Alaska Extended Forecast Discussion NWS Weather Prediction Center College Park MD 806 PM EDT Tue Jul 19 2022 Valid 12Z Sun Jul 24 2022 - 12Z Thu Jul 28 2022 ...Multiple days of heavy rain possible across portions of coastal southern Alaska and the Southeast... ...General Overview... Through the course of extended period an anomalously deep upper level low will begin to weaken as it moves southwards over the western half of the Mainland and multiple impulses of energy will eject out across the Aleutians and Gulf leading to heavy rain from the Kenai Peninsula to the Southeast. ...Guidance/Predictability Assessment... Model continue to show a highly anomalous upper low positioned over the northern Bering at the start of the extended forecast. With time, the guidance show increasing spread with the orientation of trough. The GFS has persistently hold on to a solution that takes the surface low further east as well as the cold front crossing the Gulf of Alaska by next weekend when compared to other global and ensemble guidance. The CMC has started to trend toward a similar solution as the GFS. The ECWMF also continues to be stronger with a low that emerges from south of the Aleutians by early next week with a more amplified trough in place. Although these two solutions lead to some differences in timing/location, especially after after Sunday morning. They were still utilized for the blend although the means equaled nearly 40/50% of the forecast blend by the end of the extended forecast. ...Sensible Weather... The daily maximum temperatures will mostly range in the 50s and 60s initially with a warming trend through the coming week; a few locations may reach the 70s. The overnight lows will have a cooling trend through the weekend, ranging from the upper 20s to mid 40 before beginning to warm back up to the 30s to lower 50s. There will be occasional breaks in the cloud cover, but most areas will be mostly cloudy to overcast. Much of the southern coastal areas and the Southeast will be in a prolonged wet period with multiple rounds of showers and thunderstorms. Prolonged onshore flow aided by impulses aloft that will enhance lift and instability will help generate periods of higher intensity rainfall. Given the span of time these moderate to heavy rains are expected there may be areas that receive excessive rainfall and develop localized flooding concerns. There is potential exists for some locations to pick up 4-8 inch rainfall totals. Campbell 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 - Heavy rain across portions of the Alaska Panhandle and mainland Alaska, Fri-Sun, Jul 22-Jul 24. - Much below normal temperatures across portions of mainland Alaska, Fri-Sat, Jul 22-Jul 23. 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