A frontal system pushing eastward beneath a deepening upper-level low will continue to bring widespread showers and thunderstorms with the risk of flash flooding and severe weather from portions of the Ohio/Mississippi Valleys Friday to the East Coast on Saturday.
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There is a Sight Risk of Excessive Rainfall (level 2/4) for portions of the Lower Mississippi and Tennessee Valleys Friday where access to deeper Gulf moisture will promote locally heavier rain rates and 2-3"+ rainfall totals.
The slow progression of the cold front will lead to some repeated rounds of storms over areas that saw rain Thursday, leading to the risk for some scattered instances of flash flooding.
Moderate to locally heavy rainfall will move eastward on Saturday through the Appalachians and to the East Coast, though the risk for any flooding should decrease as the front speeds up and overal totals trend lower.
However, the Storm Prediction Center has issued a Slight Risk (level 2/5) of severe weather for portions of the coastal Carolinas as moderate CAPE and deep-layer shear ahead of the cold front will lead to a line of storms with the potential to produce severe hail and damaging winds.
High temperatures will generally remain in the 80s for much of the East Friday, with some record-tying/breaking highs in the upper 80s to low 90s possible for the Mid-Atlantic.
Increased precipitation chances as the cold front approaches on Saturday will drop temperatures into the 70s for the Mid-Atlantic.
New England will remain cooler on the north side of a stationary front with highs in the 50s and 60s.
Moderate to locally heavy snow will continue Thursday evening into early Friday over portions of the Northern Plains/Upper Midwest on the northwest side of the low pressure/frontal system.
The snow should begin to taper off by later Friday evening/early Saturday, with storm total snowfall generally between 3-6", locally as high as a foot.
Gusty winds will also lead to areas of blowing snow and dangerous travel conditions.
High temperatures will remain quite chilly and much below average behind the cold front and under the influence of the upper-level low, with highs in the 30s and 40s for the Northern Plains/Upper Midwest Friday spreading into the Great Lakes and portions of the Upper/Middle Mississippi Valley on Saturday.
Highs from the Central Plains to the Lower Ohio Valley will drop from the 60s Friday into the 50s on Saturday.
Further south, ongoing showers and thunderstorms in eastern Texas will end by Friday evening as the cold front pushes off the Gulf Coast.
Conditions across the Southern Plains will turn cooler with highs generally in the 60s and 70s Friday and Saturday outside of the Rio Grande Valley.
Morning lows for portions of the Texas Panhandle and Oklahoma will dip as low as the upper 30s.
Gusty winds mixing down over the Southern High Plains combined with low relative humidity and dry antecedent conditions have prompted a Critical Risk for Fire Weather (level 2/3) from the Storm Prediction Center Friday.
Upper-level shortwave energy passing over the Intermountain West will trigger snow showers for portions of the Northern and Central Rockies Friday.
Some locally heavy accumulating snow will be possible for higher mountain elevations, particularly in the Central Rockies.
A Pacific storm system will approach the Pacific Northwest later Thursday evening increasing chances for light to moderate lower elevation coastal/valley rain and higher elevation snow here as well.
Highs will remain cool for the Northern/Central Rockies following the passage of a cold front and on the western edge of the expansive upper-level low, with highs generally in the 40s and 50s.
An upper-level ridge building off the Pacific Coast will lead to tranquil conditions and near-average temperatures for California, the southern Great Basin, and the Desert Southwest.
Highs Friday and Saturday will range between the 70s and 80s for most of California and the Great Basin with 90s in the Desert Southwest. ■
A clipper system will move quickly across the northern Plains into the Midwest Friday and the Northeast by Saturday, bringing a wintry mix of rain and snow showers ahead of a sweeping cold front.