Alaska Extended Forecast Discussion NWS Weather Prediction Center College Park MD 421 PM EST Tue Nov 29 2022 Valid 12Z Sat Dec 03 2022 - 12Z Wed Dec 07 2022 ...Heavy snow/ice and freezing rain threats from Southwest/Western Alaska into the Interior/North Slope expected... ...Guidance/Predictability Assessment and Preferences... The guidance shows good agreement concerning the general flow pattern in and around AK. A large and deep upper level vortex over Siberia broadens eastward with time, eventually enveloping the Bering Sea, Aleutians, and western AK. Detail-wise, on Friday, the 12z UKMET is faster with a low moving north and northeast of AK, so weighted its solution minimally. The biggest issue is early next week, when the GFS breaks down the top of the ridge more than the other guidance. For the 500 hPa heights, pressures, fronts, and winds, generally used a deterministic heavy blend of the 12z GFS, 12z UKMET, 12z ECMWF, and 12z Canadian early on before including up to 50% of the 12z NAEFS mean/00z ECMWF ensemble means. The QPF used 50% of the 19z NBM and 50% of a combined 12z GFS, ECMWF, and Canadian solution. The remainder of the grids were 19z NBM weighted, as usual. ...Weather/Hazards Highlights... A strong storm system north of Alaska will be responsible for generating intense winds from north of Nome on north and east along the northern Alaskan coast on Friday. Ensemble probabilities from the 00z ECMWF mean show up to a 20-30% probability range for wind gusts >50 knots across far northern Alaska (quite high probabilities for the threshold) -- related wind grids explicitly paint 50+ kt winds along the northern coast of AK and portions of the Aleutians during the day on Friday. In addition, strong southerly flow directing Pacific moisture poleward will allow for periods of snow along the Brooks Range while rain, and potentially an icy wintry mix in some cases, occurs across the North Slope and portions of interior southwest and central AK. As that low exist east, the next strong storm system tracks into the Bering Sea on Dec 4. Hazards associated with this storm system include high winds across the Aleutians on north to the Norton Sound and Seward Peninsula. Eventually this storm system will deliver heavy precipitation along the Upper Peninsula on Day 5, then towards Kodiak Island on Day 6 and potentially the Kenai Peninsula Days 6-7. There remains some question on timing and totals, but anomalous moisture should result in heavy coastal rain and mountain snow in these areas early next week. Considering the general pattern, mildness is expected across the southern and western portions of the state, with colder conditions in the interior but especially east, where low temperature may drop below -10F. Roth/Mullinax Hazards: - Heavy precipitation across portions of mainland Alaska, Fri-Sat, Dec 2-Dec 3. - Heavy precipitation across portions of the Alaskan Upper Peninsula and Kodiak Island, Sun-Tue, Dec 4-6. - High winds across portions of mainland Alaska, Fri-Sat, Dec 2-Dec 3. - High winds across portions of the Aleutians, Sat-Sun, Dec 3-Dec 4. - High winds across portions of mainland Alaska, Sun, Dec 4. Additional 3-7 Day Hazard Information can be found on the WPC medium range hazards outlook chart at: https://www.wpc.ncep.noaa.gov/threats/threats.php WPC medium range Alaskan products including 500mb, surface fronts/pressures progs and sensible weather grids can also be found at: https://www.wpc.ncep.noaa.gov/alaska/ak_5dayfcst500_wbg.gif https://www.wpc.ncep.noaa.gov/alaska/akmedr.shtml https://www.wpc.ncep.noaa.gov/alaska/ak_5km_gridsbody.html