Short Range Forecast Discussion NWS Weather Prediction Center College Park MD 358 PM EDT Thu Mar 12 2020 Valid 00Z Fri Mar 13 2020 - 00Z Sun Mar 15 2020 ...A Moderate Risk of excessive rainfall is in place over parts of Southern California and Arizona on Thursday into Friday morning... ...There is an Enhanced Risk of severe thunderstorms Mississippi/Tennessee/Ohio Valleys this afternoon and evening... ...Heavy snow over parts of the Northwest, the Rockies, and Central High Plains on Friday... ...Chance for accumulating snow and rain/freezing rain in Northern New England... An upper level trough off the coast of Southern California will advance eastward this evening with waves of heavy showers and thunderstorms drenching portions of Southern California, the Lower Colorado River Valley, and Central Arizona. The WPC has upgraded to a Moderate Risk for excessive rainfall for these areas with rainfall totals. In total, rainfall amounts of 1 to 2 inches on average is expected with localized amounts of 3 to 4 inches possible in central Arizona and the San Bernadino mountains of Southern California through Friday evening. Flash Flood Watches are also in effect for the Lower Colorado River Valley, central Arizona, and southeast California through Friday. To the east, as a surface low pressure tracking east from eastern Kansas, additional showers and thunderstorms will develop along a warm front that will extend from the Middle Mississippi Valley into the southern Appalachians this evening. The SPC has issued both Enhanced and Slight Risk areas for the mid-Mississippi Valley and into the Ohio and Tennessee Valleys due to the threat for severe thunderstorms containing large hail, damaging winds, and the potential for tornadoes. As a cold front swings through the Eastern U.S. on Friday, it will stall over Texas and lift north as a warm front later that evening. This will lead to another round of showers and thunderstorms in the Southern Plains Friday evening where rain may fall heavily at times. As the upper trough moves into the Four Corners region on Friday, so will its precipitation shield which will overrun a colder air-mass and lead to snow in the Rockies and Central High Plains. The latest forecast calls for 6 to 12 inches of snow in portions of the Colorado Rockies and Northern New Mexico. Over 6 inches of snow is expected in west-central Nebraska where Winter Storm Warnings are in place. Meanwhile, in the Northwest and Northern Rockies a cold dome of Canadian High Pressure will spill frigid temperatures into these regions Friday and Saturday. A new upper trough diving south from the Northeast Pacific will be responsible for rain in the valleys and snow in the mountains of the Northwest on Friday. Winter Storm Warnings have been issued for portions of Northern Montana in from Friday into Saturday night. Bitterly cold temperatures are also expected in northern Montana this weekend where sub zero low temperatures are forecast. Elsewhere, portions of Northern New England may pick up several inches of snow ahead of a storm system tracking into Southeastern Canada by Friday morning. Meanwhile, the Mid-Atlantic will witness spring-like temperatures with high temperatures soaring into the 70s. Both the Nation's Heartland, Great Lakes, and the Northeast will cool down this weekend in wake of a cold frontal passage late week. Mullinax Graphics available at www.wpc.ncep.noaa.gov/basicwx/basicwx_ndfd.php