Small Craft Advisory 362, NWS Anchorage, AK

Southcentral and Southwest Alaska Forecast Discussion
National Weather Service Anchorage AK
544 PM AKDT Fri Apr 29 2022

.ANALYSIS AND UPPER LEVELS...

The low in the Bering Sea had become vertically stacked with the
250 mb jet stream running south of it (and south of the Aleutians)
before bending northeast a little toward the Gulf of Alaska. This
will help to divert the energy into the surface low that will
develop in the Gulf tomorrow as the Bering Sea low dissipates.
The front from the Bering Sea low stretches through the eastern
Bering, into Southwest AK and then over Kodiak Island. The rest
of Southcentral and northward still is under enough high pressure
to keep skies mostly sunny this afternoon.

&&

.MODEL DISCUSSION...

Models remain in good synoptic agreement into the first half of
next week. One change from a day ago is that models are now
generally pushing the front from the Gulf low this weekend farther
inland into Southcentral than indicated the past few days. This
may bring in more rain to the north Gulf coast and gusty gap
winds into the Copper River, Turnagain Arm and the other usual
suspects.

&&

.AVIATION...

PANC...VFR conditions will persist. Gusty southeast Turnagain Arm
winds will prevail this afternoon and evening. The north-south
pressure gradient will then build over Cook Inlet overnight
tonight through Saturday as a strong frontal boundary lifts
northward across the Gulf, causing the Turnagain Arm winds to
bend southward and remain south of the terminal. Sometimes in the
summer, Turnagain winds can sometimes still bend northward into
the terminal as inland areas heat up despite the overall synoptic
pattern favoring a southward bend down Cook Inlet. For tomorrow
afternoon, don't think the heating over the Mat-Su will be that
significantly different than in Anchorage. Thus, favor keeping
northerly winds at the airfield on Saturday.

&&

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

Relatively quiet weather across much of Southcentral will come to
an end for some portions of the region this weekend. A front
associated with a Bering low will begin to usher clouds into the
domain beginning tonight. The aforementioned front will
essentially stall in the western Gulf, particularly around Kodiak
Island, resulting in a long period of steady rain and strong
easterly winds through Sunday. A new low will develop along the
front on Saturday, and will move just off the coast of Kodiak
Sunday morning. The aforementioned low will gradually drift
northeast, weaken, and be absorbed by a second front approaching
the region. Expect precipitation along the coastal mountains,
especially the Kenai Mountains, and 2 to 3 inches of rain through
Sunday across Kodiak Island, with the highest amounts on the east
facing slopes. Gap winds will increase ahead of the front through
Turnagain Arm, the Knik River Valley, and eventually the Copper
River Basin, and Thompson Pass.

&&

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

Gusty southeasterly winds and precipitation coverage will steadily
increase this evening as a front moves ashore along the Southwest
coast tonight. The strongest winds are expected to occur along
the immediate coast, where gale force winds (39 mph or greater)
are already being observed, particularly in Platinum. Winds
further inland are not expected to be as strong, but may still
reach 25 to 35 mph. Winds will relax along the coast as the front
pushes inland through the early morning hours on Saturday. The
greatest rainfall accumulation is expected to occur along the
northern Bristol Bay coast through the day on Saturday as the
front stalls. The front will begin to weaken as a push of drier,
northerly flow steers the front back southward. As the front
backtracks across the coast where winds previously diminished,
these locations will see a second round of gusty east to
northeasterly winds Saturday night. Drier conditions prevail
across Southwest Alaska under northerly flow for Sunday before
a shortwave tracking westward from the Gulf returns a chance of
scattered showers to the forecast Sunday night into Monday.

&&

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

A broad low centered in the central Bering bringing rounds of
widespread showers to the central and eastern Aleutians as well
as the southern AKPen through tonight. Additionally, gale force
winds will be prominent in the eastern Bering and along the
Southwest coast tonight before diminishing through the morning
hours on Saturday. The low weakens and a second low from the
North Pacific approaches the western Aleutians. Its front pushes
east across the Aleutians to the southern AKPen by Sunday night,
bringing widespread light to moderate rainfall as the low skirts
the Aleutian Chain.

&&

.Marine (Days 3 through 5: Monday through Wednesday)...

Gulf of Alaska: Easterly small craft winds Monday morning will
increase to high-end gales in the afternoon as a front pushes
into the north Gulf coast. Winds look to drop below small craft by
Tuesday afternoon as the low weakens. There is a possibility that
winds could approach small craft again Wednesday afternoon if the
low curves further north into the Gulf, though confidence is low.
Seas 10 ft Monday morning increase to near 20 ft from Monday
afternoon through Tuesday. Seas subside on Wednesday to around 8
ft and lower.

Bering: A strong low will track across the AKPEN and into the Gulf
on Monday. Northerly small craft winds are expected across the
Bering on the backside of this low. Gales are possible along the
Western and Central Aleutians nearer the low center, especially as
northerly winds channel through gaps and passes. Winds diminish to
small craft and lower by Tuesday. There remains uncertainty with a
North Pacific low that may track near the Aleutians Wednesday. So
far, models have trended towards keeping the low weaker and
further away, suggesting any winds will be low-end small craft or
less. Seas up to 16 feet in the Bering and up to 24 feet in the
North Pacific will diminish to 12 feet or less by Tuesday
afternoon.

&&

Long Term Discussion (Days 4 through 7: Tuesday through Friday)...

Unsettled weather early in the extended period will gradually give
way to calmer conditions. Confidence is good in the beginning of
the period but deteriorates by Thursday. In Southcentral, a
vertically stacked low in the Gulf will likely keep conditions
windy and wet into Wednesday. Rain near sea level and snow at
higher elevations will mostly be restricted to the coast.
Precipitation will taper off and winds will diminish as the low
weakens on Thursday. Diurnal forcing will likely dominate from
Thursday onwards as a ridge edges west from Canada and daylight
hours continue to increase in Alaska. On Friday, there is the
potential for a North Pacific low to move into the Gulf, but
confidence is low. The eventual trajectory of this low will depend
on the track of an upper level low over Southwest Alaska, which
models continue to have difficulty pinpointing. For now, the GFS
shows the low curving into the Gulf while the Canadian and Euro
keep the low further out in the North Pacific.

Conditions improve through Tuesday across Southwest and the
Aleutians as the vertically stacked low exits into the Gulf.
Northerly winds behind the low will help usher in colder and drier
air, leading to cooler temperatures and potentially clearer skies.
Colder temperatures will likely be reinforced by an upper level
low moving south across Alaska and into the northern Bering on
Tuesday. Model agreement is slowly improving but remains poor with
this feature. The GFS lingers the upper level low in the northern
Bering, while the Canadian and Euro show it reaching Bristol Bay
by Friday morning. This will have an impact on the location of
showers associated with the upper level low, as well as with the
track of a North Pacific low that grazes the Aleutians. Stay tuned
as we continue to refine the forecast.

&&

.AFC WATCHES/WARNINGS/ADVISORIES...
PUBLIC...NONE.
MARINE...Storm Warning 131.
         Gale Warning 119 120 130 132 137 138 139 150 160 180.
FIRE WEATHER...NONE.

&&

SYNOPSIS AND MODEL DISCUSSION...EZ
SOUTHCENTRAL ALASKA...NS
SOUTHWEST ALASKA/BERING SEA/ALEUTIANS...CQ
MARINE/LONG TERM...KC