041 FXUS21 KWNC 211814 PMDTHR US Hazards Outlook NWS Climate Prediction Center College Park MD 300 PM EDT September 21 2026 SYNOPSIS: A stationary front and prolonged easterly flow are expected to set up across the Florida Peninsula and the Gulf, accompanied by an elevated risk for periods of heavy rain all week-2. Another stalled front may form across southern portions of the Great Plains and Mississippi Valley may bring some enhanced rainfall to southern portions of those regions especially early in the period. No other hazards are posted under a deamplifying zonal mid-level pattern across the Contiguous U.S. (CONUS), but a few situations need to be monitored. Unseasonably hot weather is possible early in part of the south-central U.S. Meanwhile, farther west, low pressure in the Gulf of Alaska has the potential to bring increased precipitation and winds to parts of southern Alaska at times, and the continuing active tropical season in the East Pacific increases the chances that at least one disturbance impacts Hawaii. HAZARDS Slight risk of heavy precipitation for the Southern Plains, Lower Mississippi Valley, Florida Peninsula and the Gulf Coast region, Tue-Mon, Sep 29-Oct 5. DETAILED SUMMARY FOR THURSDAY SEPTEMBER 24 - MONDAY SEPTEMBER 28: https://www.wpc.ncep.noaa.gov/threats/threats.php FOR TUESDAY SEPTEMBER 29 - MONDAY OCTOBER 05: Dynamical models generally indicate a deamplifying mid-level ridge across the central and interior western CONUS from the end of week-1 into the onset of week-2 before potentially slightly strengthening by the middle of the period with troughs bookending this ridge across the Northeast Pacific and eastern CONUS. There are significant differences regarding the details of these features, regarding how amplified the trough across the East will be, translating to increased uncertainty regarding the potential for heavy rainfall. In general, stationary fronts are anticipated to drape across the Great Plains and Mississippi Valley in addition to the Gulf Coast and Florida. Furthermore, any tropical waves or low pressure systems that interact with the frontal boundary would further enhance rainfall over at least part of the Gulf Coast and Florida, The ECENS mean 500 hPa trough across the East is more favorable for more widespread and heavier rainfall across parts of the southern CONUS compared to the GEFS. The ECENS Probabilistic Extremes Tool indicates greater than 50% chances of 3-day accumulated rainfall (Sep 29-Oct 1) exceeding the 85th percentile over the Southern Plains with greater than 40% chances extending into the Lower Mississippi Valley. The GEFS PET limits probabilities of 20 to under 30% chances for these thresholds. The ECENS, GEFS, and CMCE PETs all indicate at least a 20% chance of portions of the Gulf Coast, Florida and Southern Plains/Lower Mississippi Valley exceeding one inch of rainfall in a 3-day period with thunderstorms possible in some areas. Therefore, a slight risk of heavy rain is continued across the Gulf Coast and Florida for the entirety of the period, with expansion into southern portions of the Great Plains and Mississippi Valley, with the greatest chances for heavy rainfall across the Southern Plains and Mississippi Valley at the beginning of week-2. Rainfall would be beneficial in areas where antecedent conditions have been dry. Some areas of heavy rain could be slow-moving, potentially triggering isolated flash flooding, although no particular area appears vulnerable to widespread and persistent flood conditions. Anomalously hot temperatures may linger from the end of week-1 into week-2 across the south-central CONUS, especially across southern Texas with lingering ridging across the central CONUS. Calibrated heat tools indicate a 20-40% chance of maximum heat index values exceeding the 90th percentile across this region. However, in general the mid-level heights are anticipated to be less favorable of temperature values reaching hazardous criteria in addition to decreasing sun angles in the autumn. Therefore no heat related hazards are designated in today's outlook. Mid-level troughing is expected to be centered over the Gulf of Alaska throughout week-2, supporting surface low formation over the region. In general the models indicate a more favorable pattern for a stronger low and associated onshore flow to the Gulf of Alaska toward the end of week-2 which may bring enhanced rainfall and gusty winds to south-central and southeastern Alaska. No hazards are designated at this time but will be monitored closely in the upcoming days. As the active tropical season in the East Pacific, the increase in tropical cyclone development enhances the odds that at least one system may influence conditions across Hawaii. Grounds are saturated in many areas due to periods of heavy rain over the past few months, and any additional episodes of heavy rain may renew impacts caused by the wetness, such as flooding and possibly mudslides. At this time, several areas of potential tropical development are being monitored in the East Pacific, but no specific system is identified for week-2 hazardous impacts. Refer to products from the National Hurricane Center for more detailed information, including any tropical cyclone development. FORECASTER: Melissa Ou $$