Alaska Extended Forecast Discussion NWS Weather Prediction Center College Park MD 552 PM EST Tue Mar 03 2020 Valid 12Z Sat Mar 07 2020 - 12Z Wed Mar 11 2020 ...Overview and Guidance/Predictability Assessment... Upper ridging initially poking into the Aleutians on Saturday will move eastward and flatten by next week, allowing troughing to move through the Bering Sea. That will settle over the Interior next Tue/Wed with another surge of colder than normal temperatures for the mainland. The 12Z models/ensembles were in generally good agreement to start. Weak system will skirt the North Slope as a shallow trough swings through. The larger system will be in the Bering Sea and will move eastward. Its triple point will likely rush toward the AKPEN/Kodiak then into the Gulf as (potentially) a surface wave along the front lifts toward the old parent low and perhaps combines/deepens near Bristol Bay/AKPEN around late Sun into Mon. The GFS was much less bullish on this scenario than the ECMWF (which was much more aggressive) while the UKMET/Canadian did show a sfc wave but with development just to the southeast of the AKPEN Monday. With a trend toward more development along the front, opted to weight the ECMWF enough to show such an evolution but less intense as the ensemble support was not there at this time. It seems the ECMWF has been about a cycle ahead of the other guidance lately but has also favored more phasing in its forecast than reality. By next Tue, low should move through the Gulf and into/through the Panhandle thereafter. Ensembles were in better agreement than any given deterministic model (though the GFS/ECMWF were aligned in the Bering), so favored their consensus more than the GFS/ECWMF cluster. This was a slower progression than the forecast 24 hrs ago given the trend to have the trailing surface wave slow part of the system down, but otherwise continue eastward steadily in wavy zonal flow. ...Weather Highlights/Threats... Rain/snow will increase over the Aleutians and southwestern areas later Saturday into Sunday as the lead Bering system moves through. Modest snow should overspread Southcentral Sunday near the triple point low pressure track. Precipitation will then expand across the Panhandle Monday with the lead wave then the real cold front followed by the upper trough Mon-Wed, respectively. Precipitation could be locally heavier with enhanced moisture convergence but a steady loss of subtropical connection back to the southwest. Temperatures will be trending milder from initially well below normal values over the Interior. The Panhandle will likely hold onto chillier temperatures longer with enough easterly flow out of Canada through this weekend before milder Pacific air moves in. Colder than normal temperatures will again fill in behind the departing system over western areas next week. Fracasso 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 Hazards: - Heavy precipitation across portions of the Alaska Panhandle to the coast sections of southern Alaska, Sun-Tue, Mar 8-Mar 10. - Heavy snow across portions of southern Alaska, Sun-Mon, Mar 8-Mar 9. - Much below normal temperatures across portions of eastern mainland Alaska, Fri-Sat, Mar 6-Mar 7. - Much below normal temperatures across portions of western mainland Alaska, Mon-Tue, Mar 9-Mar 10. 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