Preliminary Forecasts
Issued by NWS
Issued by NWS
321 FXUS02 KWNH 150712 PREEPD Preliminary Extended Forecast Discussion NWS Weather Prediction Center College Park MD 311 AM EDT Tue Sep 15 2026 Valid 12Z Fri Sep 18 2026 - 12Z Tue Sep 22 2026 ...Hazardous Heat subsides over the South-Central U.S. late week as heavy rain/strong thunderstorms threaten the Northern/Central Plains, Upper Midwest/Great Lakes, Southwest and Southern Rockies... ...Overview... An anomalous ridge which supported a heat wave in the Southern Plains and Lower Mississippi Valley will weaken considerably under the influence of an amplifying upstream trough as well as a closed mid-level disturbance approaching from the Gulf later this week. The upstream trough will produce heavy rainfall across portions of the Northern Plains, Upper Midwest/Great Lakes and Northeast this weekend. Meanwhile, the passage of the Central U.S. trough should reduce heavy rainfall concerns over the Southwest/Southern Plains this weekend before an East Pacific disturbance renews monsoonal storms across the region early next week. ...Guidance/Predictability Assessment... The deterministic GFS and Euro, as well as the AIGFS and ECAIFS are in good agreement on the synoptic pattern evolution across the CONUS on days 3 and 4. The GFS and AIGFS begins to diverge from consensus by day 5 regarding the north-central U.S. trough so are replaced by the GEFS and ECE means to mitigate some of the uncertainty that arises with the Central U.S. trough amplitude. The Euro suite is favored on days 6 and 7 due to inconsistencies/spread in the GFS suite. ...Weather/Hazards Highlights... A potent low pressure system will bring rounds of thunderstorms and heavy rainfall to portions of the Central U.S. later this week. Scattered showers and thunderstorms are expected to redevelop over parts of the Upper Midwest, where a slight risk (at least 15% chance) of excessive rainfall is in effect on Friday. Shower and thunderstorm focus should spread across the Great Lakes, Ohio Valley and Northeast over the weekend, before dropping south into the Mid-Atlantic early next week. Shortwave disturbances streaming north through the Southwest/Southern Plains will generate a little bit more convection over New Mexico on Friday before an amplifying trough shifts the unsettled weather into the Central/Southern Plains this weekend. An East Pacific trough dropping into the Southwest should reignite monsoon storms across New Mexico by early next week. Slot canyons and dry washes are especially susceptible to flash flooding from any storms that develop. Some record high temperatures remain possible across parts of the South into late week, but a weakening ridge should gradually moderate the heatwave into the weekend. Kebede 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 $$