Alaska Extended Forecast Discussion National Weather Service College Park MD 725 PM EDT Mon May 26 2025 Valid 12Z Fri 30 May 2025 - 12Z Tue 03 Jun 2025 ...Moderate to heavy rain expected for the Panhandle Friday to Saturday... ...Heavy rain possible from the eastern Aleutians to the Alaska Peninsula and into the Kenai Peninsula early next week... ...General Overview... Much of mainland Alaska will remain sandwiched between two main cyclone tracks during much of the medium-range period. At least a couple pieces of vorticity breaking off from the gyre over the Arctic Ocean are forecast to dip across the Bering Strait late this week and into the Bering Sea this weekend when the vorticities will interact and be absorbed by a cyclone reaching the Aleutians late this weekend. Meanwhile, a weaker cyclone is forecast to reach the Alaska Panhandle this weekend with moderate to heavy precipitation. There is decent model agreement for an upper ridge to establish across mainland Alaska late this week into the weekend followed by an increasingly amplified pattern across the Alaskan domain by early next week. ...Guidance Evaluation and Preferences... With the presence of numerous smaller scale disturbances embedded within the aforementioned two main cyclone tracks, the predictability of individual disturbances beyond Day 5 remains lower than normal. The largest model uncertainty today appears to be from the Bering Strait southward across the Bering Sea through the Aleutians this coming weekend into early next week when two or more upper lows that break off from the Arctic gyre are forecast to dip south into the Bering Sea and interact with the next North Pacific cyclone moving into the Aleutians. Models agree well that the North Pacific cyclone will become dominant and absorb the upper lows originating from the Arctic gyre. The deterministic solutions as well as the ensemble means today favor a more progressive motion of the cyclone through the Aleutians into the southeastern portion of the Bering Sea for Days 6-8. This more progressive consensus would bring the cyclone center closer the coast of southwestern Alaska by Day 8 next Tuesday. Over mainland Alaska, model guidance today continues to show decent agreement for a negatively-tilted upper ridge to establish late this week within an increasingly amplified upper-level pattern across the Alaskan domain through the weekend into early next week. Meanwhile, models are in excellent agreement for the cyclone over the Gulf of Alaska to gradually weaken with time as it is forecast to reach the Panhandle this weekend. The WPC forecast package today is based on the consensus of the 12Z ECMWF/00Z & 12Z EC mean (40%), 12Z GFS/06Z & 12Z GEFS (40%), and 12Z CMC/CMC mean (20%) with ensemble means comprising the vast majority toward the end of the forecast period. WPC continuity is well-maintained across the Alaskan domain but with a notably faster approach of the cyclone toward southwestern Alaska on Day 8. ...Weather/Hazards Highlights... Precipitation associated with a dissipating system is expected to become less heavy from the southern coastline of Alaska and through the Panhandle by the time the medium-range period begins on Friday. However, the next round of moderate to locally heavy precipitation is forecast to arrive on Friday ahead of the next quick-moving cyclone. This round of precipitation is forecast to gradually taper off later on Saturday into Sunday as the cyclone dissipates. Farther inland across the interior section of mainland Alaska, scattered afternoon and evening thunderstorms are likely to develop from southwestern through eastern interior and into northeastern Alaska in the presence of an unstable airmass. There is a tendency for these activities to become more widely scattered with time as the upper ridge is forecast to build aloft by this weekend into early next week. Across the North Slope, it will be cold enough for some wet snow to fall especially toward the high elevations of the Brooks Range late this week and perhaps near the coast this weekend. Unsettled weather ahead of an occluded cyclone is forecast to progressively move up the Aleutian Island chain this weekend, reaching into the Peninsula and southwestern Alaska followed by the Kenai Peninsula early next week. The rain is expected to be heaviest on the south-facing portion of eastern Aleutians, Alaska Peninsula and into Kenai Peninsula early next week as depicted on the WPC Day 3-7 Hazards map. Temperatures are forecast to average below normal for the entire Alaskan domain as the medium-range period begins on Friday. A slow warming trend is then forecast under a gradually amplifying upper-level ridge. The exception will be along the Panhandle where lingering clouds and precipitation will keep temperatures cooler than normal. 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