519 FXUS21 KWNC 191739 PMDTHR US Hazards Outlook NWS Climate Prediction Center College Park MD 300 PM EDT July 19 2026 SYNOPSIS: Mid-level high pressure is expected to bring an elevated risk of extreme heat to a large parts of the southern, central and western contiguous U.S. (CONUS). Brief weakening is possible, but conditions may reintensify later, so the potential hazard covers all of week-2. Hot weather and near or below normal rainfall bring an increased risk of rapid onset drought to part of the northern Great Plains. In the West, the monsoonal circulation may be periodically robust, but hazardous rainfall amounts are not expected unless moisture from a potential tropical cyclone streams in. One or more tropical cyclones might also impact Hawaii, raising the potential for heavy precipitation and gusty winds. Meanwhile, a wavering frontal boundary near the southeastern CONUS supports a heavy precipitation risk there until the middle of week-2. HAZARDS Moderate risk of extreme heat for much of the Great Plains and adjacent parts of the Mississippi Valley, the southern High Plains, and the Desert Southwest, Mon-Wed, Jul 27-29. Slight risk of extreme heat for the southern California Valley, the Southwest, parts of the Intermountain West, much of the Rockies, the Plains and adjacent Mississippi Valley, the Gulf Coast, and the adjacent Southeast, Mon-Sun, Jul 27-Aug 2. Slight risk of heavy precipitation for the central Gulf Coast, part of the South Atlantic region, and the eastern Carolinas, Mon-Thu, Jul 27-30. Rapid onset drought (ROD) possible for part of the northern Great Plains. DETAILED SUMMARY FOR WEDNESDAY JULY 22 - SUNDAY JULY 26: https://www.wpc.ncep.noaa.gov/threats/threats.php FOR MONDAY JULY 27 - SUNDAY AUGUST 02: Heading into the start of week-2, models are in good agreement featuring an amplified 500-hPa ridging over the Interior West and High Plains bookended by a pair of mid-level troughs, one over the northeastern Pacific and the other overspreading much of eastern North America. Both troughs are a little more persistent than indicated by yesterday's models, but still weaken considerably or dissipate by the end of week-2. Over time, the European ensemble (ECENS), GEFS, and Canadian ensemble (CMCE) means show the ridge essentially persisting there throughout week-2. The location of maximum 500-hPa heights may drift, and the strength may wax and wane somewhat, but these changes are expected to be subtle and inherently difficult to specify during the week-2 period, and the ridge remains relatively amplified throughout the period. The anomalous ridge is expected to take on a somewhat positive tilt over the last half of the period, with its axis eventually stretching northward from the Four Corners toward the Northern Plains. This feature favors an increased risk of extreme heat across large parts of the western, central, and southern CONUS. Both northwest and northeast of this broad area, stagnant mid-level troughs are expected to slowly weaken but remain essentially stationary through the period, likely keeping extreme heat out of the northwestern and most of the eastern CONUS. Underneath the ridging aloft, an elevated potential for heat risk continues to be supported by a number of temperature and heat tools across many parts of the southern, western, and central CONUS. Higher than normal dewpoints are also favored east of the Rockies due to a long fetch of Gulf moisture near the surface, increasing dew points and helping to drive up heat index values there. A moderate risk of extreme heat is posted for Jul 27-29, with coverage expanded to include more of the northern Lower Mississippi Valley, but trimmed slightly away from parts of southern New Mexico and the South Atlantic Coast. These adjustments are based mainly on the expected mid-level pattern evolution and internal heat index tools, which depict nontrivial chances for heat index values exceeding 110 deg F as far north as southeastern South Dakota and adjacent Iowa. The best chances for this extreme heat stretches from southern Kansas through much of Oklahoma and into adjacent Texas early week-2. Deep South Texas and part of the Desert Southwest also have significant chances for heat index values or absolute temperatures to top 110 deg F, but this is not as unusual there as it is in the locations farther north. The moderate risk covers the first few days of week-2, ending as the evolution of the mid-level ridge becomes less certain. Surrounding the moderate risk area, a large slight risk of extreme heat remains posted, although the area was trimmed slightly on the southeastern and northwestern tiers to account for the slightly stronger and more persistent mid-level troughs expected to affect these areas. Anomalously high SSTs in the waters adjacent to the Gulf and South Atlantic coasts are expected to contribute to heat and humidity there. The ECENS and GEFS Probabilistic Extreme Tools (PETs) are not as robust with the odds for extreme heat as might be expected, but are slightly more confident early in the period than yesterday. Both now display portions of the Plains with a greater than 40 percent chance for high temperatures above the 85th climatological percentile during the first few days of week-2, although the ECENS remains displaced slightly farther east. The GEFS PET also shows similar odds for portions of the Four Corners region. One factor possibly muting the PETs extreme heat likelihoods is the expected unusually high dew points east of the Rockies. This would elevate the heat index values, whereas the PETs only reflect actual temperatures. Meanwhile, antecedent dryness, anomalous warmth and dryness during week-1, and the potential for extreme heat during week-2 support an enhanced risk of Rapid Onset Drought (ROD) across portions of the Northern Plains despite uncertainty in the precipitation forecast during the 6- to 14-day period (Jul 25-Aug 2). The anticipated heat is expected to overwhelm any short-lived relief that may occur. This is expected to be an active period of tropical activity in the eastern Pacific. More than one tropical cyclone is expected, and models have consistently shown at least one of these systems moving far enough toward the central Pacific to threaten Hawaii with heavy rain and high winds. Please refer to the National Hurricane Center (NHC) for the latest tropical developments Despite the strong mid-level ridge favored across the western CONUS, the forecast position of the ridge center does not support an extreme advection of monsoonal moisture into the region, although model forecasts and the PETs today show slightly higher likelihood than yesterday. In addition, it is possible that one or more of the tropical cyclones expected in the eastern Pacific could track northward and contribute to a surge of tropical moisture into the region, which would significantly enhance rainfall amounts. Raw model output and the PETs aren't sufficiently robust to support any slight heavy precipitation risk from being posted, but with the tools trending wetter and the potential for tropical moisture incursion, the situation will need to be closely monitored. A wavering frontal boundary is likely to set up near the central Gulf and South Atlantic coastal regions in conjunction with the mid-level troughing favored over the eastern U.S. This set-up brings a slight risk of heavy precipitation to parts of the central Gulf Coast, South Atlantic region, and eastern Carolinas. Ensemble output shows the mean position of this feature to be a little farther east and south than yesterday, a trend that continued from the prior day, but most tools indicate the possibility that surface waves of low pressure along the front could push the front farther west periodically. Therefore, the slight risk of heavy precipitation is again reduced in scope relative to yesterday, and is valid Jul 27-30. Continuous heavy precipitation does not appear likely. The raw ensemble output and a preponderance of the PETs show slightly increased chances (less than 30 percent) for three-day precipitation amounts to exceed the 85th climatological percentile and 1 inch total. Despite the relatively nondescript solutions shown by much of the guidance, the position and persistence of the quasi-stationary front and abundant low-level moisture have the potential to induce scattered heavy rainfall at times. FORECASTER: Rich Tinker $$