Alaska Extended Forecast Discussion NWS Weather Prediction Center College Park MD 754 PM EDT Sat Jul 27 2024 Valid 12Z Wed Jul 31 2024 - 12Z Sun Aug 4 2024 ...General Overview... The beginning of the extended forecast period Wednesday will be featured with an anomalous upper trough situated over the northeastern Gulf along with rather cool conditions and periods of rain and high mountain snow. An incoming shortwave to its west will tend to fortify this trough across much of the Gulf going into Thursday. The slow moving upper low north of eastern Siberia will likely move slowly eastward to a position north of the Arctic Coast after idling in place for a few days. By next weekend a more organized upper trough and cold front will likely cross the Bering Sea with a downstream upper ridge trying to develop across eastern mainland Alaska. ...Guidance Evaluation/Preferences... The 12Z model guidance suite has good overall agreement on the synoptic scale pattern on Wednesday across the Alaska domain, and with high confidence on the strong upper trough across the Gulf region and the upper high south of the Aleutians. The GFS is stronger with a trailing shortwave south of the Alaska Peninsula going into Friday compared to the model consensus, but otherwise matches up well elsewhere. By Saturday, the CMC is generally located northeast of the model consensus regarding the upper low across the Gulf, and is less amplified with the strong trough organizing across the Bering late in the forecast period. Overall, the Day 7/8 forecast is in better agreement compared to yesterday with the more amplified pattern indicated in the guidance. The forecast was primarily based on a multi-deterministic model consensus through Thursday, and then gradually transitioning to about 40-50% ensemble means by next weekend. ...Weather/Hazards Highlights... Scattered to numerous showers are likely to be ongoing across much of southern Alaska on Wednesday with steeper lapse rates in place from the upper trough. This will also result in lower snow levels for the major mountain ranges, especially the Alaska Range and into the Chugach and St. Elias mountains. The unsettled conditions are also forecast to be in place across the Southeast Panhandle region through the middle to end of the week with moist onshore flow ahead of the incoming upper trough/front. Additionally, parts of the Brooks Range will likely multiple rounds of showers, some of which could be locally heavy, with some 1-2 inch rainfall totals possible. Temperatures are generally expected to be about 5-15 degrees below average for much of the state through Wednesday, with a gradual moderation trend heading into next weekend with highs returning closer to seasonal averages. This will generally equate to highs in the upper 50s to near 70 degrees for most of the Interior, and lows in the 40s to lower 50s. Hamrick 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