Short Range Forecast Discussion NWS Weather Prediction Center College Park MD 400 PM EST Fri Dec 15 2017 Valid 00Z Sat Dec 16 2017 - 00Z Mon Dec 18 2017 ...Heavy snow possible over portions of the Great Lakes... ...Well below normal temperatures from the Northern Plains to the Mid-Atlantic... ...Unsettled and wet conditions expected to persist the next few days for the Northwest U.S.... Upper level energy sweeping through the Deep South tonight and tomorrow will keep showers in the forecast from the Lower Mississippi Valley eastward through the Southeast. Embedded thunderstorms are possible along with moderate to locally heavy rainfall. Temperatures across the region will be below normal again on Thursday, eventually moderating to near normal by Friday. In the northern stream, a vigorous cold front dropping southward across the Midwest tonight will allow for mainly light accumulating snowfall across portions of the upper Great Lakes this evening and into Thursday. Favorable flow over the still relatively warm lakes however could bring some lake enhanced snows, especially across parts of the Upper Peninsula of Michigan where winter weather advisories and winter storm warnings are in effect for upwards of 6 inches of snow. The real story with this front however will be the modified arctic airmass being ushered in behind the front, initially across the Northern Plains, but eventually moving into the Ohio Valley and the Mid-Atlantic/Northeast by the end of the work week. Temperatures within this airmass will bring afternoon highs across these regions down as much as 10 to 20 degrees below normal. This could mean day time temperatures struggling to get out of the teens on Thursday, especially across far northern North Dakota and Minnesota. Finally, out west, a frontal system moving into the Pacific Northwest this afternoon will keep wet weather in the forecast across much of the Northwest states and into the Rockies through the rest of the week. Locally heavy rainfall will be possible for coastal areas of the Pacific Northwest and northern California, with snow expected in the highest elevations of the Cascades and into the Intermountain West/northern Rockies. Across northeast Washington and into northwest Montana, some light freezing rain may also be possible in some of the lower elevations. Santorelli Graphics available at www.wpc.ncep.noaa.gov/basicwx/basicwx_ndfd.php