Short Range Forecast Discussion NWS Weather Prediction Center College Park MD 351 AM EST Fri Feb 20 2015 Valid 12Z Fri Feb 20 2015 - 12Z Sun Feb 22 2015 ***Ridge out West and trough over the East*** ***Bitterly cold on Friday for eastern U.S., then warmer*** ***Developing storm system over the southern U.S.*** The overall weather pattern through the end of the week will continue to be featured with a pronounced and anomalous upper level trough over the eastern half of the country, and a big upper level ridge for the western states. This will keep most of the West Coast, the Great Basin, and the Desert Southwest warmer and drier than normal, and the central and eastern parts of the U.S. much colder than normal. Over the eastern half of the nation, we all know that it has been quite cold over the past week. An eddy of the polar vortex is leading to the coldest weather of this recent cold spell, creating a deep layer of bitterly cold air along with gusty winds. There were widespread subzero overnight lows Thursday night extending from Illinois to western Virginia, and numerous record lows were set! Highs on Friday will struggle to get out of the teens from the Ohio Valley to the Mid-Atlantic region. After Friday, temperatures are forecast to moderate and get closer to February averages as a storm system approaches from the west. In the precipitation department, a developing surface low over the southern Plains will tap moisture from the Gulf of Mexico, and result in an expanding area of rain, freezing rain, sleet, and snow from the Deep south to the Ohio Valley by Friday night. Another sleet and freezing rain event is expected from Missouri to northern Georgia, before a change-over to rain happens later on Saturday. This will reach the East Coast by Saturday, with snow changing to a wintry mix and eventually to rain for many areas of the Mid-Atlantic. Elsewhere, upslope flow near the eastern side of the Rockies will likely lead to light snow for the region on Friday and Saturday. D. Hamrick Graphics available at www.wpc.ncep.noaa.gov/basicwx/basicwx_wbg.php