Alaska Extended Forecast Discussion NWS Weather Prediction Center College Park MD 737 PM EDT Sun Sep 29 2024 Valid 12Z Thu Oct 3 2024 - 12Z Mon Oct 7 2024 ***Major storm system over the Bering Sea region becoming more likely by late in the week*** ...Overview... The overall weather pattern should remain fairly progressive going into Thursday as a fairly weak lead surface low tracks from Bristol Bay into the Gulf and towards the Panhandle, but likely much weaker than the early week system. By next weekend, a much stronger surface low enters the Bering Sea region, and will likely be slow to move as a blocky ridge builds over western Canada. This low will likely bring some impactful weather to parts of the southwest mainland coast and the Aleutians, with strong winds and possible coastal flooding. ...Guidance Evaluation/Preferences... The 12Z model guidance suite features good overall synoptic scale agreement for the beginning of the forecast period Thursday, albeit with some latitudinal differences with the low initially over the Gulf of Alaska. The UKMET becomes a more progressive solutions and ahead of the ensemble means, so this was tapered down in the forecast blend going into Friday and dropped by Saturday. There is some modest spread in the remaining guidance with the Bering low by Saturday morning, and the 12Z GEFS means serves as an excellent middle ground solution in terms of placement. There is a good chance the pressure could drop to 960mb or even a little lower as the low reaches peak intensity Friday. There should be a gradual filling of the low and thus weakening going through the weekend, with good agreement among the GFS/CMC solutions, and the ECMWF/ECENS farther east near the Alaska Peninsula. There is still uncertainty on whether a triple point low develops over the Gulf and how strong that could be, so this will be refined in future forecast as the event gets closer in time. The ensemble means were gradually increased to about half by next Monday, with more weighting to the GEFS mean given its favorable placement. ...Weather/Hazards Highlights... The Southeast/Southern Coast area should remain generally unsettled with light rain expected as a generally weak low pressure system passes from Bristol Bay into the Gulf mid to late week. However, attention then turns to a large and deeper storm system entering the Bering Sea region later in the week, with increasing rain chances along the West Coast and through the Aleutians into next weekend, and then the southern coastal mountains of the mainland. Storm force winds and extremely rough seas are expected over the open waters of the Bering, with a potential sting jet, and winds gusting in excess of 40 mph are becoming more likely for coastal areas of the western mainland, and also for the Aleutians. The potential for coastal flooding along the southwest mainland coast will also be something to closely monitor in the days ahead. In terms of temperatures, cooler than normal highs are likely over southern parts of Alaska and warmer than normal temperatures are likely for the northern two-thirds of the Mainland during the period. Readings in the 40s to low 50s are forecast for highs in most lower elevation areas, with an overall warming trend as next week progresses owing to increased southerly flow ahead of the Bering Sea low pressure system. 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