Short Range Forecast Discussion NWS Weather Prediction Center College Park MD 355 PM EDT Sun Aug 18 2024 Valid 00Z Mon Aug 19 2024 - 00Z Wed Aug 21 2024 ...Severe thunderstorms and flash flooding are expected for portions of the Mid-Atlantic into the Northeast Through Monday... ...Some relief expected for the central Gulf Coast early this week but dangerous heat and humidity to continue across the Southern Plains... ...Increased risk for spreading of wildfires from central Nevada into southeastern Oregon through Tuesday... A slow moving cold front, extending from western New York/Pennsylvania into the Gulf Coast states, will gradually translate east over the next one to two days, clearing a majority of the East Coast by Tuesday morning. Along and ahead of the cold front, anomalous moisture and thunderstorms repeating over the same locations will pose a threat for flash flooding with the greatest flash flood concern from the northern Mid-Atlantic into southern New England this evening and tonight. Severe thunderstorms will also be possible ahead of the cold front with the greatest risk being straight line winds, extending from the northern Mid-Atlantic into the Southeast, Gulf Coast states and portions of the central Plains through Monday morning. Conditions will improve in the wake of the cold front with a significant cooling trend for the Midwest and Northeast through Tuesday with high temperatures forecast to be 10 to 20 degrees below mid-August averages. High heat and surface dewpoints will persist across the southern U.S. beneath the influence of an upper level ridge centered over the southern High Plains through at least mid-week. Excessive Heat Warnings and Heat Advisories are already in place from southern Kansas into Oklahoma and Texas, eastward to the central Gulf Coast. Daytime temperatures combined with high humidity will result in heat index values ranging from 105 to locally over 115 degrees for portions of the region. A southward sagging cold front will bring cooler temperatures into the lower Mississippi Valley beginning tomorrow and continuing into Tuesday, but the heat will remain through at least mid-week for Texas, eventually spreading into New Mexico. Out West, another slow moving cold front, located over the interior of the Northwest, will remain nearly stationary until Tuesday. Temperatures from northern California into Oregon and Washington (west of the boundary) will experience high temperatures roughly 5 to 15 degrees below average along with some rain for western Washington. East of the boundary however, hot temperatures will not be the big concern but rather dry and windy conditions favoring increased risks for wildfires from central Nevada into southeastern Oregon and adjacent locations. Due to the slow movement of the upper pattern, these conditions will remain in place for multiple days. The southwestern U.S. will see monsoonal moisture continuing to favor a risk for short term heavy rain capable of localized to scattered areas of flash flooding. The flash flood risk will overlap with a risk of severe thunderstorms from Utah and portions of eastern Idaho and western Wyoming this evening, with the overlapping risk extending east into east-central Colorado for Monday. On Tuesday, the threats for severe thunderstorms and flash flooding appear lower but a localized threat will remain for the Desert Southwest into portions of Montana ahead of the aforementioned cold front. Otto Graphics available at https://www.wpc.ncep.noaa.gov/basicwx/basicwx_ndfd.php