Short Range Forecast Discussion NWS Weather Prediction Center College Park MD 400 AM EDT Sat Sep 14 2024 Valid 12Z Sat Sep 14 2024 - 12Z Mon Sep 16 2024 ...Heavy rain and flash flood threat will continue for portions of the Southeast this weekend, then the flash flood threat will shift to the Carolinas/Mid-Atlantic early next week... ...A strong low pressure system will bring unsettled weather to the West late this weekend/early next week, with wintry precipitation expected at high elevations... ...Well above average temperatures for the Central U.S. and Northeast; well below average temperatures for the West... Though it is now post-tropical, Francine will continue to bring a threat for heavy rain and flash flooding to portions of the Southeast through Sunday. The central area of low pressure will gradually sink south towards the Gulf Coast with a stationary boundary extending to the Southeast Coast and a cold front extending back towards the Southern Plains. The stationary boundary will be the main focus for convection this weekend, and training showers and thunderstorms with locally heavy rainfall will create a threat for scattered instances of flash flooding. There is a Slight Risk of Excessive Rainfall (level 2/4) for portions of Arkansas, Tennessee, Mississippi, Alabama, and Georgia today and Sunday. Flash Flood Watches are in effect for much of this area, and urban/poor drainage areas and areas that already received heavy rainfall over the past few days will be most at risk for flash flooding. A separate area of low pressure will strengthen along the stationary boundary extending from the Southeast Coast, which will maintain shower and thunderstorm chances from Florida to the Carolinas and southern Mid-Atlantic through early next week. This low pressure system is forecast to gradually track north along the East Coast early next week and will bring a heavy rain and flash flood threat to portions of the Carolinas and Mid-Atlantic. There is a Slight Risk of Excessive Rainfall (level 2/4) for eastern North Carolina on Monday where scattered instances of flash flooding will be possible. In the West, an unsettled pattern is forecast to develop this weekend as a strong upper low pushes a frontal system across the region. The system will nudge into the Pacific Northwest today, then move across northern California, the Great Basin, and the northern Rockies Sunday and Monday. Widespread showers and thunderstorms will accompany this system, and there is a broad Marginal Risk of Excessive Rainfall (level 1/4) in effect for portions of the Northern Rockies and Great Basin on Monday. This system will also usher in well below normal temperatures, which will allow for wintry precipitation to fall at higher elevations. A Winter Weather Advisory is already in effect for portions of the Sierra Nevada where up to 4 inches of snow may fall Sunday night and Monday. Precipitation chances will also increase across the Southwest/Four Corners region late this weekend into early next week as tropical moisture streams north ahead of Tropical Cyclone Ileana. Temperatures this weekend will have a large range across the United States with well above average temperatures in the Central U.S. and Northeast and well below average temperatures under the strong upper low in the West. High temperatures will be in the 80s and 90s for the Central U.S. and Northeast through Monday, which is more than 15 degrees above average for some areas in the Upper Midwest/Great Lakes. High temperatures in the West will be near to slightly below average today, then drop to 15 to 25 degrees below average in Oregon, California, and Nevada by Monday. Highs in the 50s will be common in the Great Basin, and highs will likely only reach the 30s and 40s in the Sierra Nevada. Dolan Graphics available at https://www.wpc.ncep.noaa.gov/basicwx/basicwx_ndfd.php