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FXAK02 KWNH 142205
PMDAK

Alaska Extended Forecast Discussion
NWS Weather Prediction Center College Park MD
504 PM EST Tue Jan 14 2025

Valid 12Z Sat Jan 18 2025 - 12Z Wed Jan 22 2025

...Stormy pattern later this week/weekend from Western/Southwest
Alaska through the Alaskan southern tier...


...General Overview...

It remains likely that stormy weather will continue late this week
through at least the upcoming holiday weekend for parts of the
Aleutians, western/Southwest Alaska, and the Southern Coast with
plenty of onshore flow ahead of mean troughing through the
Aleutians and Alaska Peninsula. A couple of shortwaves rotating
through the base of this trough will lift across western Alaska,
eventually working to work into strong ridging extending from the
Gulf into Mainland Alaska. Another upper low/trough looks to edge
south of the Aleutians and possibly into the Bering towards the
end of the period that would act to rebuild the downstream upper
ridge next week.

...Model Guidance Assessment...

Guidance continues a recent trend for relatively good agreement on
the overall synoptic pattern, but plenty of uncertainty in the
details. Much of the uncertainty surrounds smaller scale
shortwaves rounding through the base of the larger scale trough
over the Bering/Aleutians and as energies lift poleward on the
western periphery of an ambient and amplified blocky ridge
downstream up over the mainland. This includes individual
surface/triple point lows lifting towards the AK Peninsula to
Southern Coast into this weekend, which will work to enhance local
winds/precipitation. The bulk of guidance agrees that one
shortwave this weekend should act to briefly push upper ridging
over the Mainland/Southeast eastward to a degree, but should build
back again ahead of the next trough into the Bering/Aleutians
early next week.

Overall, prefer a composite of reasonably clustered medium to
larger scale guidance of the 12 UTC ECMWF/UKMET/Canadian to
provide maximum detail for Saturday-Monday. The 12 UTC GFS seems
to crash energy too much into the ambient blocking upper ridge
this weekend versus running system energies more up the western
periphery. Opted to transition to best compatible guidance from
the 12 UTC GEFS/ECMWF/Canadian ensemble means amid slowly growing
forecast spread through longer time frames. WPC product continuity
seems reasonably well maintained in this manner.

...Weather/Hazards Highlights...

It generally remains the case that heavy precipitation will spread
across South-central and parts of Southeast Alaska through the
holiday weekend as a broadening closed low expands slowly
eastward, shifting the atmospheric river from the Pacific slowly
in that direction with time as tempered by the blocking ridge.
Rain should linger across the Aleutians and southwest AK through
the period. Recent model runs have also indicated moderate to
heavy precipitation chances increasing for parts of
western/Southwest Alaska as well, and to a lesser extent the
Interior. Above normal temperatures will make rain the main
precipitation type in southwest AK and for coastal locations, but
wintry mixed precipitation and snow will be possible farther north
and at elevation. Rain falling on top of snow could enhance
snowmelt and lead to localized flooding concerns in some areas,
such as Kodiak Island. The strong nature of the low will also
likely produce strong gusty winds from the Aleutians to western
Alaska across the Bering Sea and Bering Strait. A lingering front
and strong pressure gradient may make the Northern Slope breezy as
well.

Schichtel


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

$$