594 FXUS21 KWNC 061811 PMDTHR US Hazards Outlook NWS Climate Prediction Center College Park MD 300 PM EDT August 06 2026 SYNOPSIS: A renewed area of mid-level high pressure over the south-central and southeastern contiguous U.S. (CONUS) supports a continuation of extreme heat risks from the Southern Plains to the Southeast early in week-2. Enhanced moisture from the North American monsoon is favored to funnel into much of the Interior West and spread eastward into the Midwest, to increase the risk of heavy precipitation. Antecedent dryness, combined with little precipitation favored over the next two weeks supports a Rapid Onset Drought (ROD) risk for portions of the Southern and Central Plains and Mississippi Valley. HAZARDS Moderate risk of extreme heat for portions of the Southern and Central Plains, Lower Mississippi Valley, and Southeast, Fri-Sun, Aug 14-16. Slight risk of extreme heat for much of the south-central and southeastern CONUS, Fri-Thu, Aug 14-20. Slight risk of heavy precipitation for the Desert Southwest, southern Great Basin, and Central and Southern Rockies, and portions of the Plains and Mississippi and Ohio Valleys, Fri-Mon, Aug 14-17. Rapid Onset Drought (ROD) risk for portions of the Southern and Central Plains and the Lower Mississippi Valley. DETAILED SUMMARY FOR SUNDAY AUGUST 09 - THURSDAY AUGUST 13: https://www.wpc.ncep.noaa.gov/threats/threats.php FOR FRIDAY AUGUST 14 - THURSDAY AUGUST 20: Late in week-1, both the GEFS and ECMWF ensemble feature an amplifying 500-hPa mean trough centered over the northeastern U.S. with weakening above-normal positive height departures overspreading the southeastern and western CONUS. However, as this troughing feature deamplifies by the start of week-2 (Aug 14), models are in agreement favoring a restrengthening ridge pattern over the southeastern CONUS, with a ridge axis extending northwestward into parts of the Northern Plains and Interior West. While the evolution of the mid-level pattern supports a brief cooldown of the anomalous warmth, temperature tools generally maintain a continued heat risk for many parts of the CONUS early in the period. With more troughing favored off of the West Coast, and the mean ridge axis displaced to the east, much of the monsoonal moisture supply is expected to ease into parts of the Desert Southwest and lower Four Corners. However, residual tropospheric moisture as well as added moisture from the Pacific looks to overspread the Interior West and into the portions of the Midwest, where there continues to be risk of heavy precipitation along the northern periphery of the anomalous ridging favored. Based on a convergence of evidence in the raw and calibrated temperature tools among the dynamical models, a moderate risk of extreme heat remains issued for the Southern Plains, adjacent Central Plains, and into the Lower Mississippi Valley with coverage added into parts of the Southeast and Florida Peninsula. Within the moderate risk area, Probabilistic Extreme Tools (PETs) show at least 30% chances of daytime temperatures exceeding the 85th percentile, and calibrated heat tools show 30-50% chances for either temperatures or heat index values exceeding the 90th percentile. For the moderate risk expansion into the Southeast, raw heat index guidance depict an uptick of mean values reaching 105-110 deg F since yesterday where the National Blend of Models (NBM) also shows a number of locations with nighttime lows nearing and/or breaking daily records, where little overnight relief to daytime heat is expected. The moderate risk area remains valid through Aug 16, before the anomalous mid-level ridging is favored to deamplify once again. A broader slight risk area of extreme heat also remains issued for much of the south-central and southeastern U.S, where tools indicate lower probabilities for heat exceeding hazardous thresholds. The slight risk area also remains valid for all of week-2 based on the favored persistence of at least 594 dm mean heights among the dynamical models throughout the period.. Across the Desert Southwest and lower Four Corners, analysis of precipitable water anomalies from the ECMWF and GEFS ensemble depict near normal values mainly over the Sonoran Desert, suggestive of a reduction of monsoonal moisture being advected into the southwestern CONUS early in week-2. While PETs maintain increased chances of 3-day amounts exceeding the 85th percentile throughout the region, raw precipitation tools also reflect a reduction of 3-day exceedance chances relative to yesterday. As a result, the moderate risk of heavy precipitation as well as the flooding possible hazard is discontinued in the updated outlook. Despite the lowered risk of heavy precipitation, this region is still prone to flash flooding even with relatively small precipitation accumulations especially along dry creek beds (arroyos) and in canyons. Caution should always be exercised in such areas should thunderstorm activity initiate nearby. Monsoonal thunderstorms can also produce dry lightning, resulting in increased wildfire risk. A slight risk over heavy precipitation remains issued over the Desert Southwest, but is now expanded to include parts of the Interior West, Great Plains, and Mississippi Valley where higher precipitable water anomalies are favored associated with enhanced moisture working its way along the northern periphery of the ridging centered over the southeastern U.S. Within the highlighted region, raw tools show increased chances of 3-day amounts exceeding an inch throughout many parts of the Midwest where localized flooding resulting from Mesoscale Convective Systems (MCS) activity is possible through the middle of week-2. A Rapid Onset Drought (ROD) risk remains designated and is expanded to include parts of northeastern Texas eastward through northern Mississippi where 30-day precipitation deficits are greater than 2 inches, and near to below normal rainfall as well as the aforementioned risks for heat to accelerate evapotranspiration rates are forecast later in August. ROD coverage is removed over portions of Kansas due to increased precipitation amounts forecast over the next two weeks to provide relief. Across the eastern Pacific, the National Hurricane Center (NHC) is monitoring a pair of areas located near 140W and 110W both with 30% chances of development during the next seven days (as of 11am PDT). For the western watch area near 140W, both dynamical model and Google AI guidance have been consistent favoring growing chances for development later next week, with a low tracking near the Hawaiian Islands. While there continues to be much uncertainty associated with this potential TC at this lead, precipitation tools continue to trend wetter with the ECMWF PET indicating increased chances for 3-day amounts exceeding the 85th percentile. For more info on this potential system, please refer to: https://www.nhc.noaa.gov/ FORECASTER: Nick Novella $$