250 FXUS02 KWBC 101938 PMDEPD Extended Forecast Discussion NWS Weather Prediction Center College Park MD 338 PM EDT Sat Oct 10 2026 Valid 12Z Tue Oct 13 2026 - 12Z Sat Oct 17 2026 ...Heavy rainfall threat continues for the Intermountain West into Tuesday... ...Record heat for the Southern Plains, Mid-South, and Southeast Tuesday-Thursday... ...Overview... An upper low will linger over the Intermountain West into midweek as anomalous moisture from the Pacific streams in. This will continue to bring a flash flooding threat across portions of the Intermountain West into the start of the medium range period on Tuesday, along with mountain snow. Meanwhile, moisture from ex- Simon will stream northward, with an expanding area of rain over the Central U.S. as the western trough drifts slowly eastward. Despite some model guidance waffling, it appears most likely that this trough will combine with strong northern stream energy to establish deep troughing in the east-central U.S. Friday-Saturday. Before then, strong upper ridging over the south-central to southeastern U.S. early in the period should allow for much above normal to record-setting warm temperatures into at least midweek, slowly moderating with time. ...Guidance/Predictability Assessment... Model guidance is in good agreement as the medium range period begins Tuesday, indicating an upper low over the central Great Basin that gradually drifts east into Wednesday. Meanwhile ridging will be in place in the southeastern quadrant of the U.S., while a shortwave or two quickly pass through the northern tier. Model spread quickly increases for the latter half of the week, as guidance has struggled with how much northern stream energy from western Canada will dive southeast into the north-central U.S. and if it will combine with the preexisting trough. Several 00/06Z model solutions, other than the GFS, had shown the southern stream low being left behind in the Southwest while the northern stream moved more progressively across the U.S./Canada border, without phasing. However, the bulk of the 12Z guidance now shows more phasing again (like a day ago), with a stronger trough and associated surface low moving across the Great Lakes and vicinity. The 12Z ECMWF seems to be the main model left showing a shallower, faster northern stream by Friday and less phasing. With the CMC/GFS/AIGFS/AIFS all now phased again, leaning this way and away from the ECMWF, plus the ensemble means, seems to represent the best middle ground forecast. Confidence is relatively low considering the model changes in the past few cycles. ...Weather/Hazards Highlights... Across the West, the low aloft along with ample moisture from the Pacific will yield additional widespread modest to locally heavy rainfall and localized flash flooding into the Great Basin on Tuesday. See the Excessive Rainfall Outlook for more information. Cold air surging behind the cold front will lower snow levels, leading to accumulating snow over higher elevations of the West. This could be the first appreciable snow for the Utah ranges. Snow is possible in portions of the Northern/Central Rockies as well Tuesday-Wednesday and perhaps lingering into Thursday. A Plains low pressure system and moisture from what is leftover from Simon may stream northward and aid in producing a widespread area of rain in the central U.S. beginning Tuesday and likely lingering through at least Thursday. Thunderstorms and heavy rain/flooding potential are likely in the Southern/Central Plains to Lower/Middle Mississippi Valley ahead of a cold front. Farther north, there is some uncertainty with how progressive the trough and surface lows could be, but the current forecast is for rain to shift across the north-central U.S. Wednesday-Thursday and toward the Northeast Friday. Elsewhere, a round of rain is possible in the Great Lakes to Northeast on Tuesday with a shortwave aloft and a cold front. Florida could see diurnally driven showers and storms later next week. Ahead of the front, temperatures in the southern Plains to the Southeast will be well above normal and likely set new daily high temperature records (upper 80s to the mid 90s). Low temperatures may only fall into the 70s for several nights, with the combination yielding widespread Moderate HeatRisk and perhaps reaching Major over south Texas. The warmer temperatures in the 90s will gradually cool back into the 80s as fronts approach. Meanwhile the upper troughing in the West will bring broadly below average temperatures there through Tuesday, along with frost/freeze threats. Gradual warming is likely in the West after that as upper ridging comes in. Tate/Santorelli 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 $$