935 FXUS02 KWBC 210620 PMDEPD Extended Forecast Discussion NWS Weather Prediction Center College Park MD 220 AM EDT Wed Oct 21 2026 Valid 12Z Sat Oct 24 2026 - 12Z Wed Oct 28 2026 ...Southern Rockies to Southern High Plains Heavy Rain threat this weekend... ...Heavy Rain threat for portions of South Florida coast this weekend... ...Overview... Unsettled weather continues across portions of the Four Corners,southern Rockies, and southern High Plains, where a slow- moving trough and associated moisture transport brings heavy rainfall concerns from the weekend into early next week. As the Pacific upper low approaches the Pacific Northwest, additional precipitation may develop through late weekend, while persistent onshore flow maintains heavy rainfall over portions of south Florida coast. The shortwave and frontal boundary over the Northern tier may bring chances for rainfall across the northern Plains into the Upper Midwest/Great lakes into early next week. ...Guidance/Predictability Assessment... The model guidance continues to support an upper trough across western U.S. early in the period, with increasing potential for the trough to split into a northern and southern component. The southern stream of energy should help maintain ascent and moisture transport across the Southwest and southern Rockies, while models show higher uncertainty on the northern stream as it progresses eastward. Furthermore, although the GFS/GEFS seems to show better agreement with the ECMWF and CMC, overall model consensus continue to show uncertainties with the evolution of the shortwave energy over northeastern Pacific through the weekend. Differences in amplitude, timing and inland progression could substantially influence sensible weather. A farther south solution would favor more widespread precipitation across the Pacific Northwest and northern California, while a more offshore solutions would allow for greater riding and drier conditions over portions of the West. Therefore, the forecast was influences by a multi-model blend of the ECMWF/CMC/GFS through the first portion of the period. The ensemble means were incorporated towards the late period to bring a reasonable compromise where the deterministic solutions diverge. ...Weather/Hazards Highlights... The upper trough and associated moisture transport should support periods of showers and thunderstorms from Saturday into early next week across portions of the the Four Corners into the Plains and eventually the Upper Mississippi Valley as the trough moves eastward. Favorable large- scale ascent, combined with sufficient deep moisture and lift, may produce locally heavy rainfall across portions of New Mexico into the Southern/Central High Plains. The greatest concern would be in areas where repeated convection develops that can lead to localized flash flooding. Therefore, the risk for excessive rainfall continues for portions of New Mexico and Texas into the Southern/Central High Plains through the weekend. Across the Northwest, the upper low/trough from the Gulf of Alaska will approach the Pacific Northwest by late weekend and will bring onshore flow. This will increase precipitation chances across the Pacific Northwest through the weekend into Monday. Higher elevations could experience a wintry mix, depending on the thermal profile and snow levels. Across the Northern tier, a shortwave may progress eastward across the northern Plains and Upper Midwest early next week, accompanied by a surface frontal boundary. This may support period of showers, followed by cooler air. Elsewhere, the persistent easterly flow will transport moisture across southern Florida, producing showers and thunderstorms. Repeated rainfall over urbanized areas and locations with poor drainage could lead to localized flash flooding concerns through the weekend. Oudit Additional 3-7 Day Hazard information can be found on the WPC medium range hazards outlook chart at: https://www.wpc.ncep.noaa.gov/threats/threats.php WPC medium range 500mb heights, surface systems, weather grids, quantitative precipitation forecast, excessive rainfall outlook, winter weather outlook probabilities, heat indices and Key Messages are at: https://www.wpc.ncep.noaa.gov/medr/5dayfcst500_wbg.gif https://www.wpc.ncep.noaa.gov/medr/5dayfcst_wbg_conus.gif https://www.wpc.ncep.noaa.gov/5km_grids/5km_gridsbody.html https://www.wpc.ncep.noaa.gov/qpf/day4-7.shtml https://www.wpc.ncep.noaa.gov/#page=ero https://www.wpc.ncep.noaa.gov/wwd/pwpf_d47/pwpf_medr.php?day=4 https://www.wpc.ncep.noaa.gov/heat_index.shtml https://www.wpc.ncep.noaa.gov/#page=ovw $$