Gale Warning 356, NWS Anchorage, AK

Southcentral and Southwest Alaska Forecast Discussion
National Weather Service Anchorage AK
444 PM AKDT Fri May 26 2023

.ANALYSIS AND UPPER LEVELS...

A cloudy, cool and wet pattern continues across southern Alaska as
an upper level low remains over the eastern Bering Sea. This low
is producing broad southerly onshore flow across the southern
Mainland, which results in more cloud cover, cooler temperatures
and a higher chance for rain showers.

Closer to the surface, rain showers will continue to move
northwestward across Southcentral Alaska. Another area of rain
showers is currently moving northward across the Kuskokwim Delta.

&&

.MODEL DISCUSSION...

Models remain in good agreement with respect to the placement and
intensity of synoptic scale features at both the surface and in
the upper levels. The most challenging aspect of the forecast
continues to be resolving small scale localized effects.

&&

.AVIATION...
PANC...VFR conditions will persist for this TAF period. Gusty
southeasterly Turnagain Arm winds will ease after 27th/09z. The
Turnagain Arm should remain down the inlet tomorrow, but a brief
period of winds clipping the airport in the afternoon is possible.

&&

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

A mostly cloudy and overall wet pattern is expected to persist
into the upcoming holiday weekend, with the worst of the heavier
rain concentrated along the coastline between Prince William Sound
and the eastern Kenai Peninsula. Very strong, gusty gap winds have
developed in all the usual spots this afternoon with support from
rapid pressure rises over the Prince William Sound behind a
shortwave lifting north towards the Copper Basin. Peak gusts
between 40 and 50 mph will remain possible through this evening
near Palmer, Gulkana and mainly the southern and western side of
Anchorage, perhaps even a bit stronger on portions of the
Hillside. The Turnagain Arm winds will bend south and out of
Anchorage after midnight tonight as a low approaches Kodiak Island
and induces a tightening pressure gradient down Cook Inlet. Aside
from the winds, scattered showers will remain possible across
mainly the Mat-Su Valleys and Kenai Peninsula, with steadier
rainfall continuing near the coast. A few weak thunderstorms will
remain possible as well, mainly across the Susitna Valley near the
Talkeetnas.

Looking towards Saturday the aforementioned low and attendant,
negatively tilted shortwave will shift slowly northeast towards
the north Gulf Coast, resulting in intensifying rainfall along
the coast where strong easterly flow ahead of the low's front
upslopes into terrain. More showery precipitation will remain
possible farther inland, possibly working up from the Cook Inlet
region towards Anchorage and the Mat-Su Valleys by Saturday
evening as upper level waves rotate in from the Gulf around the
main upper trough. Gap winds will be a bit weaker with ample cloud
cover spreading inland, perhaps even managing to stay out of
Anchorage with a decent down-inlet gradient expected to persist.

Looking towards Sunday and Monday, the low in the Gulf is expected
to move into the Prince William Sound area and dissipate, while
another low crosses over the AKPen and shifts east into the Gulf
near Kodiak Island. Prevailing flow may shift from the relentless
onshore and southeasterlies to a more northeast direction across
the southern Mainland as the next Gulf low drifts east, and this
should finally allow things to dry out a bit for Memorial Day,
with periods of sunshine possible across mainly the western parts
of Southcentral during the afternoon and evening.

&&

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

A longwave upper-level trough stretches from the western
Bering/Aleutians east through the Gulf of Alaska. A large low
embedded within the trough resides over the Bering near Nunivak
Island. At the surface, a front shears apart over the Southwest
coast while the associated low center continues to spin just to
the west of Nunivak Island. Showers are expected to prevail across
the Alaska Peninsula and Southwest mainland through most of the
weekend as the low lingers in place and sends various upper
shortwaves across the regions. The upper low will finally track
towards the Alaska Peninsula on Sunday and into the Gulf on Monday
while its surface component weakens. Thus, precipitation chances
gradually decrease Sunday into Monday. Widespread westerly small
craft winds along the southern periphery of the low, across much
of the Bering and Aleutians, also diminish as the low exits the
domain. Further to the west, a transient ridge builds in between
the aforementioned system and another weaker low that enters the
western Bering on Sunday. Rain and slightly elevated winds will
accompany this second low as it tracks southeastward across the
central Bering and then dissipates over the Alaska Peninsula on
Monday.

&&

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

The extended forecast has changed little the past 24 hours with
ensemble means continuing to depict a trough over the Gulf of
Alaska and a ridge of high pressure over the Bering Sea. Gusty
northwesterly winds may start off the period Tuesday and Wednesday
across the Eastern Aleutians and Alaska Peninsula. However, the
pressure gradient between high pressure over the Bering and a
weaker low over the Gulf does not appear to be overly strong.
Thus, perhaps low-end small craft winds will be possible east of
the Pribilof Islands, southward, into the Pacific side of the
Alaska Peninsula. Further west, a North Pacific front is progged
to push into the Western Aleutians by the middle of next week. The
same front then progresses eastward, eventually dissipating over
the Central Aleutians by the end of the week. Rainy conditions
will be possible for the Western and Central Aleutians while drier
conditions are forecast from the Eastern Aleutians into much of
Southwest.

Switching seas, the Gulf of Alaska will remain under a broad
trough through the extended period, bringing widespread clouds and
showers to the offshore regions of the Gulf. To the north of the
trough, Southcentral is expected to remain within easterly flow
aloft. The potential for multiple easterly shortwaves to track
through Southcentral should linger through the end of next week.
Thus, while there should be multiple days of clearing and sunny
skies, the threat for showers and thunderstorms will also remain
in the forecast with any shortwave activity.

&&

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