Alaska Extended Forecast Discussion NWS Weather Prediction Center College Park MD 422 PM EDT Tue Oct 02 2018 Valid 12Z Sat Oct 06 2018 - 12Z Wed Oct 10 2018 The latest models and ensemble means continues to maintain good agreement and continuity for the large scale pattern through the medium range over Alaska. Overall, these models are showing a ridge steadily strengthening and amplifying over the medium range. During the weekend, the ridge will shift eastward over western Canada as the closed low drifts eastward. However, by the beginning of the week, the upper ridge strengthens over the Aleutians and western Alaska--shifting eastward on Tuesday and Wednesday. A closed low will remain over the Bering Sea throughout the medium range period and will be an anchor for the mean trough extending into the central Pacific. Although the large scale pattern is agreed upon, the uncertainties in the forecast details derive from tropical systems. Hurricane Walaka will stay west of Hawaii as it takes a northward track toward the central Pacific. By Sunday, Walaka is expected to weaken to a tropical storm. The 00Z ECMWF continues to be slower than the 12Z GFS in the beginning of the forecast--and maintains a central of circulation in the beginning of the week as it cuts through the surface high pressure of the eastern Pacific. The 12Z GFS is faster than the 00Z ECMWF. Based on the CPHC forecast, trended toward the 00Z ECMWF and using the 06Z GEFS/00Z ECENS by day 6 and on. There is still low confidence along with lack of any guidance that can provide a template for the desired track/timing yield a conservative depiction in the manual forecast. Sensible weather effects in terms of wind and precipitation continue to be very uncertain along the southern coast of the mainland/Panhandle. The other tropical system that may impact Alaska is Super Typhoon Kong-Rey. Both the 00Z ECMWF and 12Z GFS have Kong-Rey tracking toward the Aleutians and being incorporated into the Pacific mean trough by day 7/8. Because of this, a blend of the 06Z GEFS/00Z ECENS was used. The chance of precipitation increases over the weekend across the Bering Sea and particularly across Juneau as an occluded system approaches the coastline. Because the closed low lingers through the beginning of the week, the highest chances of precipitation will be along the Aleutians and western Alaska. High temperatures will stay in the low-mid 50s, decreasing to the 40s and 30s across the interior of Alaska. Reinhart/Rausch WPC medium range Alaskan products including 500mb, surface fronts/pressures progs and sensible weather grids can be found at: http://www.wpc.ncep.noaa.gov/alaska/ak_5dayfcst500_wbg.gif http://www.wpc.ncep.noaa.gov/alaska/akmedr.shtml http://www.wpc.ncep.noaa.gov/alaska/ak_5km_gridsbody.html