Alaska Extended Forecast Discussion NWS Weather Prediction Center College Park MD 347 PM EDT Tue Aug 13 2019 Valid 12Z Sat Aug 17 2019 - 12Z Wed Aug 21 2019 With the details of southeast progression of a compact upper low/trough expected to be over eastern Siberia on Wed-Thu seemingly resolved, the extended forecast now looks somewhat less contentious. There are still the typical low-predictability embedded shortwave issues and by later in the period question marks over the relative strength/position of the larger scale features. Model/ensemble consensus shows a strong eastern Bering upper high as of early Sat being pinched/pushed northwestward, between northwestern North America/northeastern Pacific troughing (anchored by the upper low that has been meandering over the western Canadian Archipelago) and a northwestern Pacific upper low. The Pacific low should reach the Aleutians around day 8 next Wed. The downstream ridge may lead to rising heights over the mainland/Gulf of Alaska by the end of the period. Teleconnections relative to the upper low's negative height anomaly center support the ensemble means and some operational runs that bring some ridging into the mainland/Gulf by next Wed. During the first half of the period a mostly operational model blend places more weight on the 00Z ECMWF relative to the 00Z/12Z GFS or 00Z CMC as recent ensemble mean trends favor a stronger Bering ridge aloft. The blend phases out the CMC fairly quickly due to questionably far northward extent of the North Pacific low. At the same time ensemble means provide the greatest support for the 00Z ECMWF/GFS/CMC forecast of the northwest Canada upper low versus the farther eastward 06-12Z GFS runs. There is still a fair degree of uncertainty over path of this low given model variability over the past few days. The blend provides fairly good continuity for surface low pressure tracking near/southeast of the Panhandle. Expect a brief period of brisk winds behind this system. The 12Z GFS downplays a low-confidence wave that prior GFS runs had south of the Aleutians around Sun, meriting modest inclusion of that run in the overall forecast. Later in the period a model/ensemble mean blend provides a reasonable starting point as guidance continues to cluster decently. Operational input helps to enhance the means somewhat for the North Pacific/Aleutians system (which should be accompanied by enhanced winds and areas of rainfall) while the means dampen operational model differences farther northeast. The 12Z GFS may become too fast with the Aleutians system after Tue. 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 - Heavy precipitation across portions of mainland Alaska, Fri, Aug 16. 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