358 FXUS02 KWBC 160726 PMDEPD Extended Forecast Discussion NWS Weather Prediction Center College Park MD 326 AM EDT Wed Sep 16 2026 Valid 12Z Fri Sep 18 2026 - 12Z Tue Sep 22 2026 ...Heavy rainfall threatens the Upper Midwest/Great Lakes and Northeast this weekend... ...Overview... A trough will produce heavy rainfall across portions of the Upper Midwest/Great Lakes and potentially the Northeast this weekend. Meanwhile, the passage of a Central U.S. trough should reduce heavy rainfall concerns over the Southwest and Southern Plains/Rockies this weekend before an East Pacific disturbance renews monsoon storms across the region early next week. A mid- level disturbance meandering around the Florida Peninsula should generate multiple days of heavy rainfall across southern Florida beginning this weekend. ...Guidance/Predictability Assessment... The latest models are in relatively good agreement on the evolution of the northern stream pattern during the medium range period. Where models diverge from one another are over the Florida Peninsula with the timing of a retrograding closed mid-level disturbance, as well as the timing and amplitude of a trough moving into the Southwest early next week. A general model blend consisting of the available deterministic (minus the UKMET) and Ai models was used on day 3. The Canadian begins to diverge from the Euro-GFS suite consensus on day 4 so it's removed from the blend. The ensemble means are introduced on day 6 and make up a majority of the blend through day 7 due to uncertainties in the Southwest. ...Weather/Hazards Highlights... A potent low pressure system will bring rounds of thunderstorms and heavy rainfall to portions of the north-Central U.S. later this week. Scattered showers and thunderstorms are expected to spread into parts of the Upper Midwest/Great Lakes, where a slight risk (at least 15 percent chance) of excessive rainfall is in effect on Saturday. Thunderstorms and heavy rainfall focus should expand into the Ohio Valley and Northeast on Sunday, before dropping south into the Mid-Atlantic by 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 moving into the Southwest should reignite monsoonal moisture over New Mexico leading to heavy rainfall concerns by early next week. Slot canyons and dry washes are especially susceptible to flash flooding from any storms that develop. An anomalous ridge will have its final day of generating widespread record breaking temperatures in the Southern Plains, Lower Mississippi Valley and Tennessee Valley on Saturday before conditions begin to moderate across the region early next week. 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 $$