Alaska Extended Forecast Discussion NWS Weather Prediction Center College Park MD 713 PM EDT Mon Oct 18 2021 Valid 12Z Fri Oct 22 2021 - 12Z Tue Oct 26 2021 ...Pattern overview and Guidance and Predictability Assessment... A low pressure system in Bristol Bay to start the period on Friday should begin to weaken as it crosses the Alaska Peninsula and redevelops its triple point well to the southeast. This new low should lift north and east towards the Gulf with low pressure maintaining over the region into early next week as multiple upper level shortwaves into the mean upper trough act to reinforce the pattern. The notable outlier with the main low on Friday is the 12z UKMET which is much faster than the better guidance consensus. After Friday though, the 12z CMC is stronger with triple point redevelopments into/south of the Gulf. The GFS and ECMWF are more consistent with both each other and the ensemble means so the WPC blend for the first half of the period was based on these two deterministic solutions. Another low should cross well south of the Aleutians this weekend with another system dropping into the Bering Sea by early next week. With both, there are some timing and strength differences between the various models so an ensemble mean solution is preferred for now as the details continue to worked out. This approach helps to maintain reasonable continuity from yesterdays forecast, as well farther downstream across the CONUS. ...Pattern Overview and Weather/Hazard Highlights... Two deep low pressure systems, one south of the Panhandle and the other in Bristol Bay, on Friday will continue to bring moderate to locally heavy precipitation (rain near the coast, snow in the higher elevations) to parts of the Alaska Peninsula, southern Coast, and Panhandle region Friday into Saturday. The backside of the low may also continue some gusty winds for parts of the Aleutians and AKPen on Friday as the low weakens and slides southeastward. A couple of triple point developments should act to reinforce mean low pressure across the Gulf through next weekend maintaining generally soggy conditions from southeast Alaska to the Panhandle, with conditions finally starting to improve by early next week as the cold front pushes into western North America. Temperatures from the Aleutians to the Panhandle should be mostly below normal through the period as surface low pressure and upper level troughing becomes established over the region. Into the interior and northern Alaska, upper level ridging should keep daytime highs as much as 10 to 20 degrees above normal into next weekend with some moderation of temperatures by early next week as the ridge begins to break down. Santorelli 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: - High winds across portions of the Aleutians, Thu, Oct 21. 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