Short Range Forecast Discussion NWS Weather Prediction Center College Park MD 309 AM EST Sat Feb 22 2020 Valid 12Z Sat Feb 22 2020 - 12Z Mon Feb 24 2020 ...An energetic storm system expected to impact the Southwest on Saturday, Central Rockies/Plains on Sunday, and into the Mid-Mississippi Valley by Monday... ...Rain and mountain snow return to the Northwest on Sunday reaching the northern High Plains by Monday... After a day of tranquil conditions across much of the country on Friday, unsettled weather is expected to move quickly into the southwestern U.S. followed by the Pacific Northwest this weekend. A large high pressure system responsible for the tranquil weather will gradually weaken and then slide off the East Coast during the next few days. Chilly conditions across the eastern half of the country will gradually moderate to above normal levels by Monday as winds shift to a more southerly direction. Meanwhile, a low pressure system that has been developing over the eastern Pacific is taking aim at the southwestern U.S. This storm system will tap into moisture originating deep from the tropical Pacific and begin to spread rain into the Desert Southwest today with the possibility of thunderstorms this afternoon and evening across portions of Arizona and New Mexico. The heaviest rainfall looks to be concentrated in the higher elevations of western New Mexico and south-central Arizona where rainfall totals ranging between 1 and 2 inches is possible. A Slight Risk for Excessive Rainfall has been issued for these areas due to heavy rainfall rates potentially causing areas of flash flooding today. In addition, mountain snow is expected from the southern Sierra Nevada and the Wasatch to the Colorado Rockies through this weekend. By Sunday, this storm system is forecast to intensify as it moves into the central High Plains. Showers and some thunderstorms are expected to quickly develop and expand across the central Plains toward the Mid-Mississippi Valley through Sunday night. Some wintry precipitation is also possible farther to the north from across the central Plains into the upper Midwest and the lower Great Lakes Sunday night into Monday morning. The southern Appalachians could also see wintry precipitation developing Monday morning as thunderstorms will likely be moving across the lower to mid-Mississippi Valley ahead of the intensifying storm. Farther north, another low pressure system will cause an increase in showers and and mountain snow over the Pacific Northwest on Sunday. The Olympics and Cascades will receive more mountain snow while the valleys and coastal areas see rain. The storm system will then track into the northern Rockies Sunday night leading to more areas of mountain snow. The snow will then expand farther east into the northern Plains as the storm center moves into the northern High Plains by Monday morning. Kong Graphics available at www.wpc.ncep.noaa.gov/basicwx/basicwx_ndfd.php