Alaska Extended Forecast Discussion NWS Weather Prediction Center College Park MD 627 PM EST Wed Feb 17 2021 Valid 12Z Sun Feb 21 2021 - 12Z Thu Feb 25 2021 ...Overview and Guidance/Uncertainty Assessment... Higher predictability features next week will be an upper low meandering near Banks Island in the Canadian Archipelago and upper ridging in the mid-latitudes south of the Gulf of Alaska. This will maintain wavy westerly flow across the Aleutians into the Gulf/Panhandle enhanced by a shortwave or weak upper low swinging through Southcentral late Sun into early Mon (and the Panhandle late Mon into early Tue). To the west, the ensembles remain unstable and separated in timing, becoming out of phase (GEFS vs ECMWF EPS vs Canadian ensembles) as early as next Monday. Still prefer to side with the quicker group of the guidance, with support from the 12Z ECMWF/Canadian/UKMET rather than the slower, but not implausible, GFS. This did modify some timing of incoming systems but the large uncertainty out of northeastern Asia makes this tough to remain consistent day to day. Utilized an increasing weight of the ECMWF ensembles to prevent large future changes. By the middle of next week, possibility exists for a defined system to move north-northeastward into the Gulf (ECMWF/Canadian) but downplayed this newer scenario for now. ...Weather/Hazards Highlights... System into the Gulf early Sunday will yield modest to perhaps locally heavy rain/snow over the Panhandle followed by showery precipitation Monday as the upper trough moves through. Thereafter, weaker systems in the flow will produce generally light rain/snow to the Aleutians and into southwestern Alaska as they progress eastward, generally tracking through the Gulf. Moisture may attempt to spread into/through the Tanana/Yukon Valley around the middle of next week, though the ECMWF remained most bullish with this scenario. Well below normal temperatures are likely for much of the Interior and into Southcentral Sun-Mon as sub-500 dm heights rotate through the Alaska Range. The North Slope and Panhandle will see near to below normal temperatures through the period. Some moderation is forecast over the Aleutians to southwestern Alaska by the middle of next week as heights rise in advance of troughing in the far western Bering Sea. Temperatures may be 5-10 degrees above normal over the Y-K Delta into the AKPen. Fracasso Hazards: - Heavy precipitation across portions of the Alaska Panhandle, Sat-Mon, Feb 20-Feb 22. - Much below normal temperatures across portions of mainland Alaska, Sat-Tue, Feb 20-Feb 23. 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