Short Range Forecast Discussion NWS Weather Prediction Center College Park MD 347 PM EDT Mon May 17 2021 Valid 00Z Tue May 18 2021 - 00Z Thu May 20 2021 ...Damaging severe thunderstorms and potentially significant flash flooding possible through Wednesday across the Southern Plains and portions of the Lower Mississippi Valley... ...Warm temperatures and critical fire weather found across the Northern Plains... Attention continues to be drawn towards the Southern Plains and Lower Mississippi Valley this evening as multiple rounds of severe thunderstorms and flash flooding threaten the region. The setup for this continuing active weather pattern includes a stationary front extending from the Southern Rockies, across the Southern Plains and Middle Mississippi Valley, as well as into the Ohio Valley. A warm and humid airmass is also found to the south of this boundary, with continued replenishing moisture entering from the western Gulf of Mexico over the next few days. Lastly, a dryline also exists across the Southern High Plains and should help spark thunderstorm activity. The most impactful weather hazard this evening and tonight will likely be associated with damaging thunderstorms found across West Texas. These storms may produce damaging wind gusts, isolated tornadoes, and very large hail. The Storm Prediction Center has issued a moderate risk (level 4 of 5) for severe thunderstorms across the region, with an emphasis on the threat of destructive hail. Along with severe weather, flash flooding is possible overnight across the Southern Plains, Central High Plains, and sections of southern Louisiana/southeast Texas. Numerous reports of flash flooding have already occurred in southeast Texas and southwest Louisiana today. By Tuesday and Wednesday, flash flooding is forecast to become a larger concern as heavy rain falls over saturated ground from southeast Oklahoma, throughout much of East Texas, and southern Louisiana. Widespread rainfall amounts of 5+ inches are forecast, with locally higher amounts possible thanks to efficient rainfall rates found in thunderstorms across the area. Due to the forecast heavy rain and hydrologic conditions, WPC has issued a large Moderate Risk (level 3 of 4) for Excessive Rainfall on both Tuesday and Wednesday throughout the aforementioned regions. The threat of heavy rain does shift slightly southward on Wednesday and includes southern Texas. Flash Flood Watches have been issued for southern Oklahoma, much of north-central and East Texas, southwest Arkansas, and western Louisiana. Elsewhere, a cold front entering the Pacific Northwest is expected to bring light showers and high elevation snow to the Northwest and eventually into the Northern Rockies by Wednesday. Farther east, above average temperatures should be found from the Northern Plains to the Northeast. The warm temperatures will not be as welcomed across portions of the Northern Plains due to extreme droughts conditions found in the area. In fact, gusty winds and low relative humidity has led to critical fire weather in northeast North Dakota. Red Flag Warnings have are also in effect. Snell Graphics available at www.wpc.ncep.noaa.gov/basicwx/basicwx_ndfd.php