Storm Warning 6, NWS Anchorage, AK

157 
FZAK61 PAFC 251253
OFFAER

Offshore Waters Forecast
National Weather Service Anchorage AK
353 AM AKST Fri Jan 25 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.

PKZ399-260145-
353 AM AKST Fri Jan 25 2019
.SYNOPSIS FOR THE WESTERN GULF OF ALASKA...
A trough over the northern Gulf moves inland Fri afternoon. High 
pressure moves over the Gulf Sat afternoon and a front approaches the
western Gulf Sat night.

$$

PKZ351-260145-
Gulf of Alaska Offshore North of 57N and West of 144W-
353 AM AKST Fri Jan 25 2019

...GALE WARNING TODAY...

.TODAY...SW wind 30 to 45 kt diminishing to 15 to 30 kt in the
afternoon. Seas 17 to 22 ft.
.TONIGHT...SW wind 10 to 20 kt. Seas 14 to 17 ft.
.SAT...SW wind 20 kt. Seas 12 ft.
.SAT NIGHT...S wind 10 to 25 kt. Seas 9 ft.
.SUN THROUGH MON...SE wind 10 to 25 kt. Seas 8 to 13 ft.
.TUE...SW wind up to 15 kt. Seas 6 ft.

$$

PKZ352-260145-
Gulf of Alaska Offshore South of 57N North of 55N and West of
144W-
353 AM AKST Fri Jan 25 2019

...GALE WARNING TODAY...

.TODAY...SW wind 25 to 40 kt diminishing to 10 to 25 kt in the 
afternoon. Seas 17 to 20 ft.
.TONIGHT...W wind 10 to 20 kt. Seas 15 ft.
.SAT...SW wind 10 to 25 kt. Seas 12 ft.
.SAT NIGHT...S wind 15 to 30 kt. Seas 7 to 12 ft.
.SUN THROUGH MON...S wind 10 to 25 kt. Seas 9 to 14 ft.
.TUE...W wind up to 15 kt. Seas 5 to 8 ft.

$$

Southcentral and Southwest Alaska Forecast Discussion
National Weather Service Anchorage AK
525 AM AKST Thu Jan 24 2019

.ANALYSIS AND UPPER LEVELS...An active pattern continues over the
Anchorage CWA. A low positioned near the western Aleutians
continues to bring areas of precipitation and strong winds to the
western and central Aleutians. A surface closed low north of the
central Aleutians, which is associated with an elongated
shortwave upper trough, is bringing precipitation to the central
Aleutians, Bering, and Pribilofs. A surface trough associated with
that upper trough is enhancing southeast flow over Southcentral
and Southwest, continuing warm conditions and bringing
precipitation to the Gulf coast. Several North Pacific lows are
evident on satellite, and the progression of these lows will
determine the weather in Southcentral over the next few days.

&&

.MODEL DISCUSSION...Consensus among models and from run to run
remains poor for today and tomorrow in resolving the complex
setup of multiple mesoscale lows in the North Pacific. Based on
satellite data, one low is near 40N 170W and is initialized well
on the NAM, however abundant lightning associated with this low
lends the concern that the convective nature will negatively
impact the predictability of this low. Ample cold air trails to
the west of this low, thus this low is preventing cold air from
reaching east of the low. A storm force low near 49N 162W has
been resolved well in the latest NAM, GFS, and EC. The CMC does
not depict this low correctly, thus the CMC solutions have
generally been disregarded with this forecast package. This low is
expected to track north toward the AKPEN today. A baroclinic leaf
in the North Pacific is evident on satellite, and the associated
strong low is expected to form roughly near 41N 156W. The question
is how this low will proceed. The EC deepens the low shifting
toward the AKPEN much further than the GFS and NAM do, thus in the
EC solution, the low farther south that's currently developing is
not as deep, and fills once it reaches the Gulf. It then
approaches Southcentral as a front instead of a closed low. This
solution would be a Chinook setup for Southcentral, with warm
conditions, gusty winds and possible rain. Since the NAM
generally initialized the lows well, we leaned towards it in the
forecast over the next day, bringing a closed storm force low into
the Gulf towards Prince William Sound. This solution would
indicate possible snow in Southcentral, maybe even in Anchorage.
However, we don't want to completely discount the EC, as the
multitude of lows in the North Pacific, and the lack of cold air
to the east of the developing low diminishes confidence that it
will develop into the intense closed low that the NAM/GFS depict.

&&

.AVIATION...
PANC...A front is moving north along the coast now, and will move
inland by midday, bringing an end to LLWS. Some remnant Turnagain
winds will move through the terminal and last into the evening,
but they are not expected to be gusty. Another low will bring rain
Friday morning, but a lot of uncertainty exists with this low.
There is a small, but not zero chance, that snow may mix in if the
low moves east. For now going with rain and still keeping CIGS
VFR.

&&

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

The overall forecast for today remains on track for Southcentral
with the strong front over the north Gulf coast pushing inland
and to the Alaska Range by afternoon. The big forecast challenge
has been with the next storm system which will move into the area
Friday. Satellite imagery from overnight shows that low developing
near 45N 158W with ample upper level support. Due to the position
and strength of the upper level support with this low, went with
the GFS and NAM models as it heads into the forecast area
tomorrow. Both models have shown an eastward drift with the low
track and movement into Prince William Sound tomorrow. This more
easterly track will have a large impact on the forecast across the
region and there is the potential for more large changes as the
storm develops.

With the current package, the track will keep Chinook winds from
moving through Cook Inlet. There will still be a bit of
downsloping though tonight, but the strong winds coming off the
Chugach, Kenai, and Talkeetna Mountains and bringing a rapid
melting of the snow looks less likely. There will still be a
strong southerly push of wind up Cook Inlet tomorrow, and the big
question will be whether there will be deep enough cold air aloft
wrapping in from the southwest to cool temperatures for the rain
expected during the late night and early morning hours to turn to
snow by the afternoon. Currently going with a rain-snow mix over
Anchorage because the precipitation type could go either way.
I suspect that the dominant precipitation type though Friday will
be rain, but there is enough uncertainty to mention the snow
potential. This is a complicated short-term forecast that is
likely to need an adjustment or two as the low develops and moves
toward the area.

&&

.SHORT TERM FORECAST SOUTHWEST ALASKA (Days 1 and 2...Thu and Fri)...
The active pattern continues. One warm front will lift through the
area today as another compact, storm force low drives quickly
through the Alaska Peninsula by this afternoon. First, the warm
front currently lifting through is bringing widespread
precipitation across SW AK. Precipitation type varies across
Bristol Bay from rain near the coast and in the lee of the
mountains, to snow for locations further inland and farther
north. It is all snow for the YK-Delta for now. This will change
over to a rain/snow mix this afternoon as cross-barrier winds
start to mix some warmer temperatures down to the surface. Only a
couple inches of snow are expected at the most across the northern
half of the area.

The next system will be much stronger. It is coming in the form of
a tightly wound area of low pressure. It will track quickly from
the North Pacific (where it is visible on satellite right now) up
through the Alaska Peninsula today. As it rides on the left exit
region of an upper level jet, it will be able to maintain its
strength in the mid to low 970 mb range. With its compact nature,
have opted to add a small area of storm force winds into marine
zone 155 for today. Some timing differences remain with this
feature as the American models continue to advertise a faster
solution along the west coast while the ECMWF is quite a bit
slower into Fri.

As it crosses the Alaska Peninsula, it will sling a wave of
precipitation into the Bristol Bay area by this evening. It could
start initially as snow, but should change quickly over to a
rain/snow mix for most spots with gusty southeast winds. As the
system exits the area to the north by Fri morning, it will leave
Southwest AK vulnerable to moist, unstable southwest flow with
cold air advection. Thus, expect some gusty winds and widespread
snow showers. Have increased PoPs to likely in many areas with
this.

&&

.SHORT TERM FORECAST BERING SEA/ALEUTIANS (Days 1 and 2...Thu and
Fri)...
The East Bering will feature the most active weather to start the
period before it hands that title to the Western Bering Fri. One
weaker low is spinning south of the Pribilof Islands this morning.
This will continue to make for some rain/snow over those islands
early today as well as some variable wind conditions. But this
system will quickly be overwhelmed by a much stronger low by this
afternoon. This storm will bring gale force southeasterly winds to
location near the Western Capes as it passes through this evening.
It will leave gale force southwest winds on its backside through
the day Fri.

The Western Bering will start off relatively quietly with one
parent low. This low will drift to the west and slowly fill
during the period. It will keep cyclonic flow over the Western
Aleutians. By late Fri, a new developing low will move in and take
its place. This low will tap into some colder air coming off
Russia. This will allow it to deepen and bring a return to gale
force winds across the area. It will become the dominant feature
into the weekend as it encompasses the entire Bering Sea.

&&

.MARINE (Days 3 through 5)...
The weekend will see another round of low pressure in the Bering
Sea. Model guidance is not consistent, but have decided on a
forecast based on the American models. Both models have the low in
the Bering Saturday being a large and powerful one, with storm
force winds likely for the Central Bering/Aleutians, so have added
them to the forecast. We will have to hone this area of winds
over the next couple of days. The large size of this low also
means gale force winds will encompass most of the Bering Sea and
Aleutians Saturday into Sunday, with winds beginning to taper
Sunday. In the Gulf of Alaska, remnants of a low moving through
will keep gales in the northwest Gulf until Saturday, with strong
winds in Shelikof Strait as well. Things will quiet a bit after
that, but another round of winds in association with the low over
the Bering will make it into the western gulf Saturday into
Sunday.

&&

.LONG TERM FORECAST (Days 3 through 7)...
Seeing as how models can't agree farther out than two days,
confidence is low when we move into the long term with the
forecast. In coordination with WPC this morning, the solution in
the long term is to base the forecast off of ensemble guidance. We
agree with the WPC solution, so will lean that way going forward
with the forecast. Major features were able to be discerned in the
longterm, with ridging over AK on Saturday and another large low
entering the Bering Sea. After the low exits Monday, ridging is
anticipated to build in over much of the forecast area, with a
trough over the western Aleutians. Of course, details cannot be
defined at this time, so a broad brush approach was taken to the
forecast. Stay tuned as things will likely change.

&&

.AFC WATCHES/WARNINGS/ADVISORIES...
PUBLIC...NONE.
MARINE...STORM WARNING 155 119 120 351.
 GALE WARNING 125 129 130 131 132 139 150 160 165 170 171 173 174
176 178 180 352 414
HEAVY FREEZING SPRAY 185
FIRE WEATHER...NONE.

&&

SYNOPSIS AND MODEL DISCUSSION...MM/JA
SOUTHCENTRAL ALASKA...EZ
SOUTHWEST ALASKA/BERING SEA/ALEUTIANS...MO
MARINE/LONG TERM...BB