Alaska Extended Forecast Discussion NWS Weather Prediction Center College Park MD 304 PM EDT Mon Aug 13 2018 Valid 12Z Fri Aug 17 2018 - 12Z Tue Aug 21 2018 Some improvement in model/ensemble consensus was noted compared to yesterday, during days 4-5 (Fri-Sat), and model/ensemble consensus was sufficient to warrant use of a majority deterministic multi-model/ensemble blend (including the GFS/ECMWF/ECENS/GEFS) as a basis for the forecast. These solutions showed general agreement on the low pressure system approaching the eastern Aleutians and Alaska Peninsula from the south during that time frame. A trend was noted over the past day toward greater amplification of the flow in general, likely in response to the upstream extratropical transition/absorption of the remnants of Tropical Storm Hector. From day 6 (Sun) onward, uncertainty continues to quickly increase, although some very broad consensus does seem to be emerging. The amplified flow pattern will support a northward or perhaps even slight west of north track of the surface low toward the Alaska Peninsula through Mon as the system occludes. Farther west, an additional amplifying trough/upper low exiting eastern Asia are expected to absorb the remnants of Tropical Storm Hector as it recurves across the North Pacific (triggering continued broad flow amplification, as described above). This system should enter the Bering Sea on day 6 and then move relatively slowly eastward through day 8. Deterministic solutions are not quite as intense with this low as they were yesterday, but confidence in this portion of the forecast remains quite low given the complex nature of the interactions occurring. Precipitation looks fairly widespread across the North Slope and Brooks Range Fri-Sat as the Arctic shortwave energy and a frontal boundary cross the region. Farther south, onshore flow will initially support scattered showers across southern mainland and Southeast Alaska. The low pressure system approaching the Alaska Peninsula by the weekend will likely support more somewhat widespread rains for much of southern Alaska, lingering into early next week. Finally, the potential low pressure system in the Bering Sea by next weekend could result in potential rains and gusty winds for portions of the Aleutians and perhaps even western mainland, although confidence is much too low at this time to discuss specific impacts or locations. Ryan 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