Gale Warning 423, NWS Anchorage, AK

Southcentral and Southwest Alaska Forecast Discussion
National Weather Service Anchorage AK
518 PM AKDT Sat Jul 23 2022

.ANALYSIS AND UPPER LEVELS...

A large upper level low over northwestern Alaska continues to
slowly weaken as upper level jet support weakens and the pacific
jet to the south strengthens. Before this low is expected to
completely erode later in the week, we're tracking two distinct
features rotating around it. The first is a weak wiggle in the
flow south of the AKPEN. At the surface is a small 997 mb low with
an attendant warm front extending to the east. Accompanying this
low and front are rain showers across the AKPEN and SW Alaska as
well as into Kodiak. Isolated showers exist across the Gulf of
Alaska and will continue into the evening hours. The second
feature being tracked is a much stronger shortwave that is south
of Shemya. This area will see a stronger low develop and bring
stronger winds and coastal concerns to Bristol Bay later this
weekend.

&&

.MODEL DISCUSSION...

Synoptically speaking, the models are in great agreement through
Monday (~60 hours). Beyond that time bigger changes begin to show,
though the largest issues are not impactful to our area of
responsibility. Monday night and into Tuesday, the present upper
level low over northwestern Alaska will weak and begin its move
towards the Arctic. Among the big three models (Canadian, ECMWF
and GFS) the story is similar, there are just differences in
timing at this point. All models point to a similar story mid week
across the Aleutians: the next trough carving in spinning up
another weak low that will traverse the Aleutian Chain again.

&&

.AVIATION...

PANC...VFR conditions will persist. Southeast Turnagain winds will
continue into the early evening hours before shifting offshore
over the Inlet.

&&

.SHORT TERM FORECAST SOUTHCENTRAL ALASKA (Days 1 through 3: This
afternoon through Tuesday)...

A wet and cloudy pattern will return for Southcentral as a
western Gulf low and its front track across the region this
weekend. As of this afternoon, the front reached Kodiak Island
and is extending east across the entire Gulf of Alaska. The
associated steady rain, cloud cover, and strong easterly winds
will continue to spread to the Southcentral coast and Prince
William Sound areas early Sunday morning as the front pushes
onshore. Interior Southcentral is expected to be cloudy but will
remain relatively dry as rain and winds stay confined primarily
to the Gulf and coastal areas. Rain will taper off Sunday during
the day as the low exits to the east. Gusty southeasterly
Turnagain Arm and Knik Valley winds will persist through the
evening and overnight hours tonight, diminishing Sunday morning
as surface ridging weakens.

A brief break in the rain on Sunday will be brought to an end by
Sunday evening as a large frontal system arrives to the region.
With this front, rain is expected to start for Kodiak Island
Sunday evening and then for the rest of Southcentral by Monday
morning. Gusty southeasterly Turnagain Arm and Knik Valley winds
will increase again Sunday afternoon/evening as surface ridging
strengthens. Precipitation will taper off from west to east late
Monday night through Tuesday.

&&

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

Cool, showery conditions continue today across Southwest today
and tonight. Southeast gap winds will pick up today across
interior Bristol Bay as a front moves into the Gulf of Alaska and
pushes air flow through Kamishak gap. The next system pushes
towards the Southwest coast Sunday night through Monday. There is
still quite a bit of model uncertainty with this system, with
solutions going back and forth on strength and speed of the low
as it tracks towards Southwest. As a whole, expect continuous
rain showers and increased winds across the region Sunday night
through Monday. Winds should begin to decrease again Monday
evening. Increased sustained winds raise concern for high surf
potentials for Bristol Bay and the Kuskokwim Delta. There is still
uncertainty for how strong the storm surge will be, but coastal
flooding is looking less likely at this time.

&&

.SHORT TERM FORECAST BERING SEA/ALEUTIANS (Days 1 and 2)...

Overall, benign weather conditions along the Bering and Aleutians
through tonight. The next system moves into the southern Bering
on Sunday night and pushes towards the Southwest coast through
Monday. There has been a fair amount of inconsistency with this
system, but expected winds to push into gale force and seas to
build 8 to 12 feet. Additionally, expect areas of moderate to
heavy rain showers through Monday night.

&&

.MARINE (Days 3 through 5: Tuesday through Thursday)...

Gulf of Alaska: There is high confidence that high pressure
building over the eastern Bering Sea will allow westerly gales
to develop out of Kamishak Gap and through the Barren Islands
on Tuesday morning. These will persist through the day and
diminish Tuesday evening as a weak area of low pressure along
the north Gulf coast dissipates. There is also some potential
for a weak North Pacific low entering the Gulf to develop a
small area of gales northwest of the center for a brief period
on Wednesday before the low weakens on Thursday, but confidence
 is low in this scenario. Seas remain below 20 ft.

Aleutians/Bering: Tuesday night, a front approaches the
western/central Aleutians ahead of a North Pacific low. Easterly
gales will be possible along the front as it progresses slowly
northeastward across the Aleutian Chain and into the southern
Bering, reaching the eastern Aleutians early Thursday. Seas will
remain below 20 ft.

&&

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

While broad cyclonic flow is expected to remain in place across
the forecast area through the end of next week, with the upper
level longwave trough axis remaining quasi-stationary over the
Bering Sea, the trough is expected to become less prominent and
weaken somewhat. As a result, the middle of next week looks to
feature drier conditions as a shortwave ridge tracks into the
area, replacing the strong upper-level low which has been
persistent over the Bering Strait for the past week. The key
feature will be a surface high pressure system building in over
southern mainland Alaska into Wednesday, which will promote
calmer, drier weather for most of the region. However, with flow
remaining southwesterly, any embedded shortwave troughs could
provide instability to support intermittent rounds of rainfall.
Models key in on one particular feature which tracks into the
southern Gulf of Alaska on Wednesday and reaches the north Gulf
coast by Thursday. However, its track has shifted eastward since
yesterday, leading to less anticipated wind and rain impacts along
much of the western Gulf coast and Kodiak Island, and suggesting
that interior portions of Southcentral will remain dry. The Copper
River Basin would be the most likely exception to this on
Thursday, where rain showers will be most likely with a further
eastward track.

By the end of the week, there is broad agreement on a North
Pacific low tracking across the Aleutian Islands into the Bering
Sea, with its front reaching the Southwest coast by Friday
afternoon. Though confidence in the exact track this low takes
decreases by Saturday, there is higher confidence that the front
will continue to push northward across the mainland, bringing rain
into Southwest Alaska and along the Gulf coast, with rain showers
returning to Southcentral for the weekend.

&&

.AFC WATCHES/WARNINGS/ADVISORIES...
PUBLIC...High Surf Advisory: 155 161.
MARINE...Gale Warning 131 165 170 171 179-181 414.
FIRE WEATHER...NONE.

&&

SYNOPSIS AND MODEL DISCUSSION...SS
SOUTHCENTRAL ALASKA...AF
SOUTHWEST ALASKA/BERING SEA/ALEUTIANS...AB
MARINE/LONG TERM...CJ/CQ