Short Range Forecast Discussion NWS Weather Prediction Center College Park MD 413 PM EDT Mon May 15 2017 Valid 00Z Tue May 16 2017 - 00Z Thu May 18 2017 ...Conditions will be wet and cool with a storm system entering the Pacific Northwest Monday night...with late season snow expected over the higher elevations... ...Heavy rain and severe thunderstorms will be possible from the Southern/Central Plains to the Upper Midwest the next few days... ...Temperatures will be well above normal beneath an upper ridge shifting eastward from the Upper Midwest to the Great Lakes and Ohio Valley... Conditions will be wet and cool with a vigorous upper low expected to drop from the Pacific Northwest to the Central Great Basin and Rockies over the next few days. A strong surge of Pacific moisture ahead of the system should allow for periods of heavy precipitation over the favored terrain of the Pacific Northwest and northern Rockies Monday night into Tuesday...and lowering temperatures behind the associated cold front should lead to late season snowfall accumulations over the higher elevations. Heavy rain and strong to severe thunderstorms will be possible from the Southern/Central Plains to the Upper Midwest early this week as anomalous Gulf moisture continues to pull northward ahead of a mean Western U.S. upper trough. The greatest threat for excessive rainfall should be across the Upper Mississippi Valley...where the anomalous moisture will interact with multiple shortwaves and surface lows lifting through the region. However...heavy downpours will be possible within convection developing ahead of a dry line/cold front pressing through the Southern and Central Plains. Please refer to the Storm Prediction Center for the latest details on severe weather (www.spc.ncep.noaa.gov). Temperatures will be well above normal beneath and upper ridge centered over the Upper Midwest on Tuesday...with the heat and humidity expected to shift to the Great Lakes and Ohio Valley as the ridge shifts downstream on Wednesday. Gerhardt Graphics available at www.wpc.ncep.noaa.gov/basicwx/basicwx_ndfd.php