Alaska Extended Forecast Discussion NWS Weather Prediction Center College Park MD 612 PM EST Fri Nov 18 2022 Valid 12Z Tue Nov 22 2022 - 12Z Sat Nov 26 2022 ...Multi-day Southeast Alaska heavy precipitation threat starting by Thanksgiving... ...Overview... Strong ridging in place across much of the Mainland into early next week that will help deflect main storm tracks to the west and south of Alaska. During this period a series of low pressure systems are expected to track over the the Gulf of Alaska. These systems will usher in periods of gusty winds and modest to heavy precipitation to places along the Southern Coast and Southeast Alaska. The ridge is anticipated to weaken and shift eastward as an amplified upper low/trough over eastern Russia works into the Bering Sea and Western Alaska mid-later next week. Northern stream energies digging downstream through the mainland will favor an unsettling and cooling trend and subsequently could significantly phase with ample southern stream low energies lifting over the Gulf of Alaska to bring deepened lows and long fetch moisture with a heavy precipitation threat into Southeast Alaska starting around Thanksgiving and lingering into the holiday travel weekend. ...Guidance/Predictability Assessment and Preferences... Guidance seems decently clustered with the larger scale flow evolution through medium range time scales in a pattern with at least average predictability, but increasingly struggles over time with stream phasing and embedded system focus to lower forecast confidence with specifics. Prefer best clustered 12 UTC GFS/ECMWF/Canadian guidance Tuesday before transition to more compatible 12 UTC GEFS/ECMWF ensemble means by Thanksgiving. ...Sensible Weather and Potential Hazards... Initial surface lows over the Gulf of Alaska should produce some moderate to locally heavy precipitation (coastal rain/mountain snows) early next week for parts of the Southern Coast and Southeast Panhandle. Additional and potentially deep low developments up into the Gulf offer less certain developments and timings, but the overall pattern should provide quite favorable support to bring stormy weather with long fetch moisture to fuel a multi-day heavy precipitation threat (coastal rain/mountain snows) to focus over Southeast Alaska starting around Thanksgiving. Meanwhile, a cold front through western and central Alaska driven by northern stream upper troughing may also bring some precipitation in spots, but overall should be light and scattered in nature. However, strong gap winds could develop into mid-late week into southern locations in the wake of system passages. The upper ridge lingering this weekend will continue to support above normal temperatures for much the state, with the greatest anomalies across the North Slope. While the North Slope and eastern Alaska should stay above normal next week, much of the rest of the state will experience a significant cooling trend as a strong cold front moves through. Schichtel Hazards: - Heavy precipitation across portions of the Alaska Panhandle and mainland Alaska, Mon, Nov 21. - Heavy precipitation across portions of the Alaska Panhandle, Wed and Thu, Nov 23- Nov 24. 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