Alaska Extended Forecast Discussion NWS Weather Prediction Center College Park MD 748 PM EDT Fri Jul 26 2024 Valid 12Z Tue Jul 30 2024 - 12Z Sat Aug 03 2024 ...General Overview... The beginning of the extended forecast period Tuesday will be featured with an anomalous upper trough situated over southern mainland Alaska, and then reaching the northeastern Gulf going into Wednesday 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. A hint of an upper ridge tries to briefly build north across southwestern mainland Alaska Wednesday into Thursday before upper level troughing likely returns to the region going into Friday and next weekend. Meanwhile, 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. ...Guidance Evaluation/Preferences... The 12Z model guidance suite has a very good handle on the overall synoptic scale pattern on Tuesday across the Alaska domain, and with high confidence on the strong upper trough across southern Alaska and into the Gulf region. Going into Wednesday night and Thursday, the GFS remains a more progressive solution in bringing shortwave energy inland across northern British Columbia, and this is similar to earlier runs, but is otherwise reasonably comparable across the rest of the domain going through Thursday. The best agreement in the guidance by this time is with the upper high situated south of the Aleutians, and less confidence across northwestern Alaska with timing of trough/upper low arrival. Looking ahead to Friday, the GFS becomes stronger with the next trough approaching from Siberia, and also stronger with another low over the Gulf by the end of the forecast period. Model and ensemble spread increases substantially by day 8 (Saturday), with the ensemble means accounting for slightly more than half of the forecast and toning down the GFS further. ...Weather/Hazards Highlights... Scattered to numerous showers are likely to be ongoing across much of southern Alaska and also parts of the Interior on Tuesday and probably into Wednesday as well 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, but not reaching hazardous level criteria. Temperatures are generally expected to be about 5-15 degrees below average for much of the state through Wednesday, with some moderation closer to normal on Thursday before another cooling trend in time for next weekend across the northern 2/3rds of the state. This will generally equate to highs in the mid 50s to mid 60s for most of the Interior, and lows in the 40s. 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