High Surf Advisory 2, NWS Anchorage, AK

095 
WHAK42 PAFC 100035
CFWALU

Coastal Hazard Message
National Weather Service Anchorage AK
335 PM AKST Fri Nov 9 2018

AKZ155-100145-
/O.EXP.PAFC.SU.Y.0002.000000T0000Z-181110T0100Z/
Kuskokwim Delta-
335 PM AKST Fri Nov 9 2018

...HIGH SURF ADVISORY HAS EXPIRED FOR THE KUSKOKWIM DELTA 
COAST...

The High Surf Advisory has expired.

$$

Southcentral and Southwest Alaska Forecast Discussion
National Weather Service Anchorage AK
444 AM AKST Thu Nov 8 2018

.ANALYSIS AND UPPER LEVELS...

A gale force low over the northern Gulf is the main weather maker
across Southcentral Alaska. An 0720 UTC ASCAT satellite pass
confirmed the presence of gales well south of Seward and east of
Kodiak around the center of the low. Middleton Island radar shows
a large area of precipitation ongoing across Prince William Sound,
with Kenai radar showing associated precipitation bands pushing
westward towards Anchorage and Kenai. However, observations so far
show much of that precipitation over Anchorage is evaporating
before it hits the ground, so conditions have yet to deteriorate.
Relatively quiet, warm conditions are in place over Southwest
Alaska with nothing on radar. Across the Bering, the focus is a
storm-force low centered over the northwestern Bering off of the
Kamchatka Peninsula. An 0800 UTC ASCAT pass shows storm-force
winds from near the Kamchatka Peninsula extending southeastward
across a swath of the western Bering. The low is tapping much
colder air from off of Russia and moving it into the western
Bering behind an occluding front over the middle of the Bering,
approaching the Pribilofs.

&&

.MODEL DISCUSSION...

The models start out the short-term time period in very good
agreement, tracking the north Gulf low into the eastern Gulf by
tonight, and tracking the Kamchatka Peninsula low and its
associated front across the Bering and into Southwest Alaska
today. Agreement begins to diminish somewhat regarding a secondary
North Pacific low that is expected to exit the jet stream flow and
into the Southern Bering by Friday night. Likely due to a lack of
observations over the open waters of the Pacific, how this low is
handled regarding the speed and timing of arrival are still
somewhat in question. Yet another low expected to approach the
Alaska Peninsula and Kodiak Island on Saturday has even less
agreement. Regarding the Southcentral snowfall this morning,
there is still a some uncertainty as to how far west the snow
gets, how long it lasts, and how much accumulation is ultimately
seen. The model solutions on that have been highly variable the
past few days so there has been little temporal continuity.

&&

.AVIATION...

PANC...VFR conditions and generally light winds will persist.
Light snow showers are possible this morning, but weaker than
expected radar returns so far with persistent dry air still
evident on the morning sounding suggests if any reduction to MVFR
conditions occurs, it will be brief and isolated. An even lesser
chance of a snow shower or two is possible again Friday morning.

&&

.SHORT TERM FORECAST SOUTHCENTRAL ALASKA (Days 1 through 3)...
The Gulf low that has been bringing rain and snow to areas along
the north Gulf coast will weaken and track off to the east today
which will help to diminish precip over the area. By tonight only
light showers should linger over eastern portions of Southcentral
Alaska. On Friday a fragmented front will move in from the west
but with most of the energy of the supporting trough north of the
area very little new precip is expected for Southcentral Alaska.
On Saturday a new system will approach from the south bringing
strong winds back to the area as well as a long fetch of moisture
with more rain and snow expected for the north Gulf coast late
Saturday. Coastal locations look to be primarily rain while
inland locations and higher elevations should stay cold enough for
snow.

&&

.SHORT TERM FORECAST SOUTHWEST ALASKA (Days 1 and 2)...
The small upper level ridge over the Kuskokwim Delta and upper
level shortwave trough approaching the western Alaska Range will
shift east today as the frontal system in the eastern Bering
approaches the coast. The front will track inland tonight, though
weaken rather quickly with snow showers tapering off by Friday
morning. Flat ridging will bring some clearing through the day
Friday and a cold night Friday night, however a frontal system
tracking up from the south on Saturday will bring more clouds,
precipitation and some rather strong easterly flow to the area,
particularly out of the gaps and passes in the Alaska/Aleutian
Range. The increasing easterly winds will warm up the Greater
Bristol Bay area rather quickly but will need to keep and eye on
the the Kuskokwim Delta and Kuskokwim Valley where more entrenched
cold low level airmass and east-northeast winds may bring mixed
precipitation type concerns Saturday night as warmer air aloft
accompanying the frontal system overruns the area.

&&

.SHORT TERM FORECAST BERING SEA/ALEUTIANS (Days 1 and 2)...
The strong low tracking east through the western Bering this
morning with an area of storm force winds to its south will begin
curving to the northeast to reach the northern Bering tonight,
leaving a broad area of cool, unstable westerly flow stretched
across the Bering. The cold air aloft will be further reinforced
by the next upper low diving south from the Kamchatka Peninsula
and into the western Bering tonight through Friday. Rather than
taking the same track as the previous several storms, the cold upper
trough will dig south across the central and eastern Aleutians
Friday night and Saturday, spinning up a couple of surface lows
along the way. In response to this large scale shift in the upper
level pattern, a developing north Pacific low will track north to
the Alaska Peninsula on Saturday bringing a supply of warmer,
moist air with it. Given the strong baroclinic zone between these
two air masses and jet support, it looks likely that the Saturday
low and accompanying frontal systems will be strong ones.

&&

.LONG TERM FORECAST (Days 4 through 7/Saturday night through Wednesday)...
A very stormy pattern is shaping up for mainland Alaska beginning
Saturday into Sunday and continuing through much of next week. A
strong polar jet digging out of Russia across the Bering Sea Friday
will continue to dig southward across the North Pacific Saturday
through Saturday night. This will cause a ridge to pump up downstream
across the east Pacific. The end result will be a high amplitude
pattern with a trough and deep closed low centered near and to the
south of the Alaska Peninsula and a strong southerly jet centered
along 150 degrees W longitude. Models indicate a tropical connection
with the trough digging as far south as 20 degrees N latitude.
Thus, expect development of an atmospheric river which will
transport abundant moisture and warmer air northward to the Gulf
of Alaska along with parts of Southcentral and Southwest Alaska.

Conditions will be extremely favorable for cyclogenesis out ahead
of the digging trough. Expect a series of lows to develop over
the Pacific and track up into the Gulf. Over time, the strength of
these systems will help push the upper ridge eastward, shifting
the anchor trough/low into the Gulf and shifting the atmospheric
river toward the eastern Gulf and Southeast Alaska. As would be
expected in such a high amplitude/dynamic pattern, models differ
with handling of individual storm systems during this period.
However, based on the overall pattern described here, there is
high confidence in periods of heavy precipitation and high winds
along the Alaska Peninsula, Kodiak Island and the Gulf of Alaska
on up to Prince William Sound and the Gulf Coast. With the
presence of the atmospheric river would expect precipitation to be
all rain near sea level, but heavy snow is a likelihood in
coastal mountain ranges. If the atmospheric river remains pointed
at the same general area for any length of time, flooding would
also be something to watch out for. The forecast for interior
portions of Southcentral and Southwest is a little trickier as
precipitation will depend heavily on track of storms, but would
generally expect periods of snow.

Meanwhile, back on the west side of the trough deep Arctic air
will pour southward across the Bering Sea and Aleutians Sunday
night through Tuesday. This will produce persistent strong and
gusty northerly winds along with showers. The air mass looks cold
enough that much of the precipitation will fall in the form of
snow. As the low along the Alaska Peninsula shifts into the Gulf
late next week this will allow a trough to move in from the
northwest Pacific, bringing storminess back to the Aleutian chain.

&&

.AFC WATCHES/WARNINGS/ADVISORIES...
PUBLIC...None.
MARINE...Storm Warning: 185 411 412.
Gale Warning: 131 177-181 351 352 413 414.

&&

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