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 today to the East Coast on Saturday.
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The highest chance of heavy rain is forecast to be early today from the mid-Mississippi Valley and down toward the Louisiana coast with a slight risk of flash flooding as a squall line passes through the area with severe thunderstorms possible.
The rain and thunderstorms are forecast to be less intense as the front begins pushing eastward at a faster pace.
By tonight, a low pressure wave is forecast to develop quickly along the front over the Ohio Valley and then track north across the lower Great Lakes on Saturday.
The added dynamics associated with the developing wave will push a strong cold front from west to east across the East Coast Saturday and Saturday night.
Strong to severe thunderstorms are expected to precede and accompany this dynamic cold front.
Sudden onset of heavy rain along with very gusty winds are also expected with these storms.
However, the relative quick motion of the storms should limit the threat of flash flooding although isolated flash flooding cannot be ruled out.
Meanwhile, the warmth over the eastern U.S.
will reach its peak today as high temperatures are forecast to reach into the 80s for much of the East today with a few locations possibly reach 90 degrees, which will challenge some daily high temperature records.
Increased precipitation chances as the cold front approaches on Saturday will drop temperatures into the 70s for the Mid-Atlantic.
By Sunday morning, much cooler air will arrive from the west as the cold front begins pushing off the East Coast.
In contrast to the warmth in the East, moderate to heavy snow is in progress over the northern Plains into the upper Midwest on the back side of an occluded cyclone.
The snow should reach peak intensity this morning followed by gradual tapering off of the snow through the rest of today into tonight as the low pressure system weakens.
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 today for the northern Plains spreading into the Great Lakes and portions of the upper to 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 this 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 today 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 per the Storm Prediction Center for today.
Upper-level shortwave energy passing over the Intermountain West will trigger snow showers for portions of the northern and central Rockies today.
Some locally heavy accumulating snow will be possible for higher mountain elevations, particularly in the central Rockies where is snow is forecast to linger into Sunday morning.
Meanhwile, a weakening Pacific low pressure system will continue to spread light to moderate lower elevation coastal/valley rain and higher elevation snow.
Highs will remain be colder than average for the next couple of days with highs generally be 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 today and Saturday will range between the 70s and 80s for most of California and the Great Basin with 90s in the Desert Southwest. ■