Short Range Forecast Discussion NWS Weather Prediction Center College Park MD 345 PM EDT Wed May 22 2013 Valid 00Z Thu May 23 2013 - 00Z Sat May 25 2013 ...Less than a month til summer but... ...Threat of snow continues for high elevations in the Northwest...and even a chance for the higher elevations of the Appalachians later Friday!... ...Slow moving front in the east will spread showers and thundershowers before much cooler air begins to move south and eastward from eastern Canada across the Midwest across the eastern US... ...Very cool conditions will remain across the Pacific Northwest... A highly amplified flow pattern for late May will allow snow to fall at the the higher elevations of the Northwest US over the next couple days. A deep upper low will move very slowly eastward keeping very cool conditions...numerous showers and higher elevation snow across the Northwest. Winter weather advisories are currently in effect across the Cascades...Blue Mountains and across NW Montana. Another trough moving eastward across the Mississippi Valley today will also move slowly eastward. This system will be reinforced by a strong upper level trough over eastern Canada that will result in a strengthening system over the East Coast by Friday. As colder air works its way into this system...there is a chance for a very late season snowfall across the high elevations of West Virginia/western Maryland and SW Pennsylvania...perhaps one of the latest occurrences on record if it occurs. Meanwhile...rain will fall across the upper Midwest over the next couple days before cooler drier air moves in. Over the Southeast...warm humid air and scattered showers and thundershowers will dominate the next several days. Heavier showers and thunderstorms are possible later in the forecast over the Middle Atlantic States to New England as the sharpening upper trough provides lift for abundant rainfall and even the possibility of some severe weather. See SPC discussions for more detailed discussions of the threat for severe weather. As cooler air makes its way southward across the Southern Plains...southeast flow from the Gulf of Mexico will increase the chance for showers and thundershowers across Texas into the Southern Plains on Thursday into Friday. Kocin Graphics available at www.wpc.ncep.noaa.gov/basicwx/basicwx_wbg.php