Short Range Forecast Discussion NWS Weather Prediction Center College Park MD 326 PM EST Wed Dec 04 2013 Valid 00Z Thu Dec 05 2013 - 00Z Sat Dec 07 2013 ...Heavy snow and icing will continue to affect the Upper Midwest and Upper Great Lakes on Wednesday... ...A major icing event is expected across the Arklatex and into southern sections of Missouri and Illinois beginning midday Thursday... ...An arctic intrusion will bring well below normal temperatures to much of the western/central states... The active period of weather will persist through the short range forecast period extending until the end of the work week. The current National Weather Service hazards graphic is quite colorful with winter storm warnings and advisories extending from the Wasatch and Central/Southern Rockies up through the Northern Plains and Upper Midwest. Areas of Minnesota have already reported 1 to 2 feet of snow with more to come as a surface wave deepens while tracking from the Middle Mississippi Valley to the Upper Great Lakes on Wednesday. Strong vertical motions occurring to the north and west of this low track will bring another round of heavy snowfall to the northern tier of the country. The current WPC winter weather graphics indicate another 1 to 4 inches will be possible over northeastern Minnesota and extending into the Upper Peninsula of Michigan. Low-level temperature profiles will also remain favorable for a wintry mix along the rain/snow line interface. It appears the best chance for ice accumulations will occur from southeastern Minnesota up through sections of the Upper Great Lakes. Beginning midday Thursday, a potentially major icing event will be possible anywhere from the Southern Plains through the Ozarks and into the Lower Ohio Valley. The upper trof which has settled over much of the western and central U.S. has brought a significant shot of arctic air to these regions. The depth of this cold air will be rather shallow in nature with milder return flow from the Gulf of Mexico overriding this air mass. As precipitation will be ongoing when this occurs, many locations across the Arklatex will begin to see a wintry mix with freezing rain being of paramount concern. A quarter inch of ice accumulations are in the forecast from northeastern Texas through the Ozarks and into southeastern Missouri. Of course any sufficient icing may lead to a disruption in infrastructure including treacherous travel on roads and issues with aviation. Please visit the National Weather Service homepage at www.weather.gov for the most up to date information for more local concerns. The aforementioned arctic intrusion has brought temperatures to dangerously low values, particularly across the Northern Rockies and Northern Plains. During the next couple of days, forecast highs over these regions are in the negative single digits while lows plunge into the -20s Fahrenheit. Adding the element of wind will lower the apparent/wind chill temperatures to the -30s over areas of Montana and North Dakota. There will be quite the temperature contrast along the arctic front with upper 70s/lower 80s along the Gulf Coast while the northern tier is plagued by the frigid readings. Not even southern California will be spared from the surge of cold air. Hard freeze warnings are in effect for much of the Central Valley and cities such as San Diego will near record low temperatures. Elsewhere, a frontal system working its way through the Four Corners region will bring steady snowfall to the Central/Southern Rockies with accumulations being maximized across the San Juans. Looking out to the eastern states, the arctic boundary will eventually become a focal point for light to moderate rainfall over much of the Tennessee/Ohio valleys by Thursday afternoon/evening and continue into Friday. With colder air slowly filtering into the region a changeover to snow will occur on Friday across the lower Great Lakes. Krekeler/Rubin-Oster Graphics available at www.wpc.ncep.noaa.gov/basicwx/basicwx_wbg.php