425
FXAK68 PAFC 311345
AFDAFC

Southcentral and Southwest Alaska Forecast Discussion
National Weather Service Anchorage AK
545 AM AKDT Thu Oct 31 2024

.SHORT TERM FORECAST SOUTHCENTRAL ALASKA (Days 1 through 3)...

A negatively tilted shortwave trough and developing triple point
low south of Kodiak is the main forecast focus for the next 24
hours. Winter Weather Advisories for mixed precipitation are in
effect through Friday morning from the western Kenai Peninsula
north through Anchorage and into the southern Mat-Su. Most of the
event is expected to be snow for these locations, but moderate
cross-barrier flow is leading to the development of a lee-side
warm nose for these areas, as evident in the 12Z Anchorage
sounding. While the sounding has not yet crossed the 0C threshold,
should this warming continue, snow may mix with or change over to
freezing rain around noon today. Model soundings are within are
within +/-0.5 degrees Celsius of being snow and freezing rain,
resulting in overall low confidence in either solution. Typically
the NAM and most of the high-resolution guidance do have a warm
bias in developing a warm nose and freezing rain for these
locations, however the 12Z sounding does indicate some moderate
(25-30kts) of southeasterly winds between 900 and 850 mb. Surface
temperatures for the most part will be around 30 degrees for many
areas, allowing for light ice accumulations should the changeover
occur. Throughout the day surface temperatures may also climb
above freezing, but rain falling onto snow covered surfaces may
have the same effect on driving as if it was freezing rain. For
totals, please read the advisory corresponding to your area.

Moving into Friday a strong, but occluding low will move south of
Kodiak Island and into the Gulf. Light upslope flow along mainly
the eastern Kenai Peninsula will promote rain at sea level and
upper elevation snow, with overall warm temperatures. Downsloping
and northerly winds at the surface should keep most other areas
dry.

&&


.SHORT TERM FORECAST SOUTHWEST ALASKA AND THE BERING
SEA/ALEUTIANS (Today through Saturday night)...

Relatively quiet weather today will give way to much more
impactful weather by late tonight as a strong North Pacific low
makes its way towards the Central and Eastern Aleutians before
skirting along the Alaska Peninsula towards the Gulf. Expect wet
and windy conditions through Friday, with the strongest winds
expected along the Eastern Aleutians, Alaska Peninsula, and
Bristol Bay. A High Wind Watch is currently in effect for the
Alaska Peninsula, while a Special Weather Statement is in effect
for Bristol Bay south of Egegik. Stay tuned as we continue to
monitor this incoming storm.

Diving into the details... with last night`s front exiting
towards Southcentral Alaska, precipitation will gradually taper
off through today for Southwest. Expect things to stay fairly dry
for Southwest Alaska, except for a few isolated to scattered
afternoon showers as a weak trough moves through.

Otherwise, the main story continues to be a strong, moist low
moving in from the North Pacific late tonight. With its track
remaining along or south of the Aleutians and Alaska Peninsula,
the worst conditions (strong winds and moderate to heavy rain) are
expected in the Eastern Aleutians, Alaska Peninsula, and Bristol
Bay. Areas to the north (Pribilof Islands, Kuskokwim Delta and
Valley) and to the west (Central and Western Bering/Aleutians)
will certainly have their weather be influenced by this system,
but they`ll escape the worst of the winds and rain.

With regard to winds, the primary areas of concern will be the
Alaska Peninsula and southern Bristol Bay. Favorable terrain gaps
will likely enhance the strong southeasterly winds along the
front. There`s still some question of whether forecast winds will
be high enough to reach the 75+ mph threshold for a High Wind
Warning, but there will certainly be no shortage of winds for this
area on Friday.

The other area to watch will be the Eastern Aleutians, where
northerly winds wrapping back around the low could approach the 75
mph threshold around Friday evening. No product is currently in
effect for this area; while strong winds are likely, the worst
conditions still look to remain further south. In addition, the
lack of robust cold air advection along the backside of the low
will limit how strong surface winds will get. While the finer
details may be a bit uncertain, confidence is high in the overall
picture of strong winds, moderate to heavy rain, and high seas.
Stay tuned to the forecast, and please use caution if you`ll be
out and about during the height of this storm.

-Chen

&&
.LONG TERM FORECAST (Days 4 through 7: Sunday through Wednesday)...


For the extended outlook, a broad upper level trough over the
Gulf of Alaska will support a surface low that will slowly
dissipate as it moves from the Central Gulf and over South Central
Alaska by Monday evening. A broader upper level trough over the
Bering Sea will combine energies with a strong North Pacific low
early in the new week. Most of the major numeric models support a
surface low tracking from the North Pacific and across the Central
Aleutian Islands Tuesday morning and lingering in Bristol Bay
through the end of the forecast period. The surface fronts will
progress across the Central Aleutians, over the Alaskan Peninsula
and into the Western Gulf of Alaska by Wednesday. High, gale force
southerly winds will be possible with higher winds in the usual
gap areas.




&&

.AVIATION...

PANC...An upper level short-wave trough and surface occluded
front will approach from the south, bringing light snow up Cook
Inlet and arriving at the terminal around 14Z. Low level
southeast flow will strengthen across the Kenai and Chugach
Mountains. It won`t be terribly strong, but should be enough to
keep ceiling/vis from dropping real low today. However, these
winds will shut off on Friday, and with continued precipitation
cigs/vis may drop to IFR. Freezing rain remains a possibility
this afternoon, but is more likely over central Anchorage than
over the Terminal.

&&


$$