Short Range Forecast Discussion NWS Weather Prediction Center College Park MD 431 PM EDT Wed May 29 2013 Valid 00Z Thu May 30 2013 - 00Z Sat Jun 01 2013 ...Slight risk of severe thunderstorms this evening for portions of the Northeast... ...Slight to moderate risk of severe thunderstorms and a slight risk of flash flooding through tonight for much of the central U.S... ...Hot conditions expected Thursday and Friday for much of the Northeast and Mid-Atlantic states... A very busy weather pattern will remain in place across the contiguous U.S. through the end of the work week. An upper-level trough across the western half of the nation today will close off into an upper-level low on Thursday. As a result, areas across the central U.S. being affected by showers and thunderstorms will see these conditions continue through Friday. A strengthening surface low pressure system across the High Plains this afternoon. The addition of plenty of moisture from the Gulf of Mexico, a dryline, and a strong jet stream overhead is resulting in the development of widespread thunderstorms across the central U.S. The Storm Prediction center is forecasting a slight to moderate risk of severe thunderstorms across much of the central U.S. through tonight. Please refer to the Convective Outlooks products issued by the Storm Prediction Center for further details on the severe weather threat. In addition, flash flooding will be a distinct threat due to very heavy rainfall in thunderstorms, some of which may track over the same locations repeatedly. As the upper-level low closes off on Thursday, the surface frontal system will slow or even become partially stationary over the central and southern Plains. The result will be further rounds of thunderstorms across the central U.S. on Thursday and even into Friday. A warm front moving northward across the Northeast this afternoon will result in showers and thunderstorms through this evening. The Storm Prediction Center is forecasting a slight risk of severe thunderstorms for this region as well. Showers and thunderstorms should come to an end for this area by early Thursday morning as the frontal boundary moves northward into Canada and an upper-level ridge of high pressure builds into the eastern U.S. While this ridge will result in dry conditions across the Mid-Atlantic and Northeast, subsiding and warming air beneath the ridge will result in above average temperatures, with afternoon high temperatures rising into the 90s for many locations in the Mid-Atlantic and the lower elevations of the Northeast. Across the western U.S., scattered precipitation will occur from the Pacific Northwest into the northern Rockies beneath the upper-level trough, as a series of weak Pacific storm systems move onshore. Snow levels will drop some by Thursday into Friday, as low as 5000 to 6000 feet in the Pacific Northwest and 7000 to 8000 feet in the northern Intermountain West. Thus, generally scattered snow showers will be possible at the higher elevations while rain showers will occur in most areas. Ryan Graphics available at www.wpc.ncep.noaa.gov/basicwx/basicwx_wbg.php