Gale Warning 207, NWS Anchorage, AK

Southcentral and Southwest Alaska Forecast Discussion
National Weather Service Anchorage AK
435 PM AKST Tue Mar 1 2022

.ANALYSIS AND UPPER LEVELS...Generally weak systems and overall
flow are the dominant themes today. The lone exception is out
over the Western Bering where a fairly broad ~960 mb low is slowly
filling over the Western Aleutians. The upper levels show a broad
trough over the Western Bering with sharp, shortwave ridge over
the Pribilofs. Further to the east, another broad trough is
lingering over the southern mainland. Very diffuse shortwaves are
embedded within the trough. The upper level 300 mb (30,000') jet
remains mostly away from the mainland. Over the North Pacific, it
is driving quickly from west to east at 130 kt well south of the
Western Aleutians. It then turns from south to north in support of
the aforementioned trough over the Western Bering at about 70 kt.
The rest of the jet meanders over the Alaska Peninsula before
turning harmlessly back south over the Gulf of AK.

At the surface, this pattern sets the stage for plenty of low
level fog and stratus, mixed with weak showers shattered across
Southern AK. The warm temperatures during the days have allowed
enough melting to occur to create plenty of low level moisture.
This resulted in fog across the Anchorage Bowl this morning with
visibility down 1/4 SM at Ted Stevens. Stratus was (and continues
to be) more prolific seeing it observed at Bethel, King Salmon,
and over to Valdez and Gulkana. As the next wave in the pattern
begins to amplify today, it is helping to create some instability
and showers this afternoon. Most of these showers stretch from
Dillingham over to the Mat Valley, but the instability has helped
to dissipate the fog. Breezing and wet conditions persist across
much of the Central Aleutians as a new surface low develops in the
base of the trough.

&&

.MODEL DISCUSSION...Models remain in fairly good agreement with
synoptic features. This results in moderate forecast confidence.
The primary areas of concern are with the low stratus across
southern AK, the incoming shortwaves, and a developing low Thu
evening nearly the Alaska Peninsula. In general, hand edits and
persistence forecasting was used to handle the stratus and showers
associated with the shortwaves. For the stronger system, the GFS
and the EC are staunchly opposed. The GFS continues to be the
strongest, while the run to run trends of the EC are actually
weaker. The NAM represents a middle ground and was used for this
forecast package. This system will continue to be monitored for
potential high wind and blizzard impacts.

&&

.AVIATION...
PANC...VFR conditions and light north winds will persist. Some
passing showers could cause cigs to low slightly late tonight.
Conditions are expected to remain VFR. SE winds will increase over
Turnagain Arm Wed evening, which could result in some low level
wind shear late in the TAF period.

&&

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

A weak upper low over the Kenai Peninsula is currently bringing
scattered snow showers to that region. These will slowly track
northward through the evening. A front will enter the western
Gulf Wednesday morning initially brining a rain/snow mix to Kodiak
before transitioning to all rain by the afternoon. Turnagain Arm
winds will increase by Thursday morning as the front and an upper
vort max move along the coast. As such, most of the precipitation
should remain confined to coastal areas and winds should not be
overly strong in the Anchorage bowl given the decent positive
pressure gradient southward across the Kenai Peninsula. A brief
lull will occur late Thursday into early Friday as a weak upper
ridge builds in the wake of the front. However, a very similar
system will lead to the same impacts into Friday afternoon.

&&

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

Widely scattered snow showers continue across parts of Bristol
Bay this evening as a weak upper-level shortwave provides marginal
support. As the disturbance lifts northward out of the Southwest
tonight, shower activity should decrease. Low stratus and patchy
fog across portions of Southwest Alaska should continue to linger
through the overnight hours. However, by Wednesday morning, the
low stratus should begin to at least partially advect and mix out
as southeasterly winds begin to increase ahead of an approaching
front.

By Wednesday, the front, along with a developing triple point
low, reaches the Southwest Coast, bringing light snow to Bristol
Bay and the Kuskokwim Delta. Temperatures will warm into the upper
20s to mid 30s with the frontal system, limiting potential for
significant snowfall accumulations. Around 1 inch of new snowfall
is expected near and west of Dillingham through Wednesday night,
as well as areas near Iliamna over interior Bristol Bay. Locations
further south near King Salmon are expected to see downsloping,
which will limit precipitation and raise temperatures to near 40F
on Wednesday, leading to precipitation falling as rain initially,
with a rain/snow mix possible into the overnight hours.
Precipitation will taper off from southwest to northeast through
Thursday morning as the front lifts across Southwest Alaska.

Thursday night, a 970 mb low in the eastern Bering approaches the
Kuskokwim Delta coast, bringing southerly gale force winds that
are likely to overspread the delta. Despite the relatively warmer
southerly flow, temperatures are expected to remain in the lower
30s, with snow staying the dominant precipitation type. Even with
the warmer temperatures, which will lead to a wetter, denser
snowfall, significant reductions in visibility due to blowing
snow may be possible with this event.

&&

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

A front stretches from a low situated just west of Attu across the
Bering to the Alaska Peninsula. A swath of southeasterly gale
force winds is associated with the front as it brings primarily
rain to the eastern Aleutians. A triple point low has also
developed along the front today and will pivot northwest into the
central Bering Sea by tonight. This low will push the front across
the Pribilofs tonight, bringing a quick round of wet snow and
southeasterly gales before the front lifts north of the islands
early on Wednesday morning. Around 1 inch of new snow accumulation
is expected as the front lifts through the islands. The low will
then drift into the western Bering as it occludes and weakens.

A much stronger storm system will reach the eastern Aleutians
early Thursday morning from the North Pacific, bringing easterly
gale force winds and a rain/snow mix. The low is expected to
intensify as it crosses into the eastern Bering, with winds
shifting out of the west on the back side. Relatively colder air
wrapping around the south side of the low will have the potential
to produce a strong wind event for the eastern Aleutians, with
gusts on the upper end of storm force possible. This swath of
stronger winds will also extend across the southern portion of
the Alaska Peninsula, though the current track of the low favors
the strongest winds through the eastern Aleutians.

&&
.Marine (Days 3 through 5: Friday through Sunday)...

Gulf of Alaska: There is high confidence that a front up to gale force
will reach the western Gulf on Friday and push towards the Gulf
coast where a low will form by Saturday. A barrier jet up to gale
force is possible on Saturday as the front reaches the coast and
the low begins to form. Gap winds will then set up on Sunday
through the Barren Islands and typical outflow areas as the low
departs, but with a lack of cold air to the west and over interior
areas, winds should remain at low end gales to small craft. Seas
along the front and barrier jet may reach up to 20 ft should gales
materialize. Bering Sea: There is high confidence a gale to storm
force low will cross the Eastern Aleutians early Friday morning
before moving into the northern Bering and weakening early
Saturday morning. Seas up to 30 ft are possible on the Pacific
side of the chain with up to 25 ft possible north of the Alaska
Peninsula. An additional gale force low is likely to move over the
western Aleutians Friday evening and slowly weaken as it moves
north into Eastern Russia Sunday night. Forecast confidence on the
second low is high and gales are most likely east of the Pribilof
Islands. Seas of 18 to 22 ft are possible with this system.

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

The longwave pattern is expected to amplify over the long term with
a ridge building over the northeast Pacific and broad trough remaining
steady state over the Kamchatka Peninsula and Sea of Okhotsk.
This will place the Southern Mainland in predominantly southerly
flow aloft, which in combination with marginal jet support will
return active weather to the region. On Friday there is good
agreement between deterministic and ensemble forecast models that
a low will form along a front in the western Gulf, which will then
be reinforced by an additional north pacific low as it moves
towards the Prince William Sound and Gulf Coast. Temperatures
aloft appear to be conducive to widespread snow across
Southcentral; however, the low track on Friday can be conducive to
bringing in warm air through Turnagain Arm and the Knik River
Valley, so precipitation may have to overcome low-level warm air
prior to any snow accumulation for these areas. The eventual
development of a closed low in the northern Gulf should help to
pull colder air from the interior areas into the population
centers, but the timing of this transition will impact
precipitation type and accumulations. On Sunday this low departs
rapidly into the Yukon Territory. Model uncertainty increases
drastically after this point, with a closed high developing over
the Alaska Mainland in the ECMWF ensemble and deterministic
models, which would push the storm track south into Southeast
Alaska, while the GEFS and GFS continue to build the ridge and
continue the active storm track into Southwest Alaska.

&&
.AFC WATCHES/WARNINGS/ADVISORIES...
PUBLIC...NONE.
MARINE...Gale 130 131 132 150 155 170 173 175-179 185.
		 Heavy Freezing Spray 180 185.
FIRE WEATHER...NONE.

&&

SYNOPSIS AND MODEL DISCUSSION...MSO
SOUTHCENTRAL ALASKA...AP
SOUTHWEST ALASKA/BERING SEA/ALEUTIANS...CQ
MARINE/LONG TERM...CJ