Short Range Forecast Discussion NWS Weather Prediction Center College Park MD 404 AM EDT Thu Aug 30 2018 Valid 12Z Thu Aug 30 2018 - 12Z Sat Sep 01 2018 ...Heavy rain and severe weather possible for the Mississippi Valley... ...Heat wave to continue across the Mid-Atlantic and Northeast... ...Fire weather concerns begin to resurface across the western U.S.... A strong cold front is slowly moving south and east, stretching from New England to the central and Southern Plains. As this boundary slows and stalls across the Mid-Atlantic and into the Middle Mississippi Valley today, more rounds of showers and thunderstorms are expected along the boundary. Some of these thunderstorms could produce locally heavy rainfall--thus a marginal risk of flash flooding is possible from the Mid Atlantic inland through the Tennessee Valley today. Meanwhile, a portion of the front across the Southern and Central Plains will shift northward and transition into a warm front today, guided by a developing area of low pressure. As this frontal boundary continues to traverse eastward across the Plains and towards the Mississippi River Valley, thunderstorms capable of producing heavy rainfall are forecast for tonight night and Friday morning. The combination of heavy rain potential and already saturated soils have led to a slight risk of flash flooding for the middle Missouri Valley this evening and overnight. The Storm Prediction Center has also issued a marginal risk of severe thunderstorms stretching from Southern Minnesota southward into eastern Kansas and western Missouri during this time frame as well. By Friday, the cluster of storms will continue impacting the middle Mississippi Valley, especially as the center of low pressure continues to strengthen, and a deep layer of warm moist air is lifted northward from the Gulf of Mexico aiding in storm development. This will be further exasperated by another cold front dropping southeast from Canada into the northern Plains, bringing with it a surge of colder air. The clash of the two air masses could lead to strong storms across the Mid and Upper Mississippi Valleys as well as into the far western Plains. This area has been outlined as being in a slight risk for severe thunderstorms by the Storm Prediction Center for Friday. The Weather Prediction Center has also outlined much of the Upper and Mid Mississippi Valleys as being in a slight risk for flash flooding as well. With the upper ridge being the dominant feature across the Southeast, temperatures across the Northeast and Mid-Atlantic will still be well above normal through Thursday. Heat advisories and excessive heat warnings are in place through this evening. By Friday, once the cold front pushes across these regions and stalls to the south, temperatures will drop significantly. Meanwhile, precipitation will linger across the area into the weekend. This will bring high temperatures down--and end the heat advisories. Elsewhere across the U.S., fire weather concerns will be possible across the Pacific Northwest, Intermountain West and Great Basin through Friday. Red Flag Warnings and Fire Weather Watches are in place across much of Wyoming, northwest Colorado and a small portion of Utah through Thursday due to low relative humidities and gusty winds. Southwest Oregon is also still under an Air Quality Alert due to smoke from a nearby wildfire. Wix Graphics available at www.wpc.ncep.noaa.gov/basicwx/basicwx_ndfd.php