Alaska Extended Forecast Discussion NWS Weather Prediction Center College Park MD 705 PM EDT Tue Jun 28 2022 Valid 12Z Sat Jul 02 2022 - 12Z Wed Jul 06 2022 ...Overview... An upper high and warm upper ridging will be in place across eastern and northern Alaska and northwestern Canada through the end of the week, while an upper low drifts toward far eastern Russia embedded within large scale troughing over the Bering Sea. Additionally, an energetic shortwave rounding the southern side of the trough is forecast to pass near the Alaska Peninsula and into the Gulf of Alaska this weekend. Moist southerly flow ahead of this system will spread increasing rain chances generally from west to east across Alaska through the weekend. Areas influenced by the troughing, particularly southwestern Alaska, should also see cooling temperatures, but warmer than normal temperatures may persist in eastern and northern Alaska into early next week. ...Guidance Evaluation/Predictability Assessment... The first half of the period shows reasonably good agreement with the meandering upper low north of the Bering Sea, a strong ridge over the eastern/northern Mainland, and a shortwave crossing into the Gulf. The WPC forecast utilized a blend of the deterministic solutions, which helped mitigate any smaller scale detail differences. A couple of weak shortwaves may rotate around the southern periphery of the upper low, helping to disrupt the ridge over the Mainland and push it eastward some. Then, there continues to be some variability and model disagreement with the upper low/trough evolution over the Bering, likely in response to something dropping down the west side of the broader trough. This feature would act to amplify the flow over western Alaska. The ECMWF/CMC are the strongest in this more amplified evolution, while the GFS and to some extent the ensemble means, are less amplified and keep the upper low in tact across the Bering region. Given the late period timing, preferred a blend more towards the ensemble means for days 7 and 8. ...Weather and Hazard Highlights... Temperatures will continue to be rather warm across about the northeastern two-thirds of the mainland this weekend, generally 10-20F above normal (and locally higher) under the upper ridge, while southwestern Alaska starts to cool to below normal for high temperatures given the troughing/low aloft. Cooler temperatures are forecast to gradually filter north and eastward into early next week, with near to below average highs. The far eastern mainland may stay above average into early next week dependent on ridge placement. Moderate to locally heavy rainfall is possible ahead of the shortwave/low pressure system near the Peninsula and southern Coast on Saturday, spreading eastward through the weekend. Heaviest rainfall amounts appear focused across parts of the Peninsula and Kodiak Island, and possible into the southwestern Mainland. After the weekend, much of Alaska should dry out, though some light showers are possible given somewhat unstable flow aloft. The exception may be across the Brooks Range and parts of the North Slope where possibly more enhanced precipitation is possible near a lingering frontal boundary. 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: - Heavy rain across portions of mainland Alaska, Fri-Sat, Jul 1-Jul 2. - Much above normal temperatures across portions of mainland Alaska, Fri-Mon, Jul 1-Jul 4. 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