Graphical Hydro Meteorological Discussion

000
FXAK68 PAFC 291331
AFDAFC

Southcentral and Southwest Alaska Forecast Discussion
National Weather Service Anchorage AK
531 AM AKDT Thu Sep 29 2022

.ANALYSIS AND UPPER LEVELS...

An upper trough, which spans from the Bering Sea into
Southcentral, is becoming stretched meridionally this morning. An
embedded low over the eastern Bering and located on the upstream side of
the upper trough is digging southward along the Southwest coast.
Meanwhile, a smaller trough located over Kodiak Island and on the
downstream side of the upper trough is beginning to lift northward
into Southcentral. The smaller trough is following in the wake of
an occluded front, which moved inland of the Gulf coast during
the overnight hours. Scattered showers over Prince William Sound
and the Kenai Peninsula are getting shunted northward with the
front`s northward progress while, offshore, strong easterly winds
have been noted with a lingering barrier jet. Buoy 61 has observed
winds gusting to near 60 mph while buoy 82`s observed winds have
been slightly milder with gusts to only 45 mph. These winds should
steadily diminish through the morning hours with the departure of
the front to the north. This will be true for down-inlet flow
through Cook Inlet into the Shelikof Strait. Otherwise, clouds and
low stratus blanket much of the coast, as well as Kodiak Island,
while clearer conditions are noted further offshore.

Strong cold air advection and an enhanced pressure gradient over
the eastern Bering Sea are maintaining small craft to gale force
northerly winds. The axis of stronger winds stretches from east of
Saint Matthew Island, southward, to east of the Pribilofs, and into
Bristol Bay. These winds should gradually relax throughout the
rest of the day as the upper trough shifts further east. A hurricane
force low is quickly approaching the Western Aleutians. Increasing
southeasterly winds to hurricane force will precede the low
followed by southwesterly hurricane force winds later tonight. The
threat for seas ranging from 35 to 45 feet will exist by tonight
as a result.


&&

.MODEL DISCUSSION...

Models continue to come into better agreement with a hurricane
force low entering the Bering over the next few days. All guidance
takes the low immediately west of the Aleutians while also
showing the low peaking in intensity later this evening. From
there models depict the low undergoing a weakening trend while
also decelerating in forward speed, which puts the low near or
over the Pribilof Islands early Sunday morning as much weaker
system. A new Kamchatka low is forecast to emerge into the western
Bering Sea Saturday night. Models are in poor agreement with the
timing and strength of the low at this time.


&&

.AVIATION...
PANC...VFR conditions and light winds are forecast through the
period though showery conditions could potentially bring ceilings
to MVFR levels at times. There is some uncertainty with Turnagain
Arm winds bending into PANC later this afternoon, though these
winds should remain below 10 knots.

&&

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

A steady supply of upper level short-waves will track northward
across Southcentral through tonight, resulting in fairly widespread
rain showers. An upper level low and short-wave digging down the
back side of the long-wave trough will interact with a front over
the eastern Gulf and Pacific Friday-Friday night, leading to a
rapidly moving low across the eastern Gulf/Southeast Alaska and
into Canada. Rain with this system will clip at least the eastern
half of the the Copper River Basin, and perhaps as far west as the
eastern Prince William Sound, while showers diminish across the
remainder of Southcentral. Zonal flow behind the exiting upper
low/short-wave means the next long-wave trough will move in quickly,
with rain spreading to Kodiak Island Saturday then Southcentral
Saturday night.

&&

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

A weakening low stretched out along the Southwest coast will
begin to make southeastward progress today, eventually exiting
into the western Gulf later tonight. In the meantime, areas of
showers will continue to drift across much of the region as
smaller waves continue to pivot around the main upper low as it
drifts south. Most of this activity should diminish by tonight,
with even some areas of clearing possible over Bristol Bay.
However, it will likely be quite a chilly start for areas that are
able to radiate out efficiently with calming winds and the
decreasing cloud coverage, and lows could dip down to the low 30s
for spots like King Salmon early on Friday. Benign conditions will
persist into Friday as a transient ridge moves into place between
the departing Gulf low and the next item of interest soon
expected to impact much of the Bering out west.

By Friday evening, a very large, slow moving low drifting out
over the Bering will push its occluded front into the Southwest
coast and northern Alaska Peninsula (AKPen). This low will be a
remnant of current tropical storm Kulap, but neither the low nor
the front reaching the coast are expected to have notable impacts
beyond slightly increasing southerly winds and bands of rain
moving ashore. Kulap`s remnant low and weakening front will
continue to push areas of rain across Southwest through Saturday
evening as the storm`s center drifts very slowly east and
likewise becomes much weaker with time.

&&

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

Relatively quiet conditions will persist this morning compared to
what will soon be affecting a large portion of the Bering Sea
starting later this afternoon. A corridor of northwest gales
pushing into the southern Alaska Peninsula (AKPen) and eastern
Aleutians will weaken through this evening as the supporting
pressure gradient relaxes and as cold air advection associated
with a cool air mass pushing south into the Pacific ceases.
Showers moving into the southern AKPen and eastern Aleutians will
begin to subside this evening as well as a shortwave ridge moves
into place ahead of the much more impactful feature of interest
moving into place to the west.

Looking back to the west, tropical storm Kulap is already visible
on Himawari satellite this morning as it barrels straight towards
the far southwest corner of the Bering. This system is expected to
undergo a transition to a post-tropical low just before it enters
the Bering near Shemya later this evening, but the powerful wind
field associated with this low will not lose much of its punch
once it gets here. Impacts to the far western Aleutians still look
very similar compared to previous assessments. A corridor of
Hurricane force southeast wind will first move in along the
system`s developing front, pushing past Shemya and Attu into the
western Bering this afternoon. This will be followed soon after
by a core of even stronger Hurricane force winds wrapping into the
south side of the low as the center continues northeast into the
western Bering. Winds in the Shemya and Attu area with the second
batch of winds should peak in the 60 to 80 mph range, with gusts
up around 100 mph still possible at the peak intensity late
tonight or very early Friday. A High Wind Warning remains in
effect starting Noon today through Friday for the western
Aleutians.

From there on, the low should begin to weaken and slow down as it
becomes stacked and occluded, but it will take some quite some
time for the wind field to diminish. The low`s front will weaken
below gale force shortly after pushing past the Pribilofs and
Central Aleutians on Friday, with a quick period of rain also
moving past with the front. Persistent westerly winds will very
slowly weaken along the rest of the Aleutian Chain to the west,
but probably will not come down below gale force until sometime
late on Saturday night as the low begins to drift more east to
southeast and slowly spins down.

&&

.LONG TERM FORECAST (Days 4 through 7: Sunday through Wednesday)...

An area of low pressure that was formerly Kulap moves across
western parts of the Alaska Peninsula and then weakens further as
it settles in the Gulf of Alaska on Sunday. As the low progresses
into the the Gulf, additional moisture brings a return of cool,
cloudy, and rainy conditions over Southcentral heading into early
next week. Widespread rain over Kodiak Island will push northward
from the Kenai Peninsula to Prince William Sound. Isolated to
scattered showers are possible further inland, but will be drier
due to downslope easterly flow. Meanwhile, a transient ridge of
high pressure provides a brief break of drier weather over
interior Alaska between Monday and Wednesday. Another storm
system, albeit weaker, crosses the Aleutians with the next round
of wind and rain and then enters the North Pacific midweek.
Unsettled weather continues into Tuesday as the next low and front
moves southeastward from the Kamchatka Peninsula. However, models
diverge significantly in the specific details towards the end of
the period.

&&
.AFC WATCHES/WARNINGS/ADVISORIES...
PUBLIC...High Wind Warning: 191.
MARINE...Hurricane Force: 178, 411
Storm: 175, 177, 185, 412, 413
Gale: 155-170, 172-174, 176, 179-181, 414.
FIRE WEATHER...NONE.

&&

$$

SYNOPSIS AND MODEL DISCUSSION...BL
SOUTHCENTRAL ALASKA...SB
SOUTHWEST ALASKA/BERING SEA/ALEUTIANS...AS
LONG TERM...MF

000
FXAK69 PAFG 291446
AFDAFG

Northern Alaska Forecast Discussion
National Weather Service Fairbanks AK
646 AM AKDT Thu Sep 29 2022

.SYNOPSIS...
A storm over the West Coast will keep rain falling
over the West Coast and Western Interior south of Kotzebue today,
and north winds 25 to 35 mph blowing from the Bering Strait to St
Lawrence Island today. This storm will move southeast and weaken
tonight causing rain and winds to diminish tonight.

This storm is causing southerly chinook flow over the Alaska Range
that is keeping conditions warm and dry over the southeast
Interior. The chinook winds will weaken tonight.

A weather front along the Gulf of Alaska coast will move north
over the Interior today and over the North Slope tonight. This
will bring a chance of rain and snow to the Northern Interior
today, with rain and snow likely over the Northern Interior and
Central North Slope tonight, and over the Western and Central
Interior and Central North Slope on Fri. Expect 2-4 inches of
snow over the Central Brooks Range tonight through Fri night.

Another front moving north along the ALCAN Border on Sat will
bring a chance of rain and snow to the Eastern Interior Sat.

Typhoon Kulap which is now in the NW Pacific, will become extra-
tropical and move to just southwest of Shemya as a very strong
storm today, then move to the Central Bering on Fri, to the
Southeast Bering on Sat, and into Bristol Bay on Sun. This will
bring east winds increasing to 15 to 30 mph to the West Coast Fri
night and Sat with a chance of rain south of the Bering Strait.

A strong storm forecast to track northeast over Eastern Russia
into the Chukchi Sea next Wed-Thu could bring southwest gales and
the possibility of coastal flooding from the Yukon Delta to
Utqiagvik from Wed into Fri next week. Will need to monitor this
potential storm.

Aloft...
A long wave trough over Western Alaska and the Eastern Bering Sea
will move over Alaska on Fri and then migrate east over the
weekend. This is causing moderate chinook winds over the
Alaska Range that will decrease late tonight as the trough moves
east. This will allow several short waves to moves north over the
Interior over the next several days, leading to a cooler and
wetter pattern over the Interior Fri into the weekend.

One short wave trough that lies along the Gulf of Alaska Coast
will move to the Northern Interior this afternoon, over NE Alaska
tonight, and then continuing northeast. This is pushing a front
with isolate to scattered showers north that will become numerous
showers along the Brooks Range tonight.

A second short wave moving to the NE Gulf of AK on Fri will move
north along the ALCAN Border on Sat.

Surface...
A 988 mb low over the Kuskokwim Delta will weaken to 1006 mb by
4am Fri and then dissipate. A weather front stretching from this
low to Point Hope to Barter Island will weaken tonight. A 1003 mb
low developing near Barter Island today will move to 200 NM
northeast of Barter Island by by 4pm Fri, then continue moving
east.

A weather front along the Gulf of Alaska coast will move north
over the Interior today and over the North Slope tonight. This
will bring a chance of rain and snow to the Northern Interior
today, with rain and snow likely over the Northern Interior and
Central North Slope tonight, and over the Western and Central
Interior and Central North Slope on Fri. Expect 2-4 inches of
snow over the Central Brooks Range tonight through Fri night.

Another front moving north along the ALCAN Border on Sat will
bring a chance of rain and snow to the Eastern Interior Sat.

Typhoon Kulap, which is now in the NW Pacific, will become extra-
tropical and move to just southwest of Shemya as a very strong
storm today, then move to the Central Bering on Fri, to the
Southeast Bering on Sat, and into Bristol Bay on Sun. This will
bring east winds increasing to 15 to 30 mph to the West Coast Fri
night and Sat with a chance of rain south of the Bering Strait.

A strong storm forecast to track northeast over Eastern Russia
into the Chukchi Sea next Wed-Thu could bring southwest gales and
the possibility of coastal flooding from the Yukon Delta to
Utqiagvik from Wed into Fri next week. Will need to monitor this
potential storm.

&&

.DISCUSSION...
Models initialize well aloft at 00Z. Models show some differences
aloft starting now, with the GFS having a stronger low aloft
associated with Typhoon Kulap in the NW Pacific than all the other
models, and keeps it deeper through Sat as its remnants move
north then east across the Bering Sea. Since this is still a
typhoon now, favor the deeper GFS solution even though it is the
outlier solution. All models are fairly similar on most features
over Northern Alaska, but we will use the GFS for reasons given.

Snow levels range from 1000-2000 ft along the West Coast to 3000
ft over the Eastern Interior and will fall to 1000-2000 ft on Fri.
Snow will will remain at the surface from the Brooks Range north.


With precipitation, models show similar patterns with slight
differences. Will use a blend of models for location of Pops and
amounts but lean towards the GFS since it is the preferred model
at the surface. Will make sure to show likely precip over the West
Coast and Western Interior south of Kotzebue today, then precip
likely over the Central North Slope tonight and over the Western
and Central Interior and Central North Slope on Fri, with a chance
to likely precip over the Central and Eastern North Slope and
Interior on Sat.

At the surface at 06Z, all models verify a few mb too weak on the
two lows over SW Alaska. The GFS is deeper than all other models
with Typhoon Kulap in the NW Pacific, and the GFS appears to be
closest to reality with Kulap. Models show similar patterns at at
the surface over Northern Alaska, but differ on the strength of
features. Will use the GFS at the surface since it better resolves
Typhoon Kulap, but will bump up winds a few kt over SW AK through
tonight to reflect the lows over SW AK being deeper than models
indicate.

Coastal Hazard Potential Days 3 and 4...
Elevated surf north facing shores from the Bering Strait to St
Lawrence Island today.
Hooper Bay could see slightly elevated sea levels Sat and Sun.

A strong storm forecast to track northeast over Eastern Russia
into the Chukchi Sea next Wed-Thu could bring southwest gales and
the possibility of coastal flooding from the Yukon Delta to
Utqiagvik from Wed into Fri next week. Will need to monitor this
potential storm.

&&

.HYDROLOGY...
No issues.

&&

.AFG WATCHES/WARNINGS/ADVISORIES...
AK...Wind Advisory for AKZ223-226.
Wind Advisory for AKZ225.
PK...Gale Warning for PKZ201.
Gale Warning for PKZ210.
Small Craft Advisory for PKZ220.
Small Craft Advisory for PKZ225.
Small Craft Advisory for PKZ235-240.
Gale Warning for PKZ245.
&&

$$

000
FXAK67 PAJK 291413 CCA
AFDAJK

Southeast Alaska Forecast Discussion
National Weather Service Juneau AK
456 AM AKDT Thu Sep 29 2022

.SHORT TERM.../Through Thu night/ The rain and wind from the
current front in the eastern gulf is just starting to impact the
outer coast this morning. It has already brought some periods of
heavy rain to the Yakutat area and gale force winds to the gulf
waters around Cape Suckling overnight.

Northern panhandle areas should expect increasing winds and rain
as the day goes on. These will come in two separate waves. The
first will be this morning as the initial front pushes into the
northern panhandle. The second will be a shortwave along the front
that will push the wind and rain into the rest of the panhandle
this afternoon into Thu night. Highest wind will likely be this
evening as the shortwave pushes into the area with 20 to 25 kt
winds for a large portion of the inner channel areas as the system
pushes through. Likewise the heaviest rain will be with the
shortwave this afternoon and evening mainly for the northern half
of the panhandle, though all areas of the panhandle will likely
see some rain. Expected rainfall amounts will reach around 1 to 2
inches in the northern inner channels through Thu night. Rain and
winds are expected to diminish late Thu night as we get into the
break before the next system. Forecast changes were minimal with
mainly some local wind changes here and there.

.LONG TERM.../Friday through Wednesday/...The weather front
described in the short term section begins to weaken and shear
apart as it continues to progress eastward. Precipitation will
become more intermittent in nature Friday morning. This will be a
short lived lull as the next wave moves up from the N Pacific
through the afternoon. Getting better consensus on the track and
strength of this low as new model runs came in. It is now
expected to track towards the Central Panhandle coast through the
evening and then moves over the NE Gulf coast overnight before
dissipating as it enters the Yukon on Saturday. Heavy rainfall with
longest duration and highest winds are more likely over the Central
Panhandle locations with 3 hours totals of over half an inch through
the night with 24 hour totals of 1 to 3 inches. Southern regions and
the NE Gulf coast will still get heavy rain with 3 hour totals of
half an inch, but lower 24 hour totals as that heavy rain will not
last all night. As the low will stay more offshore, gulf winds
should only reach gale force with inner channel winds getting into
the small craft range. Overland gusts of 40 mph overnight are likely
along the Icy Strait corridor and Juneau but for now not expecting
any stronger winds.

High pressure ridge builds over the Gulf behind the front with
drier weather for most of the area on Sunday into Monday before
the next low moves up along the windward side of the ridge towards
the NE Gulf by Monday night. Rainfall should be limited to the NE
Gulf coast as the high pressure ridge remains over the Eastern
Gulf and Panhandle.

&&

.AVIATION...Incoming front from the west will cause rain and
lowering CIGs for the northern inner channels through 18z today.
The southern inner channels will not see the front arrive, and the
lowering conditions, generally after 00z Friday. Increased wind
speeds and wind gusts will be associated with the frontal passage.

&&

.MARINE...Gale force winds over the N Gulf Outer Coastal Waters
are occurring as another system advances across the gulf, with
winds building to small craft conditions across the remaining
outer coastal waters and inner channels as front approaches and
impacts the panhandle. Another system on Friday and Saturday will
deliver another opportunity for elevated winds across much of the
panhandle.

&&

.HYDROLOGY...With increasing confidence in rainfall totals for the
Thursday and Friday systems now have areas getting longer
duration of heavy rain narrowed down to the Northern and Central
Inner Channels and the Eastern Gulf Coast. Reaching 1 to 5 year
return intervals, especially with the Friday to Saturday system.
should see river rise with the first front, and a few nearing
bankfull while the second front will bring up levels again with
some of the more reactive rivers such as the Taiya and Jordan
Creek nearing minor stages. The NE Gulf Coast and Southern Inner
Channels are still expected to get period of heavy rain but with
a combination of shorter duration or rainfall totals well within
their 1 year return intervals.

&&

.AJK WATCHES/WARNINGS/ADVISORIES...
PUBLIC...
MARINE...Gale Warning for PKZ052.
Small Craft Advisory for PKZ012-013-022-031>036-041>043-051-053.


&&

$$

SHORT TERM...EAL
LONG TERM....PRB
AVIATION...GJS

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