208
FXAK02 KWNH 192106
PMDAK

Alaska Extended Forecast Discussion
NWS Weather Prediction Center College Park MD
505 PM EDT Sat Oct 19 2024

Valid 12Z Wed Oct 23 2024 - 12Z Sun Oct 27 2024

...Significant storm to bring heavy precipitation, high winds and
coastal flooding threats to West/Southwest through Northern and
Interior Alaska into early-mid next week...


...Overview and Guidance Evaluation/Preferences...

Predictability remains above normal in showing a significant storm
with long fetch moisture and high winds/waves from the Bering Sea
to the Arctic Ocean along with leading coastal flooding, heavy
precipitation and high wind threats inland for West/Southwest
through Northern and Interior Alaska into early-mid next week.
Prefer a composite of well clustered guidance of the 12 UTC
GFS/ECMWF/UKMET/Canadian into Wednesday-Friday. This also acts to
trend WPC guidance toward a deeper and slightly offshore shifted
upstream storm from the Southern Bering Sea to the northern Gulf
of Alaska into late next week to monitor. Prefer better clustered
guidance of the GEFS/ECMWF/Canadian ensemble means next weekend
along with limited model input amid slowly growing forecast spread
and uncertainty. This maintains good WPC product continuity.

...Weather/Hazards Highlights...

A main weather maker continues to be a deep and quite strong
surface low moving over the Arctic Ocean and its associated
trailing cold front and reinforcing flow on the backside that are
slated to slam across Mainland Alaska early-mid next week. This
system will bring impactful precipitation, mostly in the form of
snow especially for the mountains and farther into the interior,
but western/west-central areas may see periods of heavy rainfall
now mostly over short term time frames. Please refer to your local
NWS forecast office for advisories, watches and warnings for
actionable hazards. Models continue to show the potential for
several periods of focus resulting in more than a foot of snow for
the western and central Brooks Range. This storm offers a
significant maritime winds and waves threat across the Bering Sea
and open waters of the Arctic Ocean. Highest inland winds may
focus into parts of northwestern Alaska, with the highest gusts
expected in the mountains. However, this will present as a
widespread high wind threat well inland across the Interior and
into the Brooks Range/North Slope with colder snow areas
potentially having periods of local blowing snow/near
blizzard-like conditions to monitor through early-mid-week.
Persistent and strong onshore flow may lead to a significant
coastal flooding threat as well, with focus also spreading
southward through Western and Southwest Alaska.

In the wake of the main storm later next week into next weekend,
the overall flow pattern transitions to allow emergence of dynamic
system energies set to dig southeastward across the southern
Bering Sea to the Gulf of Alaska. Guidance over the past two days
have overall trended more amplified with this system and the trend
seems reasonable given supporting upstream ridge amplitude. This
favors a deeper low pressure and frontal system to enhance
winds/waves and precipitation in unsettled flow. The main weather
focus inland will shift from coastal Southwest Alaska and the
AKpen/Kodiak Island to coastal areas of SouthCentral Alaska, then
perhaps especially Southeast Alaska heading into next weekend with
advent of subsequent system energies and focus rotating around the
eastern periphery of a mean Gulf of Alaska closed low position.

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

$$