436 FXUS21 KWNC 191836 PMDTHR US Hazards Outlook NWS Climate Prediction Center College Park MD 300 PM EDT September 19 2026 SYNOPSIS: A stalled frontal boundary is expected to settle across the Florida Peninsula and drift slowly northward, increasing the risk of periodic heavy rain there for all of week-2. No other hazards are posted in a generally deamplifying mid-level pattern, but a few situations need to be monitored. Unseasonably hot weather is possible early in part of the south-central U.S. while rainfall is expected to increase over the Plains could be more beneficial than hazardous. Farther west, low pressure over the Gulf of Alaska could enhance precipitation and winds over parts of southern Alaska, and the continuing active tropical season in the East Pacific enhances the odds for one or more systems to affect Hawaii, although no specific threat is identified at this time. Above-normal precipitation is also expected over the Southwest again, but amounts are not expected to reach hazards thresholds during week-2. HAZARDS Slight risk of heavy precipitation for the Florida Peninsula and some adjacent areas, Sun-Sat, Sep 27-Oct 3. DETAILED SUMMARY FOR TUESDAY SEPTEMBER 22 - SATURDAY SEPTEMBER 26: https://www.wpc.ncep.noaa.gov/threats/threats.php FOR SUNDAY SEPTEMBER 27 - SATURDAY OCTOBER 03: Dynamical models depict quick deamplification of the mid-level ridge over the south-central Contiguous U.S. (CONUS), but 500-hPa heights remain somewhat above normal across most of North America through week-2. The weakening ridge axis wavers across the central or interior western CONUS all week, but is expected to have moved little or retrograded slightly by the end of week-2. Downstream from the ridge axis, weak to moderate surface high pressure is expected to settle across the interior eastern CONUS and remain in place most of week-2. Meanwhile, a mid-level trough remains favored along or just off the East Coast. The ensemble means are not in good agreement on the strength of this system early week-2, with the European ensemble (ECENS) stronger than the Canadian ensemble (CNENS) mean, and the GEFS mean weaker still. A compromise of these depictions is favored, but the differences in model depictions don't affect sensible weather over the CONUS much. The mid-level trough induces lower surface pressure off the East Coast, and a frontal boundary is expected to set up southward along the mid-level trough axis, then southwestward across the Florida Peninsula around the fringes of eastern CONUS high pressure. Like other aforementioned features, this front is expected to weaken but maintain some identity through week-2. Model consensus places the front across South Florida and forecasts a slow northward drift over the course of week-2, in turn expanding its influence northward with time. Continuous heavy precipitation throughout the week is not expected, but the front is expected to locally enhance convective activity, resulting in areas of heavy rain at times across the Florida Peninsula through all of week-2. The threat is focused on South Florida early and expands northward as the front drifts in that direction. Rainfall totals may be enhanced by abundant tropical moisture along and south of the front, particularly if there is any interaction with tropical disturbances. Despite the anticipated deamplification of the mid-level ridge over or near the southern Plains, 500-hPa heights are expected to remain broadly above normal across most of the CONUS, allowing unseasonably high temperatures to linger in the southeastern Great Plains and adjacent Lower Mississippi Valley early in the period. Temperatures or heat indices there may approach hazards thresholds in early week-2, but the declining 500-hPa heights and the time of year are expected to preclude any extreme heat from developing. Model consensus forecasts above-normal precipitation across the southwestern CONUS for week-2 as a whole, but the heavy amounts and potential flooding during the prior week are not expected to persist into week-2, precluding any widespread heavy precipitation threat. However, isolated locations may be affected by heavy rains and localized flash flooding, especially considering the wet antecedent conditions. Early in week-2, significant rainfall is expected to reach eastward out of the southwestern CONUS across the Plains. This rain is more likely to be beneficial than hazardous, as antecedent conditions are acutely dry across the southern half of the Plains. A mid-level trough is expected to move into the Gulf of Alaska early week-2 and remain approximately in place through week-2, with fluctuations in intensity. This is expected to induce and maintain low surface pressures south of Alaska, which would enhance precipitation totals across Southeast Alaska and possibly coastal areas farther west at times. Most models show above-normal precipitation for the week along with periods of gusty winds in variable locations, but conditions are expected to remain below hazards thresholds. Some models imply the potential for one or most former tropical cyclones to become entrained into the mid-level trough, potentially enhancing precipitation totals and winds at times. However, with no specific threat identified by any subset of the models, there is too much uncertainty to justify heavy precipitation or wind hazards due to this potential 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 threatening the island chain at this time. Refer to products from the National Hurricane Center for more detailed information, including any tropical cyclone development. FORECASTER: Rich Tinker $$