208
FXAK02 KWNH 172314
PMDAK

Alaska Extended Forecast Discussion
NWS Weather Prediction Center College Park MD
714 PM EDT Thu Oct 17 2024

Valid 12Z Mon Oct 21 2024 - 12Z Fri Oct 25 2024

...Significant storm to bring heavy precipitation and high winds
to much of western/northern through Interior Alaska into early
next week...


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

Predictability seems to be above normal in showing a significant
storm with lead long fetch moisture and high winds and waves from
the Bering Sea to the Arctic Ocean. Heavy precipitation and
swirling high winds are also expected inland from western/northern
Alaska to the Interior into early next week. This may also lead to
local blizzard conditions in gusty areas cold enough to snow.
Prefer a composite of well clustered guidance of the 12 UTC
GFS/ECMWF/UKMET/Canadian into the Monday-Wednesday timeframe. Opt
to switch to a composite of better compatible 12 UTC
GEFS/ECMWF/Canadian ensemble means as forecast spread and
uncertainties slowly grow into later next week in a less
defineable and progressive system pattern with closer to average
predictability. This plan maintains excellent WPC product and
messaging continuity.

...Weather/Hazards Highlights...

The main weather maker will be a deep and quite strong surface low
lifting from northeast Asia to the Arctic Ocean and its associated
trailing cold front as it swings eastward through Mainland Alaska
early next week. This system will bring impactful precipitation,
mostly in the form of snow especially for the mountains and
farther interior, but western areas may see periods of heavy
rainfall. Models continue to show the potential for more than a
foot of snow for the western and central Brooks Range. This storm
will offer 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. 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.

There is a slowly growing signal for addional upstream storm
development into the Bering Sea in about a week, but at this point
guidance uncertainies loom much larger for the potentially
organized system not planned to rival the lead low.

Meanwhile, less defined system energies sliding underneath in this
pattern into the Alaskan southern tier and Gulf of Alaska will
also lead to a series of systems that will periodically enhance
winds/waves and precipitation next week in less certain but
unsettled flow. Suspect main inland focus will be from coastal
SouthCentral to Southeast Alaska.

Following a weekend of near to below normal temperatures, warm air
advection ahead of the strong storm system is expected to result
in much milder conditions by next week, with daytime highs 10-20
degrees above normal for some locations from western to central
and northern Alaska Monday-Wednesday. Southeast Alaska should be
exception remaining below normal through the entire period
underneath persistent upper troughing.

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

$$