Small Craft Advisory 413, NWS Anchorage, AK

Southcentral and Southwest Alaska Forecast Discussion
National Weather Service Anchorage AK
524 AM AKDT Wed May 10 2023

.ANALYSIS AND UPPER LEVELS...

A wet pattern continues across Southcentral as a large low
pressure system in the North Pacific is resulting in largescale
onshore flow over the region.

Radar imagery shows widespread precipitation moving onshore across
the Kenai Peninsula and Prince William Sound.

&&

.MODEL DISCUSSION...

Models remain in good synoptic agreement. The biggest challenge
continues to be resolving small scale local effects.

&&

.AVIATION...
PANC...VFR conditions continue this TAF period. Low level wind
shear is likely before 00z as winds will remain light and variable
near the surface with SE 25-30kt winds aloft. Southeasterly
Turnagain Arm winds are expected after 00z.

&&

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

The Jet stream continues to pump in moisture air from the south.
This moisture will interact with a broad low pressure system with
several surface lows and fronts moving across the Gulf. The first
low is tracking towards and just south of Kodiak Island this will
bring moderate to heavy rain today across windward portions of the
Island including Kodiak City. An occluded front with slightly
cooler air will push towards the northern Gulf through tonight
keeping the rain going across Prince William Sound and across the
eastern Kenai Peninsula. Snow levels will hover near 2,000 feet
through tonight. The next shortwave trough will push across the
Gulf and reach coastal areas by Thursday morning with rain
continuing along the coast. Meanwhile a surface trough will push
across Kodiak Island Thursday morning with the rain ending with a
few lingering showers in the higher terrain. By Thursday afternoon
the shortwave moves towards western Alaska this will bring an end
to the steady rain along the coast with a more showery pattern
setting up through Friday as more shortwaves rotate around the low
pressure system across the Gulf. The gusty winds will continue
along Turnagain Arm through tonight as well as the Knik River
winds. These winds will decrease Thursday and Friday as the
pressure gradient relaxes across the area. However, the Turnagain
winds will bend into west Anchorage Thursday and Friday afternoon
but will not be overly strong with gusts up to 20 to 25 mph
possible. Finally temperatures will slowly rise closer to normal
values as a bit of sunshine mixed with clouds is possible on
Thursday and Friday this will also cause the snow levels to rise
from 2,500 to 3,500 feet.

&&

.SHORT TERM FORECAST SOUTHWEST ALASKA AND BERING SEA/ALEUTIANS
(Days 1 through 3: Today through Friday)...

A large, vertically stacked low lingering over the western Gulf
will maintain precipitation along the Alaska Peninsula and eastern
Aleutians through Friday morning. Steady precipitation will
gradually become more showery as the low weakens and continues to
dive south. In addition to precipitation, gusty east to
northeasterly winds are expected across much of Southwest, with
the Alaska Peninsula and Bristol Bay area seeing the strongest
winds. With Bering high pressure approaching from the west, the
strengthening pressure gradient will also support gusty northerly
winds through the gaps of the eastern Aleutians. The strongest
winds are generally expected this evening through Thursday
morning. Winds and chances for precipitation then taper off for
most of Friday as surface high pressure enters the region. Expect
a warming trend across Southwest through at least Friday.

Farther to the west, the aforementioned surface ridge of high
pressure has its axis approaching the western Aleutians and
Bering this morning. High pressure will continue to spread
eastward and promote drier conditions, marine stratus, and lighter
winds through Wednesday. By Thursday morning, a front reaches the
western Aleutians and appears to quickly shear apart throughout
the day. However, an incoming shortwave will revive the front over
the central Bering/Aleutians on Friday night.

&&

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

Beyond Saturday, general model consensus suggests an unsettled
pattern for Southcentral, and an active pattern for the Aleutians
and Southwest which host the passage of several more low pressure
systems. Synoptically features as just discussed have fair model
agreement with some discrepancies regarding the precise timing of
shortwaves leading to moderate forecast confidence. One such
source of model disagreement lies in timing the passage of
easterly waves coming into Southcentral over the weekend.
Additionally, the wind fields represented by the models have very
little agreement over Southcentral and the northern Gulf of
Alaska. It is expected generally that Southcentral will be seeing
an unsettled pattern with the potential for precipitation across
the northern Gulf of Alaska coastline. Features over Southwest
Alaska and the Bering are larger more synoptic features, and the
agreement on system progression there is stronger.

&&

SYNOPSIS AND MODEL DISCUSSION...ED
SOUTHCENTRAL ALASKA...RC
SOUTHWEST ALASKA/BERING SEA/ALEUTIANS...AF
LONG TERM...CL