Alaska Extended Forecast Discussion NWS Weather Prediction Center College Park MD 314 PM EDT Wed Oct 16 2019 Valid 12Z Sun Oct 20 2019 - 12Z Thu Oct 24 2019 Model/ensemble guidance has similar ideas for the overall large scale evolution during the period but there are significant uncertainties with multiple embedded features. Consensus shows a mean trough aloft (likely with an embedded low) over the Bering Sea for most of the period while progressive flow prevails across the North Pacific. From the start of the period early Sun the operational models and individual ensemble members vary on the location/strength of individual surface lows over the Bering and especially the northeastern Pacific/Gulf of Alaska. There are also divergent solutions for how a western Pacific wave may interact with the northern stream dynamics--with the ensemble means fairly agreeably consolidating low pressure near the Alaska Peninsula-Kodiak Island around the middle of next week. Solutions trend out of phase for upstream flow late in the period but there are hints of a weak wave/frontal system that could reach the Aleutians. At higher latitudes, evolution of an Arctic ridge aloft should allow an upper low to approach the northeastern corner of the mainland but with a fair amount of spread for precise upper low position. Overall the 06Z GEFS/00Z ECMWF means--with some operational input and manual adjustment where the means could be enhanced--provided the best initial starting point for today's forecast given the diverse array of guidance and in a number of cases poor model continuity. In particular this solution provided a good middle ground for the potentially strong storm near the Alaska Peninsula/Kodiak Island around midweek, with the 00Z ECMWF weak and to the east versus the 12Z/15 run that was deep/westward like the latest CMC runs. The new 12Z ECMWF has returned to a slower version of yesterday's 12Z run. The 00-06Z GFS runs were closest in principle to the ensemble mean scenario while the 12Z GFS trended slower/southward. The means also offered an intermediate path for the upper low that approaches the northeastern mainland, between the 00Z ECMWF that was westward and latest GFS runs that define the eastern side of the envelope. With uncertainty in the specifics, the general pattern should favor highest precipitation totals across the extreme southern mainland and Panhandle with some potential for significant totals to extend somewhat westward if the western side of the envelope verifies for the expected midweek storm. Strong winds will also be a possibility based on potential depth of the surface low. Rausch 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 Alaska Hazards... - Heavy precipitation across portions of the Alaska Panhandle and mainland Alaska, Tue-Wed, Oct 22-Oct 23. - High winds across portions of mainland Alaska, Wed, Oct 23. 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