Alaska Extended Forecast Discussion NWS Weather Prediction Center College Park MD 620 PM EST Mon Mar 02 2020 Valid 12Z Fri Mar 06 2020 - 12Z Tue Mar 10 2020 ...Overview and Guidance/Predictability Assessment... Upper pattern will transition toward some intermediate ridging before troughing from the Bering Sea moves through early next week. This will be forced by very strong upper ridging south of Kamchatka next Mon/Tue as the ECMWF ensemble mean forecasts 500mb height anomalies over +3 sigma which is quite high for a 7-8 day lead time. The 12Z models clustered fairly well with the multi-center ensembles more or less through the period, with two main systems of interest. The first system will be a surface low in the Bering on Friday dropping southeastward as high pressure retreats from the Interior. Weak system to the north across the Bering Strait should be of little consequence as its upper support dissipates. Though the 12Z GFS/GEFS were a bit slower aloft south of 70N, they were quicker with the sheared northern part compared to the ECMWF/Canadian/UKMET which had a more consolidated shortwave. Minority weighting of the GFS (20%) was included given its acceptable forecast for the rest of the domain. Next system in the Bering will be right behind the first one, moving through this weekend into southwestern Alaska then the Gulf next Monday. After an odd 06Z run, the 12Z GFS again clustered well with the ECMWF/Canadian and a blend with the ensembles formed a good starting point for next Sun/Mon as the main sfc low moves across Southcentral but the triple point skirts across Kodiak and near the Kenai Peninsula. Progressive upper flow should keep the system moving steadily into the Panhandle and BC. ...Weather Highlights/Threats... Aside from generally lighter rain/snow over the Aleutians to start the period, a realtively dry Saturday over the state will given way to increased rain/snow to the Aleutians and southwestern areas later Saturday into Sunday as the next Bering system moves east. Modest snow should overspread Southcentral Sunday near the low pressure track with increased moisture focused over the Panhandle by Monday before diminishing Tuesday. This could be locally heavier with enahanced moisture convergence squeezed between the main low and the sfc high to the south, but it will be fighting against a loss of subtropical connection back to the southwest. Temperatures will be trending milder from intially 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. 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 and mainland Alaska, Sun-Mon, Mar 8-Mar 9. - Heavy snow across portions of mainland Alaska, Sun-Mon, Mar 8-Mar 9. - Much below normal temperatures across portions of mainland Alaska, Thu-Sat, Mar 5-Mar 7. - Much below normal temperatures across portions of mainland Alaska, Thu-Fri, Mar 5-Mar 6. 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