Alaska Extended Forecast Discussion NWS Weather Prediction Center College Park MD 658 PM EST Sun Nov 20 2022 Valid 12Z Thu Nov 24 2022 - 12Z Mon Nov 28 2022 ...Heavy precipitation event culminates on Thanksgiving Day over southeastern Alaska together with high wind threat... ...Pattern Overview... A strong occluded cyclone curving north toward the Gulf of Alaska will deliver a heavy precipitation event for southeastern Alaska forecast to culminate on Thanksgiving Day. Heavy mountain snow and coastal rain should slowly diminish with time during the holiday weekend as the cyclone gradually weakens. Thereafter, the next occluded cyclone appears to be in the offing for western Aleutians later in the weekend, with possibly a triple-point low reaching the Alaska Peninsula by next Monday. ...Guidance/Predictability Assessment and Preferences... The 00Z EC mean as well as the 00Z CMC mean today were a bit incompatible with the rest of the guidance for the pattern evolution described above, showing cyclone locations/tracks significantly farther south of the 06Z & 12Z GFS/GEFS and the 12Z CMC/CMC mean. The 12Z ECMWF, on the other hand, was much more compatible with the rest of the model/ensemble guidance. Thus, a smaller percentage of the 00Z EC mean than usual was used to composed the 500mb and sea-level pressure field. The 12Z EC mean appears compatible as well. Thus, the Alaskan grids today were composed of a blend of the 12Z guidance, transitioning to mostly a blend of the ensemble means by Days 7-8. ...Weather/Hazards Highlights... Deep occluded cyclone will start the medium-range period with a heavy mountain snow and coastal rain on Thanksgiving Day across southeastern Alaska. The heavy precipitation will add to a year-long total at Juneau that may break their yearly record. 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. Upper troughing over the North Slope and Interior will favor unsettled conditions with some localized snows along with modest surface low/system tracks across the Bering Sea to western Alaska with overall pattern eastward translation/upper trough early in the Thanksgiving holiday weekend. Late period, there continues to be emerging model signal for another deepened low advance toward the Aleutians and southern Bering Sea over the holiday weekend. A triple-point low could reach the Alaska Peninsula by next Monday with the arrival of next round of precipitation. Kong/Schichtel 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