Small Craft Advisory 350, NWS Juneau, AK

210 
FZAK52 PAJK 092315
CWFAEG

Coastal Waters Forecast for Southeast Alaska
National Weather Service Juneau AK
315 PM AKDT Mon Aug 9 2021

Southeast Alaska Coastal Waters from Dixon Entrance to
Cape Suckling out 100 NM

Wind forecasts reflect the predominant speed and direction
expected. Seas forecasts represent the average of the highest
one-third of the combined windwave and swell height.

PKZ099-101715-
315 PM AKDT Mon Aug 9 2021
.SYNOPSIS FOR OUTSIDE WATERS...
A front moves across the region from the SW Monday evening with
offshore winds increasing to gale force. The front will pass
Tuesday morning with a wind shift from SE to SW. Outlook. Another
front will move into the northern gulf on Wednesday while a ridge
of high pressure pushes into the southern inner channels. 

$$

PKZ041-101715-
Dixon Entrance to Cape Decision-
315 PM AKDT Mon Aug 9 2021

...SMALL CRAFT ADVISORY THROUGH TUESDAY...

.TONIGHT...SW wind 15 kt early in the evening, 
becoming S 25 kt. Seas 9 ft. Rain in the evening. 
.TUE...W wind 25 kt. Seas 13 ft. 
.TUE NIGHT...SW wind 15 kt. Seas 12 ft. W swell. 
.WED...SW wind 15 kt. Seas 10 ft. W swell. 
.WED NIGHT...SW wind 15 kt. Seas 8 ft. W swell. 
.THU...SW wind 10 kt. Seas 8 ft. 
.FRI...W wind 10 kt. Seas 8 ft. 
.SAT...NW wind 10 kt. Seas 8 ft. 

$$

PKZ042-101715-
Cape Decision to Cape Edgecumbe-
315 PM AKDT Mon Aug 9 2021

...SMALL CRAFT ADVISORY THROUGH TUESDAY...

.TONIGHT...SW wind 15 kt early in the evening, 
becoming S 25 kt. Seas 9 ft. Rain.
.TUE...W wind 25 kt. Seas 15 ft. 
.TUE NIGHT...SW wind 15 kt. Seas 13 ft. W swell. 
.WED...S wind 20 kt. Seas 10 ft. W swell. 
.WED NIGHT...S wind 25 kt. Seas 10 ft. 
.THU...S wind 20 kt. Seas 10 ft. 
.FRI...SW wind 15 kt. Seas 9 ft. 
.SAT...W wind 10 kt. Seas 7 ft. 

$$

PKZ043-101715-
Cape Edgecumbe to Cape Fairweather-
315 PM AKDT Mon Aug 9 2021

...SMALL CRAFT ADVISORY THROUGH TUESDAY...

.TONIGHT...SE wind 20 kt becoming SW 30 kt late. Seas 10 ft.
Rain.
.TUE...SW wind 30 kt. Seas 15 ft building to 19 ft in the
afternoon. 
.TUE NIGHT...W wind 25 kt becoming SW 15 kt late. Seas 14 ft.
.WED...S wind 25 kt. Seas 11 ft. W swell. 
.WED NIGHT...S wind 30 kt. Seas 13 ft. 
.THU...S wind 25 kt. Seas 12 ft. 
.FRI...SW wind 15 kt. Seas 9 ft. 
.SAT...W wind 15 kt. Seas 6 ft. 

$$

PKZ051-101715-
Cape Fairweather to Icy Cape-
315 PM AKDT Mon Aug 9 2021

...GALE WARNING TONIGHT THROUGH TUESDAY...

.TONIGHT...S wind 15 kt becoming SW 35 kt late. Seas 10 ft. Rain.
.TUE...SW wind 35 kt decreasing to 30 kt through the morning. 
Seas 13 ft building to 19 ft in the afternoon. Rain in the 
morning. 
.TUE NIGHT...S wind 15 kt. Seas 14 ft. 
.WED...SE wind 25 kt. Seas 10 ft. SW swell. Rain.
.WED NIGHT...S wind 30 kt. Seas 15 ft. Rain.
.THU...S wind 25 kt diminishing to 15 kt. Seas 15 ft
subsiding to 11 ft. 
.FRI...S wind 20 kt becoming W 10 kt. Seas 8 ft. 
.SAT...W wind 10 kt. Seas 6 ft. 

$$

PKZ052-101715-
Icy Cape to Cape Suckling-
315 PM AKDT Mon Aug 9 2021

...GALE WARNING TONIGHT THROUGH TUESDAY...

.TONIGHT...S wind 15 kt becoming E 35 kt. Seas 10 ft. Rain.
.TUE...W wind 35 kt decreasing to 30 kt through the morning. Seas
12 ft building to 18 ft in the afternoon. 
.TUE NIGHT...SW wind 25 kt becoming S 15 kt late. Seas 14 ft.
.WED...E wind 30 kt. Seas 9 ft. Rain.
.WED NIGHT...S wind 30 kt. Seas 15 ft. Rain.
.THU...S wind 25 kt diminishing to 15 kt. Seas 15 ft
subsiding to 10 ft. 
.FRI...S wind 15 kt. Seas 7 ft. 
.SAT...SW wind 10 kt. Seas 6 ft. 

$$

Southeast Alaska Forecast Discussion
National Weather Service Juneau AK
236 PM AKDT Sun Aug 8 2021

.SHORT TERM.../Through Tuesday/... Rain, rain, and more rain. Two
fronts will move in during the short term period and the third
system, an atmospheric river, moves in mid-week and is further
discussed in the long term portion below. The current satellite
shows heavy rainfall rates in Cordova and rainfall starting in
Yakutat as the first front moves into the Panhandle from north to
south.

The first system is bringing heavy at times rainfall and gusty
winds. This front moves through by Monday morning, but many areas
will experience showers throughout the day before the second
front pushes in Monday evening into Tuesday. Rainfall rates are
forecasted to be lighter with this system, but back-to-back
rainfall may be enough to cause flooding and enhance run-off.
Additional information can be in found in the Special Weather
Statement.

Gusty winds are expected from both systems. Strong wind with gusts
up to 45 mph are expected in Skagway starting tonight through
tomorrow. Gusts up to 30 mph are possible across SE AK as each
front moves in. Winds 25 to 30 knots in the majority of the inside
waters, decreasing to 15 knots or less once each system passes.
Barrier jet gales forecasted along Yakutat's coast, also
decreasing as the front passes.

Temperatures are forecasted to remain in the 50s due to lower than
normal highs and warmer than normal lows from cloud cover. The
exception is the southern thirds of the panhandle with highs in
the 60s on Tuesday and an upward trend in high temperatures into
mid-week.

.LONG TERM.../Tuesday through next Sunday/ While incredible vapor
transport advects across the Panhandle all next week, the
subtleties of identifying when that moisture wrings out to
rainfall, and for our purposes, heavy rainfall will be the
challenge for the next few days. This especially holds true in
the extended forecast period.

Ensembles, to be clear not all members, generally paint a picture
of an increasingly anticyclonic curvature across the Panhandle
leading into Tuesday. This should suggest diminished forcing and
more subsidence which would serve as an inhibitor of rainfall.
However, the continued westerly flow through most levels of the
atmosphere against the complex terrain of Southeast will not erase
rain from the forecast. Rather, rainfall eases Tuesday into
Tuesday night as subtle ridging develops between systems. Where
anticyclonic curvature is greater, across the south, rain chances
should drastically fall. However, where terrain is higher across
the north and curvature is a little less anticyclonic, we still
think rain is likely to fall, but amounts will be far less than
that due Sunday afternoon/night and again Monday night.

While the earlier systems from the week each carry a good source
of moisture and should prime the soils of Southeast Alaska with a
solid dose of rainfall, it is the developing system for mid- week
that is most concerning. Our mid-week storm, fully swollen from
the entrails of post-tropical storm Nida, 91W, and Mirinae will
arrive in true atmospheric river form. As it glides into the gulf,
initial lift from a warm surge of air raises freezing levels to
near 12K feet and likely brings heavy rainfall for the northern
Panhandle. ECMWF Extreme Forecast Index states that over 90
percent of ensemble members are forecasting extreme
precipitation, basically defined as one standard deviation above
the mean forecast by the ECMWF initialized during a five week
period between 2000 and 2021, thus adding confidence. In addition,
curvature begins to bend cyclonically across the northern gulf
which would exacerbate forcing across the northern Panhandle,
aside from the higher terrain influence. Even the conservative
NBM has pushed precipitation high in this time frame, which formed
a basis for our QPF forecast, nudged with the last couple of runs
of ECMWF and GFS. All told, our initial assessment of some areas
across the north from Yakutat to Pelican/Elfin Cove across
Gustavus to Juneau could experience 5 to 7 inches of rainfall
during a five- day period (from Sunday to Thursday). How this
evolves is subject to debate. Some solutions press this
atmospheric river slowly southward through Friday albeit in
slowly weakening form. Greater spread in ensembles could account
for weakening signatures rather than the complete disappearance
of this week's series of storms. In other words, the caboose is
not yet in sight.

Two other important items to note in the forecast are an increase
in winds and increasing temperatures across the entire region,
especially on Thursday. We pushed Inner Channel winds up to small
craft Tuesday/Tuesday night with some gale force southwesterlies
across the eastern Gulf of Alaska. We fully expect to have to
increase winds even further with the Wednesday/Thursday storm, but
gradients as of yet are only hinted at. But we have begun to push
northern Inner Channel winds higher in the interim. Finally,
Ketchikan temperatures on Thursday may spike in the low 70s as
very warm ridging heats up to the atmosphere across the southern
Panhandle late in the week. An 80 is not out of the question in
Hyder. Chances of rain are still there, as these atmospheric
rivers could subtly meander at times, but increasingly likely is
that the southern Panhandle will avoid much of the mid-week storm
aimed at the north.

&&

.AJK WATCHES/WARNINGS/ADVISORIES...
PUBLIC...Strong Wind from 7 PM AKDT this evening through Monday afternoon
     for AKZ018.
MARINE...Gale Warning for PKZ051-052.
     Small Craft Advisory for PKZ012-013-022-031>033-036-041>043.

&&

KRT/JWA

Visit us at http://www.weather.gov/Juneau

Special Weather Statement
National Weather Service Juneau AK
1031 PM AKDT Sun Aug 8 2021

AKZ017>029-091500-
Cape Fairweather to Cape Suckling Coastal Area-
Taiya Inlet and Klondike Highway-Haines Borough and Lynn Canal-
Glacier Bay-Eastern Chichagof Island-
Salisbury Sound to Cape Fairweather Coastal Area-
Cape Decision to Salisbury Sound Coastal Area-
Eastern Baranof Island and Southern Admiralty Island-
Juneau Borough and Northern Admiralty Island-
Inner Channels from Kupreanof Island to Etolin Island-
Dixon Entrance to Cape Decision Coastal Area-
Southern Inner Channels-Misty Fjords-
Including the cities of Yakutat, Skagway, Haines, Gustavus,
Hoonah, Elfin Cove, Pelican, Sitka, Port Alexander, Angoon,
Juneau, Petersburg, Wrangell, Kake, Craig, Klawock, Ketchikan,
Metlakatla, and Hyder
1031 PM AKDT Sun Aug 8 2021

...HEAVY RAIN AND FLOODING POTENTIAL THIS WEEK...

Multiple weather systems bring heavy rain to the Panhandle
throughout this week with heavy rainfall at times for all parts
of Southeast Alaska. The first of two systems has already begun
moving through the Panhandle, bringing heavy rain across much of
the area. Yakutat has already measured 1.76 inches as of Sunday
evening. The rest of the northern Panhandle has seen rainfall
amounts between one half to three quarters of an inch from Sunday
afternoon through Sunday evening. This system will continue
bringing rain through Monday morning for all parts of Southeast
Alaska. The second arrives Monday evening through Tuesday
morning. Additional rainfall totals of 1 to 3 inches are expected
through Tuesday with the highest amounts across the northeast Gulf
Coast and along higher terrain. Area streams and rivers have begun
to rise Sunday night, but no flooding is expected from the first
two systems. However soils will become largely saturated.

Starting Wednesday, an atmospheric river will develop with the
axis of heaviest rain aimed at the NE Gulf Coast and Northern
Panhandle. There is still some uncertainty in the timing and
placement of the heaviest rain. However, confidence remains high
that a few areas could see an additional 3 to 6 plus inches of
rainfall from this system by Friday. Due to back to back heavy
rainfall events, please be alert to sharp rises in water levels
with some streams nearing bankful, and possible flooding, given
soil saturation. Along with flooding potential, isolated
landslides are also a concern. Stay up to date on the latest
forecasts through the week as this event evolves.