Short Range Forecast Discussion NWS Weather Prediction Center College Park MD 248 AM EST Tue Feb 04 2025 Valid 12Z Tue Feb 04 2025 - 12Z Thu Feb 06 2025 ...Unsettled weather to persist across the Northwest U.S. through the middle of the week much colder temperatures and heavy snowfall across the Cascades and the northern Rockies... ...An atmospheric river will continue to stream across northern and central California over the next couple of days with additional heavy rains and concerns for flooding... ...New storm system to bring a threat for light snow, sleet and freezing rain to portions of the Ohio Valley and the Mid-Atlantic region by Thursday... ...Record high temperatures are expected across much of the Southern U.S. over the next few days... A persistent deep layer low center and associated trough axis will continue to impact the Pacific Northwest and the northern Rockies going through the middle of the week which will continue to support widespread unsettled weather. Moist onshore flow into the higher terrain coupled with colder temperatures continuing to settle south from southwest Canada will maintain a threat for locally heavy snowfall across the Cascades and the snow levels will be low enough to support heavy snowfall also for the coastal ranges and some of lower elevations given the depth of cold air that will be in place. Heavy snowfall is also expected to continue farther inland into the interior mountain ranges such as the Sawtooth, Bitterroots, Tetons and Absaroka Range. Much of this snowfall will be connected to the persistent and strong atmospheric river that will continue to impact central and northern California over the next couple of days. Additional snowfall accumulations of 1 to 2 feet will be possible over the Cascades and the northern Rockies with locally heavier totals through early Thursday. The aforementioned atmospheric river impacting California will only gradually settle southward through the middle of the week as multiple waves of low pressure traverse the front and bring strong Pacific moisture transport into the coastal ranges, portions of the Central Valley, and the foothills of the Sierra Nevada. This will result in more heavy rain for the region with concerns for flooding which will also include the Bay Area. An additional 2 to 4 inches of rain is expected for the coastal ranges, with 3 to 6+ inches for the Sierra Nevada foothills. The Weather Prediction Center has maintained a Slight Risk (level 2 of 4) of excessive rainfall across the region to account for this. Meanwhile, for the highest elevations of the central and northern Sierra Nevada, as much as 1 to 3 feet of new snowfall is expected. Farther off to the east, the story going through today and Wednesday will be Arctic high pressure nosing southward across the northern Plains and Midwest, with this airmass in a moderating fashion gradually pushing east across the Great Lakes region and Northeast in behind a cold front. This cold air will be in place though ahead of a new storm system approaching the Ohio Valley and Mid-Atlantic region by Wednesday night and Thursday which is expected to drive a concern for some light snowfall, but also a swath of sleet and freezing rain. Hazardous winter weather driving conditions are expected across these areas. Temperatures across the Northwest U.S. and stretching east across the northern Plains will remain well below normal and especially areas of Montana where sub-zero temperatures are expected through the middle of the week. Locally the high temperatures will be as much as 10 to 20 degrees below normal. However, for areas south of the Arctic front involving the southern tier of the nation from the Southwest east across the southern Plains, Mid-South and Southeast, record high temperatures are expected with numerous locations expected to see temperatures reaching into the 80s which will be locally 20 to 30+ degrees above normal for this time of year. Orrison Graphics available at https://www.wpc.ncep.noaa.gov/basicwx/basicwx_ndfd.php