Short Range Forecast Discussion NWS Weather Prediction Center College Park MD 353 PM EDT Sat Aug 15 2020 Valid 00Z Sun Aug 16 2020 - 00Z Tue Aug 18 2020 ...Heat wave continues across the western third of the Lower 48 with record breaking heat, sizzling temperatures in the Southern Plains dip back to more seasonal levels the first half of the week.. ...A Moderate Risk for excessive rainfall continues from the central/southern Appalachians to the Mid-Atlantic as flooding rains transpire this evening and into Sunday morning... ...Severe storms possible in portions of the Upper Midwest and Plains, seasonally cool temperatures to stick around in the Mississippi Valley into the start of next week... The heat wave across the western third of the U.S. looks to continue through the remainder of the weekend and into the start of the upcoming week. There are no shortage of Excessive Heat Warnings/Watches and Heat Advisories from the U.S./Mexico border on north to the U.S./Canada border. Highs this afternoon and through Sunday will surpass the century mark from the Pacific Northwest down to the Desert Southwest where highs in excess of 115 degrees are possible. Expect some daily record highs and warm lows to be broken up and down the West Coast and into the Intermountain West. In addition, parts of the Southern Plains will also contend with sweltering temperatures through the remainder of the weekend, but a cold front looks to put a dent in the overly hot conditions by the start of the work-week. While the Pacific Northwest begins to experience the return of a slightly cooler and more maritime air-mass, the massive dome of high pressure over the Great Basin will not back down, keeping excessively hot conditions in the forecast across much of the northern Rockies, the Great Basin, and the Southwest. Lastly, Red Flag Warnings are in place across portions of the Pacific Northwest due to dry thunderstorms that could take advantage of favorable fire weather conditions that include very low humidity and gusty winds. In the East, a wave of low pressure over the southern Appalachians this afternoon advances east along a stalled frontal boundary towards the Mid-Atlantic coast this evening. Along and north of the the front, heavy downpours embedded within strong thunderstorms could lead to flash flooding in parts of the Mid-Atlantic. A Moderate Risk for flash flooding remains in place across parts of southern Virginia and northern North Carolina with a Slight Risk that extends from the central Appalachians to the North Carolina Outer Banks. Heavy rainfall may last into the day on Sunday as low pressure sits off the DelMarVa coast. Seasonally cool temperatures will also be common from the Carolinas to New England on Sunday thanks to onshore easterly flow. Periods of rain may extend up the Northeast coast Sunday evening and exit out to sea by Monday morning, but an approaching cold front will help to trigger scattered afternoon showers and thunderstorms from the Northeast to the Carolinas Monday afternoon. In the Nation's Heartland, severe storms are possible this afternoon and evening in northern Minnesota and the central High Plains. Slight Risks are in place due to the severe weather threat, including a Marginal Risk in the Middle Mississippi Valley. A frontal system responsible for today's severe weather potential in the Plains is the focal point for initiating showers and thunderstorms from northern Texas to the Midwest on Sunday. The other story in the Heartland is the continuation of cooler than normal temperatures. A slight bump to abnormally warm temperatures on Sunday should occur in parts of the Midwest, but a cold front sweeping across the region will inject yet another surge of below normal temperatures into the Mississippi Valley on Monday that looks to linger the middle of the week. Mullinax Graphics available at www.wpc.ncep.noaa.gov/basicwx/basicwx_ndfd.php