An Atmospheric River event will bring very heavy rain, mountain snow, and gusty winds to portions of southern Oregon and northern/central California Friday into Saturday.
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A Slight Risk of Excessive Rainfall (level 2/4) has been issued along portions of the Coastal Ranges of northern California where locally heavy rainfall rates of 0.5" per hour and rainfall totals of 3-5", with isolated higher amounts upwards of 7", may lead to some instances of flooding during the height of the event Friday evening/overnight into Saturday morning.
Very heavy mountain snow is expected at higher elevations (generally over 5000-6000 feet) of the Coastal Ranges and for the Sierra Nevada.
Winter Storm Warnings have been issued for forecast snowfall totals of 1-2 feet, locally higher.
In addition to the heavy precipitation, strong, gusty winds are also expected, particularly for coastal locations.
A broader area of more moderate rainfall stretches across the Pacific Northwest and south along coastal California.
Some Moderate to heavy snow is also forecast further north through the Cascades where 4-8", locally higher, can be expected.
The system will continue eastward late Friday and into the day Saturday, spreading moisture and precipitation chances further inland over the Great Basin and northern Rockies.
A mix of rain and snow can be expected at lower elevations with snow, heavy at times, for higher mountain elevations.
Winter storm Watches have been issued for the mountains of central Idaho where the heaviest snow is expected with forecast totals of 6-12".
To the east, an upper-level wave passing from the Rockies and over the Plains will help to organize a surface frontal system and encourage moist, southerly return flow from the Gulf of Mexico.
Showers and thunderstorms are forecast ahead of an eastward moving cold front across eastern portions of the central/southern Plains on Friday.
More widespread storms with moderate to locally heavy rainfall are expected on Saturday as the system continues into the Middle Mississippi/Lower Ohio Valley.
Some potentially impactful winter weather is forecast further north across the Middle Missouri Valley and into portions of the Upper Midwest where warm, moist air overriding colder temperatures will lead to a wintry mix Friday afternoon through Saturday.
Snow/sleet accumulations should remain light, but some freezing rain accretions are also expected.
These accretions may be greater than 0.1" over eastern Iowa which could lead to some tree damage and power outages.
Regardless, the wintry mix will at least likely lead to some travel troubles across the region.
Elsewhere, most lake effect snow will be tapering off Friday morning for the Great Lakes except downwind of Lake Ontario where an additional 6-12" can be expected through the day Friday.
Some light to moderate snow showers will also continue through the day Friday for the central Rockies as a cold front moves through the region.
High temperatures will remain cold and below average for much of the north-central and eastern U.S.following a frontal passage.
Forecast highs range from the teens and 20s for the northern Plains, Great Lakes, and interior Northeast; the 30s and 40s for the Ohio Valley and Mid-Atlantic/coastal Northeast; and the 50s across the Southeast.
Conditions will moderate closer to average Saturday with highs generally running 5-15 degrees warmer.
Forecast highs are generally at or above average across the West, with 40s and 50s in the Pacific Northwest, Great Basin, and Rockies; the 50s and 60s in California; and the 70s in the Desert Southwest.
Conditions in the Southern Plains/Texas will be some of the warmest and most above average compared to the rest of the country with highs into the 60s and 70s. ■
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.