Gale Warning 403, NWS Anchorage, AK

715 
FZAK61 PAFC 052258
OFFAER

Offshore Waters Forecast
National Weather Service Anchorage AK
258 PM AKDT Tue Sep 5 2017

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.

PKZ399-061300-
258 PM AKDT Tue Sep 5 2017
.SYNOPSIS FOR THE WESTERN GULF OF ALASKA...
A 987 mb North Pacific low at 55N 147W will intensify to 978 mb 
and move to 57N 149W tonight then move inland Wed morning to 62N 
160W at 985 mb. A weak front will approach the Western Gulf Thu 
morning.

$$

PKZ351-061300-
Gulf of Alaska Offshore North of 57N and West of 144W-
258 PM AKDT Tue Sep 5 2017

...GALE WARNING TONIGHT...

.TONIGHT...S wind 30 to 45 kt. Seas 12 to 19 ft. Rain.
.WED...S wind 10 to 25 kt. Seas 8 to 13 ft.
.WED NIGHT...S wind 15 kt. Seas 7 ft.
.THU...SE wind 15 kt. Seas 5 ft.
.THU NIGHT...SE wind 15 kt. Seas 5 ft.
.FRI THROUGH SUN...W wind up to 15 kt. Seas 3 to 6 ft.

$$

PKZ352-061300-
Gulf of Alaska Offshore South of 57N North of 55N and West of
144W-
258 PM AKDT Tue Sep 5 2017

...GALE WARNING TONIGHT...

.TONIGHT...S wind 20 to 35 kt. Seas 9 to 14 ft.
.WED...S wind 10 to 20 kt. Seas 7 to 10 ft.
.WED NIGHT...S wind 15 kt. Seas 6 ft.
.THU...S wind 15 kt. Seas 6 ft.
.THU NIGHT...S wind up to 15 kt. Seas 4 to 7 ft.
.FRI THROUGH SUN...W wind up to 20 kt. Seas 4 to 7 ft.

$$

339 
FZAK61 PAFC 061139
OFFAER

Offshore Waters Forecast
National Weather Service Anchorage AK
339 AM AKDT Wed Sep 6 2017

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.

PKZ399-070130-
339 AM AKDT Wed Sep 6 2017
.SYNOPSIS FOR THE WESTERN GULF OF ALASKA...
A 988 mb low at 60N 152W will move inland later this morning. An 
Aleutian low will move to 57N 150W at 996 mb Thu night.

$$

PKZ351-070130-
Gulf of Alaska Offshore North of 57N and West of 144W-
339 AM AKDT Wed Sep 6 2017

.TODAY...S wind 10 to 25 kt. Seas 8 to 13 ft. Showers and Isolated
Thunderstorms.
.TONIGHT...S wind 15 kt. Seas 7 ft.
.THU...SE wind 15 kt. Seas 6 ft.
.THU NIGHT...E wind up to 15 kt. Seas 5 ft.
.FRI...SE wind up to 10 kt. Seas 6 ft.
.SAT THROUGH SUN...W wind up to 10 kt. Seas 5 ft.

$$

PKZ352-070130-
Gulf of Alaska Offshore South of 57N North of 55N and West of
144W-
339 AM AKDT Wed Sep 6 2017

.TODAY...S wind 10 to 20 kt. Seas 7 to 10 ft.
.TONIGHT...S wind 15 kt. Seas 6 ft.
.THU...S wind 10 to 20 kt. Seas 6 ft.
.THU NIGHT...S wind up to 15 kt. Seas 6 ft.
.FRI THROUGH SUN...W wind up to 15 kt. Seas 4 to 7 ft.

$$

Southcentral and Southwest Alaska Forecast Discussion
National Weather Service Anchorage AK
442 PM AKDT Mon Sep 4 2017

.ANALYSIS AND UPPER LEVELS...
The pattern is highly amplified aloft with a mature upper level
low centered south of the Alaska Peninsula. The downstream side
of the system features a north/south oriented jet stream of 140+
kts. The jet sits atop a similarly oriented baroclinic zone in
the low levels, featuring a tight temperature gradient of 18C
over the eastern Gulf and 2C over the western Gulf at 850mb. The
interaction of these two features will be the focus for the
forecast the next two days.

The previous frontal boundary has pushed inland and dissipated
over the mainland while the remainder over the Gulf has re-oriented
and stalled. A few showers are left over the Kachemak Bay area
and a few over the eastern mainland from Cordova eastward. Inland
areas have cleared nicely behind the previous front, while
temperatures remain in the 50s. Winds for the time being are
relatively light across the area.

&&

.MODEL DISCUSSION...
Guidance is rapidly evolving and converging on a solution for a
developing low pressure system in the Gulf. Previous runs of most
models had the surface low pressure moving into Prince William
Sound. The 12z models have all strengthened and moved the surface
center farther south and west, crossing the Kenai Mountains into
Cook Inlet. The focus for this event now shifts from rainfall
amounts in southeast Prince William Sound, to wind potential
around the Anchorage Area.

&&

.AVIATION...
PANC...VFR conditions and light winds will persist until about
mid-day (20Z) Tuesday. A strong low pressure system will then
quickly approach the area. There is quite a bit of uncertainty in
the track of the low, but based on an average of the latest
guidance, expect strengthening northerly winds Tuesday afternoon
with rain and VFR ceilings. At some point late Tuesday afternoon
or evening winds will shift to southeasterly and may be very
strong (gusts to 45 kt possible). There will likely be a short
window of wind shear in there during the wind shift. Since this
is near the end of the taf period, have just indicated the general
trends for now. Will add more detail with the 06Z taf.

&&

.SHORT TERM FORECAST SOUTHCENTRAL ALASKA (Days 1 through 3)...
While the Anchorage Metro area enjoys the last vestige of
pleasant weather this evening, a mature cyclone continues to push
into the Gulf Of Alaska with the occluded low spinning just west
of Kodiak and the tail end of the cold front extending into the
North Pacific. Multiple vort lobes have been detected circulating
about the parent upper level low and will move into southcentral
and southeast over the ensuing 48 hr period. The values of
precipitable water and wind elements are running two standard
deviations above normal with a return interval 10 to 30 years on
the North American Ensemble Forecast System. All of the models are
pinging into a tight pressure gradient as the surface low moves
across the area. In the wake of the low passage there will be
robust pressure rises. All of the signatures are present for a
strong early season wind event. Bottom line, the primary impacts
will be gusty winds and rain. Gale force winds will spread north
across the Gulf and then into Prince William Sound. Strong winds
are also expected to materialize for the Portage Valley, Turnagain
Arm, Anchorage Hillside/Bowl and Cook Inlet. There remains some
uncertainty in storm track and where the strongest winds will
occur. Will monitor new guidance closely because there is some
potential for damaging winds, most likely in the form of blown
over trees.

&&

.SHORT TERM FORECAST SOUTHWEST ALASKA (Days 1 and 2)...
An upper low centered south of the Alaska Peninsula will support
the continued threat for light rain showers over parts of the
Bristol bay region and the Lower Kuskokwim Valley this evening
before upper level forcing diminishes. Most of Tuesday will begin
on the drier side before a rapidly developing low moves toward
Cook Inlet in the evening and overnight period. This low will
support increasing rain threats from the Bristol bay region to the
Lower Kuskokwim Valley with the threat for locally heavier rain
rates given the dynamic nature of this low.

&&

.SHORT TERM FORECAST BERING SEA/ALEUTIANS (Days 1 and 2)...
A gale force low, which was the former remnants of Typhoon Sanvu,
will move from the Western Aleutians tonight and slowly work
eastward through Wednesday. A continued but slow weakening trend
is expected since the low is well displaced from the subtropical
stream where most of the energy was derived. Expect light rain to
impact the Western and Central Aleutians as it moves east.

&&

.LONG TERM FORECAST (Days 3 through 7)...
The long range forecast beginning Wednesday evening remains in an
active pattern through the weekend. Lingering rain showers along the
Gulf coast and southern interior will persist during this onshore
flow pattern through Thursday. Out west, the remnants of Typhoon
Sanvu tracks across the central Aleutians and into the southwest
Gulf by thursday night, spreading gusty winds and rain along the
Aleutians and Alaska Peninsula Wednesday into Thursday. This system
will then traverse the Gulf and bring another round of showers to
Kodiak island and the Gulf coast Thursday into the weekend. High
pressure will build over the western Aleutians and Bering on
Thursday and spread eastward over much of the area by Saturday.
Guidance is struggling with the track and speed of the next system
tracking into the western Aleutians Saturday night, and progressing
further eastward into the Bering Sea by the early part of next week.
Even though there is decent agreement with regards to the Aleutians,
Bering, and southwest mainland seeing some gusty winds and rain from
this system, confidence remains low on the exact strength, track,
and timing of this system.

&&

.AFC WATCHES/WARNINGS/ADVISORIES...
PUBLIC...NONE.
MARINE...GALE WARNING 119 120 125 129 131 139 140 177 178.

&&

SYNOPSIS AND MODEL DISCUSSION...MTL
SOUTHCENTRAL ALASKA...PJS
SOUTHWEST ALASKA/BERING SEA/ALEUTIANS...JA
LONG TERM...TP