Short Range Forecast Discussion NWS Weather Prediction Center College Park MD 328 AM EDT Thu Jul 16 2015 Valid 12Z Thu Jul 16 2015 - 12Z Sat Jul 18 2015 ...Low humidities and comfortable temperatures will persist over the eastern US for a day or two and then it will become more humid as high pressure moves offshore... ...Severe thunderstorms and flash flooding are possible for portions of the Central and Northern Plains and Mid Mississippi Valley... ...Above average temperatures are expected from the Southern and Central plains to the Southeast... ...Cooler temperatures are forecast over the Northwest into the northern Rockies... High pressure will continue to build in across the eastern US on Thursday before moving offshore on Friday. Comfortable temperatures and low humidity will give way to increasing humidity on Friday as the high pressure cell moves offshore. A diffuse system of weak upper level disturbances will be associated with an area of low pressure and will spread locally heavy thunderstorms across the Mid Mississippi Valley, Northern Plains and Midwest. There is also the slight threat for severe thunderstorms across portions of Iowa, northeast Missouri and Illinois on Thursday. As an upper trough deepens across the northwestern quarter of the nation, a slight risk of severe weather will shift westward to the Central and Northern Plains with the highest risk in eastern Nebraska, South Dakota and southwestern Minnesota on Friday. Hot and humid conditions underneath a nearly stationary upper level ridge will continue across the Southeast into the Southern Mississippi Valley and across the Southern Plains. There will be little risk of rainfall especially across much of Texas, southern Oklahoma into Arkansas and Louisiana. Temperatures will mostly be in the 90s to near 100 degrees with high humidity. On the western edge of the hot southern upper ridge, a monsoonal flow of moisture will feed northward from western Mexico across the Southwest into portions of the Rocky Mountains, where best chances for thunderstorms remain in the afternoon and evening. A rather significant upper trough will drop south and eastward from western Canada across the northwestern United States and will be associated with cooler temperatures behind the front as well as an enhanced chance of showers and thunderstorms out ahead of the front. These showers and thunderstorms are likely to form across northern Nevada into southeastern Idaho and into Wyoming and Montana. Kocin Graphics available at www.wpc.ncep.noaa.gov/basicwx/basicwx_wbg.php