Alaska Extended Forecast Discussion National Weather Service College Park MD 723 PM EDT Thu Jun 19 2025 Valid 12Z Mon 23 Jun 2025 - 12Z Fri 27 Jun 2025 ...General Overview... The persistent omega blocking pattern across the Alaskan domain is forecast to relax a bit as the medium-range period begins next Monday. The now familiar upper anticyclone centered over mainland Alaska is forecast to retreat southeastward as a deep upper low downstream moves away into the Pacific Northwest through the short-range period. It appears that the retreated upper high will tend to reestablish near/over the northeast corner of Alaska during the latter half of next week. Meanwhile, the Bering closed low/trough should slide very slowly southeast toward the Aleutians through much of next week. Relatively weak waves/triple-point lows are forecast to eject eastward across the North Pacific toward the Gulf of Alaska and the Panhandle on the underside of the upper ridge/high anchored over mainland Alaska. ...Guidance Evaluation/Preferences... Model guidance today shows good agreement on the aforementioned synoptic pattern evolution through next week. The deterministic model solutions from the GFS/EC/CMC begin to diverge a bit on Day 4 regarding how much of vorticity from the Bering Sea cyclone will be retained versus how much vorticity will be carried eastward into the Gulf of Alaska by the main jet stream across the North Pacific. The ensemble means are in better agreement with one another by way of more clearly indicating the possibility of the closed high to reestablish itself near the northeast corner of Alaska, the slow southeastward progression of the Bering Sea low, and periodic eastward ejection of relatively weak waves or triple-point lows across the Gulf of Alaska toward the Panhandle through next week. The WPC Alaska medium-range forecast package was based on a consensus blend of 40% from the 12Z ECMWF/00Z EC mean, 40% from the 12Z GFS/GEFS, and 20% from the 12Z CMC/CMC mean, with increasing proportions from the ensemble means toward the end of the forecast period. WPC continuity is well maintained across the Alaskan domain but a noticeably faster eastward progression of frontal systems is depicted across the North Pacific. ...Weather/Hazards Highlights... With the anticipated retreat of the upper high over mainland Alaska, the afternoon heat across the Yukon Flats is forecast to moderate a bit early next week. However, given the possible reestablishment of the upper high near the northeast corner of Alaska later next week, there is the potential for a return of the afternoon heat for the Yukon Flats. Underneath the retreating upper high, there will also be a lingering front across northern Alaska where scattered showers and thunderstorms are expected daily along the Brooks Range and across the eastern Interior including Fairbanks through next week. Daily rainfall amounts could exceed one inch across the eastern Interior. The Alaska Peninsula, southern coastline, and into the Panhandle should start out relatively dry next week. But as low pressure waves gradually eject eastward across the Gulf of Alaska, increasingly rainy weather can be expected to overspread these areas from west to east through the latter half of next week. The southwestern coastal areas and all of the Aleutians can also expect increasing rain chances later next week as the Bering Sea low edges southward to come into a better chance of interacting with the North Pacific jet stream. More seasonable conditions are expected near the southern coast and the larger cities, with highs generally in the 50s and 60s. Kong Additional 3-7 Day Hazard Information can be found on the WPC medium range hazards outlook 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