High Wind Watch 10, NWS Anchorage, AK

345 
WWAK72 PAFC 102342
NPWALU

URGENT - WEATHER MESSAGE
National Weather Service Anchorage AK
342 PM AKDT Tue Oct 10 2017

AKZ191-111400-
/O.UPG.PAFC.HW.A.0010.171011T2100Z-171012T0900Z/
/O.NEW.PAFC.HW.W.0009.171011T1500Z-171012T0900Z/
Western Aleutians-
Including the city of Shemya and Amchitka
342 PM AKDT Tue Oct 10 2017

...HIGH WIND WARNING IN EFFECT FROM 7 AM WEDNESDAY TO 1 AM AKDT
THURSDAY...

The National Weather Service in Anchorage has issued a High Wind
Warning, which is in effect from 7 AM Wednesday to 1 AM AKDT
Thursday. The High Wind Watch is no longer in effect. 

* WIND...West to southwest 50 to 65 mph with gusts to 80 mph. 

* TIMING...Winds will increase out of the southwest tonight 
  through Wednesday morning and then peak in intensity early 
  Wednesday afternoon. Winds will begin to diminish late Wednesday
  night and continue to decrease through Thursday 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
416 AM AKDT Tue Oct 10 2017

.ANALYSIS AND UPPER LEVELS...

A rather benign weather pattern has set-up across Southcentral
Alaska as high pressure continues to build across the region. A
weak trough of low pressure continues to reside along the northern
gulf coast which is helping to keep weak offshore flow continuing
across Southcentral Alaska. Although the surface ridge continues
to build, water vapor imagery this morning suggests the upper
level ridge has begun to flatten out. Thus, cloud cover has begun
to spread across Southcentral Alaska during the overnight hours.
Southwest Alaska, on the other hand, continues to be impacted by
strong southwesterly flow advecting moisture (rain) and winds in
the range of 20 to 35 kts inland. In the mean time, the calm
before the storm is being observed across the western Bering Sea.
A 1000 mb low situated near 46N 157E will become the main attraction
this afternoon/evening as it expected to quickly move into the
western Bering Sea.

&&

.MODEL DISCUSSION...

Models once again are in excellent agreement through the vast
majority of the short-term. Guidance continues to show onshore
flow continuing across Southwest Alaska today with rainfall and
gusty winds continuing across the region while Southcentral Alaska
remains on the dry side. The rapidly developing area of low
pressure moving into the western Bering Sea this afternoon is well
progged by guidance and there are only subtle differences in the
deepest pressure the low attains prior to occluding on Wednesday.
Based on the intensity on the jet and the amount of cold air over
Russia, it seems the stronger solutions (GFS/NAM) are more likely
than the slower and further southeast solution (GEM). The biggest
question is how strong the winds will be on the back side of the
low pressure system and where the core of strongest winds will be.
The GFS was used heavily for this system due to it's impressive
model consistency over the past 36 hours.

&&

.AVIATION...

PANC...VFR conditions will prevail through the forecast period.
Light southerly winds will become gusty by mid-morning before
subsiding around midnight tonight.

&&

.SHORT TERM FORECAST SOUTHCENTRAL ALASKA (Days 1 and 2)...
Clouds and a little bit of light precipitation from the frontal
system in Southwest Alaska will overrun the Alaska range and
flattening upper level ridge to push into Southcentral Alaska
today. Another upper level ridge will build back into the area
from the west on Wednesday, shunting clouds up off to the north
for some partial clearing in the afternoon and evening. A large
frontal system pushing in from the west will continue to amplify
the ridge then push it to the east, opening Southcentral Alaska
southerly flow and to a significantly warmer and wetter air mass
on Thursday.

&&

.SHORT TERM FORECAST SOUTHWEST ALASKA (Days 1 and 2)...
Broad southwest flow will continue to promote sporadic showery
conditions over greater Bristol Bay today, with a stalled frontal
boundary keeping steadier rain focused across portions of the
Kuskokwim Delta and Lower Kuskokwim Valley before slowly lifting
northward by Wednesday morning. Precipitation will briefly trend
downward overnight as this feature moves off to the north and
weak transient ridging moves through the region, however
widespread rain will quickly return to the southwest mainland
on Wednesday as the front associated with the strong western
Bering low arrives along the coast and pushes inland during the
afternoon. This will keep rain and gusty southwest winds going
area wide through Thursday morning as the front pushes off to the
east and deep layer southwesterly flow remains focused over the
region.

&&

.SHORT TERM FORECAST BERING SEA/ALEUTIANS (Days 1 and 2)...
As one low weakens and moves into the Bering Strait this morning,
attention quickly shifts to the next system beginning to take
shape approximately 700 miles southwest of Shemya. This low will
rapidly intensify from around 995 mb this morning to the mid 950s
by Wednesday afternoon as it passes west of Attu this evening and
then takes a track very similar to the previous system, roughly
parallel to the Russian Coast and then eventually into the Gulf
of Anadyr. The primary impacts from this system will begin to be
felt over the Western Aleutians on Wednesday afternoon as the low
passes to the north and cold air begins to wrap around the back
side of the system. This cold air advection will allow strong
winds aloft to mix down to the surface, possibly bringing
hurricane force gusts to the westernmost part of the chain from
early Wednesday afternoon into late Wednesday evening. Have
therefore issued a High Wind Watch for Shemya with the morning
forecast package. Otherwise, the strongest impacts will largely
stay confined to the waters of the western Bering as a large swath
of gale to storm force winds and high seas accompanies the passage
of the system. Active weather will also be present across the
eastern half of the Bering tonight through Wednesday as the
associated front races eastward from the Central Aleutians to
southwest coast, bringing rain and gale force southerly winds to
much of the region.

&&

.LONG TERM FORECAST (Days 3 through 7)...
The mid term forecast will see the western Bering low track to the
northeast bringing strong winds to the Bering and swinging its
front through mainland Alaska Wednesday night into Thursday.
There looks to be enough of a push of warm air from the south to
keep the precip as rain for the southern mainland. As this system
leaves Thursday night another low approaches the Bering from the
south. There still remains uncertainty amongst the models with the
track and strength of this system. Because of that, ensembles
were used heading into the weekend which offered a weaker solution
than the deterministic runs.

&&

.AFC WATCHES/WARNINGS/ADVISORIES...
PUBLIC...High Wind Watch...191.
MARINE...Storm...178
         Gale....155 165 170 172 173 174 175 177 179 180 181 185

&&

SYNOPSIS AND MODEL DISCUSSION...MMC
SOUTHCENTRAL ALASKA...JR
SOUTHWEST ALASKA/BERING SEA/ALEUTIANS...CB
LONG TERM...DK