Alaska Extended Forecast Discussion NWS Weather Prediction Center College Park MD 737 PM EDT Sun Oct 30 2022 Valid 12Z Thu Nov 03 2022 - 12Z Mon Nov 07 2022 ...Heavy rain/mountain snow and gusty winds likely across southern and southeast portions of Alaska late this week... ...Overview... The pattern across Alaska late this week into the weekend should trend more amplified, although less active in terms of hazardous weather, as an amplified ridge and strong surface high pressure sets up over the Mainland. The start of the period however features a surface low pressure system near the southern Coast, directing an atmospheric river towards the Panahndle, which should shift south with time. By early next week, ridging will be firmly in place over the Mainland, with potential for another trough/surface low to impact the western Aleutians. ...Guidance/Predictability Assessment and Preferences... The latest model guidance continues to show some timing differences regarding multiple shortwaves as it rounds the main intial trough over the Mainland Thursday-Friday. A general blend of the deterministic models seemed to provide a good starting point. Models do agree that modest to locally significant QPF will impact the Panhandle, it is more a question of how quickly does it move out. After this, there is good overall agreement that the pattern will trend much more amplified over Alaska, though plenty of uncertainty in the details. This is especially true by days 7-8, where many of the models suggest a blocky type regime may set up, though differ on whether it's a Rex block (ECMWF) or Omega block (GFS/CMC), which of course has implications for another shortwave towards the western Aleutians on day 8. There is so much spread in the pattern by late period that the WPC forecast trended fairly quickly towards the more agreeable ensemble means. This helped to maintain good continuity days 4-7 compared to yesterdays forecast as well. ...Weather/Hazards Highlights... The main weather hazard over Alaska will be an atmospheric river directing ample moisture towards the Alaska Panhandle late this week with heavy snow in the mountains, and several inches of rain near the coast. The heaviest precipitation should shift quickly to the south and mostly out of the region by the weekend. On the north side of the low, gusty northerly winds may create a Gap Wind event across southern/southeast Alaska creating concerns for high winds. In terms of temperatures, strong surface high pressure over the southern and central part of the state should create an extended period of much below normal temperatures also extening into the Panhandle where daytime highs are likely to be sub-freezing and as much as 20 degrees below normal. Meanwhile, across the North Slope region, temperatures appear to trend much warmer with time as an amplified ridge builds over the region. 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 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