Gale Warning 446, NWS Anchorage, AK

Southcentral and Southwest Alaska Forecast Discussion
National Weather Service Anchorage AK
449 PM AKDT Mon Aug 1 2022

.ANALYSIS AND UPPER LEVELS...

Lingering rainfall is dissipating over Southwestern Alaska as a
low pressure system transits through Southcentral through the rest
of today where rain is currently falling. Since midnight, many
locations have had one to two tenths with a handful of places
getting between a quarter and half inch of precipitation. A few
lightning strikes were observed this morning south of Montague
Island, corresponding closely behind the frontal boundary and in
the dry slotted region of the low. The frontal boundary is over
the Copper River Basin and higher radar reflectivity is becoming
more apparent in Prince William Sound. In the upper levels, a
nearly zonal 120 kt jet is helping to move a progressive pattern
that is anticipated for the next several days. Winds are
unidirectional to the surface with mountain waves visible on
satellite over the Aleutian and Western Alaska ranges. Saint Paul
has had lower visibility due to fog. Total precipitable water
satellite imagery shows a wide plume of moisture moving north
towards the Aleutians with a low moving towards the western
Aleutians that is expected to be a part of the next system to
progress eastward.

&&

.MODEL DISCUSSION...

Models continue to remain in good agreement synoptically through
Thursday afternoon as a progressive pattern remains. Models take
an upper level low over the Western Aleutians and the western
Bering Sea and move it eastward towards the end of the week.
However, models begin to diverge on the movement of this low
Thursday afternoon as it interacts with the western Alaska
Mainland. The speed of the low moving inland will depend on the
amplitude and break down of the high pressure ridge expected to
occur on Tuesday and Wednesday.

&&

.AVIATION...

PANC...Ceilings and visibilities have continued to remain VFR
through rainfall early this afternoon, and although ceilings are
hovering around 5000 to 6000 feet, MVFR is possible, especially
for visibility, but should remain brief. Any rain is expected to
taper off and end around 7-8 PM this evening. Gusty southerly
winds should diminish by this evening with a light southerly wind
remaining overnight becoming variable Tuesday morning. VFR
conditions are mostly expected overnight, though, MVFR is
possible. There may also be a time period Tuesday am where
conditions will be MVFR for ceilings before lifting back to VFR
during the afternoon.

&&

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

A wet pattern is expected to become warmer and drier during this
forecast period as low pressure exits the region to the east and
upper level ridging builds in from the west. Rain and showers
across Southcentral will gradually taper off from southwest to
northeast this evening and tonight. Warmer temperatures and
sunnier skies will return across Southcentral on Tuesday and
Wednesday. Expect warm temperatures along the coastal locations
across the southern Kenai Peninsula due to strong off-shore flow
which will inhibit the sea-breeze from making it to Seward and
other locations in the area. Strong westerly offshore flow is also
expected in Whitter and Passage Canal on Tuesday. Gusts may reach
near gale force in Whittier during the peak of the winds.

&&

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

Light, scattered showers will persist this evening behind an
exiting low pressure and frontal system moving quickly from
Southwest into Southcentral tonight. Across the northern AKPen and
parts of Bristol Bay, gusty west to northwest winds will continue
well into Tuesday, particularly where enhanced through gaps and
passes along the Aleutian/Alaska Ranges. Gradual warming and
drying is also expected overall on Tuesday as shortwave ridging
begins to move into place. Still, a fast moving shortwave is
expected to move around the ridge during the morning, reaching the
Kuskokwim Delta first and then diving quickly southeast into
Bristol Bay later in the morning. Some model solutions have backed
off on the amplitude of this trough, making it unclear how much
accompanying precipitation will cross through with the passage of
this system. However, showers should move through quite quickly as
the shortwave progresses rapidly into the Gulf by Tuesday
afternoon, with maybe even some clearing in a few spots by the
evening hours.

Wednesday is still overall looking to be the nicest of the next
several days, with the ridge axis moving right overhead for at
least the first half of the day. The big question will be whether
any low stratus or fog develop under the subsidence inversion
forming under the strengthening high pressure, especially near
valleys and coastlines of both Bristol Bay and the Kuskokwim
Delta. Areas that are able to remain relatively cloud-free should
be treated to a fairly pleasant day through at least the early
afternoon, with potential for highs to spike up into the mid to
upper 60s. The nice day will likely be cut short, however, as a
front stemming from a large low moving across the Bering pushes
increasing cloud cover and areas of light rain inland from
southwest to northeast through Wednesday evening. The entire low
pressure system will reach the western coastline later on
Thursday, prolonging periods of rain and increasing winds from the
southwest throughout the day.

&&

.SHORT TERM FORECAST BERING SEA/ALEUTIANS (Days 1 through 3:
Tonight though Thursday)...

Sensible conditions across much of the Bering and Aleutians will
be mainly under the influence of a sprawling low pressure and
frontal system expected to trek across the outlook area through
Thursday. Rain along the leading portion of the low's front will
continue to spread north across the Western and Central Aleutian
Chain, eventually extending into the Eastern Aleutians later on
Thursday. Easterly winds up to small craft intensity will shift to
southerly behind the frontal passage across most of the Aleutians
during the day Thursday, with steady rainfall also becoming more
showery behind the front. Rain will arrive in the Pribilofs by
Thursday evening as the front continues to move north. Meanwhile,
winds will ramp up to low end gales out of the west along the
Western Aleutians on the south side of the low as the center
lifts into the western Bering, lingering into at least Wednesday
morning as the system continues north. The corridor of stronger
winds south of the low will reach the Pribilofs by early Thursday,
increasing out of the southwest to around 30 kts during the
morning. The weakening low will leave behind a long, stationary
frontal zone and moisture tap extending from the North Pacific to
near the AKPen. It's still a little early to say where the axis of
heavier rain associated with this atmospheric river will set up,
but moderate rainfall may again push up into the Central and
Eastern Aleutians by Thursday evening.

&&

.MARINE (Days 3 through 5 - Thursday through Saturday)...

Gulf: A progressive pattern continues across the Gulf. A 120+
knot upper level jet will help dig an upper trough through the
northern Gulf on Fri and Sat. A fetch of SW small craft winds
gusting to gale force will gradually expand across the western
Gulf late Thu. Winds become westerly and more widespread across
the entire Gulf through Sat. Seas peak at 10 to 15 ft.

Bering: A N Pacific low over the Bering is expected to begin
shifting eastward and into mainland Alaska on Thu with a swath of
W to SW small craft winds and gale force gusts potentially ongoing
during the morning hours. A second low will move into the Western
Aleutians late Thu and is forecast to dig across the Eastern
Aleutians, eventually shifting into the northern Gulf on Sat.
Gales appear less likely with the second low and wind directions
out of the west will inhibit potential gap winds. Seas peak at 10
to 15 ft.

&&

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

Models are bringing a broad area of positive height anomalies over
the North Pacific for the extended forecast period. However, late
in the period, the GFS is bringing in a distinct area of negative
height anomalies over Mainland Alaska. Strong high pressure in
both the upper levels and at the surface is forecasted to
retrograde and stall across the mid-latitudes of the Pacific
between Alaska and Hawaii. This will result in a fairly
progressive pattern across southern Alaska. Chances of rain will
increase for the Aleutians and stretch eastward into the southern
Mainland. An Arctic upper-level low will edge southward toward
interior Alaska late next week, and will result in bringing cooler
temperatures to the region.

&&

.AFC WATCHES/WARNINGS/ADVISORIES...
PUBLIC...NONE.
MARINE...Gale Warning 411 130 131 177 178.
FIRE WEATHER...NONE.

&&

SYNOPSIS AND MODEL DISCUSSION...VR
SOUTHCENTRAL ALASKA...ED
SOUTHWEST ALASKA/BERING SEA/ALEUTIANS...AS
MARINE/LONG TERM...BL/NS