508 FXUS21 KWNC 121810 PMDTHR US Hazards Outlook NWS Climate Prediction Center College Park MD 300 PM EDT October 12 2026 SYNOPSIS: Early in week-2, mid-level low pressure is forecast to amplify across the western contiguous U.S. (CONUS) along with potential surface low pressure ejecting out of the Rockies. This favors increased chances of heavy precipitation downstream across the Great Plains and Mississippi Valley, heavy snow over the higher elevations of the Rockies, and episodic high winds from California to the central CONUS. Following the departure of this system, a broad area of mid-level high pressure is forecast over the central and eastern CONUS favoring more tranquil weather, and above-normal temperatures for most areas east of the Rockies later in October. HAZARDS Slight risk of heavy precipitation across portions of the Central and Southern Plains and Middle and Lower Mississippi Valley, Tue-Thu, Oct 20-22. Slight risk of heavy snow across portions of the Rockies, Tue-Wed, Oct 20-21. Slight risk of episodic high winds from California through portions of the Great Basin, Rockies, Plains, and Upper Mississippi Valley, Tue-Wed, Oct 20-21. DETAILED SUMMARY FOR THURSDAY OCTOBER 15 - MONDAY OCTOBER 19: https://www.wpc.ncep.noaa.gov/threats/threats.php FOR TUESDAY OCTOBER 20 - MONDAY OCTOBER 26: The 0z ECMWF, GEFS, and Canadian ensembles depict an amplified 500-hPa height pattern across the CONUS at the start of week-2 with anomalous ridging across the East, and a trend toward stronger shortwave troughing over the West compared to yesterday. The trough across the West favors potential development of a surface low in the lee of the Northern or Central Rockies, which, when combined with enhanced southerly return flow across the central CONUS, provides a favorable set-up for enhanced precipitation. The GEFS and ECMWF Probabilistic Extremes Tools (PETs) depict an expansive area with probabilities upwards of 30 to 40 percent for 3-day precipitation to exceed the 85th climatological percentile throughout much of the Interior West into the Great Plains and Mississippi Valley. However, the highest amounts (greater than 1-inch in 3-days) are most likely to occur across the more eastern areas as reflected in the uncalibrated ECMWF and GEFS ensembles, with lower precipitation climatologies likely driving the higher percentile probabilities to the west. As a result, a slight risk of heavy precipitation is posted across portions of the Central and Southern Plains and the Middle and Lower Mississippi Valley, Oct 20-22. Farther west, closer to the developing surface low and with cold enough air at higher elevations, heavy snow is possible across the Rockies. The GEFS Snow Water Equivalent (SWE) PET depicts parts of the region having at least a 20 percent chance SWE exceeds the 85th climatological percentile and a half-inch. In addition, the uncalibrated ECMWF ensemble depicts snowfall amounts greater than 4 to, in some places, 6 inches. Given the favorable set-up and considering it is early in the season, a slight risk of heavy snow is posted across portions of the Rockies, Oct 20-21. There is also support for a slight risk of high winds throughout much of the western and central CONUS as the shortwave trough moves through the region. This is evident in both the PETs and uncalibrated guidance, which depict areas with wind speeds potentially exceeding 25-mph, particularly across the California coast and the Great Plains, with a more sporadic signal in between. Therefore a broad slight risk of high winds is posted extending from California through the Rockies and into the Great Plains/Upper Mississippi Valley, also for Oct 20-21. Following a colder period across the eastern U.S. in the days prior to the start of week-2, temperatures are forecast to trend warmer as enhanced ridging spreads over the region with the dynamical models depicting +120 to +180 meter height anomalies over the Great Lakes. This favors unseasonably warm weather across much of the eastern half of the U.S. during week-2 allowing the slight risk of much below normal temperatures to be discontinued. The National Blend of Models (NBM) indicates the potential for record warmth with high temperatures above 90 deg F over the Lower Mississippi Valley, although extreme heat is unlikely to be a concern this late in the year precluding a related temperature hazard. However, warmer temperatures combined with any residual power outages resulting from Hurricane Isaias could adversely impact those without access to air conditioning. An active storm track is favored across the North Pacific driven by enhanced troughing over the Bering Sea along with some potential for recurving tropical cyclones over the West Pacific. The GEFS and ECMWF ensembles depict a series of surface lows across the Bering Sea into the Gulf of Alaska, potentially impacting southern and southeastern parts of the state. While the PETs are marginally supportive of slight risks of heavy precipitation and high winds over these areas, there is considerable uncertainty tied to individual tracks and timing. Therefore, no hazards are highlighted across Alaska, but intermittent periods of heavy precipitation and high winds are possible across the eastern Aleutians, southern coastal Mainland, and Southeast Alaska throughout week-2. FORECASTER: Thomas Collow $$