Moisture will focus along a strong surface front entering the West Coast tonight.
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Heavy to excessive rainfall is expected to impact the southern Oregon coast down through central California tonight into early Thursday morning.
A Slight Risk (level 2/4) of Excessive Rainfall leading to Flash Flooding is in effect for much of the aforementioned areas this evening.
The Flash Flooding threat shifts southward into southern California, portions of the Central Valley and the foothills of the Sierra Nevada on Thursday as the axis of heavy rain and thunderstorms sags south into a highly sensitive and/or urbanized corridor.
A Slight Risk (level 2/4) of Excessive Rainfall is in effect for much of the southern California coast from Los Angeles County down through the San Diego metro.
Heavy Snow will expand from the Shasta Siskiyous to the Sierra Nevada tonight before spilling out over the Great Basin on Thursday and eventually portions of the Intermountain West and Rockies on Friday.
The heaviest snowfall will occur over the Shasta Siskiyous and Sierra where 1-3' feet (isolated 4') are expected.
Generally 1-2 feet are expected over the higher elevations of the western mountains with isolated 2'+ amounts possible.
Low elevation rain is also expected as there will be warm air associated with this low pressure system.
Cloudy conditions will keep temperatures cooler than average for much of the West Coast and Southwest over the next couple of days.
A strong omega block high will support above average heights and temperatures across the Central Plains and Mississippi Valley over the next few days.
Low temperatures in the 30s and 40s may break existing records tonight over parts of the Central/Southern Plains and Upper/Middle Mississippi Valley.
High and low temperature anomalies will be +20-40 degrees above average.
Elsewhere, snow showers are possible downwind of the Lower Great Lakes and interior Northeast over the next couple of days due to a low pressure system coming out of Canada.
2-4" of snowfall may accumulate over northern Maine by Friday. ■