Short Range Forecast Discussion NWS Weather Prediction Center College Park MD 410 PM EDT Wed Jul 18 2018 Valid 00Z Thu Jul 19 2018 - 00Z Sat Jul 21 2018 ...Heavy rain and severe thunderstorms possible across the North-Central United States through the end of the work week... ...Showers and thunderstorms will continue across the Southeast through the end of the work week... ...Excessive heat will continue to pose concern across much of the western and south-central United States... A low pressure system currently over the Central Plains will continue to deepen as it shifts east-northeastward through the Northern Plains and towards the Upper Mississippi Valley by the end of the work week. As this low deepens, a strong pull of warm, moist air from the Gulf of Mexico will result in the development of a fairly strong warm front, and then eventually a cold front as a colder air gets pulled in from Canada. This system will also be the epicenter for shower and thunderstorm development across this region. The Storm Prediction Center has outlined an enhanced risk for severe thunderstorm development across portions of the Central and Northern Plains for this afternoon through tonight. A marginal and slight risk have also been outlined across portions of the Mid Mississippi Valley for Thursday, shifting eastward into the Ohio Valley for Friday ahead of the developing cold front. Excessive rainfall and flash flooding will be possible with these storms as well. The Weather Prediction Center has also outlined portions of the northern Missouri River Basin as being in a marginal to slight risk of excessive rainfall this afternoon and tonight. Portions of the Upper Mississippi River Valley have a marginal to slight chance of excessive rainfall on Thursday. Meanwhile, the ongoing quasi-stationary front extending from the Southern Mid-Atlantic into parts of the Southern Plains will slowly dissipate over the Southern Plains/Lower Mississippi Valley by Thursday night, while the boundary over the Southeast remains but stalls. This front will be the epicenter for shower and thunderstorm development across the Southeast and southern Mid-Atlantic coast through the end of the work week. The Weather Prediction Center has a marginal risk of excessive rainfall across portions of these areas through the end of the week. In addition to the thunderstorm and excessive rainfall concerns, heat is also impacting many states across the U.S. A strong pull of warm air into the central portion of the United States is currently leading to well above normal temperatures in addition to high humidity values. This will only increase as the above mentioned low pressure system continues to gain strength. Large portions of the Southern Plains, Lower Mississippi Valley, as well as some locations in Nebraska and Missouri are under Heat Advisories and Warnings through the end of the work week as a result. Furthermore, much of the western United States is also feeling the effects of excessive heat. Excessive heat watches, advisories, and warnings are all in effect across California, portions of the extreme Southeast, and the Central Great Basin. Wind is aiding to the problem farther north, with Red Flag Warnings posted across portions of the Northwest and into the Northern Rockies. Wix Graphics available at www.wpc.ncep.noaa.gov/basicwx/basicwx_ndfd.php