An upper-level trough over the Four Corners region currently will move east across the Southern Plains through this evening which will help to focus a strengthening area of low pressure north of the Red River Valley as a couple of trailing cold fronts drop southeastward across Texas.
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This low center will then move into the Middle Mississippi Valley by early Friday with a cold front gradually reaching and crossing the northwest Gulf Coast.
Going through this evening and the overnight period ahead of these fronts, very moist southerly return flow from the Gulf of Mexico will result in a threat for both severe weather and some flash flooding as numerous showers and thunderstorms develop.
The best threat for this has become a little more concentrated and is generally focused across southeast Texas and southern Louisiana.
The Storm Prediction Center currently has a Slight Risk of severe weather (level 2/5) for the threat of a few tornadoes along with isolated large hail and strong wind gusts.
Additionally, some of the thunderstorms will also be capable of producing very heavy rainfall, and the Weather Prediction Center has depicted a Slight Risk of excessive rainfall (level 2/4) for much of the same area where locally a few inches of rain will be possible which may result in some areas of flash flooding.
The remainder of the broader Arklatex region and Lower Mississippi Valley should see a threat for some locally heavy rainfall overnight and early on Friday, but much of this should be beneficial in nature.
As the aforementioned low center crosses through the Middle Mississippi Valley and toward the Ohio Valley on Friday, some very localized concerns for severe weather and flash flooding could spread farther east along the central Gulf Coast.
Additional light to moderate precipitation is expected to the north of the surface low track, impacting portions of the Central Plains and Middle Mississippi Valley into early Friday, and then transitioning downstream across the Ohio Valley, Lower Great Lakes and the interior of the Northeast late Friday into Saturday.
Sufficient cold air should be in place for at least a swath of a couple of inches of accumulating snow along the northern edge of the precipitation shield.
Meanwhile, an active pattern of atmospheric river activity will impact the Pacific Northwest and spill over into the Northern Rockies heading into the weekend.
The coastal ranges and lower elevations of the Cascades will see moderate to heavy rain, with locally several inches of rain expected over the multi-day period heading through the weekend.
This may result in some river flooding concerns.
Very heavy snowfall will impact the higher terrain of the Cascades where locally a few feet of snowfall can be expected.
Travel will be difficult and hazardous due to both heavy and blowing snow.
As this Pacific moisture and energy tracks inland, heavy accumulating snowfall will also arrive across the higher terrain of the Northern Rockies where up to a couple of feet of new snow can be expected by Sunday. ■