High Wind Watch 6, NWS Anchorage, AK

046 
WWAK72 PAFC 281403
NPWALU

URGENT - WEATHER MESSAGE
National Weather Service Anchorage AK
503 AM AKST Fri Dec 28 2018

AKZ191-290315-
/O.UPG.PAFC.HW.A.0006.181229T0900Z-181229T1800Z/
/O.NEW.PAFC.HW.W.0008.181229T0900Z-181229T1800Z/
Western Aleutians-
Including the city of Shemya and Amchitka
503 AM AKST Fri Dec 28 2018

...HIGH WIND WARNING IN EFFECT FROM MIDNIGHT TONIGHT TO 9 AM AKST
SATURDAY...

The National Weather Service in Anchorage has issued a High Wind
Warning, which is in effect from midnight tonight to 9 AM AKST
Saturday. The High Wind Watch is no longer in effect. 

* LOCATION...Shemya.

* WIND...NE wind 55-70 mph with gusts up to 80 mph possible.

* TIMING...Late Friday night through Saturday morning. The 
  strongest winds are expected to develop by early Saturday 
  morning. 

* IMPACTS...High winds may move loose debris and may damage 
  property. 

PRECAUTIONARY/PREPAREDNESS ACTIONS...

A high wind warning means a hazardous high wind event is expected
or occurring. People are urged to secure loose objects that could
be blown around or damaged by the wind.

&&

$$

AKZ187-290315-
/O.CON.PAFC.HW.A.0006.181229T0900Z-181229T1800Z/
Central Aleutians-
Including the city of Atka and Adak
503 AM AKST Fri Dec 28 2018

...HIGH WIND WATCH REMAINS IN EFFECT FROM LATE TONIGHT THROUGH
SATURDAY MORNING THROUGH SATURDAY MORNING FROM ADAK WEST TO THE
RAT ISLANDS...

* LOCATION...From Adak and west to the Rat Islands.

* WIND...South wind 45-60 mph with gusts up to 80 mph possible.

* TIMING...Late Friday night through Saturday morning. The 
  strongest winds are expected to develop by early Saturday 
  morning. 

* IMPACTS...High winds may move loose debris and may damage 
  property. 

PRECAUTIONARY/PREPAREDNESS ACTIONS...

A high wind watch means there is the potential for a hazardous
high wind event. People are encouraged to closely monitor this
weather situation. Preparation for this potentially dangerous
weather event should begin now.

&&

$$

635 
WWAK72 PAFC 281417 CCA
NPWALU

URGENT - WEATHER MESSAGE...CORRECTED
National Weather Service Anchorage AK
517 AM AKST Fri Dec 28 2018

AKZ191-290315-
/O.UPG.PAFC.HW.A.0006.181229T0900Z-181229T1800Z/
/O.NEW.PAFC.HW.W.0008.181229T0900Z-181229T1800Z/
Western Aleutians-
Including the city of Shemya and Amchitka
517 AM AKST Fri Dec 28 2018

...HIGH WIND WARNING IN EFFECT FROM MIDNIGHT TONIGHT TO 9 AM AKST
SATURDAY...

The National Weather Service in Anchorage has issued a High Wind
Warning, which is in effect from midnight tonight to 9 AM AKST
Saturday. The High Wind Watch is no longer in effect. 

* LOCATION...Shemya.

* WIND...NE wind 55-70 mph with gusts up to 80 mph possible.

* TIMING...Late Friday night through Saturday morning. The 
  strongest winds are expected to develop by early Saturday 
  morning. 

* IMPACTS...High winds may move loose debris and may damage 
  property. 

PRECAUTIONARY/PREPAREDNESS ACTIONS...

A high wind warning means a hazardous high wind event is expected
or occurring. People are urged to secure loose objects that could
be blown around or damaged by the wind.

&&

$$

AKZ187-290315-
/O.COR.PAFC.HW.A.0006.181229T0900Z-181229T1800Z/
Central Aleutians-
Including the city of Atka and Adak
517 AM AKST Fri Dec 28 2018

...HIGH WIND WATCH REMAINS IN EFFECT FROM LATE TONIGHT THROUGH
SATURDAY MORNING FROM ADAK WEST TO THE RAT ISLANDS...

* LOCATION...From Adak and west to the Rat Islands.

* WIND...South wind 45-60 mph with gusts up to 80 mph possible.

* TIMING...Late Friday night through Saturday morning. The 
  strongest winds are expected to develop by early Saturday 
  morning. 

* IMPACTS...High winds may move loose debris and may damage 
  property. 

PRECAUTIONARY/PREPAREDNESS ACTIONS...

A high wind watch means there is the potential for a hazardous
high wind event. People are encouraged to closely monitor this
weather situation. Preparation for this potentially dangerous
weather event should begin now.

&&

$$

320 
WWAK72 PAFC 290103
NPWALU

URGENT - WEATHER MESSAGE
National Weather Service Anchorage AK
403 PM AKST Fri Dec 28 2018

AKZ187-290215-
/O.CAN.PAFC.HW.A.0006.181229T0900Z-181229T1800Z/
Central Aleutians-
Including the city of Atka and Adak
403 PM AKST Fri Dec 28 2018

...HIGH WIND WATCH IS CANCELLED THROUGH SATURDAY MORNING FROM
ADAK WEST TO THE RAT ISLANDS...

The National Weather Service in Anchorage has cancelled the High
Wind Watch. 

Recent model guidance shows the strongest winds will be just west
of Adak Saturday morning.

$$

AKZ191-291415-
/O.CON.PAFC.HW.W.0008.181229T0900Z-181229T1800Z/
Western Aleutians-
Including the city of Shemya and Amchitka
403 PM AKST Fri Dec 28 2018

...HIGH WIND WARNING REMAINS IN EFFECT FROM MIDNIGHT TONIGHT TO
9 AM AKST SATURDAY...

* LOCATION...Shemya.

* WIND...NE wind 55-70 mph with gusts up to 85 mph possible.

* TIMING...Late Friday night through Saturday morning. The 
  strongest winds are expected to develop by early Saturday 
  morning. 

* IMPACTS...High winds may move loose debris and may damage 
  property. 

PRECAUTIONARY/PREPAREDNESS ACTIONS...

A high wind warning means a hazardous high wind event is expected
or occurring. People are urged to secure loose objects that could
be blown around or damaged by the wind.

&&

$$

Southcentral and Southwest Alaska Forecast Discussion
National Weather Service Anchorage AK
532 AM AKST Thu Dec 27 2018

.ANALYSIS AND UPPER LEVELS...

A broad northeasterly oriented long wave trough, stemming from an
Arctic low, encompasses the Bering with several short waves
embedded within the flow. Northerly flow and strong cold air
advection is occurring over the western and central Bering. The
first short wave extends over the central Aleutians and is
associated with a surface low. The surface low is bringing
precipitation to the islands and weak westerly flow over the
eastern Aleutians. The second shortwave extends from the western
mainland over Kodiak Island and into the southern Gulf. A large
band of increased vorticity runs the western coast into the Gulf
mimicking the location of the short wave. This shortwave is also
associated with a surface low that is gaining momentum and moving
northeast. A front ahead of the low is moving northward into the
northern Gulf which is creating south to southeasterly winds and
slight warm air advection. In the northern Gulf, a deformation
zone is passing over Southcentral which is bringing showers to
Southcentral. Radar shows the showers concentrated over the
northern Gulf. The next weather feature to watch is an
intensifying front and associated North Pacific low that is
approaching the western Aleutians.

&&

.MODEL DISCUSSION...

Synoptically, models are in decent agreement early on. Model
consistency in regards to the low south of the central Aleutians
quickly dissipates as the models diverge tonight. The EC/Canadian
models are moving faster towards Bristol Bay while the NAM/GFS
are lacking behind. With this specific low and its track, the NAM
was selected as the model of choice. Regarding the low in the
southwestern Gulf, models have finally settled on a track just
east of Prince William Sound tonight. The next main feature to
note is the approaching front and associated North Pacific low.
Models are in decent agreement with the front placement but they
differ greatly on the strength of the low. The GFS has the
strongest solution with the low about 20 mb lower than the other
solutions. This causes the winds with the front to be
significantly stronger. By Saturday morning models diverge further
as the placement of the low and the intensity of the winds greatly
differ. A combination of models was used with this system, but
confidence regarding wind speeds remains low.

&&

.AVIATION...

PANC...VFR conditions will prevail until midday before light snow
develops and drops ceilings to and visibilities down to MVFR at
times through early evening. Confidence in the intensity and
precise location of the strongest portion of the snow band however
remains low given continued model differences. If the heaviest
portion of the band sets up right over PANC, conditions could drop
to IFR for a couple hours and if the band drifts more quickly
west than current model runs are depicting, the snow be lighter
and end earlier. Following the snow band, a secondary upper
trough swings through with cold advection which will support
additional snow showers along the mountains tonight, these
however, should remain well east of the terminal.

&&.SHORT TERM FORECAST SOUTHCENTRAL ALASKA (Days 1 through 3/Today
through Saturday night)...

A deepening surface low over the central Gulf will track toward
Cordova today, with an upper level short-wave extending W-NW from
the low. This system is looking more impressive than numerical
models originally depicted, so have upped precipitation amounts in
the latest forecast. In particular, as the low nears the coast, a
deformation band will set up across the Kenai Peninsula up to
northern Cook Inlet and into the southern Susitna Valley. There is
some uncertainty in exactly where the heaviest snow will set-up,
but guidance is now placing at least parts of Anchorage under the
deformation band. This could be yet another event where west
Anchorage sees more snow than the rest of the city. The
deformation band will last for about a 6 hour period - from
approximately Noon to 6pm. The low will then head inland east of
Cordova while the trailing short-wave then lifts northeastward.
Snowfall with this trailing wave looks notably lighter.

The next storm system, currently south of the eastern Aleutians,
will track across the western Gulf Friday then up to near the
Kenai Peninsula Friday night. While the surface low looks weak,
the upper trough is looks strong and negatively tilted and will
be accompanied by strong cold air advection. With such strong
forcing, have trended more aggressive with the snow forecast and
strengthened winds in the cold advection. This does look like a
relatively quick moving trough, so do not anticipate issuing any
advisories or warnings at this point, but will continue to
evaluate potential for heavy snowfall accumulation.

The active weather will continue, as a frontal system then
approaches the Gulf Saturday night. A deep storm out along the
Aleutians will help amplify the pattern, which will ultimately
lead to warmer temperatures as we head through the weekend.

&&

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

Below normal temperatures have ended for now across most of
Southwest Alaska. Snow showers associated with a weak upper level
front will move northeastward with time, and the associated cloud
cover will prevent any radiational cooling that would allow for
continued below normal temperatures. Light snow showers and some
patchy fog in Bristol Bay is likely to continue into tonight. A
new low approaches the Alaska Peninsula late tonight as an upper
level low and associated front move in from the west. The
combination of these two features will cause a deformation band to
develop early Friday morning. A surface low tracking up Shelikof
Strait will pump moisture into Southwest Alaska over the Aleutian
Mountains. Meanwhile, the cold air advancing from the west in
combination with a strong upper level front will add lift to the
atmosphere. As a result, widespread light snow will develop early
Friday morning over Bristol Bay and spread north into the Lower
Kuskokwim Valley by the afternoon. Most areas east of a Dillingham
to Sleetmute line are expected to get about 2 to 4 inches of snow
through Friday night. Higher amounts closer to 6 inches are
possible along the western slopes of the Alaska Range in the lower
Kuskokwim Valley as the mountains add additional lift locally.

In the wake of the upper level low and front, a very cold Arctic
air mass will move into the Kuskokwim Delta early on Friday and
overspread Bristol Bay and the Lower Kuskokwim Valley by Friday
night. Assuming calm winds, clearing skies, and a fresh snow cover
will allow temperatures to plummet to around 20 below in interior
areas of Southwest Alaska on Saturday morning. The cold snap will
be very short-lived as a strong front approaches the coast
Saturday evening, bringing another more significant round of snow
with much warmer temperatures to all of Southwest Alaska on
Sunday.

&&

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

Low pressure systems will impact portions of the Bering Sea
through Saturday. The first is a relatively weak low whose center
is tracking south of Dutch Harbor. Behind the low, very cold air
spilling directly out of the Arctic is wrapping around the low
center. A band of heavier snow along the strongest temperature
gradient north and west of the low is moving east. It is expected
to reach Dutch Harbor around midday today and persist into the
evening, as the low is relatively slow moving. Thus, any rain or
mixed precipitation in Dutch Harbor is expected to transition to a
heavy, wet snow that will be blown around in 20 to 30 mph winds.
Thus, expect a significant reduction in visibility in blowing snow
all over Unalaska Island today. The snow will move east overnight,
impacting the Alaska Peninsula, and then will track into Shelikof
Strait during the day on Friday.

Leaving behind the first low, a second much stronger low and
associated front are expected to move into the western Aleutians
starting late tonight. The front will bring warmer air to that
region. The models are still having a hard time pegging down where
the low is and perhaps more importantly, how strong it will be.
For the most part, the models are agreeing that the front will
produce hurricane force winds in the waters around Attu and Shemya
late tonight. The front will weaken somewhat during the day on
Friday. A secondary low will follow behind that front Friday
evening, intensifying as it goes. This will make for a second
round of hurricane force winds, primarily across the waters north
of Shemya and Attu late Friday night through Saturday morning,
followed by slow weakening. Further east, the low will help
advance the initial front across the eastern Aleutians on
Saturday, bringing widespread gale force winds. It will move into
Bristol Bay Saturday night. While the winds will be the most
hazardous aspect of the front, occasionally heavy rain associated
with it is also expected along the entire Aleutian Chain through
into Sunday morning.

&&

.LONG TERM FORECAST (Days 4 through 7)...

The forecast period commences with a longwave ridge from the Gulf
Of Alaska to the Brooks Range with a deep upper level trough over
NE Russia and the Western Aleutians. Meanwhile at the surface at
12z Sunday, both the GFS and the ECMWF have a deep low between
Attu and Adak with a post frontal surface trough extending towards
Hokkaido Japan. Where these two models differ at 12z Sunday is
east of the parent low. The GFS has another surface low over
Bristol Bay and the ECMWF simply has weak troughing. Also the
ECMWF has a secondary low feature south of the chain which the
GFS doesn't have at all and then the GFS spins up a low by 18z
south of the ECMWF's position. This does not bode well for the
confidence level with the remainder of the longterm forecast
package since the divergence amplifies as time elapses. There is
good confidence that this will generally be a wet and windy
pattern for the Aleutians, but the timing of the sensible weather
highlights are a function of the precise track of the lows that
develop. This forecast package reflects a blend of operation and
ensemble data from the models.

&&

.AFC WATCHES/WARNINGS/ADVISORIES...
PUBLIC...None.
MARINE...Hurricane Force Wind Warning: 178.
         Gales: 119 155 172 174 175 176 177 351 352 411 413.
         Heavy Freezing Spray: 180 185.

&&

SYNOPSIS AND MODEL DISCUSSION...RA
SOUTHCENTRAL ALASKA...SEB
SOUTHWEST ALASKA/BERING SEA/ALEUTIANS...JPW
LONG TERM...PS