Alaska Extended Forecast Discussion NWS Weather Prediction Center College Park MD 708 PM EST Tue Nov 7 2023 Valid 12Z Sun Nov 12 2023 - 12Z Thu Nov 16 2023 ***Two intense Bering Sea low pressure systems to monitor with high winds and increasing snowfall chances*** ...Guidance Evaluation and Preferences... The model guidance has improved overall in the extended forecast period compared to this time yesterday, and there is above average forecast confidence even going into the middle of next week. The CMC is now more in line with the ECMWF and GFS on the main low pressure systems, although some timing and mesoscale differences remain, including a more northerly track for the low near the Bering Strait. The low track for the Bering Sea storm is similar overall compared to yesterday's model runs, although the ECMWF is the stronger solution. The models are also suggesting a potentially even stronger low to follow behind it, and the guidance suggests it could take a more southerly track across the Bering with central pressures possibly into the 950-960 mb range. Ensemble means accounted for 30-40% of the forecast blend by next Tuesday and Wednesday. ...Overview and Weather/Hazards Highlights... The overall weather pattern across the Alaska domain is forecast to remain quite active for this weekend through the middle of next week, particularly across the maritime regions. There will be an occluded surface low across the northern waters of the Gulf Saturday, followed by a steady weakening trend through early Monday as the upper low/trough dampens and loses strength. The resulting strong pressure gradient will cause gale force winds across the coastal waters of southeast Alaska, along with heavy terrain enhanced snow for the coastal mountain ranges, and a cold rain for the lower coastal elevations. There will also be steep lapse rates in association with the anomalous 500mb low, so some hail and thunder are within the realm of possibility with the heavier showers. Some improvement is expected going into Sunday, but unsettled weather is expected to make a return for early next week as a new but weaker low pressure systems tries to develop in the same general area, and then track southeast and weaken. Things get even more interesting across the Bering and eastern Siberia with two powerful low pressure systems expected. The first storm is forecast to track from the Kamchatka Peninsula towards the western portion of the Bering Strait Sunday into Monday afternoon, with storm force winds south of the low across portions of the western Bering and far western Aleutians. Although the greatest impacts are currently expected to remain west of the mainland, portions of the western mainland coast may be impacted by high winds gusting over 40 mph, and the potential for elevated tides also exists. Warm air advection ahead of the storm will likely bring a period of light to locally moderate snow for portions of the western mainland Sunday into early Monday, with several inches of accumulation possible for the some of the Interior valley locations. Perhaps an even more impactful storm system is appearing on the horizon after this first storm departs, with a track potentially farther to the southeast. This would also produce widespread storm force winds, extremely rough seas, and coastal flooding problems. Temperatures are generally expected to be in the 10s to middle 20s for highs across most of the mainland, and 30s for the southern coastal areas. Hamrick Hazards: -High winds across portions of northwest mainland Alaska, Sunday, Nov. 12 -High winds across portions of the Alaska Peninsula and the Aleutians, Saturday, Nov. 11 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