Small Craft Advisory 276, NWS Anchorage, AK

Southcentral and Southwest Alaska Forecast Discussion
National Weather Service Anchorage AK
526 AM AKDT Mon Mar 28 2022

.ANALYSIS AND UPPER LEVELS...

An amplified pattern is in place over the region. Vertically
stacked lows are located over the Kamchatka and Alaska
Peninsulas, while longwave ridges are located over the Bering Sea
and eastern Gulf of Alaska. The jetstream winds between these
features.

The main weather maker has been the vertically stacked
low on the Alaska Peninsula, whose influence stretches from the
Eastern Aleutians through the north Gulf coast. To its west, gusty
northerly winds continue over the Pribilofs and Unalaska. Its
front has brought snow and gusty winds through Southwest Alaska,
producing blowing snow and leading to reduced visibilities
overnight. Winds have been especially strong through the Kamishak
Gap and into Bristol Bay; peak gusts so far measure 45 kt in King
Salmon and almost 50 kt in Koliganek, though winds are beginning
to diminish.

In Southcentral, precipitation persists over much of the Gulf
coast. Conditions in Kodiak have improved markedly overnight as
snow has transitioned to rain and winds have diminished greatly.
In contrast, gusts of 40 kt and greater continue in Portage
Valley, combining with periods of moderate snowfall to reduce
visibilities to as low as one-quarter mile.

Out west, a robust front associated with the stacked Kamchatka low
is making its way across the Bering Sea and Aleutian Chain. Winds
are beginning to shift southerly in Adak as the front approaches.
This front will bring the next round of unsettled weather as the
low over the Alaska Peninsula continues to weaken.

&&

.MODEL DISCUSSION...

Models remain in decent agreement at the synoptic scale. There
are some differences with a surface low that moves from the North
Pacific into the Gulf on Tuesday. However, as the feature looks
to remain in the eastern Gulf, impacts will be limited in our
area. In the Bering, model differences arise as a triple point low
forms along the front and merges with the parent low Monday
night. The GFS and Canadian suggest that the triple low will
dominate and the parent low will be quickly subsumed, while the
NAM suggests the parent low's center will linger for longer. As
such, tighter gradients associated with the GFS and Canadian
solution maintain stronger, gale-force winds across the northern
Bering as compared to the NAM. Looking forward to Wednesday
evening, differences in how the models handle additional lows
forming along the front will impact the timing of precipitation
and winds through Southwest Alaska.

&&

.AVIATION...
PANC...VFR conditions will persist. Flurries/sprinkles are
possible Monday morning and evening, though confidence is low.

&&

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

The main low will remain over the Alaska Peninsula area, but the
front associated with it is the source of the weather across
Southcentral Alaska today. Early this morning, the front is
approaching the southern tip of the Kenai Peninsula and stretches
into the Gulf of Alaska. This front will slow down in its northern
movement and weaken as it does so. This will still keep strong
winds occurring ahead of the low and the strong winds through
Portage Valley and possibly Turnagain Pass into the early
afternoon. Portage has had some blizzard conditions last evening
and at times overnight, but this is suspected to be mainly
localized to there. Temperatures have remained just above freezing
all night so although there is snow and low visibility due to the
intensity, the accumulations should be mitigated due to the
temperatures. As one goes up Turnagain Pass there should be more
snow accumulation there with heaviest intensities being through
this morning.

Precipitation type will also be a bit of a question in Valdez.
Temperatures are expected to reach the mid 30s around there but
the precip type may remain mostly snow all day, so snow
accumulation were increased in the morning forecast.

Kodiak should remain rain today in the easterly flow and the
warmer air that is in the lower atmosphere. Yesterday Kodiak had
some blizzard conditions in strong east winds which is a bit
unusual. Today should be a clear cut case of all rain at the lower
elevations including Kodiak City.

Tonight, the front will make its way through Southcentral leaving
the 500 mb low over the area and colder air aloft. This will
bring in scattered snow showers across the area for Tuesday with a
brief break Tuesday night. The next system will move into the
region Wednesday and bring with it warmer air than the system that
is over Southcentral today.

&&

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

Gusty easterly winds and periods of snow and blowing snow will
continue through this morning across northern Bristol Bay and the
Kuskokwim Delta, north of a low. However, prolonged periods of
significantly reduced visibilities are no longer expected. The
low will weaken by afternoon as it becomes vertically stacked and
fills in, and thus widespread snow will taper off and winds will
gradually diminish. Snow showers will remain possible on Tuesday,
particularly along the coast, as an upper shortwave tracks over
the region. The next significant system will be a front that
approaches on Wednesday morning. Given the deep, southerly fetch,
precipitation may mix with or change to rain, especially during
daytime hours as temperatures will rise to near 40 for many
locations.

&&

.SHORT TERM FORECAST BERING SEA/ALEUTIANS (Days 1 through 3: Today
through Wednesday)...

An active pattern will persist across the Bering over the coming
days. A low centered over the AKPEN is bringing snow showers and
gusty northerly winds to the eastern Aleutians. These will
gradually shift eastward and taper off through the day as it
becomes vertically stacked and weakens. Quiet conditions are
expected Tuesday under an upper ridge. A front tracking west to
east across the western Aleutians will bring rain and gusty
southerly winds through Wednesday as it tracks across the Chain.
Snow showers will develop in a colder, northerly flow on the
backside of its parent low.

&&

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

Gulf of Alaska: A strong frontal system from the eastern Bering
will cross over the Gulf Thu morning bringing widespread gales
and large seas up to 20 ft across the western Gulf through Fri
morning. Over the Cook Inlet and Shelikof Strait, stronger gusts,
gales, and seas up to more than 14 ft are expected there through Thu
night. GFS remains most aggressive of all the solutions,
suggesting the potential for storm force winds Thu and Thu night.
For now, anticipate a broad swath of gales and seas of 15 to 20 ft
near Kodiak Island and 15 to 17 ft along the northern Gulf Fri
morning.

Bering Sea: A weakening low over the central Bering will keep
gales and seas up to 15 ft west of the Pribilof Islands until Wed
evening. Meanwhile, strong winds and potentially gale force winds
and seas of 12 to 15 ft will briefly brush through the western and
eastern Aleutians Thu morning into Thu afternoon. For the most
part, benign seas and wind conditions will persist along the
eastern and southern Bering until the next strengthening low
enters the Bering Sea Fri afternoon. This latter system could
bring widespread gales and seas up to 24 ft over the western
Bering and the western Aleutians Fri afternoon into Fri night.

&&

.Long Term Discussion (Days 4 through 7: Thursday through
Sunday)...

Weak transient upper-level ridging will build over Southcentral
through Thursday. As the West Pacific Oscillation strengthens in
the positive phase, upper-level troughing will gradually deepen
across the Bering/Aleutians. This pattern will produce cloudy and
wet conditions across Southcentral due to broad onshore
geostrophic flow. Southcentral can expect to see the cloudy and
wet conditions continue through Sunday, as multiple lows and
upper-level waves rotate around/through the area. Models are
depicting a broad upper-level low moving into the western Bering
Sunday with it tracking towards the central Aleutians and then
exiting the domain. Scattered snow showers and mixed precipitation
can be expected along the Aleutians as the aforementioned low
tracks through the area.

&&

.AFC WATCHES/WARNINGS/ADVISORIES...
PUBLIC...Winter Weather Advisory: 125.
MARINE...Gale: 119 120 130 131 139 155 165 170-172 174 411-414.
FIRE WEATHER...NONE.

&&

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