Short Range Forecast Discussion NWS Weather Prediction Center College Park MD 206 AM EST Fri Feb 02 2018 Valid 12Z Fri Feb 02 2018 - 12Z Sun Feb 04 2018 ...Unsettled weather with locally heavy rain and snow will impact the Pacific Northwest and the Northern Rockies... ...Much colder temperatures are expected to set up across the Northern and Eastern U.S... ...A new storm developing over the Midwest will bring a threat of snow to areas of the Great Lakes, Central Appalachians and Northeast by the end of the weekend... The weather is expected to remain unsettled today and into the weekend across portions of the Pacific Northwest and spreading over the Northern Rockies as a series of storm systems over the Gulf of Alaska drop southeast and inland across the region. This will bring heavy rain for the coastal ranges of Washington state. However, for the higher terrain of the adjacent Cascades and especially the interior ranges of the Northern Rockies such as the Bitterroots and Tetons, expect heavy accumulating snow with locally as much as 2 to 3 feet of new snowfall through the weekend. Meanwhile, in the wake of a cold front pushing off the East Coast this morning, arctic high pressure over the Midwest will be advancing east and will allow daytime temperatures across much of the Eastern U.S. to drop to as much as 10 to 20 degrees below normal, and with many locations over the Ohio Valley, Mid-Atlantic and Northeast dropping to below freezing during the day. This area of high pressure will advance quickly east toward the Mid-Atlantic region on Saturday and then move offshore the East Coast by Sunday. This will allow temperatures to begin to moderate a bit as southerly winds begin to return. However, as this area of high pressure moves offshore, a complex storm system will be developing over the Central Plains and Middle Mississippi Valley as some of the energy impacting the Northwest U.S. drops southeast. Multiple waves of low pressure will impact the broader Midwest this weekend and foster a threat of accumulating snow across the Great Lakes, Central Appalachians and the Northeast. Generally a cold rain with possibly some some snow initially along with pockets of freezing rain can be expected over the Mid-Atlantic region. Heavier rain meanwhile is expected farther south from the Tennessee Valley south to the Gulf Coast states and parts of the Southeast as a separate area of low pressure impacts these areas and brings plenty of moisture in off the Gulf of Mexico. Much colder air with a reinforcing shot of arctic high pressure is then expected to drop south from Canada by Sunday and begin spilling over much of the Northern U.S. and with a particular focus on the Northern Plains and Upper Midwest. Daytime temperatures will only reach the single digits and nighttime lows will be well below zero. These temperatures coupled with the wind will result in dangerously cold windchill values. The remainder of the country is expected to see dry and tranquil weather through the weekend and this will include the Southwest U.S. where again temperatures will generally be above average. Orrison Graphics available at www.wpc.ncep.noaa.gov/basicwx/basicwx_ndfd.php