Storm Warning 77, NWS Anchorage, AK

776 
FZAK61 PAFC 090000
OFFAER

Offshore Waters Forecast
National Weather Service Anchorage AK
300 PM AKST Fri Mar 8 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.

PKZ399-091345-
300 PM AKST Fri Mar 8 2019
.SYNOPSIS FOR THE WESTERN GULF OF ALASKA...

A front pushes across the Gulf and dissipates Sun afternoon. A
gale force front enters the Western Gulf Sat afternoon and drives
over the North Gulf Coast and Southeast Alaska by Sun afternoon.
Another front approaches the Western Gulf Sun afternoon.

$$

PKZ351-091345-
Gulf of Alaska Offshore North of 57N and West of 144W-
300 PM AKST Fri Mar 8 2019

...GALE WARNING SATURDAY AND SATURDAY NIGHT...

.TONIGHT...SW wind 10 to 25 kt. Seas 9 to 12 ft.
.SAT...S wind 15 to 30 kt becoming SE 30 to 45 kt in the
afternoon. Seas 10 to 18 ft. Rain.
.SAT NIGHT...S wind 30 to 45 kt becoming SW 25 kt after midnight.
Seas 15 to 20 ft. Rain.
.SUN...SW wind 25 kt. Seas 15 to 19 ft.
.SUN NIGHT...SW wind 15 to 25 kt. Seas 15 to 20 ft.
.MON THROUGH TUE...S wind 15 to 30 kt. Seas 11 to 19 ft.
.WED...SE wind 35 kt. Seas 16 to 26 ft.

$$

PKZ352-091345-
Gulf of Alaska Offshore South of 57N North of 55N and West of
144W-
300 PM AKST Fri Mar 8 2019

...GALE WARNING SATURDAY AND SATURDAY NIGHT...

.TONIGHT...SW wind 20 kt becoming S after midnight. Seas 11 to
15 ft.
.SAT...S wind 30 to 45 kt. Seas 13 to 21 ft. Rain.
.SAT NIGHT...SW wind 30 to 45 kt. Seas 17 to 20 ft. Rain.
.SUN...SW wind 30 kt. Seas 18 to 26 ft.
.SUN NIGHT...SW wind 20 to 30 kt. Seas 20 to 24 ft.
.MON...W wind 20 to 30 kt. Seas 18 to 21 ft.
.TUE...S wind 25 kt. Seas 14 to 17 ft.
.WED...SE wind 25 to 40 kt. Seas 18 to 28 ft.

$$

Southcentral and Southwest Alaska Forecast Discussion
National Weather Service Anchorage AK
414 PM AKST Thu Mar 7 2019

.ANALYSIS AND UPPER LEVELS...
The upper level pattern shows a closed upper level low over the
Bering Sea with a highly amplified Upper level ridge in the Gulf
of Alaska extending northward along the Alcan border. Between
these two features, a jet streak from the due south is approaching
100 kt (at 250 mb) over the Bristol Bay region. The main 250 mb
jet stream is running south of the low and just south of the
Aleutians today and it is expected to remain south of the forecast
area. At the surface, the large Bering Sea low is sitting right
along the 180 meridian this afternoon and has already begun to
weaken. By Friday afternoon it will have be absorbed into the low
currently well southwest of Attu which is sitting in the sweet
spot along the 250 mb jet stream for rapid low strengthening.

&&

.MODEL DISCUSSION...
While models are once again in good agreement through the weekend,
there is a noteworthy change that the major models have shifted to
since yesterday. The low that will be moving through the Bering
Sea on Friday through the weekend (not the one currently in the
Bering Sea) looks to be a little stronger than expected yesterday.
This low will absorb the current low and then keep the expected
track, but the structure of the low and its two centers will be
important to the weekend forecast. This is not only for the Bering
Sea and Southwest Alaska regions, but in Southcentral Alaska as
well. The location of the individual low centers and the northern
boundary to where the pressure gradient will significantly tighten
will have an impact on the Turnagain Arm and Knik Valley winds
and therefore the temperatures across the Cook Inlet region
Saturday into Sunday.

&&

.AVIATION...
PANC...A front near the area this afternoon could cause some
showers in the vicinity, but what snow that does make it around
the terminal will be very light and should not reduce ceilings or
visibility to MVFR conditions. Wind shear will likely develop
overnight as winds in the 2000 ft level increase to an east-to-
southeast direction with surface winds remaining northerly. This
wind shear, once it develops, should persist through Friday
afternoon.

&&

.SHORT TERM FORECAST SOUTHCENTRAL ALASKA (Days 1 through 3)...
The first of a series of fronts is currently draped across the
northern Gulf coast, bringing areas of precipitation - coastal
rain and inland snow - throughout the region, with the steadiest
of the precipitation along the coast. As this first front weakens
overnight, a second front currently impacting Kodiak Island will
lift north bringing another round of heavy precipitation for the
eastern Kenai Peninsula and northern Gulf coast for Friday. The
biggest challenge with this system will be the precipitation type
inland. Along the coast, precipitation may start as snow, but
quickly change to rain as warmer air arrives on southerly winds.
For inland areas, precipitation will be on the lighter side as
southerly winds aloft provide a drier downsloping component. Where
precipitation does fall, it should also start as snow.
Temperatures, however, are expected to warm along Cook Inlet
north through the Mat-Su Valleys, so any snow initially should at
the very least change to a rain/snow mix. As the pressure gradient
increases with the advance of this front, winds will also be on
the increase, especially within favored east/west gap locations
and along the Anchorage hillside.

As this system lifts north Friday night, weak cold air advection
will allow any lingering precipitation to turn back to snow
before tapering off. The exception here will be along the
immediate coast, where it should remain warm enough in the low
level for rain to persist.

Yet another front lifts from the western Gulf to the northern Gulf
late Friday through Saturday. Again, Kodiak Island will be
impacted first wit this system, as rain and gusty southerly winds
ramp up overnight Friday into early Saturday. This system lifts to
the Kenai Peninsula by Saturday afternoon and to the northern
Gulf coast by early Sunday morning. Ahead of the front, gap winds
will again ramp up, peaking late Saturday for east/west gap
locations as well as other areas like the Anchorage hillside and
around Palmer, where downsloping will again limit precipitation
amounts. Widespread precipitation will overspread the eastern
Kenai Peninsula and northern Gulf coast ahead of and along the
front, with precipitation type continuing to be a challenge.
However, given the stronger winds with this system, it is likely
that temperatures with this system will be warmer, meaning rain
not only for coastal locations but for many more inland areas as
well.

&&

.SHORT TERM FORECAST SOUTHWEST ALASKA (Days 1 and 2...Tonight
through Saturday afternoon)...

The weakening front over Southwest continues to bring residual
showers over the Kuskokwim Delta and AKPEN. With weak winds and
ample moisture over the eastern Bering, areas of fog may develop
overnight tonight and early Friday morning especially along the
coast. While this front gradually moves eastward overnight,
another round of precipitation generated by a weakening low over
the central Bering will arrive over the Southwest coast Friday
afternoon. Perhaps the more important story is the incoming storm
force low Friday night. The low center drops to 953 mb Friday
night as its center approaches the Pribilof Islands. Meanwhile,
the leading front stretches well to the east, producing an area
of gales with embedded storm force winds over the eastern Bering
and southern AKPEN. Upper level dynamics strongly support a
strengthening front as it moves inland, thanks to a digging trough
and a more meridional jet streak orientation directly over the
southwest coast Saturday morning. This will allow the front to
strengthen, bringing storm force winds with higher gusts to the
Southwest coast beginning Friday evening and lasting through
Saturday morning. Precipitation associated with this front will
fall mostly as rain due to southerly flow and warming temperatures.
Northern coastal areas such as Nunivak Island, Hooper Bay, and
Toksook Bay may see a rain/snow mix for Saturday afternoon.

&&

.SHORT TERM FORECAST BERING SEA/ALEUTIANS (Days 1 and 2...Tonight
through Saturday afternoon)...

A vertically stacked low centered over the western Bering continues
to weaken this afternoon. On the south side of the low, an area
of westerly gales over the Rat Islands and central Aleutians will
eventually diminish Friday morning as the low breaks down just
west of the Pribilofs.

More notably, a storm force low arrives in the western Bering
Friday afternoon. Its leading front will bring southerly gales
over the central Aleutians beginning Friday afternoon. By Friday
evening, the low center will be just north of Adak while its
associated front will move over the eastern Bering. Gale force
winds are expected over the Pribilofs Friday night and as the low
strengthens, gale force winds will increase to storm force winds
over the eastern Bering late Friday night into early Saturday
morning. On the backside as well as the south side of the low,
gales persist over the western Bering and western and central
Aleutians through Saturday afternoon.

&&

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

...Southern Coastal Waters along the Aleutians/AKPEN...

The main area of interest for the extended period is from Adak
eastward towards Kodiak Island on Sunday. For these locations,
sustained winds in the high-end gale range combined with good
fetch length will yield seas in the 30 to 36 feet range. Storm
force gusts are expected as well. After Sunday, winds will
decrease below gales and seas will subside as well.

...Bering sea and northern coastal waters of the Aleutians/AKPEN...

As an area of low pressure moves from the eastern Bering into
southwest Alaska, mid-range sustained gales are likely across the
western and southern portions of the sea southwards towards the
island chain. A few low-end storm force gusts aren't out of the
question as well, with seas generally in the 20 to 25 feet range.
Conditions will improve for Monday and Tuesday.

...Gulf of Alaska...

Following Sundays frontal passage/strong wind event, look for
small craft criteria winds and waves to persist across Shelikof
Straight and the Kodiak Island coastal waters northeastward
towards Prince William Sound on Monday, with improving conditions
expected on Tuesday.

&&

.LONG TERM FORECAST (Days 3 through 7)...
A strong eastern Bering low will move ashore across the coastal
Kuskokwim Delta on Sunday, with several disturbances crossing the
region in the cyclonic flow. Another low looks to move along the
Aleutian chain towards Bristol Bay for Monday into Tuesday, with a
third low rapidly deepening as it lifts towards Kodiak Island for
the Wednesday and beyond. All of this points to a showery pattern
continuing across most of southwest Alaska and the Aleutians.

Further east, some gusty winds are expected for the Turnagain arm
and Upper Hillside on Sunday, with the higher elevations near
Prince William Sound also getting in on the act. This will occur
in association with an occluded front crossing the region.
Precipitation will be a decent bet as well for most locations,
especially along coastal Prince William sound due to orographic
lift. The exception to this will be the Anchorage Bowl, where
down-sloping effect to the lee of the Chugach Mountains will
develop.

For Monday into Tuesday, the frontal system will weaken due to
frontolysis (the weakening of a front), as it outruns its upper
level support. This will lead to a decrease in the potential for
precipitation.

Our attention then Turns towards the Kodiak low mentioned above.
The latest trend in the models is for a slower and stronger low to
develop as it enters the western Gulf mid-week. The European Model
(ECMWF) has trended towards the more persistent GFS solution, with
the Canadian in between. Should a stronger solution develop
verify, a pattern change may be in store for the region.

&&

.AFC WATCHES/WARNINGS/ADVISORIES...
PUBLIC...NONE.
MARINE...Storm Warning 160 174 176 180.
 Gale Warning 119 150 155 165 170 172 173 175 177 179 181 185.
FIRE WEATHER...NONE.

&&

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