Alaska Extended Forecast Discussion NWS Weather Prediction Center College Park MD 739 PM EDT Tue Aug 02 2022 Valid 12Z Sat Aug 06 2022 - 12Z Wed Aug 10 2022 ...Heavy rainfall possible from the southeastern mainland to the Panhandle late this week and next week... ...Much cooler temperatures will gradually spill into the state from the north through the first half of next week... ...Overview... A shortwave/surface frontal system crossing into the Gulf around Sunday will bring potentially heavy rainfall to parts of especially the southeastern Mainland and the Panhandle this weekend. After this, a stronger shortwave rotating around a deep upper low over the Arctic will drive a cold front across western/central Alaska and again into the Gulf, with rounds of showers (and possibly snow) across the Mainland, and another chance for heavy rainfall into southern Alaska and parts of the Panhandle early to mid next week. The deep low north of Alaska may attempt to drop slowly southward through the period, but regardless, will bring a much colder regime to Alaska by next week. ...Guidance/Predictability Assessment... The latest models seem to have a relatively good handle on about the first half of the period through Monday, although the UKMET and CMC were a little faster with the shortwave into the Gulf this weekend. A blend towards the ECMWF and GFS was preferred and was more consistent with the ensemble means for that system. After this, models begin to diverge more especially concerning details surrounding the deeper low across the Arctic. Initially, the 12z GFS was noticeably quicker with a shortwave into western Alaska compared to the rest of the deterministic guidance. Then around Tuesday/day 7, some of the guidance (the 12z ECMWF and CMC) pull the core of the upper low south and into mainland Alaska, while the 12z GFS and the ensemble means (including the new 12z runs) keep it farther north. This was a shift in the 12z ECMWF as the 00z ECMWF kept the low north like the GFS, so this will need to continue to be monitored to see if this southward pull is a trend or not. Of course, the evolution of this system and the details will have strong implications for how cold it gets over Alaska and also whether any, or none, of the associated precipitation is snow. At such, the Alaska forecast for today trended strongly towards the ensemble means late period to help mitigate these larger and smaller scale differences. ...Sensible Weather... Precipitation, heavy at times, should be ongoing across the southern half of the interior as the period begins Saturday, with enhanced amounts likely in Southcentral Alaska and the Alaska Range into the southeastern mainland and the Panhandle. Mostly rain is forecast in those areas, though precipitation in the highest elevations of the Alaska Range could fall as snow. Activity across the Southeast and Panhandle should wind down by Sunday, but the rest of the Mainland Alaska looks to remain rather unsettled into next week as a cold front/trough moves through the state. This should cause some daily showers across much of the state, some of which could fall as snow in higher elevations. As the cold front reaches the southern Mainland and Gulf early next week, another round of possibly heavy rainfall is likely along the southern Coast and Panhandle. Much colder than normal temperatures will be filtering into northern and northwest Alaska by Saturday and should continue to track southward through the weekend. By early next week, much of Alaska, including the Panhandle, could be seeing daily high temperatures as much as 10 to 20 degrees below normal. The highest anomalies will feature across the North Slope region, where daytime highs could be 30+ degrees below normal and morning lows below freezing. 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 the Alaska Panhandle and mainland Alaska, Fri, Aug 5 and Mon-Tue, Aug 8-Aug 9. - Much below normal temperatures across portions of northern mainland Alaska, Sat-Tue, Aug 6-Aug 9. 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