Short Range Forecast Discussion NWS Weather Prediction Center College Park MD 334 AM EDT Sat Jul 12 2014 Valid 12Z Sat Jul 12 2014 - 12Z Mon Jul 14 2014 ...A very active weather pattern for many areas of the US with heavy rain and strong thunderstorms affecting areas of the Rocky Mountains, the Central Plains into the Midwest and Ohio Valley... ...Hot weather will be building across the Far West as temperatures climb past 100 across interior California and into the 90s into western Washington... ...On the flip side of the coin, unusually cool air for July will begin pushing into the Northern Plains by Saturday night. By late Monday, the coolest air in North America will be located over the upper Midwest... A monsoonal flow pattern over the western US will bring moisture northward across the Desert Southwest, Great Basin and central and southern Rockies. With afternoon heating, widespread but scattered thunderstorms will develop again over this region especially over the high terrain, where the threat for flash flooding and fire weather due to lightning strikes will persist for the next several days. While some of the monsoonal moisture will even work its way into the Pacific northwest, temperatures will be rising over the next several days with temperatures exceeding 100 degrees over northern interior California, 90s into Portland and near 90 degrees in Seattle. As the heat builds in the west, cooler air more typical of September or October will make its way southward over Canada, reaching the Northern Plains on Saturday night and reaching across much of the Central and Northern Plains, the middle and upper Mississippi Valley and into the Midwest by Monday night. With cold air aloft, instability showers and thundershowers may also accompany the chilly airmass that will drop temperatures to autumn levels even during the day on Monday. In between the advancing cooler air and a pool of stagnant hot air across the Southern Plains, the monsoonal moisture moving northward across the Rockies accompanied by weak upper level disturbances will generate pulses of heavy rain and thunderstorms from the Central Plains eastward across the mid Mississippi Valley on Midwest on Saturday. With the cold front advancing eastward, the thunderstorms will also move eastward, affecting the Ohio Valley and Northeast on Sunday. As the main core of the cooler air drops into the US on Monday, a widespread outbreak of thunderstorms and possible severe weather may affect parts of the Midwest and East on Monday into Tuesday. Kocin Graphics available at www.wpc.ncep.noaa.gov/basicwx/basicwx_wbg.php