Alaska Extended Forecast Discussion NWS Weather Prediction Center College Park MD 600 PM EST Tue Feb 16 2021 Valid 12Z Sat Feb 20 2021 - 12Z Wed Feb 24 2021 ...Overview and Guidance/Uncertainty Assessment... Ensembles show upper troughing or a weak upper low swinging through the Interior and Southcentral next week on the southwest side of a parent/deeper upper low near the Canadian Archipelago. As the child upper feature continues eastward into the Yukon next Monday, the parent upper low will continue its slow march westward through the Arctic Ocean. This will maintain cold temperatures over the interior of the state with a storm track over the Aleutians and across the Gulf into the Panhandle. This will lead to bouts of modest to locally heavier rain/snow to the Panhandle for the period, especially this weekend. Broad consensus served as a reasonable starting point though with uncertainty in timing of smaller-scale features in the rather quick west-to-east flow along 55N Sat-Mon. 12Z GFS was a bit off in timing compared to the 12Z ECMWF and ensembles, but was not necessarily implausible. Agreement was good on the deepening of the system into the Gulf by early Sunday as the system pushes through the Panhandle. Thereafter, quick and weak to modest intensity systems will fly through the Bering/Aleutians next Mon-Wed with little predictability downstream of a fast W Pac jet. Ensembles diverged as well with the ECMWF/Canadian ensembles leading the slower GEFS ensembles. Given the strong jet upstream translating eastward, relied mostly on the quicker ensembles but with the caveat that a deeper system upstream could buckle the flow enough to slow things down in future runs. ...Weather/Hazards Highlights... Defined system into the Gulf (lead weaker system Saturday then the stronger one by Sunday) will yield modest to perhaps locally heavy rain/snow over the Panhandle followed by showery precipitation Monday as the upper trough moves through. Next week, weaker system in the flow will produce generally light rain/snow to the Aleutians and into southwestern Alaska as they progress eastward. Well below normal temperatures are likely for much of the Interior and into Southcentral by Monday as the sub-500 dm heights rotate through the region. The North Slope and Panhandle will see near to below normal temperatures through the period. Some moderation is possible 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. 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