594
FXAK02 KWNH 292337
PMDAK

Alaska Extended Forecast Discussion
NWS Weather Prediction Center College Park MD
737 PM EDT Sun Sep 29 2024

Valid 12Z Thu Oct 3 2024 - 12Z Mon Oct 7 2024

***Major storm system over the Bering Sea region becoming more
likely by late in the week***


...Overview...

The overall weather pattern should remain fairly progressive going
into Thursday as a fairly weak lead surface low tracks from
Bristol Bay into the Gulf and towards the Panhandle, but likely
much weaker than the early week system.  By next weekend, a much
stronger surface low enters the Bering Sea region, and will likely
be slow to move as a blocky ridge builds over western Canada.
This low will likely bring some impactful weather to parts of the
southwest mainland coast and the Aleutians, with strong winds and
possible coastal flooding.


...Guidance Evaluation/Preferences...

The 12Z model guidance suite features good overall synoptic scale
agreement for the beginning of the forecast period Thursday,
albeit with some latitudinal differences with the low initially
over the Gulf of Alaska.  The UKMET becomes a more progressive
solutions and ahead of the ensemble means, so this was tapered
down in the forecast blend going into Friday and dropped by
Saturday.  There is some modest spread in the remaining guidance
with the Bering low by Saturday morning, and the 12Z GEFS means
serves as an excellent middle ground solution in terms of
placement.  There is a good chance the pressure could drop to
960mb or even a little lower as the low reaches peak intensity
Friday.  There should be a gradual filling of the low and thus
weakening going through the weekend, with good agreement among the
GFS/CMC solutions, and the ECMWF/ECENS farther east near the
Alaska Peninsula.  There is still uncertainty on whether a triple
point low develops over the Gulf and how strong that could be, so
this will be refined in future forecast as the event gets closer
in time.  The ensemble means were gradually increased to about
half by next Monday, with more weighting to the GEFS mean given
its favorable placement.


...Weather/Hazards Highlights...

The Southeast/Southern Coast area should remain generally
unsettled with light rain expected as a generally weak low
pressure system passes from Bristol Bay into the Gulf mid to late
week.  However, attention then turns to a large and deeper storm
system entering the Bering Sea region later in the week, with
increasing rain chances along the West Coast and through the
Aleutians into next weekend, and then the southern coastal
mountains of the mainland.  Storm force winds and extremely rough
seas are expected over the open waters of the Bering, with a
potential sting jet, and winds gusting in excess of 40 mph are
becoming more likely for coastal areas of the western mainland,
and also for the Aleutians.  The potential for coastal flooding
along the southwest mainland coast will also be something to
closely monitor in the days ahead.  In terms of temperatures,
cooler than normal highs are likely over southern parts of Alaska
and warmer than normal temperatures are likely for the northern
two-thirds of the Mainland during the period.  Readings in the 40s
to low 50s are forecast for highs in most lower elevation areas,
with an overall warming trend as next week progresses owing to
increased southerly flow ahead of the Bering Sea low pressure
system.

Hamrick


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

$$