Short Range Forecast Discussion NWS Weather Prediction Center College Park MD 338 AM EST Tue Dec 03 2013 Valid 12Z Tue Dec 03 2013 - 12Z Thu Dec 05 2013 ...Heavy snow will be possible across the Wasatch, Colorado Rockies, and San Juans through Thursday morning... ...Significant snow and ice accumulations are expected over the Northern Plains, Upper Midwest, and Great Lakes region... ...Well below normal temperatures will affect the Western/Central U.S... It will continue to be a very busy weather pattern during the first full week of December. The current National Weather Service hazards map shows winter storm warnings and advisories in place over a significant portion of the higher topography across the Western U.S. while extending eastward through the Northern Plains/Upper Midwest. The culprit is a strong upper low which is currently dropping southward across the Upper Intermountain West. Over the course of the next 12 to 24 hours, this system should split into two with one feature dropping south across the Central Great Basin while the other migrates eastward toward the Northern Plains. With regard to the batch of energy moving through the Intermountain West, strong vertical lift in response to the upper low combined with favorable upslope flow will lead to areas of enhanced snowfall. The region of the most persistent ascent will be across the Wasatch, Colorado Rockies, and San Juans where amounts ranging from 1 to 2 feet will be possible. Given the air mass settling into place will sufficiently lower the local snow levels, many valley locales can expect accumulating snows. Looking to the northern tier of the country, it will also be quite active given the trof energy migrating from the Northern Rockies toward the Upper Midwest. Unlike the system to the west, this region of the nation will have better access to low-level moisture as the return flow continues from the Gulf of Mexico. A slow-moving frontal system advancing through the middle of the country will consist of a myriad of surface waves riding along the boundary. Large upward vertical motions are expected just north and west of the surface waves which will aid in moderate to heavy snow production. It appears the heftiest snowfall totals are expected across eastern Minnesota extending into northern Wisconsin and the upper peninsula of Michigan where over a foot is possible. The other facet of this winter storm will be the threat for ice accumulations. A tongue of milder air overriding a modified arctic air mass at the surface will bring the threat for freezing rain from central Wisconsin into the lower Great Lakes. The other headliner with this winter storm is the frigid air invading the Western/Central U.S. By mid-week, high temperatures are forecast to struggle to get above the 0 degree Fahrenheit mark across the Northern Rockies/Northern Plains while lows plunge well into the negative 10s/20s. Locations further west will not be spared either as highs are only in the 20s across the Central Great Basin while 50s more commonplace along the West Coast. The persist onshore flow from the Gulf of Mexico will bring scattered showers and thunderstorms to the southeastern U.S. No significant mechanism aloft will be present to focus a more organized event. Thus, coverage will remain on the scattered side with rainfall amounts on the lower end of the spectrum. Rubin-Oster Graphics available at www.wpc.ncep.noaa.gov/basicwx/basicwx_wbg.php