Alaska Extended Forecast Discussion NWS Weather Prediction Center College Park MD 608 PM EST Wed Nov 18 2020 Valid 12Z Sun Nov 22 2020 - 12Z Thu Nov 26 2020 ...Strong system may approach Kodiak early Monday... ...Overview and Guidance/Predictability Assessment... Progressive and active pattern will continue into next week, driven in part by an energetic jet stream from Japan and across the North Pacific. To the north, upper ridging will stretch WNW to ESE across the Arctic Ocean into the Canadian Archipelago. 12Z models were in good agreement in the larger scale to start the period Sun-Tue except for the GFS. Main system of concern will deepen just astride the eastern Aleutians Sunday and track to a location just off Kodiak by 12Z Mon as a potentially strong (960s mb) surface low. The GFS was notably weaker/east as a result of less (or no) phasing which remains a possibility, but not a higher likelihood solution given the trend and ensemble clustering. This did shift the low much closer to the coast than 24 hrs ago along with lower pressures. That system should move eastward to the Panhandle but continue steadily eastward. Next system will move through the central Bering around Mon into Tue, but this has shown poorer continuity in the deterministic runs. However, latest 12Z ECMWF/Canadian were close enough and plausible that a modest blend with the ensemble means (mostly ECMWF ensemble mean) offered a good starting point, taking the parent low along the eastern Russia coast as the triple point develops across the AKPen and into the Gulf. Broad cyclonic flow west of 150W could support a trailing cold front across the Aleutians. ...Weather/Threats Highlights... Mon-Tue system has the potential for widespread modest rain/snow along the eastern Aleutians and over Kodiak to the southern Kenai along with breezy/windy conditions (40kts+). This could continue eastward to the Panhandle but with a jog southeastward it may focus into the southern Panhandle to British Columbia. Next system in the Bering may have a less favorable moisture source but could still bring some rain/snow to the island chain on southwesterly flow ahead of the front. Too early to tell how much precipitation may expand over Southcentral next Tue-Wed but at this point it appears generally light to perhaps modest amounts. Temperatures will start well above normal along northern areas thanks to upper ridging, but will trend closer to more typical values in time. Southeastern third of the mainland into the Panhandle will see near to below normal temperatures. Fracasso Hazards: - Heavy precipitation across portions of mainland Alaska, Sat, Nov 21. - High winds across portions of mainland Alaska, Sat, Nov 21. 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