Short Range Forecast Discussion NWS Weather Prediction Center College Park MD 411 PM EDT Thu Aug 12 2021 Valid 00Z Fri Aug 13 2021 - 00Z Sun Aug 15 2021 ...Stifling heat wave continues in the Northeast, Mid-South, and Pacific Northwest... ...Daily rounds of strong-to-severe storms from the Mississippi Valley and Great Lakes to the Northeast, monsoon showers and storms could lead to areas of flash flooding in the Southwest... ...Poor air quality due to wildfire smoke remains in the western and central U.S.;Tropical Depression Fred to reach the Florida Straits by the start of the weekend... Oppressively hot weather will continue through the work-week in the Northeast and the Pacific Northwest, as numerous Heat Advisories and Excessive Heat Warnings stretch over portions of these regions. In the East, heat indices could soar to 100 degrees over the majority of the region, with some locations including Boston, New York City, and Philadelphia approaching 105-110 degrees. Moreover, little relief from the heat is anticipated tonight across the East as very warm low temperatures hover in the mid-upper 70's to low 80's. Very hot and humid conditions also persist over the Central U.S. through at least today, before an approaching cold front ushers in more seasonal conditions on Friday, although the Northeast will have to wait until Saturday for cooler conditions to arrive. The Pacific Northwest will also bake as high temperatures soar into the triple digits, which will threaten daily numerous record highs tomorrow, including the Portland and Seattle metropolitan areas. By Saturday, the bulk of the hottest temperatures will shift east of the Cascades, where several daily records could be threatened once again. The aforementioned cold front will inch its way south and east over the next couple days across the eastern half of the Lower 48. The front's relatively slow movement results in daily episodes of widespread showers and thunderstorms from the central Plains to the Northeast. The best chance for organized severe weather lies just ahead of the front, specifically part of the Midwest and the Northeast today. An Enhanced Risk of severe weather is in effect over portions of eastern Ohio into Central Pennsylvania today, for an enhanced severe wind threat. Thunderstorm development is already underway across the region, and a Severe Thunderstorm Watch extends across the Northeast with the impending storms. A Slight risk also resides over the Missouri Valley today, also for a wind threat. Excessive rainfall rates are also possible given the unstable airmass in place ahead of the front, making it possible for areas of flash flooding to transpire. A Slight Risk of Excessive Rainfall partially overlaps the severe weather area today in Missouri/Illinois, where the most intense rain rates are expected. Elsewhere, the Gulf Coast can expect scattered showers and thunderstorms each afternoon and evening with locally heavy rainfall totals. In the Southwest, showers and thunderstorms will be a daily occurrence, helping to maintain temperatures at seasonally cooler levels. That said, some areas of flash flooding are possible due to a pocket of abundant atmospheric moisture centered over the region. Accordingly, a Slight Risk of Excessive Rain is highlighted over the portions of the Southwest every day through Sunday. In addition, wildfires and their coalesced area of smoke remains a problem for many residents in the West, most notably in the central Rockies and High Plains where Air Quality alerts remain in place. Farther north, the coolest temperatures in the mainland U.S. will be found in the Northern Plains thanks to cool air behind a pair of passing cold fronts. Last but certainly not least, eyes are turning to the tropics as Tropical Depression Fred is forecast to approach South Florida from Cuba Friday night. Forecast to reach the Florida Keys as a tropical storm, some squalls associated with the outer rainbands of Fred could begin to impact southern Florida on Friday. These squalls out ahead of Fred would likely contain heavy downpours, where a Slight Risk of Excessive Rainfall from Saturday-Sunday is in effect. Please visit the National Hurricane Center homepage for the latest forecast information on Tropical Depression Fred. Asherman/Mullinax Graphics available at www.wpc.ncep.noaa.gov/basicwx/basicwx_ndfd.php