Area Forecast Discussion
Issued by NWS Anchorage, AK

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FXAK68 PAFC 240055

Southcentral and Southwest Alaska Forecast Discussion
National Weather Service Anchorage AK
455 PM AKDT SUN OCT 23 2016


Upper levels: A ridge remains the dominant upper level feature for
much of mainland Alaska this afternoon. It is centered across
Southwest Alaska, oriented meridionally. From the ridge axis east,
skies are nearly completely clear. This includes all of
Southcentral. Further west, a vertically stacked low is tracking
along the Bering coast of eastern Russia. Between these two
features, warm advection is keeping the ridging in place across
mainland Alaska.

Southcentral: Surface high pressure is slowly sliding eastward
ahead of the aforementioned upper level ridge. The relative low
pressure center over the Gulf has been moving southeast down the
Panhandle and away from our area. As a result, the winds of
yesterday are notably lighter today, though still somewhat gusty
through the Valdez Narrows and the Copper River Delta.

The temperatures are the primary weather story over Southcentral,
as a fresh snow pack, completely clear skies, and calm winds made
for nearly ideal radiational cooling conditions. The result was
many areas seeing by far their coldest temperatures of the fall so
far. The Susitna Valley, east Anchorage, and interior Kenai
Peninsula saw lows falling into the single digits. Anchorage
International fell to 17, a full 9 degrees colder than its
previous coldest night. The most impressive cooling was in the
Copper River Basin, as Gulkana hit a low of 10 below, 11 degrees
colder than its previous coldest night.

Southwest Alaska: High pressure moving east and an approaching
front have allowed for more extensive cloud cover over Southwest
Alaska from Bristol Bay eastward. However, the soundings from King
Salmon and Bethel both show that all of this cloud cover is high
in the atmosphere, as an extensive layer of dry air persists from
the mid levels down to the ground. The cloud cover prevented most
areas of Southwest from getting as cold last night as some
previous nights. The notable exception was King Salmon, which fell
into the single digits for the first time this fall last night.

Bering: A deep low pressure system that`s influencing nearly all
of the weather in the Bering is centered near the coast of Russia
this afternoon. The associated front near the west coast has
weakened considerably. However, a several hour deluge of rain
occurred this morning in Dutch Harbor, which recorded 1.28" of
rain in 6 hours, so the front does have some bite still left in

High Wind Warnings are in effect for the central and western
Aleutians, and a Coastal Flood Watch is in effect for the
Kuskokwim Delta area in association with the next storm moving
towards the Aleutians for tomorrow and Tuesday. More on that



The models are in good agreement with the track of the lows
expected to traverse the Bering over the next two days. The low
currently near the coast of Siberia will be pulling the next
stronger low moving near Attu tonight further west due to the
Fujiwara effect. The outlier model is the Canadian, which keeps a
consolidated low pressure center intact as such through its entire
track across the western Bering. All of the other models keep a
deeper low centered near the coast of Russia Monday afternoon with
the trailing front being responsible for the high winds and seas.
The primary forecast challenge will be the resultant impacts
regarding timing the strongest winds with local high tides. A
change in the strongest winds and highest seas of only a few hours
makes the difference between the seas simply being higher than
normal, and a coastal flood situation with seas well above highest
high tides. Confidence is high regarding the track of the low and
the resultant high winds, but much lower timing the possibility of
coastal flooding.


An upper level ridge continues to build in from the west as it
settles into the Southcentral region. Therefore, look for sunny
skies during the daytime with clear skies through the overnight
hours through Tuesday. While, the coldest temperatures will occur
in the Copper River Basin as the cooler air filters into the area
from the north. Meanwhile, the pressure gradients continue to
weaken resulting in diminishing gap winds with continued offshore
flow. By Tuesday evening, the upper level ridge moves farther
eastward allowing the upstream warmer air to advect into the
Southcentral region bringing warmer temperatures as we head into
the midweek time-frame.



Except for some lower clouds along the coast tonight, the
southwest will be cool and dry with high clouds through Mon. On
Mon night a front brings clouds as it approaches the coast, with
rainy conditions arriving on Tue.



A strong Pacific low will bring rain and dangerous winds to the
western and central Aleutians tonight through Mon evening as it
moves northeast. This will also result in Hurricane Force winds
over the central Bering as well as the marine areas surrounding
the western half of the Aleutians through Mon night. On Tuesday
the storm will weaken as it moves east, with diminishing winds and
showers in the west.

Over the eastern Aleutians and Akpen a front will bring rain and
strong wind through channeled terrain tonight. Conditions will
improve in this area on Mon, but the weakening storm from the west
will bring rain and strong wind to this part of the Bering and
Aleutians through Tue.


.LONG TERM FORECAST (Days 3 through 7)...
An persistent and amplified trough over the Bering will continue
into late in the work week. This pattern will bring a series of
gale-storm force low`s throughout the Bering and southwest
Mainland, bringing widespread rain and gusty southerly winds.
Depending on the exact track and strength of these low`s and
associated fronts, there will also be the potential for coastal
erosion/high surf issues to south exposures of the Southwest
coast (such as Kuskokwim Bay). This will need to be monitored
over the coming days for more details regarding timing and
strength, but it certainly looks like an active week ahead for the
Bering Sea region.

To the east of the Alaska Range, a blocking ridge will prevent
the active weather over the Bering from moving into Southcentral
or the northern Gulf. This will keep generally sunny and benign
weather over the region with daytime highs slightly above normal.
By late next week there is good agreement that this blocking
ridge will shift eastward, allowing for more active weather to
move into the Gulf and south Mainland. This trend will then
continue into early next week with no sign of a return to the ridging
and sunny weather that the south Mainland is currently enjoying.


PUBLIC...Coastal Flood Watch zone 155. High wind warnings 187 191
MARINE...Hurricane Force 173 175 176 177 412 413. Storm 170 172
179 185 411 414. Gales 155 165 171 180.



LONG TERM...DEK is the U.S. government's official web portal to all federal, state and local government web resources and services.