615 FXUS21 KWNC 121808 PMDTHR US Hazards Outlook NWS Climate Prediction Center College Park MD 300 PM EDT September 12 2026 SYNOPSIS: A cool air mass is forecast for portions of the Northeast bringing chances for first frosts and freezes to parts of the region. Another round of enhanced mid-level moisture is favored to overspread the western and central CONUS, potentially bringing heavy precipitation and possible flooding over portions of the Four Corners. In Alaska, a potent area of low pressure is forecast in the Gulf of Alaska that may bring chances for heavy precipitation and high winds to portions of the southeastern Mainland and Southeast Alaska. HAZARDS Slight risk of much below normal temperatures for parts of northern New England, Sun-Tue, Sep 20-22. Slight risk of heavy precipitation for the Four Corners region, Sun-Tue, Sep 20-22. Slight risk of heavy precipitation for parts of Southeast Alaska and southeastern Mainland Alaska, Sun-Mon, Sep 20-21. Slight risk of high winds for parts of Southeast Alaska and southeastern Mainland Alaska, Sun-Mon, Sep 20-21. Flooding possible for portions of the Desert Southwest, Great Basin, and Rockies. DETAILED SUMMARY FOR TUESDAY SEPTEMBER 15 - SATURDAY SEPTEMBER 19: https://www.wpc.ncep.noaa.gov/threats/threats.php FOR SUNDAY SEPTEMBER 20 - SATURDAY SEPTEMBER 26: The GEFS, ECENS and CMCE remain in good agreement in regards to the evolution of the 500-hPa pattern next week. A mid-level ridge amplifies over central and eastern Canada during week-2 bringing positive height anomalies back to the central and eastern contiguous U.S. (CONUS) with time. A longwave trough is forecast upstream over the Gulf of Alaska. Much of the enhanced subtropical ridging that has been established for quite some time is expected to ease resulting in cooler and drier conditions for many areas east of the Rockies. Tied to a transient trough progressing through the northeastern CONUS, a slight risk of much below normal temperatures remains posted for northern New England valid for Sep 20-22. Within the highlighted areas, there continues to be agreement in uncalibrated temperature tools showing increased chances for temperatures falling below 40 deg F, with the ECENS Probabilistic Extremes Tool (PET) favoring 20-30% chances of minimum temperatures falling below the 15th climatological percentile. While near freezing temperatures are not markedly unusual for this time of year (climatological first freezes occur by late September for the highlighted areas), any frost and/or freezes associated with the favored cold air mass may be impactful to some vegetation. Much of the CONUS remains favored to see above normal temperatures during week-2 and the GEFS PET maintains increased chances for temperatures remaining above the 85th percentile much of the country, however chances of extreme heat are diminished based declining climatologies and on lower heat index values indicated by the tools by the start of week-2, thus no corresponding hazard areas are posted. Continued above-normal temperatures may exacerbate dry ground conditions and sustain an increased wildfire risk, but given the relatively cooler temperatures favored and decreasing sun angles with the start of autumn soon approaching, the prospect of additional impacts associated with the persistent warmth is lower overall. Some model guidance continues to bring elevated chances for heavy precipitation to parts of the southeastern CONUS. A lingering frontal zone is forecast across the region and southerly return flow could bring elevated tropical moisture into the region. Uncertainty remains too high to post a precipitation hazard at this time; this area will continue to be monitored. Weak troughing and onshore flow favored near the West Coast along with the potential for additional tropical moisture from the eastern Pacific, a slight risk of heavy precipitation remains posted (Sep 20-22) over the Four Corners where uncalibrated tools maintain elevated chances for 3-day precipitation amounts exceeding a half an inch, and in some locations more than one inch. In addition, given the continued indications of potentially heavy precipitation during the next week or so, a possible flooding hazard remains posted for portions of the Four Corners. This region is prone to flash flooding and caution should be exercised near canyons and creek beds, and additional rainfall may hamper recovery efforts from recent flooding in the Grand Canyon. Multiple model ensembles depict surface and mid-level low pressure over the Gulf of Alaska resulting in enhanced onshore flow and the potential for heavy precipitation and high winds along portions of the southern and southeastern coast of Alaska. The model guidance indicates the potential for 3-day precipitation totals to approach hazardous criteria with widespread strong probabilities of 3 day precipitation amounts exceeding 2 inches and isolated areas of more than 3 inches throughout much of southeastern Alaska. Correspondingly, PETs indicate elevated chances for winds to exceed the 85th climatological percentile and 40mph near the coast. Therefore, a slight risk of heavy precipitation is posted from the Kenai Peninsula through all of Southeast Alaska for Sep 20-21 and a corresponding slight risk of high winds is posted from Prince William Sound through Southeast Alaska for the same period. Across the eastern Pacific, the National Hurricane Center (NHC) is currently monitoring TC Norbert, as well as a pair of watch areas located near 150W and 115W with 10% and 90% chances of development, respectively, during the next week. While the latter higher likelihood area looks to be more of a factor in regards to the enhancing moisture advection into the CONUS, a continued westward track from Norbert beyond the official forecast track from NHC, as well as the lower likelihood watch area in proximity to Hawaii may pose an additional heavy precipitation threat to the state during the next few weeks. Any additional TC related precipitation may worsen already saturated grounds across parts of Hawaii, as there has not been much time for recovery following the impacts associated with TCs Lowell, Moke, and Lala this season. FORECASTER: Ryan Bolt $$