Gale Warning 548, NWS Anchorage, AK

892 
FZAK61 PAFC 261146
OFFAER

Offshore Waters Forecast
National Weather Service Anchorage AK
346 AM AKDT Fri Oct 26 2018

Offshore waters forecast for the Gulf of Alaska West of 144W

Wind forecasts reflect the predominant speed and direction
expected. Sea forecasts represent an average of the highest
one-third of the combined wind wave and swell height.

PKZ399-270130-
346 AM AKDT Fri Oct 26 2018
.SYNOPSIS FOR THE WESTERN GULF OF ALASKA...

A 978 mb low at 59N 151W moves to 56N 154W at 995 mb Fri night and
then dissipates. A complex 985 mb North Pacific low moves to 50N 
147W Fri night and then moves to 56N 148W at 986 mb Sat night.

$$

PKZ351-270130-
Gulf of Alaska Offshore North of 57N and West of 144W-
346 AM AKDT Fri Oct 26 2018

...GALE WARNING SATURDAY...

.TODAY...S wind 15 to 30 kt. Seas 9 to 14 ft. Showers and isolated
thunderstorms.
.TONIGHT...S wind 10 to 25 kt. Seas 8 to 11 ft. Showers and isolated
thunderstorms.
.SAT...E wind 20 to 35 kt. Seas 8 to 13 ft.
.SAT NIGHT...E wind 25 to 40 kt. Seas 9 to 16 ft.
.SUN...NE wind 10 to 25 kt. Seas 8 to 16 ft.
.MON THROUGH TUE...SW wind 15 kt. Seas 5 to 9 ft.

$$

PKZ352-270130-
Gulf of Alaska Offshore South of 57N North of 55N and West of
144W-
346 AM AKDT Fri Oct 26 2018

.TODAY...SW wind 15 to 30 kt. Seas 8 to 13 ft. Showers and isolated
thunderstorms.
.TONIGHT...S wind 10 to 25 kt. Seas 7 to 11 ft. Showers and isolated
thunderstorms.
.SAT...E wind 15 to 30 kt. Seas 6 to 11 ft.
.SAT NIGHT...E wind 15 to 30 kt. Seas 8 to 16 ft.
.SUN...NE wind 10 to 25 kt. Seas 9 to 14 ft.
.MON THROUGH TUE...W wind up to 20 kt. Seas 5 to 9 ft.

$$

Southcentral and Southwest Alaska Forecast Discussion
National Weather Service Anchorage AK
457 AM AKDT Thu Oct 25 2018

.ANALYSIS AND UPPER LEVELS...

A large area of low pressure currently over the Gulf is likely
the last of the deep lows for the foreseeable future. The low is
producing a large area of gale force winds over the open waters of
the Gulf, but impacts on land have been relatively minimal
thus far. There will likely be localized areas of storm force
winds associated with any fronts rotating about the low enhancing
the winds in those areas. The Anchorage and King Salmon soundings
from yesterday afternoon show much of the lower atmosphere to be
unstable. This should help any precipitation from the Gulf low to
become more showery as it moves into the area. The low is also
bringing a final round of warm air in the middle levels of the
atmosphere, which is helping support the well above normal
temperatures we are currently experiencing across Southcentral.
The cloud shield associated with the Gulf low has overspread
nearly all of Southern mainland Alaska. Meanwhile out over the
Bering, the area's first influx of cooler air racing south out of
Russia has made for periods of time where the rain showers have
become snow showers in both Adak and Atka last evening. That cold
air will be slowly progressing eastward into mainland Alaska over
the next few days and will be a player in upcoming weather this
weekend. There are a few weak lows embedded in the northerly wind
flow across the Bering that are locally enhancing the shower
activity as well as they race southward.

&&

.MODEL DISCUSSION...

The models are having a very difficult time handling the track and
eventual landfall of the low currently over the Gulf. As such,
forecast confidence regarding the timing and intensity of the
winds associated with both the low itself and the fronts rotating
around it is lower than normal. The EC has the most
straightforward track, slowly progressing the center westward
over the Barren Islands by this time tomorrow. The Canadian splits
the low into two, with one low approaching near the Barren Islands
at the same time as the EC, but tracking it southward along the
east coast of Kodiak Island, while the second stronger low loops
around the central Gulf and eventually makes landfall south of
Seward Saturday morning. Both the NAM and GFS start off doing the
same thing with the single low, looping it well east of Kodiak
Thursday night. That's where the similarities end. The GFS takes
the center to near Kodiak City Friday night and stalls it there.
The NAM takes a longer time to complete the initial loop and
brings the center into the Barren Islands Saturday afternoon. To
complicate things further, most of the models bring a new, weaker
low north out of the Pacific into the Gulf by Saturday afternoon,
then stall it somewhere over the Gulf, occasionally rotating
pieces of energy and moisture into Southcentral into the weekend.

&&

.AVIATION...
PANC...VFR conditions and light winds will persist into the
afternoon, after which a weak front will increase the chance for a
few rain showers in the vicinity along with gusty north winds
developing Thursday evening.

&&

.SHORT TERM FORECAST SOUTHCENTRAL ALASKA (Days 1 and 2)...

The Gulf of Alaska is filled with yet another storm-force low
today. This low is a bit different in its structure in that the
center is elongated from west-to-east through the middle of the
Gulf. This is keeping the strongest winds in the marine areas and
will delay the strongest winds along the North Gulf Coast until
later today. At this time, it looks like this afternoon will be
when those winds will make it into Cordova and then into Prince
William Sound before reaching the eastern Kenai Peninsula later this
evening. This low is also different from Tuesday's in that it
will not push through the region to Norton Sound like that one
did, but will remain in the Gulf of Alaska. This is important
since this track will keep the strong pressure rises out of
Cordova and Whittier which was a major cause of the damaging wind
gusts.

The low remaining in the Gulf will also keep Inland areas mostly
dry through Friday with the best chance for precipitation being right
as the trough passes over Southcentral this evening. At least
that is until the low has mostly dissipated by Friday night and
the remaining moisture moves over southcentral which will bring
in more rain showers Friday night and Saturday.

&&

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

A mid-level ridge slowing drifting east to west across Southwest
Alaska will continue to keep conditions rather quiet through the
next 24 hours. The exception to this is a weak trough skirting the
lower Kuskokwim Delta this morning that is setting off a few
widely scattered showers across the area. Northerly winds across
the region, coupled with an increase in high clouds from a low
moving into the northern Gulf, has also helped to limit areas of
fog this morning. By late Friday, a trough moving east over the
Southwest will begin to usher in colder temperatures as a push of
arctic air dives south along the polar jet. This trough slows its
forward momentum on Saturday as a the remnants of the Gulf low
track northwest across the Alaska Range. The stalled trough over
the southwest then beings to advance east late Saturday into
Sunday as both the remnants of the Gulf low dissipate and a second
system upstream over eastern Russia slides across the Bering. As
the colder air moves across Southwest Alaska this weekend, any
precipitation that falls is expected to fall as snow, or a mix of
rain and snow Saturday changing to snow Sunday closer to the
Alaska/Aleutian Ranges. Light accumulations are possible along the
the higher terrain where a persistent northerly flow will allow
for upslope. Little to no snow accumulation is expected for lower
elevations and valley locations.

&&

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

As the polar jet continues to dive south through the Bering, a
series of weak surface troughs and mid-level shortwaves embedded
in the overall flow will help maintain gale-force winds through
the Bering and across the central Aleutians. This northerly push
will slide east and slowly weaken as the trough axis reaches the
western coast late Friday. As it slows, mixed rain/snow showers
will linger across the eastern Bering south to the eastern
Aleutians and AKPEN. Farther west, a strengthening north Pacific
low will push a warm front across the western Aleutians for
Friday. This system is then expected to slide south of the chain
with minimal to no impact. On Saturday, another low developing
over eastern Russia will begin to move into the northern Bering
over top a building ridge in the western Bering.

&&

.LONG TERM FORECAST (Days 3 through 7)...
(Saturday through Wednesday)

The synoptic pattern will change little over the next few days,
before a pattern shift commences as we head into next week.
A series of low pressure systems will lift north into the Gulf by
Saturday, and then absorb the remnants of Thursday's low, as they
rotate around each other in a Fujiwhara-like fashion. This will
keep a periodically wet theme continuing through the weekend for
southwest and southcentral Alaska, before lifting northeast into
Canada by Monday. This will also allow for our warm afternoon
temperatures to continue.

A push of colder air which will feature temperatures returning
much closer to seasonable normals will move into Southwest Alaska
this weekend. As the cold air moves southeastward across the
Alaska Range during the day on Sunday, moisture from the
persistent low across the Gulf is expected to progress
northwestward into Southcentral. This will make for the
possibility for Anchorage and the Mat-Su Valley's first bout with
accumulating snow this winter come Sunday night into Monday.
Specifics this far out are very uncertain as usual, but with the
ingredients for snow looking to come together all at once,
confidence is increasing. This would likely result in Anchorage's
first freeze and first measurable snowfall occurring at about the
same time. Preparations should begin over the next few days to
prepare for the first snowfall. With the general time frame of
the snow starting Sunday night and persisting into Monday morning,
Monday morning rush hour traffic may be adversely impacted.

Low temperatures in the 20s the next several nights following
this event will ensure the snow and ice on the ground persist,
with any melting from the day resulting in patchy black ice with
each night's refreeze. Stay tuned to future forecasts over the
next few days as the details on the upcoming snowfall become more
clear.

&&

.AFC WATCHES/WARNINGS/ADVISORIES...
PUBLIC...None.
MARINE...Storms: 119 351 352
Gales: 120 125 130-132 139 155 165-185 412-414

&&

SYNOPSIS AND MODEL DISCUSSION...JPW
SOUTHCENTRAL ALASKA...EZ
SOUTHWEST ALASKA/BERING SEA/ALEUTIANS...TM
LONG TERM...PD/ JPW