Alaska Extended Forecast Discussion
National Weather Service College Park MD
639 PM EDT Sun Aug 30 2026

Valid 12Z Thu 03 Sep 2026 - 12Z Mon 07 Sep 2026


...Pattern Overview...

An amplified pattern will be in place over the Alaska region to
start the extended range on Thursday with a strong ridging over
the Mainland and a deep upper low over the western Bering Sea. The
upper low over the Bering Sea will be the main focus for the
forecast as it meanders over the Bering with multiple impulses of
energy rounding the base. This drives a strong cold front into
western Alaska around Thursday, bringing moderate to heavy
rainfall threats to western and interior Alaska, and possibly the
Southern Coast region. Another low/cold front approaches the
Aleutians next weekend, but with much more uncertainty on its
track and impacts.

...Guidance Evaluation and Preferences...

Overall good synoptic agreement on the pattern, but plenty of
uncertainty in the details during the forecast period. Despite
some timing uncertainties still with the cold front into Western
Alaska, a blend of the deterministic/AI guidance worked as a good
starting point.

After this, the forecast becomes highly uncertain. Distributions
of energy within mean Bering Sea upper low and waves rounding the
base of the trough lead to increasing differences with the second
low towards the Aleutians next weekend. The main outlier here is
the GFS which is much faster than other guidance bringing the low
into the Gulf early next week. The ECMWF is sharper with the upper
shortwave leading to a track south of the Aleutians, and the CMC
and EC-AIFS are closer to the Aleutians, possibly bringing the low
into the Bristol Bay region by Day 7 or 8. Ensemble means
completely wash out this system, suggesting significant
variability with individual members. The late period WPC forecast
was based more heavily on the ensemble means, but with some
deterministic/AI guidance inclusion to include at least a
semblance of this second low pressure. Forecast confidence in the
late period solution remains highly uncertain and more than likely
to change.

...Weather/Hazards Highlights...

The Wednesday into Thursday period may be fairly quiet and dry
across much of the Mainland as upper ridging builds over the
region ahead of the strong system in the Bering Sea. Behind this,
the deep and stagnant upper low over the Bering Sea will drive a
strong cold front into Mainland Alaska later on Thursday, bringing
threats for widespread moderate to locally heavy rainfall into
the weekend. The main focus for rainfall may be along the western
facing slopes of the Alaska range. Especially considering a recent
wet pattern for the Interior, maintained a broad Heavy Rainfall
hazard on the WPC Days 3-7 hazards chart today for parts of the
western and central Interior valid Thursday and Friday. Some
potential for locally heavy rainfall across parts of the Southern
Coast and Southeast as the cold front slows and weakens over
central Alaska into next weekend. Expect gusty winds to accompany
this system as well, especially over the eastern Bering and West
Coast. The warm front of this system may stall as it weakens over
northern Alaska, leading to some chances for precipitation across
the Brooks Range and North Slope region. If the next low towards
the Aleutians next weekend tracks closer to the Aleutians or into
the Gulf (as the GFS would suggest), possibly moderate to heavy
rainfall could be realized across the Southern Coast and Southeast
early next week, but amounts and impacts are highly uncertain.


Santorelli



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