Alaska Extended Forecast Discussion National Weather Service College Park MD 704 PM EDT Mon Jun 2 2025 Valid 12Z Fri 06 Jun 2025 - 12Z Tue 10 Jun 2025 ...Overview... The extended range period starts Friday with a weakening upper- low over mainland Alaska that will linger into the weekend. To the South, an upper-level low and accompanying surface frontal system will lift northeastward from the northeastern Pacific and into the Gulf of Alaska. Both lingering precipitation chances from the initial upper-low and the approach of the next system will keep unsettled weather in the forecast at least through the weekend, with a general downward trend in precipitation as the Gulf system begins to weaken early next week. The presence of the initial upper-low and quick approach of the next upper-low will keep mean troughing in place and a period of generally below average temperatures for the state. ...Guidance Evaluation/Preferences... Most of the guidance remains in generally good agreement on the overall synoptic pattern late this week, through the weekend, and even into early next week. All models show an upper-low lingering over the mainland following a Gulf system and period of heavy rainfall, particularly along the southern coast, during the middle of this week. Models then show another upper-low/accompanying surface frontal system over the northeastern Pacific lifting northeastward into the Gulf of Alaska during the Friday-Saturday timeframe. Thereafter, the latest runs of the GFS diverge compared to both the ECMWF/CMC as well as the ensemble means, bringing the upper-low northeastward and inland over southeastern portions of the state/northwestern Canada faster as it transitions into an open wave, with the system at the surface weakening faster over the Gulf as a result. The rest of the guidance, including the ECMWF/CMC as well as the ensemble means, shows a slower progression and the weakening system remaining in the Gulf longer into Sunday/Monday. Then, all guidance besides the GFS shows a broadening area of higher pressures over the northeastern Pacific/Gulf, extending northwestward over the Aleutians, while the GFS depicts a weak upstream system moving into the Bering Sea. The other guidance does indicate another system upstream may approach the Bering Sea/Aleutians, helping to break down the ridging, but likely later into the middle of next week beyond the current forecast period. The updated WPC forecast follows a similar guidance blend as the prior forecast based on this consistent pattern, initially using a composite blend of the GFS/ECMWF/CMC before favoring the ECMWF/CMC and an increasing contribution from the ECens/CMC ensemble means later in the period. The most notable trend in the updated forecast is a slightly faster and stronger depiction of the Gulf system this weekend, which will need to be monitored for potential associated impacts. ...Weather/Hazards Highlights... Precipitation chances will continue into the weekend and next week broadly across the mainland as a lingering upper-low remains in place, possibly reinforced by additional energies from the Arctic and incoming from the northeastern Pacific. Showers and possible thunderstorms will be most likely/widespread Friday before diminishing in coverage and intensity in the following days. A more concentrated area of heavier rainfall is likely along the southern coast and into the Southeast this weekend as another upper-low/accompanying surface frontal system lifts northeastward from the northeastern Pacific and into the Gulf bringing another fetch of Pacific moisture. At least a couple inches of rainfall will be possible, possibly higher, especially from Cordova southeast past Yakutat and into northern portions of the Southeast. Shower chances may linger into early next week as the system weakens but with much lighter amounts of rainfall expected. Some lighter showers will also be possible on the backside of the system along the Alaska Peninsula and portions of the Aleutians. High temperatures across much of the state will remain below average through the weekend and into early next week as mean troughing remains in place in the upper levels. Most of the state will see highs 5-15 degrees below average, with even greater anomalies along the North Slope of 15-25 degrees. Forecast high temperatures are generally in the 30s for the North Slope, 40s and 50s for western interior/coast and Aleutians, 50s for the Southeast, and 50s to low 60s for the central/eastern interior and Southcentral. While temperatures will remain cooler and below average, there does look to be a slow but steady warm up through the period, with temperatures rising a degree or two each day. Putnam 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