Gale Warning 210, NWS Anchorage, AK

104 
FZAK61 PAFC 172333
OFFAER

Offshore Waters Forecast
National Weather Service Anchorage AK
333 PM AKDT Sun Mar 17 2019

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.

PKZ399-181345-
333 PM AKDT Sun Mar 17 2019
.SYNOPSIS FOR THE WESTERN GULF OF ALASKA...

A 981 mb low at 54N 151W Sun afternoon moves over Kodiak Island at
990 mb by Mon morning. A front enters the Gulf Tue afternoon
associated with a 985 mb North Pacific low at 53N 152W.  

$$

PKZ351-181345-
Gulf of Alaska Offshore North of 57N and West of 144W-
333 PM AKDT Sun Mar 17 2019

.TONIGHT...SE wind 20 to 30 kt. Seas 14 to 17 ft.
.MON...S wind 20 kt. Seas 12 to 16 ft.
.MON NIGHT...SW wind 10 to 20 kt diminishing to less than 10 kt after
midnight. Seas 11 to 14 ft.
.TUE...NE wind 15 to 30 kt. Seas 11 ft.
.TUE NIGHT...SE wind 20 to 30 kt. Seas 12 ft.
.WED THROUGH THU...SE wind 10 to 25 kt. Seas 9 to 14 ft.
.FRI...SE wind 20 to 30 kt. Seas 17 to 20 ft.

$$

PKZ352-181345-
Gulf of Alaska Offshore South of 57N North of 55N and West of
144W-
333 PM AKDT Sun Mar 17 2019

.TONIGHT...SE wind 15 to 30 kt. Seas 13 to 18 ft.
.MON...SW wind 10 to 20 kt. Seas 11 to 16 ft.
.MON NIGHT...W wind up to 15 kt becoming NE 10 to 20 kt after 
midnight. Seas 9 to 14 ft.
.TUE...NE wind 15 to 30 kt. Seas 9 to 13 ft.
.TUE NIGHT...SE wind 15 to 30 kt. Seas 13 ft.
.WED THROUGH THU...SE wind 10 to 25 kt. Seas 9 to 17 ft.
.FRI...S wind 10 to 25 kt. Seas 15 to 20 ft.

$$

Southcentral and Southwest Alaska Forecast Discussion
National Weather Service Anchorage AK
507 PM AKDT Sat Mar 16 2019

.ANALYSIS AND UPPER LEVELS...
A warm and rainy weather pattern continues along the Gulf coast
this afternoon as a front associated with a low near Kodiak
continues to lift northward into the North Gulf Coast. Rain
showers have been observed on radar, along with gusty conditions,
extending from Kodiak Island to east of Cordova along coastal
areas. Interior Southcentral has remained mostly dry, with
temperatures remaining above freezing today and gusty conditions
through Turnagain Arm and other favorable gaps in the terrain.
Looking out west, fairly benign conditions remain throughout most
of the Bering with the only feature being a weak low moving
eastward from the central Bering towards Bristol Bay. Snow showers
were occurring today along the Aleutian Chain and over much of the
Bering Sea including the Pribilofs. A shortwave over the
Southwest continues to bring below snow, strong winds, and
reduced visibilities to coastal areas. Temperatures are also well
below freezing in the Kuskokwim Delta area with the northwesterly
flow on the west side of the low.

&&

.MODEL DISCUSSION...
The numerical models are in good agreement over much of southern
Alaska and the Bering Sea through Monday afternoon. The important
exception is how they deal with a low moving into the western Gulf
from the south on Sunday morning through its transition into
southwest Alaska Sunday night into Monday morning. The NAM is the
furthest east and fastest with this low, and was not used in the
forecast. The ECMWF begins as the slowest, then catches up to and
possibly passes the GFS Monday morning. The GFS was the preferred
model for this low and was used in the afternoon forecast.

&&

.AVIATION...
PANC... VFR conditions are expected to persist through Sunday
afternoon. Gusty southerly winds are expected through this
evening, then end overnight as the next system approaches from the
south. Wind shear is then expected as the surface winds turn
northerly and the winds aloft become strong from the southeast.

&&

.SHORT TERM FORECAST SOUTHCENTRAL ALASKA (Days 1 and 2: Today
through Monday)...
A series of low pressure systems moving across Southern Alaska
will keep the area in a very active weather pattern over the next
couple days. A weakening low pressure system over Southwest Alaska
continues to keep a strong southeasterly wind going across the
Gulf and into Southcentral. This onshore flow is leading to
widespread upslope precipitation across coastal areas and the
adjacent mountains all along the Gulf Coast. For immediate coastal
communities, such as Seward, Valdez, and Whittier, the
precipitation has been primarily rain, but in the mountains,
steady snow will continue through into Monday.

Once the low currently over Southwest Alaska moves into the
interior and dissipates tonight, a second low will move south of
Kodiak Island Sunday morning, which will continue the onshore flow
and upslope precipitation. The low will slowly track north,
passing Kodiak late Sunday night and move into Cook Inlet on
Monday. Then it will dissipate as it moves into the Susitna
Valley late Monday. Along this track, onshore flow will persist
along the Gulf Coast the entire time, resulting in the mountain
snows and coastal rains.

The lows following this track will also keep the gap winds through
Turnagain Arm, the Knik and Matanuska Valleys, and the Copper
River Basin going through Monday. While the Turnagain Arm wind
will persist, it will vary in intensity and position, so Anchorage
will not be subject to it constantly through Monday, just at
certain times. However, its warming and drying effect will still
persist regardless of where the strongest winds are. Thus,
relatively little precipitation and highs in the 40s are expected
the next couple days. Those temperatures will approach the daily
records. The other areas subject to the gusty winds, like the
Matanuska Valley and Copper River Basin, will also see highs
spike well into the 40s for the same reason. With relatively
little sunshine due to the onshore flow, expect nighttime lows to
also remain relatively warm with a diminishing number of
locations seeing temperatures drop below freezing. Thus, the March
thaw will continue until there is a substantial weather pattern
change.

&&

.SHORT TERM FORECAST SOUTHWEST ALASKA (Days 1 and 2)...
A deformation zone has setup over southwest Alaska which has
brought a mix of rain and snow to the area. Eastern locations are
seeing more rain with areas farther west seeing primarily snow.
Tonight it will slowly shift east and setup over the Bristol Bay
area and extend north into the Lower Kuskokwim Valley. It will
linger there through Sunday as it gets reinforced with a low
approaching from the south. The deformation zone will then
diminish on Monday as high pressure and cold air move in from the
west.

&&

.SHORT TERM FORECAST BERING SEA/ALEUTIANS (Days 1 and 2)...
Cold air will remain over the Bering through the forecast period
with broad westerly flow shifting to northerly flow as high
pressure builds in from the west beginning Sunday night. This
pattern is also conducive for light snow showers over the area.
Similarly, the Aleutians will begin with westerly flow but winds
over the islands will switch to the east as a North Pacific low
approaches on Sunday. The low will stay south of the Aleutians but
will bring some warmer air to the eastern Aleutians and a mix of
rain and snow on Monday.

&&

.MARINE (Days 3 through 5)...
(Tuesday through Thursday

...Bering Sea/Aleutians...

The numerical models aren't in the best agreement, so this
forecast may change in the coming days. In general, a broad
cyclonic flow pattern looks to persist, with rain and snow showers
crossing the region through Wednesday north of the Aleutian
chain. Here, seas look to remain in the 5 to 15 feet range for
most areas. The exception to this will be south of there, where a
series of lows will trek eastward from the central Aleutians
towards the western Gulf in the Tuesday through Wednesday time
frame, where seas will build to near 20 feet with high-end Small
craft/low-end sustained gales likely.

Then on Thursday, some of the models want to bring a sub 975 mb
low towards Shemya, resulting in high-end gales for western
portions of the chain and Bering, with the other half indicate
winds under 15 knot's with a light sea state. All of this will be
determined by the eventual track of a strong low (~955 to 965 mb
range) heading towards Kodiak on Friday, as the overall pattern
(surface and aloft).

Forecast confidence: Low

...Gulf of Alaska...

An active pattern will continue for the region, as one low moves
ashore from the Gulf on Wednesday,with small craft criteria winds
and seas of 10 to 15 feet expected. An even stronger system will
affect starts to affect the area on Thursday, moving into the
Gulf on Friday. This next storm is where the forecast confidence
goes down hill, as model guidance has almost a 200 nm displacement
of where the low goes, and at what strength, leading to a
difference between small craft wind conditions near the coast and
gales for the outer waters and storm force near the Barren Islands
(all winds sustained). This would have a large effect on wave
height given the good fetch length as well. Thus, additional
forecast changes are almost a certainty in the coming days.

Forecast confidence: Moderate Wednesday, low by Thursday evening

&&

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

A high degree of uncertainty exists for the long term portion of
the forecast, as model continuity quickly disintegrates. Overall,
what we do know is a series of lows will trek northward through
the Gulf into Southwest Alaska. The question remains as to what
track? Overall, look for the first low to on Wednesday to bring
another surge of moisture and increasing temperatures to the
eastern into southwest and southcentral Alaska, with a front also
moving into the western Bering and Aleutians.

After this, virtually all models show a strong low lifting north
northwest into the western or central Gulf for Thursday into
Friday evening, with the GFS suggesting a low moving towards the
gulf from sough of Adak getting absorbed into the larger system,
where as the other models don't show this. Additionally, they all
show another storm approaching Shemya, but the isobaric pattern at
the surface and aloft are out of phase amongst the numerical
members.

Heading into early next week, the spaghetti plots are all over the
place with no sign of model agreement south of the Aleutian chain,
nor over southwest/south central Alaska through the Gulf, with
some modest agreement over the northwest Bering. This all looks to
be related to how quickly a downstream ridge becomes more
progressive, and less upper air observations across the
Bering/island chain compared to points further east.

That said, pattern persistent has been the dominate mode as of
late, so will hedge the forecast in that direction. This leads to
a warm and active pattern for the eastern Bering/AKPEN into
southcentral and the Gulf, with a general showery pattern driven
by cyclonic flow for the west.

Forecast confidence: Low

&&

.AFC WATCHES/WARNINGS/ADVISORIES...
PUBLIC...NONE.
MARINE...Gale Warning 119 120 125 130 150 176 351
         Heavy Freezing Spray Warning 185
FIRE WEATHER...NONE.

&&

SYNOPSIS AND MODEL DISCUSSION...AH/BL
SOUTHCENTRAL ALASKA...JW
SOUTHWEST ALASKA/BERING SEA/ALEUTIANS...DK
MARINE/LONG TERM...PD