107 FXUS21 KWNC 211923 PMDTHR US Hazards Outlook NWS Climate Prediction Center College Park MD 300 PM EDT July 21 2026 SYNOPSIS: Persistent mid-level high pressure is expected to bring an elevated risk of extreme heat to a large portion of the contiguous U.S. (CONUS) from the Ohio and Tennessee Valleys and Southeast westward to the West. 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 with localized enhanced rainfall, but due to high uncertainty no associated precipitation hazard is designated at this time. Additionally, enhanced moist flow associated with the monsoon may increase humidity and resulting increased heat index values across parts of the West. One or more tropical cyclones might also impact Hawaii, raising the potential for heavy precipitation and gusty winds. Meanwhile, a possible surface low tracking across the eastern U.S./Canadian border and associated wavering frontal boundary across the southeastern CONUS and southern Mid-Atlantic supports a slight risk of heavy precipitation for these regions until the middle of week-2. HAZARDS High risk of extreme heat for portions of the Central and Southern Plains, and Lower Mississippi Valley, Wed-Thu, Jul 29-30. Moderate risk of extreme heat for much of the Great Plains and adjacent parts of the Mississippi Valley, Central Great Basin, and the Southwest, Wed-Fri, Jul 29-31. Slight risk of extreme heat for many parts of the Gulf Coast and Florida, Ohio and Tennessee, and Mississippi Valleys, Great Plains, Central and Southern Rockies, Great Basin, Southwest, and California Valley, Wed-Tue, Jul 29-Aug 4. Slight risk of heavy precipitation for the central Gulf Coast, part of the South Atlantic region, and the eastern Carolinas, Wed-Sat, Jul 29-Aug 1. Rapid onset drought (ROD) possible for part of the northern Great Plains. DETAILED SUMMARY FOR FRIDAY JULY 24 - TUESDAY JULY 28: https://www.wpc.ncep.noaa.gov/threats/threats.php FOR WEDNESDAY JULY 29 - TUESDAY AUGUST 04: Models continue to be in good agreement featuring a persistent amplified 500-hPa ridging over the western and central CONUS and troughing across the northeastern region. Ridging is generally more amplified across the models compared to yesterday, centered over the Four Corners region and expanding westward with time. The ridge is anticipated to be located initially focused across the central CONUS before expanding westward by week-2. Troughing across the Northwest is initially anticipated to linger from week-1 into the onset of week-2 but transition to ridging with the westward expansion early in the period. This feature favors an increased risk of extreme heat across large parts of the western, central, and southern 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 across some parts of the east-central CONUS and Southeast. Due to the more amplified ridge forecast and increasing signals for heat, a high risk (>60% chance) of extreme heat has been designated across portions of the Central and Southern Plains, and Lower Mississippi Valley Jul 29-30, where and when there are significant chances in heat tools and PETs for extreme heat. A moderate risk (40-60% chance) is posted for Jul 29-31, with coverage expanded to include more of the Mississippi Valley, Great Plains, Southwest, and Great Basin. A broad surrounding area is highlighted with a slight risk, throughout week-2, with slight increase in coverage to the Central Great Basin and California Central Valley. Additionally, enhanced moisture from the Southwest Monsoon may bring increased humidity to parts of the West that could increase heat index values. Anomalously high SSTs in the waters adjacent to the Gulf and South Atlantic coasts are expected to contribute to heat and humidity east of the Rockies. Absolute temperatures or heat index values may reach 105 Deg F across parts of the California Central Valley, Gulf Coast, and Florida, 105 to 110 Deg F across the Great Plains and Lower Mississippi Valley, and 115 Deg F across the Desert Southwest. According to the National Blend of Models (NBM), southern portions of the heat risk area such as the Desert Southwest, Southern Plains, Gulf Coast and Florida may experience near or record breaking high nighttime temperatures in the upper 70s to low 80s, which would provide little overnight relief. In general the ECENS PET is not as robust with the odds for extreme heat compared to the GEFS across the West but has increased probabilities for heat across the Southern Plains and Lower Mississippi Valley. Surface lows are possible across the Interior West during week-2, which could support periods of gusty conditions. There is insufficient certainty regarding the specifics of high winds to designate a high wind hazard. Regardless, the combination of hot temperatures, dry conditions, and wind gusts could lead to enhanced wildfire risk across the West, especially across areas already experiencing active wildfires. 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. The anticipated heat is expected to overwhelm any short-lived relief that may occur. Week-2 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. Multiple models indicate a surface low tracking along the eastern U.S./Canadian border at the beginning of week-2, with an associated wavering frontal boundary near the central Gulf and South Atlantic coastal regions in conjunction with the mid-level troughing favored over the eastern U.S. This pattern supports slight risk of heavy precipitation to parts of the central Gulf Coast, South Atlantic region, and eastern Carolinas, Jul 29-Aug 1. There is uncertainty about how much rainfall occurs over the land versus offshore, thus only a slight risk is designated. There is currently a designated limited threat of flooding by the National Water Center across parts of the East and Gulf Coasts for week-1, thus heavy rainfall could support localized flooding. The ECENS PET and uncalibrated ensemble output is more favorable of heavy rainfall occurring over land compared to the GEFS, indicating at least a 20% chance of 3-day rainfall exceeding the 85th percentile climatologically and one inch. Across the West, the pattern and model guidance is less favorable for high winds across southwestern Oregon and northern California, thus this hazard has been discontinued in today's outlook. FORECASTER: Melissa Ou $$