Alaska Extended Forecast Discussion National Weather Service College Park MD 657 PM EDT Sun Jun 1 2025 Valid 12Z Thu 05 Jun 2025 - 12Z Mon 09 Jun 2025 ...Moderate to heavy rain to impact portions of the Southern Coast and Alaskan Panhandle into the end of the week... ...Overview... The extended range period starts Thursday with a weakening upper low over mainland Alaska. Energy rotating around this low and also combination with an Arctic low to the north will help maintain general troughing over Alaska through at least the weekend. To the South, an upper low/surface low will slide east south of the Aleutians and in a more northerly direction towards the Peninsula/Southern Coast as upper ridging builds over the Gulf and Panhandle late week. Moderate to heavy rainfall may be a concern early in the period (mid next week), but a generally unsettled pattern may continue through the period. Another round of heavier rain may impact the Southern Coast region late in the period, but with a lot more uncertainty in the timing and amounts still at this point. ...Guidance Evaluation/Preferences... Overall, there is generally good agreement on the pattern, moreso in the early part of the period. The guidance becomes more chaotic by about Day 6 with the evolution of the trough/low south of the Aleutians and its eventual track northward. The GFS was the biggest outlier suggesting a splitting of energies, sending a weak shortwave into the Gulf and maintaining a much stronger cut- off low south. The better consensus of models and ensembles suggests stronger ridging over the Gulf and a general east to north east progression of this system (maintaining one trough, rather than split flow). Much of the guidance shows another surface low reaching the Southern Coast by next weekend. Even bigger questions arise Day 7 and 8 (Sunday and Monday) with the evolution of this trough/low, with the ECMWF a bit of an outlier right now showing a very blocky flow pattern beginning to set up next Monday. The WPC forecast today used a blend of the deterministic solutions Days 4 and 5, but begin increasing influence of the ensemble means Day 6 and especially day 7 and 8 (with no inclusion of the GFS at all past Day 5). Overall, this maintained pretty good continuity with yesterdays forecast. ...Weather/Hazards Highlights... A weakening low and cold front in the Gulf will continue a steady stream of moisture directed towards Southeast Alaska on Thursday, slowly drifting southward on Friday. Moderate to heavy rainfall may be possible with this system. After this, rainfall intensity should decrease but showers will continue all along the coastal regions from the Aleutians to the Panhandle, and even farther inland towards the Brooks range with general troughing around. Ridging into the Panhandle may help keep things more dry for that region. Another low lifting northward may increase precipitation again for parts of the Peninsula and Southern Coast but with much more uncertainty in the amounts and impacts. High temperatures across much of the state will be below normal through the period underneath of weak troughing. Some moderation at times is possible, particularly for southwest or southern regions as upper ridging moves through. The greatest below normal anomalies will be across the Northern Slope region under the influence of an Arctic upper low. Santorelli 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