Coastal Flood Warning 1, NWS Anchorage, AK

746 
WHAK42 PAFC 051415
CFWALU

Coastal Hazard Message
National Weather Service Anchorage AK
515 AM AKST Sun Dec 5 2021

AKZ155-061200-
/O.CON.PAFC.CF.W.0001.000000T0000Z-211206T1200Z/
Kuskokwim Delta-
515 AM AKST Sun Dec 5 2021

...COASTAL FLOOD WARNING REMAINS IN EFFECT UNTIL 3 AM AKST MONDAY
FOR THE KUSKOKWIM DELTA COAST...

* LOCATION...Low lying areas along the coast.

* COASTAL FLOODING...Sea levels rising 3 to 6 feet above normal 
  high tides. 

* TIMING...Until Monday morning. The highest water levels are
  expected Sunday afternoon. 

* IMPACTS...Low lying areas could see minor flooding. Ice could 
  pile up on the beach. Boats and other items in low lying areas 
  could be damaged. Water could flow through cracks in the ice 
  causing ponding water over shorefast ice. 

PRECAUTIONARY/PREPAREDNESS ACTIONS...

A coastal flood warning means that flooding is occurring or
imminent. Coastal residents in the warned area should be alert
for rising water, and take appropriate action to protect life and
property.

&&

$$

AKZ161-061200-
/O.CON.PAFC.CF.Y.0002.000000T0000Z-211206T1200Z/
Bristol Bay-
515 AM AKST Sun Dec 5 2021

...COASTAL FLOOD ADVISORY REMAINS IN EFFECT UNTIL 3 AM AKST
MONDAY FOR THE BRISTOL BAY COAST...

* LOCATION...Low lying areas along the coast, primarily on the 
  north side of Bristol Bay. 

* COASTAL FLOODING...Sea levels rising 2 to 4 feet above normal 
  high tides. 

* TIMING...Until Monday morning. The highest water levels are 
  expected Sunday afternoon. 

* IMPACTS...Low lying areas could see minor flooding. Ice could 
  pile up on the beach. Boats and other items in low lying areas 
  could be damaged. Water could flow through cracks in the ice 
  causing ponding water over shorefast ice. 

PRECAUTIONARY/PREPAREDNESS ACTIONS...

A coastal flood advisory indicates that onshore winds and tides
will combine to generate flooding of low areas along the shore.

&&

$$

364 
WHAK42 PAFC 060100
CFWALU

Coastal Hazard Message
National Weather Service Anchorage AK
400 PM AKST Sun Dec 5 2021

AKZ155-061200-
/O.CON.PAFC.CF.W.0001.000000T0000Z-211206T1200Z/
Kuskokwim Delta-
400 PM AKST Sun Dec 5 2021

...COASTAL FLOOD WARNING REMAINS IN EFFECT UNTIL 3 AM AKST MONDAY
FOR THE KUSKOKWIM DELTA COAST...

* LOCATION...Low lying areas along the coast.

* COASTAL FLOODING...Sea levels rising 3 to 6 feet above normal 
  high tides. 

* TIMING...Until Monday morning. 

* IMPACTS...Low lying areas could see minor flooding. Ice could 
  pile up on the beach. Boats and other items in low lying areas 
  could be damaged. Water could flow through cracks in the ice 
  causing ponding water over shorefast ice. 

PRECAUTIONARY/PREPAREDNESS ACTIONS...

A coastal flood warning means that flooding is occurring or
imminent. Coastal residents in the warned area should be alert
for rising water, and take appropriate action to protect life and
property.

&&

$$

AKZ161-061200-
/O.CON.PAFC.CF.Y.0002.000000T0000Z-211206T1200Z/
Bristol Bay-
400 PM AKST Sun Dec 5 2021

...COASTAL FLOOD ADVISORY REMAINS IN EFFECT UNTIL 3 AM AKST
MONDAY FOR THE BRISTOL BAY COAST...

* LOCATION...Low lying areas along the coast, primarily on the 
  north side of Bristol Bay. 

* COASTAL FLOODING...Sea levels rising 2 to 4 feet above normal 
  high tides. 

* TIMING...Until Monday morning. 

* IMPACTS...Low lying areas could see minor flooding. Ice could 
  pile up on the beach. Boats and other items in low lying areas 
  could be damaged. Water could flow through cracks in the ice 
  causing ponding water over shorefast ice. 

PRECAUTIONARY/PREPAREDNESS ACTIONS...

A coastal flood advisory indicates that onshore winds and tides
will combine to generate flooding of low areas along the shore.

&&

$$

954 
WHAK42 PAFC 061202
CFWALU

Coastal Hazard Message
National Weather Service Anchorage AK
302 AM AKST Mon Dec 6 2021

AKZ155-061315-
/O.EXP.PAFC.CF.W.0001.000000T0000Z-211206T1200Z/
Kuskokwim Delta-
302 AM AKST Mon Dec 6 2021

...COASTAL FLOOD WARNING HAS EXPIRED FOR THE KUSKOKWIM DELTA
COAST...

The threat of coastal flooding has ended.

$$

AKZ161-061315-
/O.EXP.PAFC.CF.Y.0002.000000T0000Z-211206T1200Z/
Bristol Bay-
302 AM AKST Mon Dec 6 2021

...COASTAL FLOOD ADVISORY HAS EXPIRED FOR THE BRISTOL BAY COAST...



$$

Southcentral and Southwest Alaska Forecast Discussion...CORRECTED
National Weather Service Anchorage AK
730 AM AKST Sat Dec 4 2021

.ANALYSIS AND UPPER LEVELS...

A sharp upper level ridge extends north-south through the middle
of the state early this morning. From this ridge of high pressure
eastward, temperatures were generally below zero with coastal
locations a little warmer in the teens. A sharp trough/front was
moving over the western portions of the state, including the
eastern Aleutians. This system was drawing relative warm and moist
air into the region. Areas of precipitation, mainly snow were
occuring with temperatures mostly above zero.

Two surface lows have developed over the western Gulf. One is
located south of Seward, which was helping to draw moisture into
the PWS and EASTERN Kenai Pen areas. The other was generally
south of Kodiak, moving slowly north and east.

Farther west, an area of southerly gale force winds was moving
into the far southwest Bering Sea and far western Aleutian
Islands, ahead of the next storm system.

&&

.MODEL DISCUSSION...

In the short term, model solutions are once again in good
agreement taking the upper level trough across the state, with it
weakening as it moves east. The surface low in the western Gulf,
while fairly weak, is expected to move closer to the PWS area.
This will keep adequate moisture flowing into the region.

Models are also fairly consistent with the next system moving
across the Bering the latter half of the weekend. This is a much
more dynamic system, rapidly occluding as a strong jet streak
punches eastward along the southern Bering/Aleutian Chain. While
models are in general agreement on overall timing/placement, there
are differences, which could be significant, including the
strength and orientation of the jet streak as it moves across
forecast area, as well as any of the potentially numerous vort
max/impulses or shortwaves translating through the flow as the
trough swings around the low.

We remain confident in an active winter weather pattern across
the southern half of the state through the next several days,
however the details of snow amounts and the potential for
rain/snow mix in some locations continue to be worked out.

&&

.AVIATION...

PANC...Little has changed. Fog/stratus remains the challenge.
Expect mostly VFR conditions through the TAF period, however there
is potential for fog over the terminal again early this morning,
reducing conditions to LIFR.

&&

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

A weak short-wave trough will approach Southcentral from the west
this afternoon through tonight, leading to some weak overrunning
out ahead of it. This will produce some areas of very light snow
tonight through Sunday morning, but expect very little in the way
of accumulation.

All attention will then shift to a major storm system out west.
The computer models have shifted over the past 24 hours, not only
changing how the timing and impacts for Southcentral, but also
introducing even more uncertainty into the forecast. It now looks
like there will be two distinct phases to the storm. First, a
strong upper level trough and surface front will approaching from
the west on Sunday, driven by a 125kt+ upper level jet streak and
with a tap of moisture from the tropics. Snow will begin in the
Cook Inlet region Sunday afternoon and quickly spread north and
east. With a cold airmass in place, expect low density (fluffy)
snow, as has largely been the norm in recent weeks.

Strengthening low level south to southeasterly flow ahead of the
front will lead to areas of blowing snow. It won't take much wind
to cause significant reduction of visibilities. One of the big
questions is whether these gusty winds will make it into Anchorage
and the Matanuska Valley. With a cold dome of air near the
surface, suspect it will take time for winds to erode the colder
denser air. It is however looking increasingly likely that there
will be some wind. This will cause the temperature to jump up,
though precipitation will remain safely all snow. There is higher
confidence in southeasterly winds from Homer northward along the
Sterling Highway. Thus, have issued a Winter Weather Advisory for
the western Kenai Peninsula.

The strong upslope low level flow will also enhance snowfall
across the Susitna Valley and Prince William Sound. While upslope
flow will cause snow to continue, the initial upper level short-
wave trough will exit northward Sunday night. We will then
transition to phase two of this event, with a strong short-wave
crossing the North Pacific and leading to cyclogenesis along the
south end of the extremely long cold front. Guidance disagrees on
the exact track of this low, but it generally looks like it will
take a path along the Alaska Peninsula and ultimately into the
northern Gulf. The track and depth of this low will be critical
to determining which areas will receive the heaviest snowfall as
well as how warm temperatures might get in Southcentral. For this
forecast package, have issued a Winter Storm Warning for the
Susitna Valley, where a prolonged period of strong upslope flow
seems most likely. Have also hoisted Winter Storm Watches for all
of the Prince William Sound zones, where there is potential for
heavy snow depending on the low track.

This storm now looks like it will linger all the way through
Tuesday, with colder air moving in behind it. There could be a
quick shot of heavy snow for portions of Anchorage and the
Matanuska Valley some time Monday night into Tuesday. Stay
tuned for updates to the forecasts and warnings as this long
duration event unfolds.

&&

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

The biggest newsflash for Southwest AK is the Winter Weather
Warning for Kuskokwim Delta (effective 9 pm this evening) and
Bristol Bay (effective 3 am Sun), as well as a Winter Weather
Advisory (effective 3 am Sun) for the lower Kuskokwim Valley.
Heavy snow and blowing snow will reduce visibilities frequently to
well below 1 mile for the warned areas, with the strongest winds
expected along the coasts. Snow could very likely mix or
transition to rain mainly along the coastal areas starting this
evening. Over the Kuskokwim Delta and Bristol Bay, gusts up to 50
to 55 mph are expected with the onset of the front. Inclement
conditions associated with the front could last through Sun night
if not sooner. Models are on track by keeping the progressive
front moving across the region into early Mon morning.

Warmer temperatures enhanced by southerly winds connected to the
front will become more evident across Southwest the next few days.
This could pose challenges to forecasting rain/snow mix but
essentially if temperatures are warm enough especially along the
coast, then rain could remain in the forecast through the short
term while rain/snow mix could spread farther inland and more
noticeable as the frontal boundary advances eastward Mon/Mon night.

&&

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

A dominant low and trailing frontal system will impact the entire
forecast area for the short term. A North Pacific low treks
northeast near the Kamchatka Peninsula as it rapidly deepens
this afternoon into tonight until it reaches the Bering Strait
Sunday morning. To the south, the associated frontal system will
bring a broad swath of gale to storm force winds that will affect
nearly the entire Bering/Aleutians at one point or another, with
impacts from wind and precip mainly in the form of heavy rain
beginning earliest over the western Bering/Aleutians today. The
strong winds and rain with the front will shift quickly eastward
across the southern Bering today, eastern Aleutians and Pribilofs,
with storm force winds reaching the Southwest Coast and Alaska
Peninsula by Sunday morning. The supporting low pressure center
will stall in the northern Bering and support another area of
westerly winds up to storm force, mainly over the northern and
western Bering from Sunday to early Monday.

&&

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

Gulf of Alaska: Flow becomes southerly and reaches gale force as a
front enter the Western Gulf on Monday. Cyclonic development
within the front near Prince William Sound shifts wind directions
to west-northwest across the Gulf by Tuesday afternoon. Gales are
likely initially through the Barren Island, becoming widespread
across the Gulf throughout the rest of the day Tuesday. The GFS is
hinting at a brief period of low end storm force winds through
and east of the Barren Islands on Tuesday night.

Bering Sea: A series of lows move in and out of the Bering through
the early week. Two Russian lows skim the northern edge of the
Bering Sea before drifting over Western Alaska, both of with look
to produce widespread north-northwesterly gale force winds. The
second low may bring a period of storm force winds to the northern
Bering on Wednesday, per the GFS. A third, stronger, system out
of the North Pacific enters the southern Bering on Wednesday
night. The GFS solution is quite a bit more aggressive, but it is
likely there will at least be areas of storm force winds Wednesday
night into Thursday.

&&

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

Teleconnections support the amplified Rossby Wave pattern to
continue across the North Pacific during the extended period. The
Alaskan mainland will primarily remain under an upper trough which
will allow for these cold temperatures to continue. Thursday
appears to have the greatest chance of sunshine as the moderately
positive Eastern Pacific Oscillation will weaken which supports a
greater likelihood of upper level ridging to move over
Southcentral. There is good ensemble agreement on this upper
level ridge moving over Southcentral on Thursday, though it will
be very short lived. Temperatures will remain cold as the upper
ridging will help decrease cloud cover while the surface pressure
set up will allow for a dry offshore flow pattern. This pattern
can be conducive to nocturnal radiational cooling (clear skies
and light winds) which allows for very cold temperatures
overnight.

With respect to snowfall, there is good deterministic agreement
that a weak surface low pressure system will linger along the
northern Gulf south of the Kenai Peninsula on Tuesday which will
allow for snow showers to move from the northern Gulf into Prince
William Sound. There is a high degree of uncertainty with respect
to how much snow is expected. This surface low will then move
southeastward and allow for cold air advection across Southcentral
on Wednesday.

Farther out west, there is the potential for a strong low pressure
system to move across the Bering/Aleutians Wednesday through
Friday. There is extremely low forecast confidence at this time
due to poor agreement between deterministic and ensemble guidance.
Both the GFS and GEM ensemble guidance show differences of 1.5
standard deviation or more between ensemble members which is a
good indicator of a large variation of possible solutions.
However, one common denominator expected with this low is a large
area of gale force winds with the possibility of a smaller area of
storm force winds within the aforementioned area of gale force
winds.

&&

.AFC WATCHES/WARNINGS/ADVISORIES...
PUBLIC...
WINTER WEATHER ADVISORY 121 152
WINTER STORM WATCH 125 131 135
WINTER STORM WARNING 145 155 161
. MARINE...
GALE 138 150 171 178
STORM 155 160 165 170 172 173 174 175 176 177 179 180 181 185 411
412 413 414
HEAVY FREEZING SPRAY 127 128
. FIRE WEATHER...NONE.

&&

SYNOPSIS AND MODEL DISCUSSION...NR
SOUTHCENTRAL ALASKA...SB
SOUTHWEST ALASKA/BERING SEA/ALEUTIANS...CB
MARINE/LONG TERM...KM/ED