Short Range Forecast Discussion NWS Weather Prediction Center College Park MD 358 AM EDT Wed Mar 11 2020 Valid 12Z Wed Mar 11 2020 - 12Z Fri Mar 13 2020 ...There is a slight risk of severe thunderstorms over parts of the Lower Mississippi/Tennessee Valleys... ...There is a slight risk of excessive rainfall over parts of Southern California and Arizona on Thursday into Friday morning... ...Temperatures will be 10 to 15 degrees above average over parts of the Plains... ...There is a Red Flag Warning over parts of the Central High Plains... T First of all, much needed rain is currently spreading farther inland into the Southwestern U.S. ahead of an occluded cyclone approaching from the eastern Pacific. This first wave of moisture is bringing occasional heavy rain across southern California into the Desert Southwest. By Wednesday, the bulk of the moisture will move farther inland across Arizona with a slightly lower chance for heavy rain on Wednesday. However, a second wave of moisture is expected to move toward the Desert Southwest from Northern Mexico later on Thursday. This will once again increase the potential of flash flooding Thursday evening into Friday morning as the chance of heavy rain increases area-wide. Meanwhile, a cold front will bring mainly light rain for the East Coast through Wednesday morning. Farther west, a stronger upper-level trough will spread a period of mountain snow down the Northern Rockies through Wednesday. This upper-level trough is forecast to interact with a nearly stationary front across the Southern Plains to the Tennessee Valley to result in the development of a low pressure system in the Middle Mississippi Valley on Thursday. The same stationary front will be the focus for showers and thunderstorms over parts of the Lower Mississippi/Tennessee Valleys. Some of the storms may become severe on Wednesday. It appears that rain and thunderstorms will expand eastward across the Tennessee Valley into the Southern Appalachians on Thursday as rain chances increase and expand eastward farther north toward the Ohio Valley. Meanwhile, the upper Great Lakes will be cold enough to support wintry precipitation on Thursday as the low pressure system intensifies. Ziegenfelder Graphics available at www.wpc.ncep.noaa.gov/basicwx/basicwx_ndfd.php