Alaska Extended Forecast Discussion NWS Weather Prediction Center College Park MD 549 PM EST Sun Jan 19 2020 Valid 12Z Thu Jan 23 2020 - 12Z Mon Jan 27 2020 ...Well below average temperatures to return to most of mainland Alaska by late in the week... Models/ensembles show good consensus that an upper level ridge should build northward across the Aleutians and into the Bering Sea from Thu onward, with a closed upper high center eventually migrating toward eastern Russia by early next week. The downstream implication for much of mainland Alaska will be a strong surface high intensifying near the Bering Strait and increasingly cold conditions. High and low temperatures approaching 20 deg F below average are possible by late week into the weekend, especially across the Interior, southwestern mainland Alaska, and northern Alaska Peninsula. Arctic shortwave energy should dive south along the eastern periphery of the upper ridge, the amplitude of which now looks sufficient to interact with additional shortwave energy from an active North Pacific jet, resulting in potential development of a closed upper low somewhere near southern mainland Alaska or perhaps in the Gulf of Alaska by next weekend. This setup should keep the Aleutians as well as Southeast Alaska with relatively high precipitation chances due to the active storm track. Although greater precip chances may work their way north into southern mainland Alaska by the weekend as the upper low develops overhead. Models continue to struggle with the evolution and progression of low pressure systems crossing the North Pacific and the Gulf of Alaska during the extended period, although somewhat better clustering was evident among ensemble members today relatively to yesterday. Needless to say, that aspect of the forecast remains quite chaotic with very low predictability. A blend of the ECWMF/CMC along with the ECENS/GEFS ensemble means was used throughout the extended forecast period. More weight was placed on the ECMWF relative to other guidance early in the forecast period, with a gradual shift to heavier weight place on ensemble means through time. Ryan 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 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