Gale Warning 26, NWS Anchorage, AK

Southcentral and Southwest Alaska Forecast Discussion
National Weather Service Anchorage AK
535 AM AKST Tue Jan 7 2025

.SHORT TERM FORECAST SOUTHCENTRAL ALASKA (Days 1 through 3/Today
through Thursday night)...

The strong storm system which brought widespread hazardous travel
conditions to Southcentral tracked inland overnight, with the
surface low dissipating as it interacted with the mountains.
Strong pressure rises behind the low, on the order of 2 to 3 mb
per hour, are leading to strong and gusty gap winds early this
morning. However, winds have peaked in most areas and will
diminish through the morning hours as both pressure gradients
and pressure rises weaken.

Meanwhile, a series of upper level short-waves are tracking
northward across Southcentral this morning and combining with
weak instability and upslope flow along the mountains to produce
areas of precipitation. Temperatures are well above freezing
for nearly all of lower elevations of Southcentral, leading to
primarily rain. However, this continues to lead to hazardous
walking and driving conditions for many sidewalks, driveways,
and neighborhood roads as water flows over top of ice. This is
especially the case for Anchorage and the Mat-Su. Snow is falling
at higher elevations, including Tahneta Pass and the western
Copper River Basin as well as Thompson Pass. Winter Weather
Advisories have been extended for all of these areas.

Precipitation and wind will generally diminish through the day.
However, additional upper level waves combined with the upslope
flow will keep showers going along the south side of mountains.
Areas most favored for continued precipitation include the Cordova
and Valdez areas as well as the northern Susitna Valley and Broad
Pass. There will be an uptick in winds overnight tonight for
Turnagain Arm into Anchorage and the Knik River Valley into
Palmer in response to an upper level short-wave and weak surface
low tracking northward across Southwest AK. The continued presence
of winds will keep surface temperatures around or a bit above
the freezing mark tonight for most of Southcentral (the notable
exception being colder temperatures in the Copper River Basin)
despite colling temperatures aloft. Still, this could be just
cold enough to refreeze some of the water on area roadways.
Temperatures will then climb back above freezing during the day
Wednesday.

A new storm system will form over the North Pacific today and
rapidly deepen tonight as it tracks northward toward the Gulf.
A leading frontal system will reach the Gulf by late Wednesday
afternoon and Southcentral by Wednesday night. This will bring
another round of strong winds and rain to Kodiak Island and the
Gulf coastal waters. Winds over Southcentral will continue to
lighten and shift around to northerly as this storm moves into the
Gulf. This will allow temperatures to fall below freezing for most
of Southcentral Wednesday night, leading to refreezing of any
water on the roads.

There are some key differences when comparing this new storm to
the storm that just moved through. It will take a more easterly
track across the central Gulf and toward Prince William Sound.
The low will also bottom out over the Pacific and be in a
weakening phase as it approaches Southcentral. Thus, impacts for
Southcentral will not be as great, with the bulk of precipitation
and winds confined to the coast. There is a chance of some light
precipitation spreading inland late Wednesday night through
Thursday, but it should be brief in any one location and not
pose any major problems to travel. There is a better chance of
precipitation Thursday night as the low dissipates and an upper
trough tracks across Southcentral. With colder air accompanying
the trough this could lead to some minor snow accumulation.

-SEB

&&

.SHORT TERM FORECAST SOUTHWEST ALASKA/BERING SEA/ALEUTIANS (Days
1 through 3: Monday through Thursday morning)...

A broad upper trough now extends from the central and eastern
Bering Sea into Southwest Alaska this morning, with several
smaller embedded features drifting within this broad region of
cyclonic flow aloft. A weak, stacked low is focusing a few
rain/snow showers near the southern end of the Alaska Peninsula as
the already weak wind field around it continues to slacken.
Farther northwest, a closed upper low continues to drift just off
to the west of the Pribilof Islands, where a small surface low is
expected to develop sometime later today. A corridor of moderately
cold air is continuing to spread south to the west of the low
across the western Bering Sea, helping to spur off convective snow
showers that are occasionally drifting into the western half of
the Aleutian Chain. Across Southwest, a deformation band of light
snow associated with a very potent low pressure system heading
into the Interior is lifting slowly north into the Kuskokwim Delta
and Lower Kuskokwim Valley. Some areas of fog and drizzle have
filled in behind the earlier snowfall, mainly across the northern
coastline of Bristol Bay.

In terms of the forecast for the next few days, conditions are
expected to stay fairly quiet and low impact by early January
standards. The surface low expected to form later this afternoon
near the Pribilofs will not really have much to work with in terms
of steering flow aloft, allowing the center to meander in place
over the central Bering through Wednesday evening. Periods of snow
showers will likely impact the Pribilofs near this low in the
meantime, with sporadic snow showers also continuing to push south
and east into the Aleutian Chain at times through Wednesday night.
Most of Southwest will also remain showery as a pair of weak
shortwave troughs lift north from later this afternoon into
Wednesday.

By early Thursday, two separate systems will being to affect
opposing ends of the outlook area. First, a storm force low
entering the Gulf will spread northeast winds to low end storm
force between the AKPen and Kodiak Island early Thursday morning,
while a mix of rain and snow spreads northwest into portions of
the AKPen and Bristol Bay. Much farther to the west, a North
Pacific low will push a frontal boundary into the central/western
Aleutians on Thursday as well, extending easterly winds up to
gale force into the Chain along with snow transitioning to mostly
rain by Thursday evening. The parent low will move near or just
south of the vicinity of Nikolski by late Thursday night,
spreading more unsettled conditions farther along the Aleutian
Chain and out towards the AKPen.

-AS

&&

.LONG TERM FORECAST (Days 4 through 7: Friday through Monday)...

A very active weather pattern will continue for much of southern
Alaska through the end of the week and into next weekend. The
longwave pattern features a strong upper level low dominating much
of the Bering Sea-western mainland Alaska and a steep ridge of high
pressure along the Canadian Coast and Eastern Alaska. The high
pressure ridge will weaken and retreat eastward slightly along the
Gulf of Alaska and Southern Alaska allowing a very strong North
Pacific low and its associated fronts to travel northward into the
Gulf and into the Alaskan Peninsula Thursday and into Friday before
being absorbed by the long wave trough of low pressure over the
Baring Sea. This pattern will bring unseasonable warmer temperatures
and mixed precipitation along the coastlines near the surface and
has the real potential for heavy snow accumulations in the higher
elevations.

The upper level low will gradually retreat back into Eastern Siberia
and the Chukchi Sea as the Ridge of high pressure reasserts its
dominance Friday and into Saturday. This will flatten out the
southern portion of the long wave trough allowing several compact
surface lows and their associated fronts to transit along the
Aleutians and coastal southern Alaska.

Confidence in the model guidance is moderate with a slight bias
between the GFS and European solutions through Thursday. The
European and Canadian better handle the synoptic features Friday and
into Saturday.

&&

.AVIATION...

PANC...Southeasterly winds will peak early this morning with
pressure rises behind a strong low which tracked inland overnight.
Winds will diminish through the morning hours, but remain gusty.
Winds will then strengthen a bit after 06Z as a weak low tracks
northward across Southwest AK, leading to strengthening of the
Turnagain Arm jet.

Steady light rain is likely through about 18Z this morning as an
upper short-wave moves through and low level flow shifts from
southeasterly to south-southwesterly. This will lower ceilings,
but chances are they remain in the VFR category.

&&

Preliminary Local Storm Report
National Weather Service Anchorage AK
1146 AM AKST Tue Jan 7 2025

..TIME...   ...EVENT...      ...CITY LOCATION...     ...LAT.LON...
..DATE...   ....MAG....      ..COUNTY LOCATION..ST.. ...SOURCE....
            ..REMARKS..

0724 PM     Freezing Rain    2 NW Butte              61.57N 149.10W
01/06/2025  U0.00 Inch       Matanuska-Susitna  AK   Public

            Significant ice on roadways from rain
            freezing on the frozen ground while ambient
            temperature is above freezing, roadways are
            extremely treacherous as water flows down
            the ice covered road.

&&

ME

Preliminary Local Storm Report
National Weather Service Anchorage AK
1147 AM AKST Tue Jan 7 2025

..TIME...   ...EVENT...      ...CITY LOCATION...     ...LAT.LON...
..DATE...   ....MAG....      ..COUNTY LOCATION..ST.. ...SOURCE....
            ..REMARKS..

0720 PM     Rain             2 NW Butte              61.57N 149.10W
01/06/2025  M0.60 Inch       Matanuska-Susitna  AK   Public

            Rain started lightly around 10 am and has
            been medium intensity since until recently
            when rain has become heavy with extremely
            treacherous roads with water flowing down a
            solid sheet of ice.

&&

ME

Preliminary Local Storm Report
National Weather Service Anchorage AK
1203 PM AKST Tue Jan 7 2025

..TIME...   ...EVENT...      ...CITY LOCATION...     ...LAT.LON...
..DATE...   ....MAG....      ..COUNTY LOCATION..ST.. ...SOURCE....
            ..REMARKS..

0722 PM     Flood            2 NW Butte              61.57N 149.10W
01/06/2025                   Matanuska-Susitna  AK   Public

            Minor flooding of farm fields and low lying
            areas.

&&

ME

Preliminary Local Storm Report
National Weather Service Anchorage AK
1208 PM AKST Tue Jan 7 2025

..TIME...   ...EVENT...      ...CITY LOCATION...     ...LAT.LON...
..DATE...   ....MAG....      ..COUNTY LOCATION..ST.. ...SOURCE....
            ..REMARKS..

0203 PM     Freezing Rain    Hillside East           61.12N 149.71W
01/06/2025  U0.00 Inch       Anchorage          AK   Public

            The temperature has warmed up to 34F and the
            light snowfall we were were receiving
            earlier has changed to a wintry mix of light
            rain and freezing rain.

&&

ME

Preliminary Local Storm Report
National Weather Service Anchorage AK
1250 PM AKST Tue Jan 7 2025

..TIME...   ...EVENT...      ...CITY LOCATION...     ...LAT.LON...
..DATE...   ....MAG....      ..COUNTY LOCATION..ST.. ...SOURCE....
            ..REMARKS..

0757 AM     Flood            8 SSW Trapper Creek     62.13N 150.54W
01/07/2025                   Matanuska-Susitna  AK   Cocorahs

            CoCoRaHS observer reported 0.63 inches of
            rain since 8 PM with ongoing light rain and
            heavy bursts overnight. Creek overflow and
            standing water on trails have made
            backcountry travel hazardous. Snowpack is 6
            inches of soft, punchy snow. South winds
            caused at least one treefall near the cabin.
            Travel not recommended due to soft trails,
            significant water, and potential for
            additional fallen trees.

&&

ME

Preliminary Local Storm Report
National Weather Service Anchorage AK
149 PM AKST Tue Jan 7 2025

..TIME...   ...EVENT...      ...CITY LOCATION...     ...LAT.LON...
..DATE...   ....MAG....      ..COUNTY LOCATION..ST.. ...SOURCE....
            ..REMARKS..

1238 PM     Flood            Anchor Point            59.77N 151.84W
01/07/2025                   Kenai Peninsula    AK   Emergency Mngr

            Water flowing over Anchor Point Rd from an
            ice jam downstream of the Old Sterling Hwy
            Bridge. The flooded area is along Anchor
            Point Rd, between Ann Rd and the Old
            Sterling Hwy. The water is currently 1/2
            foot deep and flowing.

&&

ME