Short Range Forecast Discussion NWS Weather Prediction Center College Park MD 325 AM EDT Thu Sep 11 2014 Valid 12Z Thu Sep 11 2014 - 12Z Sat Sep 13 2014 ***Strong cold front brings major temperature changes*** ***Wintry weather for parts of the northern Rockies*** A major pattern change is underway across the country as a cold airmass from Canada surges across the Plains, upper Mississippi Valley, and Great Lakes. The anomalously strong high at the center of the cold air mass is forecast to move out of the northern Rockies and down the Plains. The potential exists for record low temperatures from the northern Rockies to the Upper Midwest for the end of the week. The cold air will continue working its way towards the southern Plains and Ohio Valley Thursday into Friday, although it will gradually modify with time. The front will eventually stall in the southeast and waves of low pressure moving along the front may cause a period of showery weather Thursday night and Friday. As the cold front crosses the northern Rockies, a storm will cause higher elevation snows in parts of Montana, Wyoming, and the Black Hills of South Dakota, eventually reaching into the mountains of northern Colorado. Freeze warnings are in effect for valley areas in parts of Montana and Wyoming. Frost advisories are in effect for parts of northern North Dakota and Minnesota. Elsewhere across the continental U.S., widespread showers and thunderstorms are likely ahead of the cold front across the southern Plains, and extending to the Mid-Atlantic region. Once the storm causing the northern Rocky Mountain snows moves east, rain and showers will develop over the central Plains Friday and move northeast towards the upper Mississippi Valley and upper Great lakes Friday and Friday night. A few weak tropical waves should bring a threat of showers to south Florida and also far southern Texas. Petersen Graphics available at www.wpc.ncep.noaa.gov/basicwx/basicwx_wbg.php