181 FXUS21 KWNC 101907 PMDTHR US Hazards Outlook NWS Climate Prediction Center College Park MD 300 PM EDT October 10 2026 SYNOPSIS: Mid-level low pressure moving out of the Northeast favors cold surface high pressure over the eastern Contiguous U.S. (CONUS) early week-2, supporting increased chances for much below normal temperatures and the first fall frosts and/or freezes over coastal and southern New England, the northern Mid-Atlantic, much of the central and northern Appalachians, and the eastern Great Lakes. This system moves off the East Coast by midweek, ushering in warmer air. Farther west, rainfall enhanced by low-level southerly flow could approach hazards thresholds across the central Gulf Coast toward mid-week, but timing and intensity are highly uncertain, so no related hazard is posted. Over Alaska, mid-level troughing and cyclonic flow over the Gulf of Alaska supports periods of above-normal precipitation and high winds from the south-central Mainland through Southeast Alaska, but conditions are expected to remain below hazard thresholds. HAZARDS Slight risk of much below normal temperatures for southern and coastal New England and parts of the eastern Great Lakes, northern and central Appalachians, and northern Mid-Atlantic, Sun-Mon, Oct 18-19. DETAILED SUMMARY FOR TUESDAY OCTOBER 13 - SATURDAY OCTOBER 17: https://www.wpc.ncep.noaa.gov/threats/threats.php FOR SUNDAY OCTOBER 18 - SATURDAY OCTOBER 24: The hazards perspective largely remains on track since yesterday. The latest 0z guidance from the European ensemble (ECENS) and GEFS feature a moderately-amplified 500-hPa trough moving out of the Northeast early in the period, with a moderately-amplified mid-level ridge upstream extending from the western and central CONUS into southern Canada. At the surface, a surface low pressure system and associated cold front is expected to sweep across much of the eastern two thirds of the CONUS near the end of week-1, followed by a fairly strong and cold surface high pressure moving in from Canada by the start of week-2. Probabilistic guidance from the ECENS, GEFS, and Canadian ensembles (CMCE) shows enhanced chances that this may result in the first frost or freeze of autumn in some of the higher latitudes in the eastern CONUS early in the period. A slight risk for much below normal temperatures is posted in these regions for days 8-9 (Oct 18-19), avoiding parts of Upstate New York and interior New England where near- to below-freezing temperatures have already occurred. On day 8 (Oct 18), the ECENS Probabilistic Extremes Tool (PET) shows chances for minimum temperatures below the 15th climatological percentile range from 30 percent in eastern Ohio to more than 60 percent across Maine. The GEFS PET is more muted, showing a 30 to 40 percent chance throughout the area of enhanced risk. On day 9 (Oct 19), the ECENS is faster to push out the cold air than the GEFS. The GEFS PET keeps the odds for much below normal temperatures between 20 and 30 percent across the region while the ECENS PET shows similar probabilities restricted to New England and a small part of adjacent Upstate New York. Given the uncertainty in the timing of moderating temperatures, the time frame for the much below temperature threat remains the same as yesterday, Oct 18-19. But no matter how quickly the cold air retreats eastward, the dynamical models and ensembles all show the surface high pressure moving off the East Coast before midweek, resulting in low-level warm air advection throughout the eastern CONUS that ends the much below normal temperature threat. Farther west, this low-level southerly flow is expected to bring an anomalous push of tropical moisture northward across the Gulf and into the central Gulf Coast States. The ECENS and GEFS PETs both show marginally enhanced chances (just over 20 percent) for 3-day rainfall totals to exceed the 15th climatological percentile and 1 inch along and near the Gulf Coast from eastern Texas to southern Alabama or the western Florida Panhandle beginning on or after Oct 19. The dynamical European model (ECMWF) and the European Artificial Intelligence Forecast System models (ECMWF-AIFS) both show 3-day totals of 2 to locally 4 inches of rain falling on parts of the Lower Mississippi Valley and adjacent Gulf Coast around mid-week, but the ECENS, GEFS, and CMCE means, along with the GFS-AI dynamical model, are much drier. Given the uncertainty, no hazard is posted at this time, but the situation will need to be monitored. Over Alaska, mid-level troughing remains favored late week-1 centered over the Gulf of Alaska. Deamplification is favored early week-2, but the ensemble means today show the potential for a weakened 500-hPa trough to reload and effectively remain in place throughout the period. This maintains fairly weak cyclonic mid-level flow over the Gulf of Alaska, which favors unsettled weather from the south-central Mainland through Southeast Alaska. Given how high precipitation normals are in this region during October, it seems unlikely that amounts will reach hazards thresholds, and the weak nature of this system does not favor high winds reaching hazards thresholds either. But there is the potential for any tropical cyclone activity in the western Pacific to recurve northward and become incorporated into the extratropical westerlies, resulting in a more amplified mid-level pattern with an incursion of tropical moisture. So although no hazards are posted at this time, the mid-level pattern over the northern Pacific will continue to be monitored. FORECASTER: Rich Tinker $$