Alaska Extended Forecast Discussion NWS Weather Prediction Center College Park MD 741 PM EDT Wed Jul 26 2023 Valid 12Z Sun Jul 30 2023 - 12Z Thu Aug 03 2023 ...Pattern overview with Guidance Evaluation/Preferences and Predictability Assessment... An increasingly uncertain pattern is expected over Alaska during the medium range period. Even as early as day 4 into day 5, there are a lot of questions remaining on the evolution/tracking of an upper low initially near the southern coast of Alaska. The 12z GFS (with support from the ensemble means) track this low out into the Gulf keeping it there well into next week while the 12z ECMWF (and previous 00z run) tend to track the low northward into the Mainland and weaken it given a more certain and blocky upper ridge over northwest Canada. Also uncertainty in timing of an initial trough through the Bering Sea mid-next week and additional troughing moving over northern Alaska. The next system should cross the western Aleutians around Tuesday-Wednesday moving into the Bering by Thursday. GFS pulls this low north (it has stronger troughing over the Arctic/northern Alaska) while the ECMWF spins this up into a well defined upper low over the Aleutians. The CMC is well to the west of consensus lifting it north into eastern Russia due to a much stronger ridge over the Bering at the same time. Given the uncertainty throughout the entire period, it seemed to make the most sense to lean on the more agreeable ensemble mean guidance, along with the GFS which was closest to the mean solutions with the upper low over the Gulf. Used a little bit of the 00z ECMWF (which was better than the 12z run) due to better consistency with the GFS over the Bering Sea system which got very washed out in the ensemble means. This approach helped maintain fairly good continuity with yesterdays forecast as well which seemed reasonable given there is not enough agreement yet to diverge from continuity. ...Weather/Hazards Highlights... Showers can be expected over eastern, northern, and southern parts of the Mainland with some local enhancement along favorable terrain. Wet weather should also advance east through the Aleutians as a series of systems moves through the region. Temperatures are most likely to be above normal across the Interior sections of Alaska where upper ridging should prevail most of the period. Southern and northern Alaska shouldbe more near or below normal given influence from upper troughing. 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 No significant hazards are expected over Alaska during this forecast period. 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