Small Craft Advisory 189, NWS Juneau, AK

479 
FZAK51 PAJK 291200
CWFAJK

Coastal Waters Forecast for Southeast Alaska
National Weather Service Juneau AK
400 AM AKDT Mon Mar 29 2021

Southeast Alaska Inside Waters from Dixon Entrance to Skagway

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

PKZ098-300215-
400 AM AKDT Mon Mar 29 2021
.SYNOPSIS FOR SOUTHEAST ALASKA INNER CHANNELS COASTAL WATERS...
A ridge of high pressure pressure will continue shifting
eastward over the Panhandle into Monday morning. A front will 
ride over the top of the ridge and spread precipitation across 
Southeast Alaska from north to south beginning on Monday
morning. Outlook: A stronger front pushes through the eastern 
Gulf and Panhandle starting on Tuesday evening. 

$$

PKZ011-300215-
Glacier Bay-
400 AM AKDT Mon Mar 29 2021

.TODAY...S wind 10 kt. Seas 2 ft or less. 
.TONIGHT...S wind 10 kt. Seas 2 ft or less. 
.TUE...S wind 10 kt. Seas 2 ft or less. Rain in the afternoon. 
.TUE NIGHT...SE wind 15 kt. Seas 3 ft. Rain and snow. 
.WED...S wind 20 kt. Seas 4 ft. 
.THU...N wind 15 kt becoming SE. Seas 3 ft. 
.FRI...NE wind 10 kt. Seas 2 ft or less. 

$$

PKZ012-300215-
Northern Lynn Canal-
400 AM AKDT Mon Mar 29 2021

.TODAY...S wind 10 kt. Seas 2 ft or less. Snow and rain in the 
afternoon.
.TONIGHT...S wind 20 kt. Seas 4 ft. Rain.
.TUE...S wind 25 kt. Seas 5 ft. Rain.
.TUE NIGHT...S wind 25 kt. Seas 5 ft. Rain.
.WED...S wind 25 kt. Seas 5 ft. 
.THU...S wind 15 kt. Seas 3 ft. 
.FRI...N wind 10 kt becoming E. Seas 2 ft or less. 

$$

PKZ013-300215-
Southern Lynn Canal-
400 AM AKDT Mon Mar 29 2021

.TODAY...S wind 15 kt. Seas 3 ft. Snow. Rain in the afternoon. 
.TONIGHT...S wind 20 kt. Seas 4 ft. Rain.
.TUE...S wind 20 kt. Seas 4 ft. Rain in the morning, then
periods of rain in the afternoon. 
.TUE NIGHT...S wind 25 kt. Seas 5 ft. Rain.
.WED...S wind 25 kt diminishing to 15 kt. Seas 5 ft subsiding to 3
ft.
.THU...SE wind 10 kt. Seas 2 ft or less. 
.FRI...E wind 10 kt. Seas 2 ft or less. 

$$

PKZ021-300215-
Icy Strait-
400 AM AKDT Mon Mar 29 2021

.TODAY...S wind 15 kt becoming E. Seas 3 ft. Snow in the morning.
Rain.
.TONIGHT...S wind 20 kt. Seas 4 ft. Rain.
.TUE...S wind 20 kt. Seas 4 ft. Rain.
.TUE NIGHT...S wind 20 kt. Seas 4 ft. Rain.
.WED...S wind 20 kt. Seas 4 ft. 
.THU...SE wind 10 kt. Seas 2 ft or less. 
.FRI...E wind 10 kt. Seas 2 ft or less. 

$$

PKZ022-300215-
Cross Sound-
400 AM AKDT Mon Mar 29 2021

...SMALL CRAFT ADVISORY THROUGH TONIGHT...

.TODAY...W wind 15 kt becoming E. Seas 10 ft. Snow in the
morning. Rain.
.TONIGHT...W wind 25 kt. Seas 11 ft. Rain.
.TUE...SW wind 20 kt. Seas 10 ft. Rain.
.TUE NIGHT...S wind 20 kt. Seas 11 ft. Rain.
.WED...SW wind 15 kt. Seas 10 ft. 
.THU...E wind 10 kt. Seas 8 ft. 
.FRI...E wind 10 kt. Seas 7 ft. 

$$

PKZ031-300215-
Stephens Passage-
400 AM AKDT Mon Mar 29 2021

.TODAY...S wind 15 kt. Seas 3 ft. Rain. Snow in the afternoon.
.TONIGHT...S wind 15 kt. Seas 3 ft. Rain in the evening, then
periods of rain late. 
.TUE...S wind 20 kt. Gusts to 35 kt in the afternoon. Seas
4 ft. Periods of rain in the morning, then rain in the afternoon.
.TUE NIGHT...SE wind 25 kt. Seas 5 ft. Rain.
.WED...S wind 30 kt diminishing to 20 kt. Seas 6 ft subsiding to 4
ft.
.THU...SE wind 15 kt. Seas 3 ft. 
.FRI...E wind 15 kt. Seas 3 ft. 

$$

PKZ032-300215-
Northern Chatham Strait-
400 AM AKDT Mon Mar 29 2021

.TODAY...S wind 15 kt. Seas 3 ft. Rain in the morning. 
.TONIGHT...S wind 15 kt. Seas 3 ft. Rain.
.TUE...S wind 15 kt. Seas 3 ft. Rain.
.TUE NIGHT...S wind 20 kt. Gusts to 35 kt. Seas 4 ft. Rain.
.WED...S wind 20 kt. Seas 4 ft. 
.THU...SE wind 15 kt. Seas 3 ft. 
.FRI...SE wind 15 kt. Seas 3 ft. 

$$

PKZ033-300215-
Southern Chatham Strait-
400 AM AKDT Mon Mar 29 2021

.TODAY...SW wind 15 kt. Seas 3 ft, except 9 ft near ocean
entrances. 
.TONIGHT...S wind 15 kt. Seas 3 ft, except 10 ft near ocean
entrances. Rain late. 
.TUE...S wind 15 kt. Seas 4 ft, except 10 ft near ocean 
entrances.
.TUE NIGHT...S wind 25 kt. Seas 5 ft, except 12 ft near ocean
entrances. Rain.
.WED...S wind 30 kt becoming SW 15 kt. Seas 6 ft subsiding
to 3 ft. 
.THU...S wind 15 kt. Seas 3 ft. 
.FRI...SE wind 15 kt becoming NW. Seas 3 ft. 

$$

PKZ034-300215-
Frederick Sound-
400 AM AKDT Mon Mar 29 2021

.TODAY...S wind 15 kt. Seas 3 ft. 
.TONIGHT...S wind 15 kt. Seas 3 ft. 
.TUE...S wind 15 kt. Seas 3 ft. 
.TUE NIGHT...S wind 20 kt. Gusts to 35 kt. Seas 4 ft. Rain.
.WED...S wind 25 kt diminishing to 15 kt. Seas 5 ft subsiding to 3
ft.
.THU...SE wind 20 kt. Seas 4 ft. 
.FRI...E wind 15 kt. Seas 3 ft. 

$$

PKZ035-300215-
Sumner Strait-
400 AM AKDT Mon Mar 29 2021

.TODAY...Light winds becoming SE 15 kt. Seas building to 3 ft. 
Near ocean entrances, seas 7 ft. 
.TONIGHT...SE wind 15 kt becoming SW late. Seas 3 ft, except 8 ft
near ocean entrances. Rain late. 
.TUE...SW wind 20 kt. Seas 4 ft, except 8 ft near ocean
entrances. 
.TUE NIGHT...SW wind 20 kt. Seas 4 ft, except 10 ft near
ocean entrances. Rain.
.WED...SE wind 20 kt becoming SW 10 kt. Seas 4 ft subsiding to 2 
ft or less.
.THU...S wind 15 kt. Seas 3 ft. 
.FRI...SE wind 10 kt becoming light. Seas 2 ft or less. 

$$

PKZ036-300215-
Clarence Strait-
400 AM AKDT Mon Mar 29 2021

.TODAY...NW wind 10 kt becoming SE in the afternoon. Seas 2 ft or
less. Near ocean entrances, seas 6 ft. 
.TONIGHT...SE wind 15 kt. Seas 3 ft. 
.TUE...S wind 15 kt. Seas 3 ft, except 6 ft near ocean
entrances. 
.TUE NIGHT...S wind 20 kt. Seas 4 ft, except 7 ft near ocean
entrances. Rain.
.WED...S gale to 35 kt becoming SW 25 kt. Seas 7 ft subsiding to 5
ft. Near ocean entrances, seas 12 ft subsiding to 8 ft. 
.THU...S wind 20 kt. Seas 4 ft. 
.FRI...SE wind 10 kt. Seas 2 ft or less, except 4 ft near ocean
entrances.

$$

Southeast Alaska Forecast Discussion
National Weather Service Juneau AK
255 PM AKDT Sun Mar 28 2021

.SHORT TERM.../Sunday evening through Wednesday morning/
Northwest flow responsible for the drying trend across Southeast
Alaska Monday afternoon will be short lived as flow becomes
onshore later tonight. Northerly outflow winds will quickly
diminish through the Inner Channels by midnight tonight. Winds
turn southerly by Monday afternoon; however conditions should
remain under small craft levels for the Inside Passage.

A strengthening baroclinic zone between a ridge over the north
pacific and a digging trough over the Bering will put the region
in persistent westerly flow over the next couple days. A weak area
of low pressure developing in the northern gulf combined with
flow coming off the water will allow moisture to quickly stream
back into the Panhandle. Periods of precipitation move in from NW
to SE early Monday and continue through the rest of the short
term. With westerly flow setting up, the colder, drier air at the
surface will slowly erode away through the day. Expect P-type to
start as snow for the entire Panhandle, mixing with rain first
along the coast then inland through the afternoon and evening.
Minor snowfall accumulations possible from Petersburg to Sitka and
northward. A general 1 to 2 inches is expected with isolated
higher amounts up to 2 to 4 inches possible in Juneau. Expect
Upper Lynn Canal to be rain shadowed in this type of westerly flow
pattern, so have lowered POPs and QPF significantly for that
area. A complete changeover to rain should occur for most places
by Monday evening, and stay rain through Tuesday afternoon. The
most persistent rainfall will be focused along westerly facing
slopes, with periods of rain elsewhere. Rainfall amounts through
Tuesday will range from a quarter to a half inch across the south
to over an inch along the terrain of Baranof Island and the Coast
Mountains.

The next weather system arrives late Tuesday into early Wednesday
morning as a surface low develops in the northern gulf in
response to a digging trough moving SW out of the Bering. A minor
atmospheric river sets up ahead of this next system as strong
100+ kt jet transports ample moisture northward from the central
Pacific into Southeast Alaska. Heaviest precipitation will begin
across the NE Gulf coast Tuesday afternoon and evening, then slide
southeastward across the rest of the Panhandle Tuesday night into
Wednesday morning. 1000-850mb Thickness values drop to around
1290m just ahead of this system Tuesday afternoon and evening as
cooler air (-7 to -8C at 850mb) moves in aloft. There is a
possibility that precipitation may start as a brief period of snow
before warmer, southerly flow transitions everything to rain.
Rainfall amounts of 1 to 2 inches possible from Tuesday morning
through Wednesday morning across the northern half of the
Panhandle. Rain and snowfall amounts will be monitored closely
over the next few days, expect minor adjustments to them in future
forecast packages as the finer details become clearer.

Overall confidence is at or above average for the short term. For
Wind, POP and QPF used a blend of the NAM/GFS, more of the NAM
during the first 24 hours of the forecast.

.LONG TERM.../Tuesday through Sunday as of 10 pm Saturday/ The
extended range forecast features a shifting upper level pattern in
the middle of next week. A rather flat upper level ridge over the
area on Tue will get replaced by a cold upper through that moves
in from the W. This trough sort of stalls over the area late week
and persists into the weekend. No disagreement from guidance on
this other then how strong that trough will eventually become by
the weekend and whether or not a reinforcing shot of cold air
will help keep the trough in place into the late weekend.

Lower in the atmosphere, the overall theme of the forecast is wet
with a cooling trend into the weekend. The wettest (and also
warmest period) is from Tue into Wed as the flat ridge both aloft
and at the surface allows a weak atmospheric river to bring
precipitation to the area. This culminates in a more organized
frontal band developing over the Gulf on Tue night, with it
sweeping through the panhandle on Wed. There are a few new
forecast developments with this system over the previous forecast.
First guidance has this front moving through the panhandle quicker
then previously forecast (the heavier frontal precip now is out
of the panhandle by Wed evening). This results in less rainfall
now expected for various areas. The wind forecast was also
affected by this timing change with the higher winds now moving
through at in a quicker timeframe. The second development is a
warm up noted (especially for the northern inner channels) from
the southerly flow ahead of the front. This has resulted in
warming some overnight lows on Tue night for quite a few areas.
There now is a larger area of the panhandle that stays above
freezing Tue night with more rain apparent in the new forecast.
Forecast for this frontal band remains uncertain as guidance
shifts timing and speed of the system.

Past Wed night, a low lingers in the northern gulf sending
westerly onshore flow and showers into the panhandle for the late
week while the incoming upper trough drags colder air into the
region. The northern half of the panhandle at least will likely
see these showers mostly in the form of snow as 850 mb temps drop
into the -8 to -9C range with some accumulations possible.
Forecast becomes increasingly uncertain rapidly into the weekend
as differences on how the upper trough and the northern gulf
surface low evolves with everything from continued showers to a
drying and warming trend possible.

&&

.AJK WATCHES/WARNINGS/ADVISORIES...
PUBLIC...Small Craft Advisory until 7 PM AKDT this evening for AKZ019-025.
MARINE...Small Craft Advisory for PKZ012-013-022-031>036-041>043-051-052.

&&

CM/EAL

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