Short Range Forecast Discussion NWS Weather Prediction Center College Park MD 250 AM EDT Wed Sep 10 2014 Valid 12Z Wed Sep 10 2014 - 12Z Fri Sep 12 2014 ...Snow and Freezing Temperatures for the Northern Rockies... ...Severe thunderstorms and locally heavy rainfall possible from the mid Mississippi Valley to the Ohio Valley... An early outbreak of cold Canadian air will combine with return upslope flow to produce snow in the northern Rockies Wednesday. Winter storm warnings are in effect in the mountains of northwest Montana near Glacier National Park. Much colder temperatures will funnel further east across the northern Plains and upper Mississippi Valley. The downstream front in the midwest will be the focus for more showers and thunderstorms as the developing storm moves towards the Great Lakes Wednesday, resulting in large areas of showers and thunderstorms. Flood watches cover large portion of the area from the mid Mississippi Valley to the Great Lakes and adjacent Ohio Valley. As the cyclone moves into eastern Canada Thursday, showers and storms continue to develop in advance of the trailing cold front moving into the lower Mississippi Valley and Tennessee Valley, upper Ohio Valley, lower Great Lakes and central and northern Appalachians. A weak tropical wave drifting west from the Bahamas will aid sea and lake breeze boundaries and high available moisture in producing scattered to locally numerous showers in south Florida Thursday. Petersen Graphics available at www.wpc.ncep.noaa.gov/basicwx/basicwx_wbg.php