Short Range Forecast Discussion NWS Weather Prediction Center College Park MD 239 AM EST Fri Jan 05 2018 Valid 12Z Fri Jan 05 2018 - 12Z Sun Jan 07 2018 ...An arctic outbreak will keep temperatures 20 to 30 degrees below average across the northeastern U.S... ...Wet conditions expected from northern California into the Pacific Northwest... ...A threat for accumulating ice is likely over interior Washington/Oregon... Early this morning, a powerful Nor'easter was lifting into Nova Scotia spreading heavy snow and intense wind fields to far eastern Canada. While conditions have begun to improve across the northeastern U.S., the arctic surge is already underway accompanied by brisk winds at times. Dangerously low wind chill temperatures are to be expected the next couple of days with some blowing snow possible. The current National Weather Service hazards map features a combination of wind chill advisories and warnings extending from the upper Midwest across the Great Lakes/Ohio Valley and from the Carolinas northward. Forecast high temperatures through Saturday will struggle to get above the single digits across the Upper Midwest, Great Lakes, central/northern Appalachians, and much of New England. This easily reaches the 20 to 30 degree below climatology range which supports a chance for many daily temperature records to be broken. Frigid temperatures also extend down into the southern U.S. as lows plunge into the 20s down along the eastern Gulf Coast and into central Florida. Many daily records may be broken across this sector of the country as well. The persistent shots of arctic air will provide further chances for lake effect snows into the weekend. Extremely cold temperatures aloft moving over many unfrozen lake surfaces will foster the development of widespread snow showers over all the major Great Lakes. Per recent observations, just under a quarter of the lakes are frozen, particularly the western section of Lake Erie. Based on the latest forecast, the heaviest snow is expected to be southeast of Lake Ontario with 6 to 10 inch amounts possible. This would affect areas anywhere from Rochester to Syracuse, New York. A broad upper trough across the eastern Pacific will push toward the Pacific Northwest increasing the threat for coastal rains and higher elevation snows. Multiple disturbances moving inland will act to keep wet conditions in place with a broad area of 1 to 2 inches of precipitation expected across the Washington Cascades. During the next couple of days, many mountain ranges over the western U.S. should see accumulating snows with the highest amounts likely over the Colorado Rockies with the potential for over a foot. Meanwhile, maritime flow overriding a sub-freezing surface layer should make conditions favorable for freezing rain across sections of central/eastern Washington down into eastern Oregon. While the eastern states will continue to be impacted by another arctic surge, mild conditions are likely from the Four Corners northward along the High Plains. Downsloping flow is forecast to bring well above normal temperatures for these locations into the weekend. By Saturday, expect highs to reach the upper 40s up into the Black Hills which would be around 15 to 20 degrees above climatology. However, heading east away from the downsloping regime will bring readings back into the teens on the far eastern side of the northern Plains. Rubin-Oster Graphics available at www.wpc.ncep.noaa.gov/basicwx/basicwx_ndfd.php