Alaska Extended Forecast Discussion NWS Weather Prediction Center College Park MD 543 PM EST Mon Nov 02 2020 Valid 12Z Fri Nov 06 2020 - 12Z Tue Nov 10 2020 ...Guidance/Predictability Assessment... Troughing is forecast to push through much of the state in progressive flow, bounded by upper ridging anchored in the northeastern Pacific but at times nosing into southeastern areas. The 12Z guidance offered good clustering to start the period Fri-Sat with a weakening Bering system into western Alaska and high pressure near the Panhandle in western/northwestern Canada. Tail-end of the Bering system will linger south of the Aleutians as a mid-latitude/subtropic system lifts northward toward the eastern Aleutians late Sat. By early Sun, 12Z GFS slips the surface low east of the other models (closer to Kodiak) which was a shift westward from its 06Z run. Preferred to side with the larger ECMWF-led consensus that included both the Canadian and UKMET that take the surface low across the AKpen and into Bristol Bay, then into southwestern areas before translating eastward across the Interior. Triple point low should develop into the Gulf late Sun and head into the Panhandle Mon per the consensus. Next system of interest will enter the western Bering around late Sun, moving eastward next Mon/Tue. 12Z ECMWF/Canadian paired better with the ensemble means than the GFS, and again preferred that cluster of solutions. However, ECMWF/Canadian outpaced the ensemble means which was certainly plausible given the quicker flow, but how quickly the system may develop into the western Bering to begin with remains in question. Therefore, trended toward a mostly ensemble mean solution by the end of the period. ...Weather/Threats Highlights... Weakening system in the Bering Fri will bring lingering coastal rain and inland/northern snow to the region with breezy conditions as milder air attempts to push northeastward. Reforming boundary astride the North Slope will support well above normal temperatures near the Brooks Range southward over much of the Interior. By contrast, below normal temperatures are expected over the Panhandle and southeastern areas Fri with high pressure over Canada. That may persist for several days thereafter until it slips southeastward late in the weekend. Back to the west, approaching Pacific system will bring increasing coastal rain and inland snow to southwestern portions of the state late Sat into Sun on southerly to southeasterly flow. Precipitation may be heavy with several inches (liquid) possible in favored areas. In-house bias-corrected QPF shows 3-5 inches over southeastern Kenai eastward toward Yakutat and some locally higher amounts into Mon. Next system over/near the western to central Bering Sea next week should spread another area of precipitation and strong winds across the Bering Sea/Aleutians. 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, Nov 8. - Heavy precipitation across portions of the Alaska Panhandle, Mon, Nov 9. - High significant wave heights for coastal portions of mainland Alaska, Thu, Nov 5. 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