Short Range Forecast Discussion NWS Weather Prediction Center College Park MD 359 AM EDT Thu Jun 21 2018 Valid 12Z Thu Jun 21 2018 - 12Z Sat Jun 23 2018 ...Threat for flash flooding across the lower Texas coast, Ohio Valley/lower Mid-Atlantic, and mid-South... ...Increasing chances for severe weather on Friday over the southern/central High Plains and south-central U.S... ...Hot weather in store over the Desert Southwest with 110 to 120 degree temperatures likely... Multiple sectors of the country continue to warrant a close eye on flash flood concerns the next couple of days. More short term in nature, an upper low wobbling about the lower Rio Grande valley is collocated with a substantial plume of moisture lifting out of the Bay of Campeche. This combination remains a focus for heavy rainfall along the lower Texas coast early this morning. As the parent upper low pivots back toward northeastern Mexico, the strong lift in the atmosphere will exit allowing for improvement in conditions along the western Gulf Coast. Farther north, in advance of a slow moving upper low, a wavy frontal zone will stretch out across the Ohio Valley and lower Mid-Atlantic. While bounding markedly different air masses, it should also provide a means to persistent threats for convection the next couple of days. Given many locations have saturated soils from previous bouts of heavy rainfall in the past week, additional precipitation will likely lead to runoff issues. Thus, Slight Risks for excessive rainfall are being advertised the next couple of days over this region. Lastly, organized convection will likely unfold from the Arklatex eastward into the mid-South. This should ultimately afford a flash flooding risk on Friday. While the severe weather potential today is somewhat muted given only Marginal risk areas advertised by the Storm Prediction Center, the action should pick up by the following day. As the earlier mentioned upper low pushes toward the Ohio Valley on Friday, strong jet energy sliding underneath it will enhance the potential for severe thunderstorms from southern Arkansas/northern Louisiana eastward to northern Alabama. Farther west, a broad upper trough approaching the Central Rockies will quickly augment upslope flow in the lee of the terrain. Numerous thunderstorms should evolve over the mountains before pushing into the adjacent High Plains. Large hail and damaging winds appear to be the primary threats, particularly across southeastern Colorado into southwestern Kansas and the Oklahoma panhandle. A sprawling upper ridge is forecast to dominate the weather over the southwestern U.S. As such, local forecast offices have hoisted up widespread excessive heat watches and warnings ahead of the event. While departures from climatology will likely only maximize in the 5 to 10 degree range, the corresponding highs should be quite impressive. Expected high temperatures will reach the 110 to 120 degree range over the Desert Southwest. The usual hot spot should be Death Valley, California with readings in the 120 to 125 degree range. Meanwhile, the greatest departures from average on the opposite sense will be over the Middle Mississippi Valley. Abundant cloud cover and shower activity underneath the upper low should keep highs in the mid/upper 60s. Such numbers are around 10 to 15 degrees below average for mid/late June. Rubin-Oster Graphics available at www.wpc.ncep.noaa.gov/basicwx/basicwx_ndfd.php