Short Range Forecast Discussion NWS Weather Prediction Center College Park MD 439 AM EDT Fri May 21 2021 Valid 12Z Fri May 21 2021 - 12Z Sun May 23 2021 ...Additional heavy rain associated with a developing low pressure center over the western Gulf of Mexico could impact areas from Texas Gulf Coast to Louisiana today followed by eastern Texas tonight... ...Thunderstorms could become severe ahead of a cold front through the High Plains for the next couple of days... ...Late-season snow will linger across higher elevations from the Sierra Nevada to the northern Rockies into the weekend... ...Critical Risks of fire danger remain in place for portions of the central Great Basin and Southwest... Winds circulating around a large high pressure system centered over the northeastern U.S. will continue to direct a stream of tropical moisture from the Gulf of Mexico toward the western Gulf states. Meanwhile, latest observations indicate that a low pressure center is forming in the western Gulf of Mexico as it begins to move northward toward the western Gulf Coast. The National Hurricane Center is monitoring this area for the potential for tropical cyclone formation. Heavy rain ahead of this developing circulation continues to move across coastal Louisiana early this morning. Additional heavy rain could impact areas from the Texas Gulf Coast to Louisiana today as the developing low pressure center moves toward the western Gulf Coast. The continued threat of heavy rain will keep a Slight to Moderate Risk of flash flooding over southern Louisiana to the upper Texas coast today. A deep upper-level low settling into the western U.S. will be slow to exit the area for the next couple of days. Areas along the High Plains will remain under the threat of thunderstorms that could turn severe as a strong cold front is forecast to approach from the west during the weekend. Underneath the upper low, temperatures are expected to remain below normal for much of the western U.S. High temperatures are forecast to be more than 30 degrees below average for portions of Montana, with temperature anomalies of 20 degrees below normal common for the Intermountain West. These cold temperatures will support wet snow from along the Sierra Nevada, to the higher elevations of Nevada, into the Intermountain West and the northern Rockies as the upper trough lingers. Winter Storm Warnings remain in effect for portions of Montana into early this morning where snow totals could be over a foot. The mountain snow is expected to linger into the weekend and then pick up again on Sunday as a low pressure system is forecast to intensify over Wyoming. Meanwhile, gusty winds across the interior West together with dry conditions will continue to elevate the risk of wildfires. Critical fire risk is forecast for much of the Central Great Basin into the Four-Corners region. Elsewhere, the northeastern U.S. can expect increasing chances for scattered showers and thunderstorms to end the week due to a meandering front. Warmer than average temperatures are forecast to continue for the Great Lakes/Ohio Valley and Northeast/Mid-Atlantic over the next several days, with highs rising well into the 80s and even into the 90s. The northern Plains will continue to see periods of rain with embedded thunderstorms as low pressure waves associated with a front move across the area from time to time. Kong/Tate Graphics available at www.wpc.ncep.noaa.gov/basicwx/basicwx_ndfd.php