corners region this afternoon is responsible for periods of snow in the higher terrain of the southern Rockies, in addition to a plume of Gulf of Mexico moisture fostering the threat for Excessive Rainfall and severe weather.
The Weather Prediction Center (WPC) issued Slight Risks for the Upper Texas coast and parts of southern Oklahoma and north-central Texas.
The Storm Prediction Center (SPC) has a Slight Risk in place for West Texas, as well as a Marginal Risk that stretches north into the Texas Panhandle due to the potential for large hail, damaging wind gusts, and possibly tornadoes.
The second upper level disturbance and its associated cold front are racing south and east through the Northern Rockies, ushering in a colder air-mass and causing periods of snow to ensue across the Intermountain West.
By the morning of Christmas Eve, the cold front formerly over the Northern Rockies will dash across the Great Plains, forcing precipitation to fall in the form of snow from the Central Rockies to the Dakotas.
Up to a few inches of snow is possible in these areas, as well as minor ice accumulations thanks to a wintry mix along the Columbia River in eastern Nebraska on north into the Red River Valley of the North and northern Minnesota.
To the south, the conveyor belt of rich Gulf moisture will stretch from the central Gulf Coast to the central Plains.
WPC posted Slight Risks for Excessive Rainfall in portions of these regions.
By Christmas Eve night, both the East and West Coasts will generally be dry, while the Mid-South on north through the central Plains and Upper Mississippi Valley can expect unsettled weather.
Motorists and reindeer should be sure that their headlights and noses are lit up brightly in areas where snow and rain are expected Christmas Eve.
As the sun rises on Christmas Day, the storm system in the Central Plains will strengthen further and become a significant winter storm from northern Kansas and eastern Nebraska into eastern South Dakota and northern/western Minnesota.
For Nebraska and eastern South Dakota, this will make for a White Christmas, but snow will fall heavily at times and blustery winds may cause near blizzard conditions.
WPC's Probabilistic Winter Storm Severity Index (WSSI-P) shows moderate chances (40-60%) for hazardous driving conditions in southeast South Dakota and northeast Nebraska.
For portions of northern and western Minnesota, there is a growing concern for treacherous ice accumulations greater than 0.1" in some areas.
The WSSI-P does depict moderate chances (40-60%) for Minor Impacts due to ice accumulations in southwest Minnesota, across Interstate 94 in central Minnesota, and as far north and east as the Minnesota Arrowhead.
To the south, the Excessive Rainfall threat continues to march east into the Southeast U.S.
as WPC has a Slight Risk in place for the Florida Panhandle and a Marginal Risk that reaches as far north as the southern Appalachians.
Temperature-wise, it will not begin to feel a lot like Christmas for much of the Midwest on east to the East Coast this extended holiday weekend.
After an exceptionally mild day throughout the Heartland on Saturday, by Christmas Eve, record warm minimum temps will be common in the Midwest where many low temps will be considerably higher than the average high temps for late December.
Even parts of the Southern Plains and Middle Mississippi Valley may witness record breaking warm highs and lows on Christmas Eve.
By Christmas Day, the most unusually mild temperatures are expected in the Upper Midwest and Great Lakes where highs could range between 15-25 degrees above normal.
The East Coast will not witness quite the anomalous warmth that the Midwest and Great Lakes will, but daily average temps will still be rather mild and could still range between 10-15 degrees above normal in parts of the Northeast by Christmas Day.
In contrast, the central/southern Plains and central/southern Rockies will be the coolest versus normal thanks to a recent cold frontal passage injecting the region with an air-mass that feels a lot more like Christmas compared to their neighbors on the East and West Coasts. ■