Short Range Forecast Discussion NWS Weather Prediction Center College Park MD 321 PM EDT Fri Jul 19 2019 Valid 00Z Sat Jul 20 2019 - 00Z Mon Jul 22 2019 ...Dangerous heat wave ongoing from the Central U.S. to the East Coast this weekend... ...Strong to severe thunderstorms and heavy to excessive rainfall possible tonight and Saturday across parts of the Upper Midwest and Great Lakes... The big story this weekend continues to be an oppressive and dangerous heat wave gripping much of the Central and Eastern U.S. where a large area of excessive heat warnings and heat advisories are in effect. Daytime temperatures in the mid to upper 90s combined with high humidity will result in heat indices as high as 115 for some. Even overnight will provide little relief as temperatures struggle to get below the upper 70s or even low 80s. This would challenge or break records for a large number of stations from the Midwest to the East Coast. A cold front dropping into the Central U.S. should bring some relief to portions of the Midwest this weekend, but dangerous heat will continue in the East through Sunday. Please see www.weather.gov for the latest on the coverage of warnings and advisories, and also tips on how to stay safe in this heat. A slow moving frontal boundary crossing the Great Lakes and Upper Midwest will focus convection this evening and overnight, with SPC highlighting central Minnesota to to northern lower Michigan within an enhanced to moderate risk for severe thunderstorms. The system should be fairly progressive which would limit a widespread flood threat, but heavy rainfall within thunderstorms may bring mainly localized flash flooding. The overall threat should shift just slightly southward on Saturday across Iowa to southern Michigan. Elsewhere, showers and thunderstorms are expected to increase across the Ohio Valley by Sunday along the frontal boundary, while much of the Southeast can expect the typical diurnally driven showers and storms. California and the Northwest should stay mostly dry and cooler than normal through the weekend. Santorelli Graphics available at www.wpc.ncep.noaa.gov/basicwx/basicwx_ndfd.php