FXAK02 KWNH 202342

PMDAK



Alaska Extended Forecast Discussion

National Weather Service College Park MD

742 PM EDT Sun Sep 20 2026



Valid 12Z Thu 24 Sep 2026 - 12Z Mon 28 Sep 2026



...Heavy Rainfall and High Winds for the Aleutians, Alaska 

Peninsula, and western/southern Mainland late next week...



...Overview...



The low initially over the eastern Gulf will weaken by mid-week as

high pressure builds over the Mainland ahead of the next storm

system, which will allow for a brief break in precipitation. This

next low pressure system will likely have some tropical influence

and will create heavy precipitation and high winds across the 

Aleutians, Alaska Peninsula, and southwestern Mainland late next 

week into next weekend. 





...Guidance Evaluation and Preferences...



The 12Z model guidance suite features good overall agreement

across the Alaska domain for the beginning of the forecast period

across the mainland. However, some timing differences become

apparent as early as Thursday with the strong Bering Sea low 

pressure system. The GFS and UKMET solutions are faster to bring 

the low towards the Alaska Peninsula and then reform in the 

northern Gulf. The ECMWF/AIFS/CMC/means are slower and farther 

northwest with the main low center over the southeastern Bering 

going into the end of the week, and going with this group of 

solutions was preferred given better continuity with earlier WPC 

forecasts across this domain. There has been an increase with the 

expected QPF across much of southern Alaska from the Kenai 

Peninsula to the St. Elias Mountains with this update given a 

longer period of moist onshore flow expected.



For fronts and pressures, a general deterministic blend with

slightly less of the UKMET and GFS was used for the end of the

week, and then primarily ECMWF/AIFS/CMC going into the weekend,

with ensemble means increasing to about 50% by next Monday.





...Weather/Hazards Highlights...



By the middle of the week, the next low pressure system will move

towards the Aleutians. This system will develop from the 

combination of a northern stream low pressure system moving out of

Russia and the remnants of Typhoon Dujuan moving up from the 

North Pacific. The combination will result in a strong low 

pressure system in the Bering Sea. Tropical moisture streaming 

ahead of the system will increase the prospects of heavy rainfall

that will spread from the Aleutians into western Alaska and 

eventually into South-central Alaska as the system progresses 

late next week into the weekend. The heaviest precipitation is

expected to focus over upslope terrain in Southwest and 

South-central Alaska. 



The strong pressure gradient surrounding this system will also 

bring strong gusty winds to the Aleutians, Alaska Peninsula, and 

coastal Southwest Alaska. The Bering Sea low is expected to 

gradually weaken and shift into the Gulf next weekend, which may 

prolong heavy rainfall over Southcentral Alaska and expand heavy 

rainfall towards Southeast Alaska. Temperatures will gradually 

trend warmer as the modified tropical air mass moves into the 

region, followed by a cool down for the northern half of the state

towards the end of the forecast period. 



Hamrick/Dolan





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