166 FXUS21 KWNC 242045 PMDTHR US Hazards Outlook NWS Climate Prediction Center College Park MD 300 PM EST December 24 2025 SYNOPSIS: Continued mid-level high pressure over eastern Siberia and mid-level low pressure over the Gulf of Alaska is favored to keep very cold air in place over much of Alaska, while strong pressure contrasts at the surface between the warmer ocean and the frigid interior promote strong winds along the southern and southeastern coast of Alaska. Moist onshore flow persists over the West Coast, bringing potentially heavy rain and snow and high winds to much of the western Contiguous U.S. (CONUS). Early in week-2 a surface low pressure system is favored to move over New England, ushering in potentially hazardous cold and windy conditions. HAZARDS Moderate risk of much below-normal temperatures for southern Alaska, the central and eastern Interior, the Alaskan Peninsula, and the northern Panhandle, Fri-Wed, Jan 2-7. Slight risk of much below-normal temperatures for all of Alaska with the exception of the North Slope, Thu-Wed, Jan 1-7. Slight risk of high winds for the Alaska Peninsula, southern Mainland Alaska, and southeastern Alaska, Thu-Wed, Jan 1-7. Slight risk of heavy snow for the southern and central Sierra Nevadas, Thu-Sat, Jan 1-3. Slight risk of heavy snow for the Wasatch, and mountains of western Colorado and southern Wyoming, Thu-Mon, Jan 1-5. Slight risk of heavy snow for the Cascades, Klamath, and northern Sierra Nevadas, Sat-Wed, Jan 3-7. Slight risk of heavy snow for the Northern Rockies, Sat-Wed, Jan 3-7. Slight risk of heavy precipitation for California south of San Francisco Bay and much of the Desert Southwest, Wed-Fri, Jan 1-3. Slight risk of heavy precipitation for northern California, and western Oregon and Washington, Fri-Wed,Jan 3-7. Slight risk of high winds along the West Coast, Thu-Sun, Jan 1-4. Slight risk of high winds for western portions of the Southern and Central Plains, Thu-Sat, Jan 1-3. Slight risk of much below normal temperatures for parts of the Northeast, Thu-Sat, Jan 1-3. Slight risk of high winds for parts of the Great Lakes and Northeast, Thu-Fri, Jan 1-2. DETAILED SUMMARY FOR SATURDAY DECEMBER 27 - WEDNESDAY DECEMBER 31: https://www.wpc.ncep.noaa.gov/threats/threats.php FOR THURSDAY JANUARY 01 - WEDNESDAY JANUARY 07: Todays model solutions are in fair agreement regarding an active synoptic pattern as depicted by 500-hPa height anomalies over the North Pacific and North America, however there is quite a bit of model spread with regard to the placement of key synoptic features throughout the forecast period. Early in week-2 ensemble solutions depict amplified ridging over eastern Siberia, weak troughing over the Canadian Pacific coast, moderate ridging over the central CONUS, and amplified troughing over the Northeast U.S. Of these features, only the Siberian ridge and the downstream trough are well-agreed upon. Both features persist throughout the forecast period, while model solutions diverge significantly downstream beyond the outset of week-2, leading to lower forecast confidence, particularly east of the Rockies. At the surface, high pressure persists across much of Alaska and the Yukon throughout week-2. Conversely, mean low pressure is favored in the Gulf of Alaska. The pressure gradient between these features brings increased chances for episodes of high winds across much of southern Alaska from the central Aleutian Islands through Southeast Alaska. High winds would be particularly favored in gaps and inlets. Probabilistic Extremes Tools (PETs) show enhanced chances of wind speeds exceeding the 85th climatological percentile. Therefore, a slight risk of high winds is posted for most of southern and southeastern Alaska for all of week-2. PETs continue to highlight enhanced chances for temperatures to fall to near hazardous thresholds across much of southern, Interior, and Southeast Alaska, driven in part by the pressure gradient discussed above. A moderate risk is posted for southern Alaska, the central and eastern Interior, the Alaskan Peninsula, and the northern Panhandle valid Jan 2-7, while a broader slight risk is posted for all of Alaska with the exception of the North Slope for all of week-2. Temperatures between -20 deg F and -35 deg F are predicted to be widespread across much of inland Alaska, with -40 deg F temperatures indicated by the PETs over the eastern Interior to the north of Fairbanks. Closer to the coast, temperatures are expected to range between 0 and -15 deg F (Anchorage near -10 deg F), while the southern half of Southeast Alaska is predicted to be somewhat milder, with high temperatures about +10 deg F. The combination of very cold weather and high winds along the southern tier of the state increases the threat for heavy freezing spray at times near larger bodies of water. The 0z ECENS, 0z GEFS, and 0z CMCE model solutions depict persistent mid-level troughing over the North Pacific throughout the forecast period. The Integrated Vapor Transport (IVT) tool also indicates moderate low-level moisture streaming into the West Coast throughout the forecast period, with both the ECMWF and GEFS showing probabilities above 40% for much of the week for IVT to exceed 150 kg/m/s. Todays forecast solutions initially place the heaviest precipitation over the southwestern CONUS, then gradually shift back north over the Pacific Northwest. The PETs and uncalibrated precipitation guidance supports a slight risk of heavy precipitation for California south of the Golden Gate as well as much of the Desert Southwest for Jan 1-3, as well as a slight risk for Northern California, and western Oregon and Washington for Jan 3-7. The incoming moisture associated with this atmospheric river is likely to push well inland, resulting in potentially heavy snow for many mountain ranges across the West. Uncalibrated probabilities from both the ECENS and GEFS for daily accumulations of over 6 inches exceed 40% in some locations throughout the week, and the GEFS PET for snow water equivalent (SWE) indicates at least a 20% chance of 3-day SWE to exceed the 85th climatological percentile and at least 1 inch for much of the southern Cascades, Sierras, and Northern and Central Rockies during various portions of week-2. Based on the GEFS PET and uncalibrated daily snowfall totals, a slight risk of heavy snow is posted for Jan 1-3 covering the southern and central Sierra Nevadas, and Jan 3-7 for the Cascades, Klamath, and northern Sierras. Further east, a slight risk of heavy snow for the Wasatch, and mountains of western Colorado and southern Wyoming is indicated for Jan 1-5. Additionally, a slight risk is posted for much of the Northern Rockies valid Jan 3-7. Along with heavy precipitation and snow, high winds reaching hazardous criteria are also possible associated with this atmospheric river (AR) event. Model ensemble maximum wind speeds from the ECMWF and GEFS exceed 20mph along the entire West Coast during the first half of week-2, warranting a slight risk of high wind along the coast covering the period Jan 1-4. Further inland, surface low pressure in the lee of the Rockies early in the forecast period is favored to enhance winds over portions of the Great Plains. Based on ensemble mean wind speeds from the GEFS and ECMWF, a slight risk of high winds is posted for western portions of the Southern and Central Plains for Jan 1-3. Given a lack of antecedent rain and/or snow, fuels are unusually dry, elevating the potential for prairie fires. Early in week-2 a deep trough is depicted over the Northeast U.S., resulting in strong northwesterly flow and colder temperatures across the region. Ensemble mean wind speeds approach 20mph over much of the Great Lakes, warranting a slight risk of high winds for Jan 1-2. PETs for minimum temperatures also indicate at least a 20% chance of temperatures falling below -10F across northern New England during the first half of week-2. When paired with enhanced winds, apparent temperatures may fall below hazardous thresholds where these two factors combine, therefore a slight risk of much below-normal temperatures is posted for non-coastal portions of northern New England for Jan 1-3. FORECASTER: Danny Barandiaran $$