018 FXUS21 KWNC 311821 PMDTHR US Hazards Outlook NWS Climate Prediction Center College Park MD 300 PM EDT July 31 2026 SYNOPSIS: A broad area of mid-level high pressure is anticipated to shift from the western to the central contiguous U.S. (CONUS) throughout week-2. This pattern favors above-normal temperatures for the week-2 mean, with increased chances for extreme heat shifting eastward as well over time. The combination of anomalously warm and drier than normal conditions is expected to enhance the risk for wildfire activity where numerous wildfire incidents have been reported within highlighted heat risk areas. Antecedent dryness along with the likelihood of above-normal temperatures and below-normal precipitation during the next two weeks supports an increased risk for the Rapid Onset of Drought over parts of the Central and Southern Plains, and Middle and Lower Mississippi Valley. A favorable monsoonal circulation supports an increased and potentially prolonged risk of heavy precipitation across the Desert Southwest and lower Four Corners. HAZARDS Moderate risk of extreme heat for portions of the West, Central and Southern Plains, Middle and Lower Mississippi, Ohio, and Tennessee Valleys, and Southeast, Sat-Sun, Aug 8-9. Slight risk of extreme heat for most of the CONUS excluding the Great Lakes region, Northeast, and Appalachians, Sat-Fri, Aug 8-14. Slight risk of heavy precipitation for parts of the Desert Southwest and adjacent regions, Sat-Fri, Aug 8-14. Rapid onset drought (ROD) possible for parts of the Central and Southern Plains, and Middle and Lower Mississippi Valley. DETAILED SUMMARY FOR MONDAY AUGUST 03 - FRIDAY AUGUST 07: https://www.wpc.ncep.noaa.gov/threats/threats.php FOR SATURDAY AUGUST 08 - FRIDAY AUGUST 14: Multiple ensembles indicate amplified mid-level ridging across much of the CONUS peaking at the end of week-1, shifting from the western to east-central CONUS throughout week-2. There are significant differences across model ensemble means regarding the specifics of the magnitude and location of the ridge, with the ECENS maintaining more amplified ridging with the greatest 500-hPa heights reaching 596 dm across the Southwest at the start of week-2 (GEFS with 594 dm). The ECENS indicates more amplified heights lingering across the West until mid week-2 before weakening and shifting to the central and east-central CONUS, whereas the GEFS significantly decreases heights on days 9-10 (Aug 9-10) and re-strengthens them towards the end of the period across the central and east-central CONUS. These model differences regarding the mid-level pattern translates to increased uncertainty regarding the evolution of the extreme heat risk. The GEFS favors more of the heat remaining across the west and central CONUS for a longer duration in week-2, whereas the ECENS shifts most of the heat to the eastern half of the CONUS by the latter part of the period. Broad areas are highlighted with slight and moderate risks of extreme heat with the expectation that the heat will shift eastward with time. A moderate risk (40-60% chance) is posted for portions of the West, Central and Southern Plains, Middle and Lower Mississippi, Ohio, and Tennessee Valleys, and Southeast, Aug 8-9. Today’s outlook has trimmed some areas for the moderate risk of extreme heat with decreased coverage across the northern and southwestern periphery compared to yesterday, with a slight extension farther east into more parts of the Tennessee and Lower Mississippi Valleys based on various temperature tools including the WPC experimental probabilistic HeatRisk tool indicating major or higher risk in addition to the pattern evolution. A broader area of slight risk (20-40% chance) is highlighted across most of the CONUS excluding the Great Lakes region, Northeast, and Appalachians throughout week-2 with no changes to the spatial coverage. Enhanced dewpoints east of the Rockies may support higher heat index values. Dry air temperatures or heat index values may exceed 110 deg F across parts of the Desert Southwest and central CONUS, and 100 deg F in many other of the highlighted heat risk areas. The National Blend of Models (NBM) forecasts temperatures in some locations across the Southern Tier to approach and/or break records for nighttime minimums, implying little overnight relief to the heat. The combination of anomalously warm and drier than normal conditions is expected to be favorable for wildfire activity where numerous wildfire incidents (both contained and ongoing) have been reported within these elevated heat risk areas. A Rapid Onset Drought (ROD) risk is designated for parts of the Central and Southern Plains, and Middle and Lower Mississippi Valley where 30-day precipitation deficits are greater than 2 inches and continued dryness and heat are forecast through early August. Across the Southwest, deterministic and ensemble based ECMWF solutions continue to point to increased dewpoints and total precipitable water content overspreading the Sonoran Desert, consistent with a Gulf of California moisture surge event by late next week. Given that tropical cyclone activity in the eastern Pacific is favored to calm down in the wake of Genevieve, any gulf surge potential is most likely tied to the precursor pairing of a strong thermal low established over Arizona and easterly wave activity moving off of the Sinaloa Highlands of western Mexico to initiate a moisture event. Based on raw and calibrated precipitation tools, a slight risk of heavy precipitation remains posted and continues to be valid for all of week-2 due to the persistence of wet signals in the ECMWF PET associated with a favorable monsoonal circulation where additional gulf surge events are possible later in the period. FORECASTER: Melissa Ou $$