Alaska Extended Forecast Discussion
NWS Weather Prediction Center College Park MD
712 PM EDT Fri Sep 13 2024

Valid 12Z Tue Sep 17 2024 - 12Z Sat Sep 21 2024

...Bering Sea Storm to impact the Aleutians and Southwest
Alaska/Alaska Peninsula early next week...


...Guidance Evaluation/Preferences...

Guidance continues to herald a protracted period of highly
energetic and progressive flow with a series of potent storms to
impact Alaska over the next week. A composite of now reasonably
well clustered guidance of the 12 UTC GFS/ECMWF/UKMET/Canadian
offers good system detail consistent with above normal system
predictability and WPC product continuity Tuesday into Thursday.
Prefer a switch to best compatible ensemble means at longer time
frames as predictability lowers closer to normal amid growing
forecast spread.

...Weather/Hazards Highlights...

Lead storm energy digging through and exiting the eastern Gulf of
Alaska into Tuesday will support lingering unsettled weather to
include some enhanced rains/winds/waves over the Gulf of Alaska
and inland across the far southern Panhandle.

Upstream, forecast confidence continues to rise through above
average levels regarding the details for yet another major storm
slated through the early through middle part of next week. Expect
a deepened/potent low track through the Aleutians and southern
Bering Sea into with earnest Southwest Alaska will also with
downstream energy transfer reform over the northern Gulf of Alaska
and track near/offshore the Alaskan southern tier, eventually and
actively crossing Southeast Alaska later Wednesday into Thursday.
This would focus the majority of precipitation to the southwestern
mainland and southern to southeastern Alaska. This storm will
again also produce widespread maritime threats of high winds and
waves. Onshore, the WPC Hazards Outlook depicts an associated risk
of high winds and coastal impacts from the Aleutians to Southwest
Alaska and the Alaska Peninsula given dynamic system strength and
speed. The pattern seems to remain favorable for additional storm
systems upstream in this flow. Predictability lowers to average
for developments and tracking, most likely from the southern
Bering Sea/Aleutians/northern Pacific into the Gulf of
Alaska/Alaska southern tier next Friday/Saturday to monitor. 

Meanwhile to the north, lingering low pressure centering over the
Interior along with the uncertain passage and digging of shortwave
energies aloft over the mainland may support persistence of
scattered light precipitation into next week in the wake of a
highly energetic leading short range storm. Activity on the
northern periphery of the next main Bering Sea storm through next
midweek may also lead to some locally/terrain enhanced gusty winds
and precipitation.

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