559 FXUS21 KWNC 241838 PMDTHR US Hazards Outlook NWS Climate Prediction Center College Park MD 300 PM EDT August 24 2026 SYNOPSIS: Models continue to favor a long-duration extreme heat event from the southern tier of the contiguous U.S. (CONUS) northward into the Central Plains and the Middle Mississippi Valley. The greatest risk is focused from the Southern and Central High Plains eastward to the Lower (and portions of the Middle) Mississippi Valley, under amplified and long-lived mid-level high pressure. Some areas may experience heat more typical of mid-summer into the first week of September. Meanwhile, unusually hot and dry conditions over the past few weeks are expected to continue through much of week-2, supporting a Rapid Onset Drought (ROD) risk for portions of the Central and Southern Plains, and the Middle and Lower Mississippi Valley. HAZARDS High risk of extreme heat for the Central and Southern Plains, Lower and portions of the Middle Mississippi Valley, Tue-Wed, Sep 1-2. Moderate risk of extreme heat for the Desert Southwest, Southern Rockies, Southern and Central Plains, Lower and Middle Mississippi Valley, and some adjacent areas, Tue-Thu, Sep 1-3. Slight risk of extreme heat for southern portions of California, the southern Great Basin,Central and Southern Rockies,Central and Southern Plains, Middle and Lower Mississippi, Tennessee, and Lower Ohio Valleys, eastern Gulf Coast region, and southern portions of the Eastern Seaboard, Tue-Mon, Sep 1-7. Rapid Onset Drought (ROD) risk for portions of the Central and Southern Plains, the Lower Mississippi Valley and adjacent areas. DETAILED SUMMARY FOR THURSDAY AUGUST 27 - MONDAY AUGUST 31: https://www.wpc.ncep.noaa.gov/threats/threats.php FOR TUESDAY SEPTEMBER 01 - MONDAY SEPTEMBER 07: Early in week-2 the 0z ECENS, 0z GEFS, and 0z CMCE solutions predict a maximum 500-hPa height of 593-594 dm associated with the subtropical ridge in the vicinity of southern New Mexico. The GEFS and ECENS show standardized 500-hPa height anomalies topping out at 1.0-1.5 standard deviations above climatology on days 8-9, which represents some weakening compared to several days ago. This is consistent with a long-duration, major heat wave over much of the central and southern CONUS through at least the first half of week-2, and perhaps well into early September in some areas. The three ensemble mean models depict a slightly anomalous mid-level trough near the West Coast, helping to temporarily displace the western portion of the subtropical ridge slightly towards the east. The mid-level ridge is bookended by a pair of mean troughs near the West Coast and over the northeastern CONUS. Towards the end of the week-2 outlook period, the flow pattern is predicted to deamplify significantly. The National Blend of Models (NBM) depicts 2 stations with near-record or record-breaking daytime high temperatures in the Southern High Plains on day 8 (Sep 1), decreasing to zero stations by day 10 (Sep 3). This downward trend continues to support the idea of a slight break in the extreme heat across the region, though it will likely still be very hot. Underneath the amplified ridge, a high risk (greater than 60% chance) of extreme heat remains posted early in week-2 (Tue-Wed, Sep 1-2) from the Southern Plains and southern half of Kansas eastward into the Lower (and parts of the Middle) Mississippi Valley. The ECENS and GEFS Probability of Extremes Tools (PET) depict slightly reduced chances (compared to several days ago) of maximum temperatures exceeding the 85th historical percentile across the southwestern CONUS early in week-2, with the GEFS PET being slightly more extensive with its heat coverage compared to the ECENS, as has been the case for much of this summer. The eastern portion of the high risk area covering much of the Mississippi Valley, is largely based on the expectation that dew points will elevate heat index values considerably above actual air temperatures. A moderate risk (40-60% chance) of extreme heat is posted across a larger area surrounding the high risk area, continuing westward across the Desert Southwest, and is valid for one additional day (Tue-Thu, Sep 1-3). A slight risk (20-40% chance) of extreme heat is extended for the duration of week-2 (through Mon Sep 7) across a large part of the central and southern CONUS. With temperatures in the Mid-Atlantic region forecast to fluctuate during the period, it was decided not to bring the slight risk area any farther north than southeastern Virginia. The slight, moderate, and high risk areas of favored extreme heat are largely based on a subjective consensus of objective tools such as the skill weighted and calibrated (and raw) hybrid forecast between the GEFS and the ECENS, skill-weighted and bias-corrected hybrid forecast (using probability of exceedance thresholds of 105 deg F and 110 deg F, daily max uncalibrated 0z ECENS/GEFS/CMCE 2-meter temperatures and anomalies, and the Probabilistic Extremes Tool (PET) temperature guidance from the three ensemble means. The ECENS is more bullish today relative to the GEFS on expanding the heat into the Ohio Valley during week-2. If the ECENS and/or the GEFS supports this expansion of heat associated with the mid-level ridge tomorrow, the hazardous temperature map may be adjusted to reflect this development. The episode of extreme heat is being exacerbated by feedback processes associated with rapidly drying soils and drought within many of the highlighted regions. The hot and dry conditions favored are also expected to elevate the risk of fire weather conditions during the period. In addition, a Rapid Onset Drought (ROD) risk is designated across portions of the Central and Southern Plains and Lower (and parts of the Middle) Mississippi Valley. This area has registered 30- to 45-day precipitation deficits greater than 2 inches below normal and/or under half of normal, with less than an inch expected during the next two weeks. The possible exceptions include southeastern Louisiana and southern Mississippi, where up to 3 inches of rain is predicted. This amount of precipitation would be enough to overcome 2-inch deficits, plus take into account one week of climatological rainfall. The ROD shape was trimmed back accordingly to reflect these precipitation forecasts in the Mississippi Delta region. Nearly all of this ROD area is within the moderate and high risk areas of extreme heat, and the resulting increase in evapotranspiration rates are likely to accelerate surface moisture depletion. Colder temperatures are predicted for the Brooks Range in Northern Alaska during week-2. Though precipitation amounts are not expected to reach hazardous criteria, the region may experience its first snowfall of the season. FORECASTER: Anthony Artusa $$