Gale Warning 642, NWS Anchorage, AK

Southcentral and Southwest Alaska Forecast Discussion
National Weather Service Anchorage AK
505 AM AKDT Wed Oct 26 2022

.ANALYSIS AND UPPER LEVELS...

Let it snow, let it snow, let it snow throughout Southern Alaska!
A very stout 175 kt jet streak is the culprit to our snow tonight.
The jet streak continues to amplify as it digs South-southeastward
over the North Pacific and Gulf of Alaska. Meanwhile, a strong
and vertically stacked low pressure system continues to spin over
the Bristol Bay land zone and move South-southeastward as well.
Bethel continues to report snowy conditions on the backside of the
storm system, while King Salmon radar reveals convective rain
showers around and south of King Salmon and crossing over Bristol
Bay and the northern Alaska Peninsula.

Further out west, shortwaves continue to pivot southward around
the storm system in the Kuskokwim Valley. One cluster of weak
shortwaves made their way through the Pribilofs earlier last night
with light rain reported and are headed to the central and
eastern Aleutians. While the 175 kt jet streak continues to dig
South-southeastward, westerly to northwesterly winds continue to
be enhanced across the Aleutians. Buoy 75 in the North Pacific
south of Cold Bay has gale force gusts of up to 40 kts along with
18 to 20-foot waves. Meanwhile, Shemya reports lower cloud
ceilings and Buoy 71 near Kiska has northwest winds gusting to
around 20 kts and 11-foot waves.

Back to the east, an upper shortwave continues to lift up Cook
Inlet as it pivots around the Bristol Bay low and is responsible
for the snowy conditions around Anchorage and Kenai and the
Susitna Valley. Also aiding in the active weather is moist
southwest flow in the middle to upper level of the atmosphere from
roughly the Barren Islands to the Alaska Range. While Anchorage
continues to report light snow, Homer has warmed up enough for
rain, while Palmer remains dry. An even closer look at the surface
shows a new surface low spinning up in the western to central
Gulf of Alaska slowly drifting off to the east. Kenai Radar shows
an area of snow affecting the northwestern Kenai Peninsula where
light snow returns are present for the Anchorage and the lower
Susitna Valley. Middleton Island Radar shows a precipitation
shield and cyclonic flow around the developing low pressure in the
Gulf.

&&

.MODEL DISCUSSION...

The latest operational model runs are in decent agreement with the
placement and intensity of synoptic features throughout the upper
levels in the short term. However, a point of contention in the
east domain remains the evolution of the low developing in the
Gulf of Alaska currently and specifically at the surface with
position and track. 00z NAM/CAN and somewhat the ECMWF take the
system well to the north and west by Wednesday morning,
approaching Prince William Sound with more impacts from wind and
precipitation. Meanwhile, the 00z GFS, which seems to best line
up with current observations from Middleton Island Radar showing
the potential location of where the center of circulation resides
currently in the Gulf. The 00z GFS solution takes the system
further south and east with time, and while still impacting Prince
William Sound with wind and precipitation, there would be less of
them with this solution. With that, we are giving more
credit/credence to the GFS for now in the eastern domain in the
short term.

Out west and towards the end of the short term, a point of
contention is a surface low pressure poised to enter the western
Bering Sea. While all deterministic guidance depict a storm
affecting the western Aleutians, position and track are in
question. While the 00z ECMWF is the most progressive of the
solutions and takes the system to the central Bering by Thursday
night, the 00z GFS/CAN/NAM keep the system back towards the
western Bering and western Aleutians. These solutions then take
the system to south of the Alaska Peninsula around Cold Bay Friday
evening, while the 00Z ECMWF has the system around the Gulf of
Alaska. Therefore, we are giving more credit/credence to the
GFS/CAN/NAM for track and GFS/CAN for depth of the surface
feature.

Overall forecast confidence for both domains remains moderate at
this time due to surface feature track disagreements, which will
have an effect on exactly who see what when it comes to
precipitation, precipitation type, and winds. Stay tuned as
details continue to be ironed out in the short term.

&&

.AVIATION...

PANC...Snow will continue to wind down and taper off this morning
as better forcing for ascent moves further to the east in
association with the low pressure in the Gulf. Therefore, the
current IFR visibilities and MVFR ceilings should improve to VFR
later on this morning as dry conditions arrive and should dominate
the rest of the TAF period. The only uncertainty is for the
possibility of low level clouds to hang around in the presence of
the northwest winds as they could bank up against the Chugach
Range into the afternoon. The threat for low-level windshear has
also ended as the system in the Gulf draws winds through the
column uniformly from the north.

&&

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

The upper level jet and short-wave which brought widespread snow
to Southcentral yesterday/last night has exited eastward to
Southeast Alaska. The upper level low which has been sitting over
Southwest Alaska will move over top of a surface low spinning near
Middleton Island  this morning, then slowly exit eastward this
afternoon through tonight. Areas of snow will linger through this
evening near the northern Gulf low center and into the Copper
River Basin as short-waves rotate up and around this center.

Meanwhile, snow will taper off across the rest of Southcentral
this morning as cold (and dry) air advection kicks in. The
combination of cold air advection and tight pressure gradients
will lead to a long period of strong gusty winds across the
Gulf of Alaska coastal waters and through bays/passes along
area mountains. The strongest winds are on track for the western
Gulf and Kodiak Island tonight, along the axis of strongest cold
air advection and area of best upper level forcing on the poleward
side of an upper jet streak and front side of a Bering Sea ridge.
Temperatures will steadily fall across the region through the end
of the week. A new storm will arrive from the Aleutians Friday
night. At this point in time there is quite a bit of uncertainty
in the details. However, with arctic air in place across mainland
Alaska and generally fast zonal flow aloft, expect this storm to
take a southerly track, likely only impacting Kodiak and the Gulf
coast as we head into the weekend.

&&

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

Winds across Southwest Alaska will pick back up today as a mature
low shifts southward towards Kodiak Island. Strong cold air
advection wrapping around the low will filter into Southwest today
as well. Increased winds should help keep temperatures from
dropping too much, but anticipate highs in the mid-20's to
low-30's and lows dropping into the teens (single digits for the
lower Kuskokwim Valley) by Thursday night. Precipitation will
diminish through Thursday morning in most places, with areas along
the AKPen seeing snow into the evening hours. Additionally, winds
should begin to come down early Friday morning.

&&

.SHORT TERM FORECAST BERING SEA/ALEUTIANS (Days 1 through 3)...

Storm force winds pick up along the eastern Bering and Southwest
Coast this morning, extending across the Alaska Peninsula and
surrounding waters. Gusts 75-80 mph are expected for the
previously mentioned areas through today. Anticipate winds
remaining gusty through the bays and passes south of the AKPen
through tonight.

The next system moves into the western Bering late Thursday night.
There is still a fair amount of model inconsistency with this
system and wind speeds are being particularly problematic. There
are hints of possible high end gales to low end storm force winds
possible on the western edge of the system Friday night near the
Central/Eastern Aleutians. There is good consensus for widespread
precipitation along the front.

&&

.LONG TERM FORECAST (Days 4 through 7: Saturday through Tuesday)...

Not much has changed for the long term since the previous
discussion. Colder temperatures will continue to be the main
headline for southern mainland Alaska as a longwave trough
settles over the state through at least Monday. Synoptic scale
model agreement is decent, with uncertainty increasing into Monday
as model solutions diverge.

The extended period will begin on Saturday with a surface low
dipping south across the Alaska Peninsula and moving into the Gulf
of Alaska. The GFS and ECMWF deterministic models are in good
agreement with this feature, though the Canadian model has this
low moving faster across the Gulf and remaining further south. For
now, it looks like a tight circulation around this low will keep
snow limited mostly to Bristol Bay, Kodiak Island, and the North
Gulf coast. The primary hazard for this system will likely be
winds, with winds of at least gale force (with storm force
possible) around this low. Given uncertainties in the low track,
where the strongest winds will set up remain uncertain. However,
ensembles are suggesting it is more likely than not that outflow
winds through Kamishak Gap and across the Alaska Peninsula will be
gale force from Saturday through Sunday.

As we head into Monday, model agreement worsens as they struggle
with how two upper level shortwaves (one in the Western Bering
Sea and one in the North Pacific) will phase late Sunday. Among
the different solutions, the GFS's looks like it would be the most
impactful as it shows these two features merging to produce a 963
mb Bering Sea low that moves into Western Alaska on Tuesday. The
surge of warm air northward with this solution, as well as winds
at storm force, could be hazardous for Western Alaska. The
Canadian solution shows a similar track, though it keeps the low
weaker. Finally, the ECMWF models shows the bulk of the energy
remaining along the Aleutians rather than Western Alaska. Overall,
unsettled weather is expected by Monday and Tuesday, though the
details remain uncertain at this time.

&&

.AFC WATCHES/WARNINGS/ADVISORIES...
PUBLIC...Winter Weather Advisory 131.
         High Wind Warning 181.
         High Surf Advisory 155 161.

MARINE...Storm Warning: 414 352 351 180 165 160 155 150 138 130-132.
         Gale Warning: 411-413 185 181 179 172-174 170 139 137
                       136 121-119.

FIRE WEATHER...NONE.

&&

SYNOPSIS AND MODEL DISCUSSION...DAN
SOUTHCENTRAL ALASKA...SEB
SOUTHWEST ALASKA/BERING SEA/ALEUTIANS...KM
LONG TERM...KC

PRELIMINARY LOCAL STORM REPORT
NATIONAL WEATHER SERVICE ANCHORAGE AK
241 PM AKDT WED OCT 26 2022

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

0930 AM     SNOW             4 WSW STERLING          60.49N 150.91W
10/26/2022  M9.5 INCH        KENAI PENINSULA    AK   COCORAHS

            COCORAHS OBSERVER MEASURED 12.0 INCHES BUT
            ADJUSTED FOR GRASS AND REDUCED TO 9.5
            INCHES.

&&

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PRELIMINARY LOCAL STORM REPORT
NATIONAL WEATHER SERVICE ANCHORAGE AK
250 PM AKDT WED OCT 26 2022

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

0930 AM     SNOW             4 WSW STERLING          60.49N 150.91W
10/26/2022  M9.5 INCH        KENAI PENINSULA    AK   COCORAHS

            COCORAHS OBSERVER MEASURED 12.0 INCHES BUT
            ADJUSTED FOR GRASS AND REDUCED TO 9.5
            INCHES.

0700 AM     SNOW             8 SSE ANCHORAGE         61.11N 149.78W
10/26/2022  M0.7 INCH        ANCHORAGE          AK   COCORAHS

0700 AM     SNOW             7 SSE ANCHORAGE         61.11N 149.85W
10/26/2022  M1.1 INCH        ANCHORAGE          AK   COCORAHS

0700 AM     SNOW             5 SSW ANCHORAGE         61.15N 149.93W
10/26/2022  M2.3 INCH        ANCHORAGE          AK   COCORAHS

            24 HOUR SNOWFALL REPORTED: 2.3 INCHES SNOW
            DEPTH: 2.5 INCHES.

0700 AM     SNOW             5 SSW ANCHORAGE         61.15N 149.96W
10/26/2022  M3.2 INCH        ANCHORAGE          AK   COCORAHS

&&

PRELIMINARY LOCAL STORM REPORT
NATIONAL WEATHER SERVICE ANCHORAGE AK
253 PM AKDT WED OCT 26 2022

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

0800 AM     SNOW             5 ESE WASILLA           61.56N 149.31W
10/26/2022  E0.0 INCH        MATANUSKA-SUSITNA  AK   COCORAHS

&&

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PRELIMINARY LOCAL STORM REPORT
NATIONAL WEATHER SERVICE ANCHORAGE AK
256 PM AKDT WED OCT 26 2022

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

0800 AM     SNOW             3 NE GLENNALLEN         62.11N 145.53W
10/26/2022  M2.6 INCH        COPPER RIVER       AK   COCORAHS

            LIQUID: 0.18 INCHES.

&&

BL

PRELIMINARY LOCAL STORM REPORT
NATIONAL WEATHER SERVICE ANCHORAGE AK
257 PM AKDT WED OCT 26 2022

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

0700 AM     SNOW             7 S TALKEETNA           62.23N 150.07W
10/26/2022  M1.4 INCH        MATANUSKA-SUSITNA  AK   COCORAHS

&&

BL

PRELIMINARY LOCAL STORM REPORT
NATIONAL WEATHER SERVICE ANCHORAGE AK
258 PM AKDT WED OCT 26 2022

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

0700 AM     SNOW             9 SSW TRAPPER CREEK     62.13N 150.53W
10/26/2022  M4.6 INCH        MATANUSKA-SUSITNA  AK   COCORAHS

&&

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