983 FXUS21 KWNC 041805 PMDTHR US Hazards Outlook NWS Climate Prediction Center College Park MD 300 PM EDT May 04 2026 SYNOPSIS: Mid-level high pressure is forecast across the western contiguous U.S. (CONUS) leading to above-normal temperatures and extreme heat concerns emerging across the Southwest into the California Central Valley, and gradually shifting into portions of the Central and Southern Plains. Conversely, persistent mid-level low pressure across the Great Lakes and Northeast favors anomalously cool weather across the region, especially early in the period. There remains the potential for late season frosts over the more northern and higher elevation areas. HAZARDS Moderate risk of extreme heat across the southern California Central Valley, Tue, May 12. Moderate risk of extreme heat across portions of the Desert Southwest, Tue-Wed, May 12-13. Slight risk of extreme heat across portions of the southwestern CONUS and the California Central Valley, Tue-Fri, May 12-15. Slight risk of extreme heat across portions of the Southern Plains extending into southern Kansas, Wed-Fri, May 13-15. Slight risk of extreme heat across central and southern Florida, Tue, May 12. Slight risk of much below normal temperatures across portions of the Great Lakes, Ohio Valley, Appalachians, and Northeast, Tue-Wed, May 12-13. Slight risk of high winds across the northern coast of California and coastal Oregon, Tue-Thu, May 12-14. DETAILED SUMMARY FOR THURSDAY MAY 07 - MONDAY MAY 11: https://www.wpc.ncep.noaa.gov/threats/threats.php FOR TUESDAY MAY 12 - MONDAY MAY 18: The 0z ECMWF, GEFS, and Canadian ensembles depict a strong mid-level ridge (+120 meter positive height anomaly) over the western CONUS late in week-1 and continuing into the start of week-2. This feature leads to anomalously warm temperatures over much of the West and, while still early in the season, an increased chance for extreme heat over the Southwest. The National Blend of Models (NBM) and uncalibrated dynamical models depict the potential for record daily high temperatures, possibly above 100 deg F across the Desert Southwest into the southern California Central Valley. The ECMWF Probabilistic Extremes Tool (PET) depicts high probabilities (greater than 60 percent) for maximum temperatures to exceed the 90th climatological percentile over these areas, and skill weighted calibrated heat risk guidance also indicates elevated probabilities for heat to exceed the 90th climatological percentile. The ECMWF and GEFS ensembles are quicker to flatten the ridge compared to yesterday, and shift it toward the Plains by the middle of the period. Therefore, while increased heat is likely across the Southwest, it is forecast to be transient, with impacts starting prior to the start of week-2. A moderate risk for extreme heat remains in place over the southern California Central Valley through day-8 (May 12), and across the Desert Southwest on days 8 and 9 (May 12-13). A slight risk for extreme heat extends farther north through the remainder of the California Central Valley and into southern Nevada, and is valid through May 15. The substantial heating forecast across the West favors thermal low development and an increased pressure gradient along parts of the West Coast. The uncalibrated 0z GEFS and ECMWF ensembles both show enhanced probabilities for wind speeds above 25-mph across coastal portions of northern California and Oregon early in week-2, and this signal is also apparent in the PETs. Therefore, a slight risk of high winds is posted across these areas, May 12-14. As the ridge axis shifts into the south-central CONUS, a warming trend is likely across the Central and Southern Plains. High temperatures in the mid to upper 90s deg F are depicted in the uncalibrated 0z GEFS and ECMWF ensembles across parts of western Texas and Oklahoma, extending into southern Kansas, with daily records being depicted in the NBM toward the middle of week-2. Areas of extreme drought across the Texas Panhandle into western Oklahoma also favor hotter temperatures. Due to these signals, in addition to support from CPC heat risk guidance and the PETs, a slight risk of extreme heat is introduced across portions of the Southern Plains into southern Kansas, May 13-15. A persistent trough linked to the negative phase of the North Atlantic Oscillation (-NAO) remains forecast across the Great Lakes and Northeast into week-2. This continues to favor below-normal temperatures across the region. Despite it getting later into May, the ECMWF and GEFS PETs depict parts of the Ohio Valley, Great Lakes, Appalachians, and Northeast having at least a 20 percent chance minimum temperatures fall below the 15th climatological percentile and 40 deg F early in week-2. Late season frosts still cannot be ruled out across more northern and higher elevation areas, and the slight risk for much below normal temperatures remains in place, May 12-13. Dynamical models continue to indicate a frontal system across the eastern U.S. late in week-1. However, this system is quick to exit with most precipitation timing off prior to the start of week-2, with only lingering areas of precipitation possible into day-8 (May 12). Therefore, the slight risk of heavy precipitation across the East is removed in today's outlook. Enhanced subtropical ridging continues to support a slight risk of extreme heat across central and southern Florida, May 12. The GEFS and ECMWF PETs depict at least a 20 percent chance maximum temperatures exceed the 85th climatological percentile and 90 deg F. Antecedent dry conditions may also help push temperatures upward further justifying the increased risk. Dynamical models generally indicate heat signals decreasing across the region by day-9 (May 13) following a frontal passage, but relatively warmer temperatures may again return by the end of the period. Over the Alaska region, surface low pressure across the Bering Sea favors increased southerly flow and occasional enhanced precipitation and gusty winds along the southern and southeast coasts. However, hazards criteria are not anticipated to be reached. Troughing favors generally near- to slightly below-normal temperatures over most of the state. The typical peak of the river ice breakup season is approaching, and ice jam flooding can occur this time of year with little or no notice as conditions on frozen rivers can change quickly. Please check with the Alaska Pacific River Forecast Center for the latest conditions and advisories. FORECASTER: Thomas Collow $$