Area Forecast Discussion
Issued by NWS Anchorage, AK

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000
FXAK68 PAFC 200039
AFDAFC

Southcentral and Southwest Alaska Forecast Discussion
National Weather Service Anchorage AK
439 PM AKDT Thu May 19 2022

.ANALYSIS AND UPPER LEVELS...

A large area of high pressure continues to dominate the weather
over all of southern mainland Alaska. Nearly clear skies are
prevalent from King Salmon north. A healthy cumulus field has
developed over the Copper River Basin based on satellite, which
is keeping that area somewhat cooler and cloudier. Showers are
possible from any of the taller cumulus through this evening. It
is the warmest day of the year so far for many stations across
mainland Alaska due to the full sunshine and a Springlike air mass
moving across the area.

All the active weather over the area is over the Alaska Peninsula,
Bering, and the Aleutians. A large North Pacific low well south of
Dutch Harbor is gradually approaching the Chain this afternoon.
Its leading front is spreading rain into Dutch Harbor. The rain is
spreading north towards the southern Alaska Peninsula as well.

In the upper levels, a large high centered near Anvik is
overspreading much of southern mainland Alaska, resulting in the
beautiful sunny and warm conditions we are experiencing this
afternoon. A large vertically stacked low is swirling well south
of the Aleutians. There are no significant jet streaks in our
area.

&&

.MODEL DISCUSSION...

The models are in excellent agreement this afternoon with a nearly
stagnant weather pattern persisting over the area, meaning any big
changes in the weather are slow to occur. The only disagreement of
any significance is the timing and intensity of the leading front
around the Aleutians low as it moves north across Kodiak on
Saturday. The US models are faster and generally more intense with
the precipitation, while the Canadian is the slowest and the
driest. Overall forecast confidence is very high.

&&

.AVIATION...
PANC...VFR conditions and light winds will persist. On Friday
afternoon, the Turnagain Arm wind is expected to move over the
airport, resulting in gusty southeasterly winds into the evening.

&&

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

Sunny skies and above-average temperatures will continue across
the region through Friday. A front will enter the Gulf Friday,
bringing rain and gusty easterly winds to Kodiak Island. Winds
will likewise increase over Turnagain/Knik Arm at this time as
well. There remains some uncertainty as to how far the front will
progress northward through the weekend. It appears much of the
rain will remain offshore and only increased cloud cover would be
expected over Southcentral. The strong upper ridge will eventually
break down by early next week, however precipitation will be
disorganized and there does not look to be any impactful systems
for the foreseeable future.

&&

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

A ridge of high pressure will slowly move east as a front
extending from a low in the southern Bering Sea lifts
northeastward. As the front advances, southeasterly winds will
increase tonight across the Alaska Peninsula in response to a
tightening pressure gradient between the mainland high and Bering
low. Additionally, winds funneling through Kamishak gap will also
increase for the eastern corridor of Bristol Bay, including
Koliganek and New Stuyahok. Along and ahead of the front, a decent
plume of moisture and warmer air aloft will advect from south to
north. Rain is expected to start sometime Friday afternoon and
evening for the Alaska Peninsula and Southwest regions. The bulk
of the precipitation will be concentrated along the coastline,
while the interior valleys stays relatively dry as the ridge
dominates over the mainland. Because of the southeasterly
component, moisture associated with this system will be mostly
limited to upslope favored areas on the Kuskokwim and Aleutian
Mountains. Light rain will continue for most of the coastal areas
as we head into the weekend with another low pressure system
tracking near the western Gulf of Alaska by Sunday.

&&

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

Marine stratus and patchy fog trapped in the subsidence inversion
underneath the ridge blankets most of the Bering Sea and Aleutian
Islands. As the ridge axis shifts slowly east, an area of low
pressure is expected to lift northward near Dutch Harbor. The
attendant front will bring gale force winds with higher gusts for
the central and eastern Aleutians beginning tonight. Along and
ahead of the front, a decent plume of moisture and warmer air
aloft will advect northward, bringing rain for the same regions
through the weekend. As the low weakens and becomes stationary
south of Atka, winds are expected to subside below small crafts
with rain pushing westward between Kiska to Attu by Sunday
afternoon.

&&.MARINE (Days 3 through 5: Sunday through Tuesday)...

Gulf of Alaska: A front enters the Southern Gulf Sunday, and
moves across the Gulf through Monday. A surface low will move
over Kodiak Island by Monday. Gusty Easterly winds with the front
stretch across the Gulf, with areas of gales over Kamishak Bay,
Shelikof Strait, Sitkinak and along the Alaska Peninsula coast,
diminishing Saturday. An Easterly gale force barrier jet forms
along the North Gulf Coast. Seas to over 10 feet possible east of
of Kodiak Island. Cyclonic flow will persist over the Gulf for
the remainder of the forecast period.

Bering Sea: A mature low remains South of the Aleutians through
Tuesday. Widespread gusty winds expected for the North Pacific
low, with areas of gales from Bristol Bay into the Central Bering,
diminishing Sunday. Seas to 14 feet on the Pacific side of the
Alaska Peninsula, subsiding Saturday, and 10 feet or less over the
Bering, subsiding Monday and Tuesday.

&&

.LONG TERM FORECAST (Days 4 through 7: Monday through
Thursday)...

A Rex Block pattern is likely during the extended period as upper
level ridging extends across the central/northern Bering and into
northern Alaska. At 500 mb there are 2 closed lows south of the
chain and GFS keeps those lows south of the chain through Friday.
The ECMWF shows a similar evolution of the mass fields at 500 mb
this forecast period, but these two models are definitely not a
clone of each other. Expect an area of persistent ridging but also
expect a lingering closed low over the Gulf Of Alaska. Sensible
weather-wise the GFS keeps positive height anomalies over mainland
Alaska this forecast period which will translate to warm
temperatures at the surface and the continuation of snow melting.

With the closed low in the Gulf, expect easterly waves/shortwaves
to get ejected from this feature and move over portions of
Southcentral. But it is too soon to tell were these shortwaves
will track. All the global models have a closed low in the Gulf
with numerous shortwaves embedded in them.

&&

.AFC WATCHES/WARNINGS/ADVISORIES...
PUBLIC...Flood Advisory 141.
MARINE...Gale Warning: 131 132 137 138 150 155 160 165 170 172 174
         180 351 352 414.
FIRE WEATHER...NONE.

&&

$$

SYNOPSIS AND MODEL DISCUSSION...JW
SOUTHCENTRAL ALASKA...AP
SOUTHWEST ALASKA/BERING SEA/ALEUTIANS...MF
MARINE/LONG TERM...PS


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