High Wind Watch 3, NWS Anchorage, AK

957 
WWAK71 PAFC 301229
NPWAER

URGENT - WEATHER MESSAGE
National Weather Service Anchorage AK
429 AM AKDT Sun Aug 30 2020

AKZ101-301330-
/O.CAN.PAFC.HW.A.0003.200830T2100Z-200831T0900Z/
Anchorage-
Including the cities of Anchorage, Eagle River, Indian, 
and Eklutna
429 AM AKDT Sun Aug 30 2020

...HIGH WIND WATCH IS CANCELLED THROUGH LATE SUNDAY NIGHT FOR THE
TURNAGAIN ARM AND HIGHER ELEVATIONS...

While strong winds will develop through Turnagain Arm and the
Anchorage Hillside this afternoon through evening, the winds gusts are
now expected to remain in the 55 to 65 mph range. Therefore the
High Wind Watch is cancelled. 

$$

For more information from the National Weather Service visit
http://weather.gov/afc

Southcentral and Southwest Alaska Forecast Discussion
National Weather Service Anchorage AK
538 AM AKDT Sat Aug 29 2020

.ANALYSIS AND UPPER LEVELS...

A strengthening ~150 kt upper level jet extends from eastern
Russia through the North Pacific. A broad 500 mb low is likewise
intensifying in its left exit region. As the vertically stacked
surface low fills it, its associated front is bringing widespread
rain and gusty southeasterly winds as it moves over the eastern
Aleutians. Scattered showers are observed across much of the rest
of the Bering region given the large circulation. Conditions are
much more quiet farther east. A weak ridge remains centered over
Southcentral. As with yesterday morning, patchy fog is occurring
around Cook Inlet.

&&

.MODEL DISCUSSION...

As features are of relatively large-scale, synoptic models remain
in generally good agreement. All show the aforementioned Bering
low stalling northwest of Adak today as well as a front moving
into the northern Gulf with gales through the Barren Islands and
gusty Turnagain/Knik winds developing this afternoon.

Models are in fairly good consensus regarding the incoming
impactful low to the central/eastern Aleutians and Southwest
Alaska. While the GEMs show a weaker central pressure in Bristol
Bay, they do agree with other models on storm force winds south
of the circulation with thr RGEM currently the only model showing
hurricane force winds on the Pacific side of Unalaska Island.
Other major synoptic models show the central pressure deepening to
approximately 965 mb and making "landfall" slightly north of the
GEMs near Togiak, with the American models being slightly faster.
In any case, confidence continues to grow with each forecast and
impacts would be similar no matter what exactly verifies.

&&

.AVIATION...

PANC...Patchy fog could produce brief periods of IFR/LIFR
conditions this morning. Otherwise, VFR ceilings and light winds
will persist. Gusty southeasterly winds up to 25 kts will develop
this afternoon and diminish by late-evening, however winds aloft
will remain higher when this occurs and thus shear is expected to
continue overnight tonight into Sunday morning. There is also a
chance of showers this evening through Sunday morning, although
VFR ceilings should persist. Much of the shower activity and lower
ceilings are expected closer to the mountains.

&&

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

The first of two fronts is southwest of the Gulf of Alaska early
this morning and should reach Kodiak Island this afternoon. The
front will reach the north Gulf coast tonight and bring a swath of
gale force winds to many of the marine areas. Pre-frontal ridging
along the north Gulf coast this afternoon and evening will bring
gusty Turnagain Arm winds as well as along the Copper River. The
Turnagain Arm winds will bend into Anchorage this afternoon and
evening, but then become northerly and diminish sometime around
midnight. Winds in Turnagain Arm will persist into Monday as the
pressure gradient does not let up between systems.

The bigger event will be Sunday when a large and unseasonably
strong low moves into Bristol Bay from the southwest which will
send a strong front across Southcentral. This will bring wind and
rain across the region. Rainfall will be heaviest along the Gulf
coast where 2 to 2.5 inches of rain is likely over the course of
the weekend and into Monday. The areas on the eastern shores of Cook
Inlet will see a bit of downsloping until the front passes through
on Sunday and then rain will increase. Timing of the front
through Anchorage looks to be Sunday evening.

Winds will increase across the region for Sunday into Monday as
the track of the Bristol Bay low will bring strong winds into
Anchorage Sunday afternoon through then evening. Winds will then
shift to more of a south-southwest direction but remain gusty into
Monday.

A change to this forecast package is with the winds in the Seward
area on Sunday. After the second front moves through, the pressure
rises behind it will suddenly, and significantly, increase the
south winds. The winds are expected to be variable as the front
passes through and then quickly become southerly at 25 to 35 mph
shortly after frontal passage.

&&

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

The first of two low pressure systems is currently arriving on the
Southwest Coast. This low will bring weak gale force along the
coast, but will quickly weaken as it moves inland. It will also
spread rain across almost all of of Southwest AK.

The more significant of the two lows will arrive tomorrow and
still looks to be the first major low of the fall storm season.
The low center is anticipated to move ashore near Cape Newenham
tomorrow afternoon. The low will maintain strength all the way
until landfall, bringing storm force winds to the coastline and
strong winds pushing into interior areas of Bristol Bay and the
Alaska Range. It will also spread a large swath of soaking rains
through Southwest AK.

Most importantly, a long fetch of southwest winds moving into
Bristol Bay Sunday into Monday will create the potential for
coastal flooding in Bristol Bay. Therefore, a Coastal Flood Watch
has been issued for the coastline of Bristol Bay. While models are
honing in on this low and increasing confidence, its still a
little early to pull the trigger on upgrading the watch to a
warning. Therefore, we held off on an upgrade tonight but expect a
decision on coastal flooding within the next day. As of now,
impacts from any flooding look minor, but stay tuned to the
forecast as this is an evolving situation.

&&

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

Weak low pressure can be observed exiting the eastern Bering and
moving into Southwest AK. It is bringing weak gale force winds and
rain as it goes.

However, the main weather story continues to be the powerful low
anticipated to move into the Eastern Bering out of the North
Pacific tomorrow. Models are honing in this system and it
continues to pack a punch, so it's still looking to be the first
major storm of the fall storm season. Models continue to show
strong winds wrapping around the south side of the low. With
increasing confidence in model guidance, hurricane force winds
were added to marine zone 172.

Also of note, the the low center is currently forecast to cross
into the Bering directly over Dutch Harbor. With the position of
this low center, there is potential for hurricane force winds to
impact Dutch Harbor based on historical low tracks. However, with
this system hurricane force winds look to remain south of the
island. This will need to be watched though, if the low center
moves north of the island it will bring them over Dutch Harbor.
Right now we have increasing confidence in the low track as models
have been depicting this better in the past day. With that said,
this low does bear close watching, especially since it is the
first of the year and it is not typical for a low of this strength
moving into the eastern Bering quite this early. So, stay tuned
to the forecast today and tomorrow.

&&

.MARINE (Days 3 through 5/Monday through Wednesday)...

Gulf of Alaska: For the Monday morning into Monday evening time
period the Gulf of Alaska especially the western side will
continue to be experiencing southwesterly gale force winds as a
tight pressure gradient remains across the region. Gale force
winds will subside to small crafts overnight along with
diminishing waves as the pressure gradient eases. These winds
and waves will continue to further diminish throughout the day
Tuesday. A fairly benign pattern is expected for Wednesday with
generally light winds and low waves. However, this time period
for Wednesday is being watched as some model guidance is showing a
system moving up into the eastern Gulf of Alaska with increased
winds and waves potentially. The strength, track, and intensity
remain uncertain at this time and will be fine tuned in the coming
days.

Bering Sea and Aleutians: The beginning of the forecast period
will feature a mainly northerly to northwesterly wind flow regime
on the back side of the low pressure on Monday. Small craft
advisory criteria winds are expected through at least Monday
evening especially across the eastern Bering Sea to Bristol Bay.
The overall trend beyond Monday evening will be continued
diminishing winds and waves as a more benign pattern sets up for
Tuesday into Wednesday. Model guidance is hinting at an upper
level disturbance moving through the western Bering/Aleutians
Tuesday into Wednesday that may bring a slight uptick in winds to
maybe low end small crafts. This will continue to be monitored.

&&

.LONG TERM FORECAST (Days 4 through 7/Tuesday through Friday)...

Upper level troughing is expected to dominate much of the long
term forecast period with multiple upper level waves moving
through the flow. This will support a showery, wet, and cool
pattern for much of Mainland Alaska and the Bering Sea/Aleutians.
The timing, strength, and intensity of these individual waves will
be fine tuned each day as the new model guidance comes in. Towards
the very end of the period, model guidance is hinting at some
upper level ridging nudging northward into Southcentral Alaska
east to the AlCAN border and Southeast Alaska. The placement of
this upper level ridging is very uncertain at this time with the
apex being over Southeast Alaska or over the North Pacific. This
will affect the sensible weather as if it is further west, it
would provide a respite from the wet, cool, and cloudy weather to
end next week.

&&

.AFC WATCHES/WARNINGS/ADVISORIES...
PUBLIC...Coastal Flood Watch: 161.
MARINE...Hurricane Force Wind Warning: 172.
         Storm Warning: 155 160 165 170 171
         Gale Warning: 119 120 130-132 137-139 150 173 174 176
                       178 180
351 352 411-414 FIRE WEATHER...NONE.

&&

SYNOPSIS AND MODEL DISCUSSION...AP
SOUTHCENTRAL ALASKA...EZ
SOUTHWEST ALASKA/BERING SEA/ALEUTIANS...BB
MARINE/LONG TERM...MV

SPECIAL WEATHER STATEMENT
National Weather Service ANCHORAGE AK
1102 AM AKDT Sat Aug 29 2020

AKZ152-155-161-302015-
Lower Kuskokwim Valley-Kuskokwim Delta-Bristol Bay-
Including the cities of Aniak, Sleetmute, Bethel, Hooper Bay,
Nunivak Island, King Salmon, Dillingham, Naknek, and Pilot Point
1102 AM AKDT Sat Aug 29 2020

...WET AND WINDY CONDITIONS EXPECTED AS THE FIRST BIG STORM OF
THE FALL SEASON MOVES INTO SOUTHWEST ALASKA SUNDAY INTO MONDAY...

A strong low moving in from the Bering on Sunday into Monday will
produce strong winds, periods of heavy rain, and potentially high
water levels along the Bristol Bay Coast.

Rainfall will move into Southwest Alaska Sunday afternoon
associated with this system, which will continue through Monday.
Areas across interior Bristol Bay and the Kuskokwim Valley can
expect to see over an inch of rain through this time period.
Strong southwesterly winds will move into Bristol Bay by Sunday
afternoon impacting coastal locations from Togiak to Port Heiden,
with the possibility for high water levels. Elevated water levels
are also expected along the Iliamna River late Sunday into
Monday.

Please stay tuned for the latest forecast throughout the weekend.

SPECIAL WEATHER STATEMENT
National Weather Service ANCHORAGE AK
1244 PM AKDT Sat Aug 29 2020

AKZ101-111-121-125-131-135-141-145-301400-
Anchorage-Matanuska Valley-Western Kenai Peninsula-
Western Prince William Sound-Northeast Prince William Sound-
Southeast Prince William Sound-Copper River Basin-Susitna Valley-
Including the cities of Anchorage, Eagle River, Indian, Eklutna,
Palmer, Wasilla, Sutton, Chickaloon, Kenai, Soldotna, Homer,
Cooper Landing, Whittier, Seward, Girdwood, Moose Pass, Valdez,
Thompson Pass, Cordova, Glennallen, Eureka, McCarthy, Paxson,
Slana, Talkeetna, Willow, and Cantwell
1244 PM AKDT Sat Aug 29 2020

...WET AND WINDY ACROSS SOUTHCENTRAL THIS WEEKEND...

A couple of weather systems will sweep across Southcentral this
weekend bring generally widespread wind and wet conditions. The
first culprit will be a weather front which moves north across
Southcentral this evening/tonight. This system will locally gusty
southerly winds across the Copper River Basin, out of Knik Arm,
with strong southeast winds across Turnagain Arm and higher
elevations this afternoon and evening. The brunt of the rain will
be along the Gulf Coast with inland areas leaning toward the drier
side with downslope drying.

The next system which will be much stronger is associated with a
rapidly developing storm center which moves into Bristol Bay late
Sunday afternoon. It will bring widespread winds and rain to
Southcentral. Winds in the aforementioned areas will strengthen
throughout the day peaking during the evening hours Sunday. The
strongest winds will likely be along Turnagain Arm and Higher
elevations in the Anchorage Bowl where gusts could approach
warning levels.

Additionally, rainfall will be moderate to heavy at times along
the Gulf Coast from the Kenai Peninsula near Seward to Cordova
and over the western Susitna Valley with up to a couple of inches
expected through early Monday morning. Rivers and streams in the
Seward area and Western Susitna Valley (Yentna and Skwentna) will
experience elevated water levels beginning Sunday night and
continuing into Tuesday.

Please stay tuned for forecast updates.