890 FXUS21 KWNC 081915 PMDTHR US Hazards Outlook NWS Climate Prediction Center College Park MD 300 PM EDT September 08 2026 SYNOPSIS: Model ensembles continue to favor anomalous mid-level high pressure across the southern and central Contiguous U.S. (CONUS) and above normal temperatures across much of the Lower 48, although the risk of extreme heat is diminishing as we move into the second half of September. An unseasonably cool Canadian air mass is forecast to move into the northcentral and northeastern states, providing a taste of early fall weather. A potential surge of moisture from the Gulf of California may result in heavy precipitation over portions of the Desert Southwest and Great Basin. Antecedent dryness, combined with little precipitation favored over the next two weeks supports a Rapid Onset Drought (ROD) risk for portions of the Central and Southern Plains, Lower and Middle Mississippi, Ohio and Tennessee Valleys. However, significant precipitation is predicted to occur over eastern Kansas and southern Missouri during this two-week period. HAZARDS Slight risk of much below normal temperatures for parts of the northcentral and northeastern CONUS, Wed-Sun, Sep 16-20. Slight risk of heavy precipitation from the Four Corners region northeastward into Nebraska, Wed-Fri, Sep 16-18. Flooding possible for portions of the Desert Southwest and Great Basin. Rapid Onset Drought (ROD) risk for portions of the Central and Southern Plains and the Middle and Lower Mississippi, Tennessee, and Ohio Valleys. DETAILED SUMMARY FOR FRIDAY SEPTEMBER 11 - TUESDAY SEPTEMBER 15: https://www.wpc.ncep.noaa.gov/threats/threats.php FOR WEDNESDAY SEPTEMBER 16 - TUESDAY SEPTEMBER 22: Dynamical model guidance remains in good agreement regarding elevated chances for mid-level ridging and positive 500-hPa height anomalies persisting from the Southwest and the Rocky Mountain states eastward across the Central and Eastern CONUS early in week-2. Heights are forecast to rise across the northwestern CONUS as the period progresses, due to an expanding mid-level ridge centered near Southeast Alaska. These ridges lend themselves to continued elevated chances for above normal temperatures for most of the western and southern CONUS. The model ensembles forecast falling mid-tropospheric heights and surface temperatures over a broad region that encompasses the area (approximately) from the Northern High Plains eastward to the Great Lakes and Northeast. South of this region, support for extreme heat hazards continues to dwindle. The Probabilistic Extremes Tools (PETs) show very little potential for maximum temperatures to exceed the 95th climatological percentile (the favored threshold during shoulder seasons), and daily ensemble calculated heat indices no longer show much signal above 105F. However, temperatures are likely to remain well above normal for parts of Texas and the Gulf Coast region. Those sensitive to heat should continue to exercise caution. Early in week-2, an unseasonably cool air mass is predicted to overspread portions of the northcentral and northeastern CONUS. The GEFS and ECENS PETs forecast overnight low temperatures near or below 40 deg F for much of these northern states, with some of the coolest locations approaching freezing. Therefore, according to these model ensembles, most areas have a greater likelihood of getting frost rather than a freeze. Much below normal temperatures are posted across the Dakotas, northern Minnesota, and far northern portions of New York state and New England, Sep 16-20. Uncalibrated temperature tools favor slightly milder overnight temperatures. In either case, outlying areas of frost appear to be more likely than a 32-degree freeze for most areas. Model ensembles indicate a mid-level trough near the West Coast early in week-2. This may combine with enhanced moisture from the Gulf of California due to tropical activity over the Eastern Pacific to generate heavy precipitation over the Four Corners region. Uncalibrated probabilities from the GEFS and ECENS both indicate at least a 20% chance of 3-day precipitation totals to exceed half an inch (with little signal for 1-inch) over the region into the middle of the forecast period. Similarly, both model PETs (especially the ECENS) indicate at least a 20% chance of 3-day precipitation to exceed the 85th climatological percentile for days 8-10 (Sep 16-18). Therefore, a slight risk of heavy precipitation is posted for Sep 16-18 across most of the Four Corners region, spreading northeastward into Nebraska. Additionally, given the continued indications of potential heavy precipitation, a flooding possible hazard remains posted for portions of the Four Corners region during the week-2 period. This region is prone to flash flooding and caution should be exercised near canyons and creek beds, and additional rainfall may hamper recovery efforts from recent flooding in the Grand Canyon. A Rapid Onset Drought (ROD) risk remains designated for parts of the Southern Plains and Lower Mississippi Valley and adjacent portions of the Central Plains, Ohio, Tennessee and Middle Mississippi Valleys, and Southeast U.S. This area has seen 20-40% of normal precipitation and deficits of 1-2 inches over the past 30 days. Above normal temperatures are forecast for this region over the next two weeks increasing evapotranspiration rates into the third week of September. The best chance for any significant precipitation is across southern Missouri and eastern Kansas near a mean baroclinic zone. FORECASTER: Anthony Artusa $$