Gale Warning 368, NWS Anchorage, AK

Southcentral and Southwest Alaska Forecast Discussion
National Weather Service Anchorage AK
544 AM AKDT Tue May 31 2022

.ANALYSIS AND UPPER LEVELS...

An upper-level ridge parked over Southcentral continues the
clear, warm, and dry conditions for the majority of the southern
mainland. This low is aiding in the formation and movement of the
marine stratus impacting some of the coastal communities. Marine
stratus persists for much of the Bering Sea as well as the Gulf of
Alaska with extensions up Cook Inlet spreading as far north as
Nikiski this morning. Nighttime Microphysics is revealing clouds
spreading out ahead of a large North Pacific low that is tracking
northward towards the Aleutian Chain. The aforementioned clouds
are noticed across the Alaska Peninsula and into the Southwest.
Another North Pacific low near the western Aleutians is pushing
higher-level clouds over the western Aleutians as well.
Accompanying the low out west, rain and stronger easterly winds
are noticed.

&&

.MODEL DISCUSSION...

Overall, model agreement continues to be strong. Minimal
differences arise when looking at the timing and position of
shortwaves over the Gulf of Alaska. However, despite these
differences, chances for unsettled weather over the western Gulf
will increase by mid- week, while chances for showers and
thunderstorms across the Copper River Basin increase by Thursday.

&&

.AVIATION...

PANC...VFR conditions will persist. A sea breeze will transition
to a Turnagain wind today and bring gusty south-southeasterly
winds to the terminal. Confidence is high that there will be some
gusty winds, but low in the time of arrival.

&&

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

More warm and dry weather is in store for the southern mainland
the next few days. The ridge of high pressure that used to be over
the west coast has now transitioned all the way to the Copper
River Basin. A low from the North Pacific has reached its furthest
northward extent this morning. It associated front is just south
of Kodiak Island. These two features will work in tandem through
the middle of the week to stretch the ridge of high pressure from
east to west across Southcentral.

Under the high pressure, marine stratus/fog continues to plague
the Gulf of AK and coastal sites. The stratus made another run up
Cook Inlet this morning and will flirt with Kenai. We have
adjusted temperatures down a few degrees to account for it. However,
it will not last long this morning with some increasing northeast
flow and the long days of late May. For inland areas, the ridge
will bring another very dry day with continued warming
temperatures. As the Susitna Valley heats up through the day,
expect another surge of the Turnagain Arm (SE) winds to clip West
Anchorage and the lower hillside late this afternoon/early
evening.

Things will remain largely unchanged for Wed before the ridge
starts to break down some on Thu. The ridge will get split by a
shortwave dropping in from the north Thu afternoon. This feature
is looking more impressive on each subsequent model run. With the
warming airmass (850mb temperatures around 12 to 13C), there will
be a decent amount of instability. Thus, we have introduced
fairly wide chances for thunderstorms from the Talkeetna Mountains
up through the Alaska Range.

&&

.FIRE WEATHER...

There are two things to be on the lookout for through the course
of the week. First, recoveries in some of the higher terrain were
abysmal this morning. Glen Alps only limped into the mid 20%
range. With another warm and dry day expected, this recovery
certainly will not help the finer fuels. The Turnagain Arm wind
will spike up again late this afternoon and push into West
Anchorage and the Hillside. Timing of these winds looks to be
closer towards the early evening (6-7pm). So, while it might not
be completely coincidental with the peak of heating, it will still
be plenty warm and dry to be a cause for concern.

The other feature comes Thu afternoon. After several days (weeks)
of warm and dry conditions, we are keeping a very close eye on
convective potential. Models are now starting to come into much
better agreement with a shortwave sliding into the area from north
of the AK Range. With the warm conditions, there will be some
decent instability over the Talkeetna Mountains up through the
Alaska Range. While parameters don't look overly impressive at
this time, they should be enough to trigger some thunderstorm
development. This set-up bears watching as it is the first signs
of the ridge breaking down that we've seen in some time.

&&

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

Ridging remains in place over Southwest through Thursday, thus,
anticipate warm and dry conditions, and mostly sunny skies to
continue. A front pushed against the southern AKPen is generating
increased winds again today across Bristol Bay and the AKPen and
will slowly diminish through the evening.

&&

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

Two systems are generating impactful weather along the Aleutians
and parts of the Bering Sea. One low is spinning west of the
Western Aleutians, bringing widespread small craft and gale force
winds as well as widespread rain showers. The other is placed
south of the AKPen, and is less impactful than the previous.
Mainly, a small area of small craft and gale force winds south of
the AKPen, areas of low cloud ceilings across the Southern AKPen
and Eastern Aleutians, and some light rainfall. High pressure will
remain over the central/eastern Bering through Thursday, producing
areas of low marine stratus and patchy fog at times.

&&

.MARINE (Thursday through Saturday)...Expect winds less than
35 kts and seas less than 20 ft for the Day 3 through 5 period.

&&

.LONG TERM FORECAST (Friday through Monday)...

The long term forecast period will feature a gradual shift away
from the summer-like pattern we have been seeing towards more of
a spring like one. The hot, dry, and sunny conditions will start
giving way one-by-one, starting with the sunny conditions.

On Friday, with the thermal trough in place but a weakening upper
level ridge, we will continue to increase the coverage of expected
afternoon and evening showers and thunderstorms across much of the
Copper River Basin over to the Susitna Valley. A weakening and
stalling out upper level front approaching from the north will
draw moisture northward towards it which will be enhanced by the
Alaska Range. With less in the way of forcing further west, no
convective activity is expected from Anchorage west across
Southwest Alaska.

On Saturday, afternoon shower and thunderstorm chances will expand
westward to encompass much of southern mainland Alaska. Increasing
easterly flow off the Gulf should also mean more cloud cover which
will tamp down on the temperatures during the afternoons going
forward.

By Sunday and Monday there is considerable uncertainty as to the
timing of a strong easterly wave circulating around an upper level
low over the southern Gulf. Depending on how it aligns with solar
heating, much more widespread precipitation is likely area-wide
Sunday afternoon, but the amount of activity will depend on how
quickly the wave moves east. Regardless, by Monday there will be
a strong southeasterly upper level flow which will transport much
more Gulf moisture into the area. Thus, it's looking generally
cooler, cloudier, and probably rainy as well, particularly the
closer to the Gulf Coast you get.

Across the Bering, the trend will be opposite of that over mainland
Alaska. As the troughing associated with cooler cloudy weather
moves east, upper level ridging will build over the western
Bering, especially Sunday and Monday. The same upper level low
that is near the Western Aleutians right now will be ejected from
that area by Saturday and will be responsible for the cooling
conditions across the mainland Sunday and Monday.

&&

.AFC WATCHES/WARNINGS/ADVISORIES...
PUBLIC...Flood Advisory: 141.
MARINE...Gale Warning: 175-178, 411.
FIRE WEATHER...NONE.

&&

SYNOPSIS AND MODEL DISCUSSION...NS
SOUTHCENTRAL ALASKA...MO
SOUTHWEST ALASKA/BERING SEA/ALEUTIANS...KM
MARINE/LONG TERM...JW