Alaska Extended Forecast Discussion NWS Weather Prediction Center College Park MD 653 PM EST Tue Nov 09 2021 Valid 12Z Sat Nov 13 2021 - 12Z Wed Nov 17 2021 ...Overview and Guidance Evaluation/Preferences... This weekend, the pattern over Alaska will be characterized by slow-moving troughing aloft extending over the central/eastern mainland and into the northeastern Pacific, while upper ridging moves in behind. At the surface, a low over the Gulf of Alaska will migrate eastward while another surface low tracks northeast through the northeastern Pacific, consolidating likely just south of the Panhandle by Sunday night. A surface high is forecast to strengthen over the central/northern mainland into the early part of next week. This weekend pattern appears to have reasonable agreement amongst the model guidance. Though, some differences arise with yet another surface wave moving northeast through the Pacific toward the southern Panhandle by Monday, as shown by the GFS runs but not really in other guidance. But overall a multi-model blend of the 12Z deterministic guidance (ECMWF, GFS, CMC, and UKMET) served as a reasonable starting point for the forecast through the weekend. As the workweek begins, guidance somewhat diverges upstream regarding a negatively tilted upper trough coming into the Bering Sea. Overall this system and its associated surface low/frontal system seems to be trending faster. The ECMWF runs and the EC ensemble mean take a slower/southern track, which was somewhat closer to WPC continuity. This is eventually leads to model guidance being out of phase with one another, even between the 12Z GEFS and 00Z EC ensemble means over the Aleutians for example by the end of the period. For day 6-7 (Mon-Tue), attempted to split the difference initially with a middle ground track of the troughing and surface low, with some incorporation of the EC and GEFS means as well as the deterministic 12Z ECMWF, GFS, and CMC. By Day 8/Wed, ended up with a fronts/pressures model blend that was 50% EC mean, 20% GEFS mean, and 10% each EC/GFS/CMC. Note the new 12Z EC ensemble mean appears to have a faster track than the 00Z run but not as fast as the GEFS mean, supporting this blend. ...Weather/Hazard Highlights... Precipitation could linger into Saturday after a wet day in the Panhandle on Friday with moist inflow from a low pressure system. Then depending on the exact track of the next low system moving through the northeastern Pacific, enhanced precipitation may be possible for southern parts of the Panhandle by Sunday-Monday, but most may stay south into western Canada. Light to moderate precipitation is likely along with some possibly enhanced winds over the Aleutians by early next week with the frontal system. Below normal temperatures will be most pronounced in terms of anomalies and persistence over the southwestern mainland, somewhat easing by around next Wednesday. Meanwhile, the North Slope should see above normal readings (especially for lows) through the forecast period. The eastern mainland and Panhandle will initially see highs not too far from normal and lows above normal, followed by a cooling trend toward more below normal temperatures. Tate 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 Hazards: - Heavy precipitation across portions of the Alaska Panhandle, Fri, Nov 12. 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