Alaska Extended Forecast Discussion NWS Weather Prediction Center College Park MD 539 PM EST Thu Feb 25 2021 Valid 12Z Mon Mar 01 2021 - 12Z Fri Mar 05 2021 ...Robust Bering Sea/Aleutians system Monday... ...Overview and Guidance/Uncertainty Assessment... The medium range period will be driven by a strong upper positive height anomaly moving off Hokkaido this weekend (+3 to +3.5 sigma 500mb heights per the ECMWF ensemble mean) and into the Bering Sea by the middle of next week. This will favor downstream robust yet progressive troughing out of the Bering ahead of the ridge into the Gulf of Alaska in general west-to-east flow. With a rather defined wavelength, the models/ensembles were in good to very good agreement overall. A blended deterministic solution was utilized for the first few days of the period Mon-Wed (12Z GFS/ECMWF/Canadian/UKMET) in order to capture the depth of the Bering low Monday and as it made its way to the Gulf of Alaska well behind the surface front. By next Thu/Fri, GFS/ECMWF paired well enough with their ensemble means (and each other) to use a majority of their agreement to define the next system into the Bering as the Gulf low slowly weakens. The 12Z parallel version of the GFS was preferred over the operational version due to its better handling of lead-in flow south of the Gulf and upstream system tracks. Upper pattern may flatten by next weekend suggesting lower predictability. ...Weather/Hazards Highlights... Bering system on Monday will bring windy conditions to the region, mostly over the Aleutians, with 50kts possible across the island chain and 60kts over the open waters around the low. Precipitation will be light to modest due to the progressive flow. As it moves through the Panhandle, another round of rain/snow is likely for areas that have seen an active pattern. Light to moderate snow will spread across southwestern areas ahead of the occlusion and around the trailing surface low. Precipitation will then again focus on the Panhandle for the end of the week as the upper trough digs into/through the Gulf. Temperatures will generally be below normal over much of the state next week, focused over the western/southwestern portion of the state as the upper low moves through. Fracasso Hazards: - High winds across portions of mainland Alaska and the Aleutians, Sun-Mon, Feb 28-Mar 1. Additional 3-7 Day Hazard information can be found on the WPC medium range hazards 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