A deep upper level trough is currently swinging towards the eastern U.S. while a wave of energy rounds the base of the trough and slingshots towards the Northeast.
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This wave will allow a coastal low pressure system to quickly strengthen and push across the Mid-Atlantic and Northeast tonight through Wednesday.
Widespread precipitation is expected to develop, falling as rain near the coast and a mixture of snow, sleet, and freezing rain for inland areas.
A swath of Winter Weather Advisories have been issued from the central Appalachians through Maine, and higher elevations will likely see significant accumulations of wintry precipitation.
Heavy snow is expected across northern Maine on Wednesday, and Winter Storm Warnings are in effect for this area.
The low pressure system will lift northeast into the Canadian Maritimes late Wednesday into Thursday, and cold west-northwesterly flow on the backside of the system will cause lake effect snow to develop in the Great Lakes region.
Heavy lake effect snow is expected Wednesday and Thursday with significant snow accumulations possible, especially downstream of Lake Erie and Lake Ontario.
Winter Storm Watches are in effect for these areas.
Total snowfall accumulations will be highly dependent on where snow bands develop and could shift significantly with changes in wind direction.
A cold front will approach the region late Thursday into Friday and southwesterly flow ahead of the front will help to decrease snowfall amounts by pushing snow bands offshore over the lakes, but periods of lake effect snow will remain possible each day through the end of the week.
Out West, mostly dry weather is expected through the end of the work week as high pressure builds across the region.
Strong Santa Ana winds will return to southern California today and persist through the end of the week.
High Wind Warnings and Wind Advisories are in effect through Wednesday for portions of southern California where 40-60 mph wind gusts are likely.
Anomalously cold air has surged across the CONUS and will likely stick around through at least the end of this week.
Temperatures are forecast to be 10-20 degrees below normal for most of the nation with some locations experiencing temperatures as low as 25 degrees below normal.
The coldest temperature anomalies will likely be in the Central U.S. behind a cold front that will move south on Thursday.
High temperatures below freezing will be common across the region Thursday and Friday. ■
Modified arctic air combined with a moisture-laden area of low pressure along the Gulf Coast will continue to allow for a broad area of winter weather impacts from the Lower Mississippi Valley to the Southeast today into early Saturday morning.