Alaska Extended Forecast Discussion NWS Weather Prediction Center College Park MD 730 PM EDT Sat Jul 24 2021 Valid 12Z Wed Jul 28 2021 - 12Z Sun Aug 01 2021 ...Guidance/Predictability Evaluation... The latest ensemble means from the ECMWF, GFS, and CMC agree reasonably well with the synoptic evolution across Alaska through Day 8. It appears that a general model compromise together with their deterministic solutions should work well as a starting point. This will keep the relatively deep low lingering and then slowly weakening over eastern Siberia into late next week. By later next weekend, the 12Z ECMWF is bringing a deeper cyclone into the Bering Sea, possibly after ingesting some moisture from T.S. Nepartak. On the other hand, the GFS tends to be the fastest solution with regard to bringing the associated upper trough from the Bering Sea towards western Alaska as a surface low pressure wave develops and heads towards the West Coast. This scenario is depicted in the 12Z CMC as well. The WPC Alaskan forecast package for Days 7-8 leans towards to slower ensemble means solutions, which would keep a slightly stronger ridge over southern Alaska next weekend. A general even blend of the 12Z ECMWF/00Z EC mean, 12Z GFS/12Z GEFS, together with some contributions from the 12Z CMC/CMC mean was adapted for Days 4-6. ...Weather/Threats Highlights... The main areas of precipitation and unsettled weather will be focused across the western and northwestern mainland throughout the period as southerly flow ahead of the Bering Sea cyclone interacts with a stalled stationary boundary across the North Slope. The best chance for heavier precipitation will be Tuesday and Wednesday across parts of the Seward Peninsula, and northward. Moderate to locally heavy rains may continue after Wednesday, but confidence in the amounts and particular locations remains low at this time. High waves and gusty winds may also present themselves near the West Coast. The next developing cyclone moving into the Bering Sea and Aleutians later in the week could lead to some higher waves and precipitation for parts of the Aleutians especially by next weekend. For western and northern parts of Alaska, temperatures should remain below normal, but should trend warmer for eastern parts of the state as upper level ridging builds in aloft. Kong/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