Small Craft Advisory 255, NWS Juneau, AK

503 
FZAK51 PAJK 051129
CWFAJK

Coastal Waters Forecast for Southeast Alaska
National Weather Service Juneau AK
329 AM AKDT Wed May 5 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.

PKZ098-060230-
329 AM AKDT Wed May 5 2021
.SYNOPSIS FOR SOUTHEAST ALASKA INNER CHANNELS COASTAL WATERS...
A low pressure system will move into the Eastern Gulf Thursday.
High pressure in Canada will cause increasing winds and waves
across Southeast Alaska through Friday.   

$$

PKZ011-060230-
Glacier Bay-
329 AM AKDT Wed May 5 2021

.TODAY...Light winds becoming N 10 kt. Seas 2 ft or less. 
.TONIGHT...N wind 15 kt. Seas building to 3 ft late. 
.THU...N wind 15 kt. Seas 3 ft. 
.THU NIGHT...Light winds. Seas 2 ft or less. 
.FRI...SE wind 10 kt. Seas 2 ft or less. 
.SAT...S wind 10 kt. Seas 2 ft or less. 
.SUN...S wind 10 kt. Seas 2 ft or less. 

$$

PKZ012-060230-
Northern Lynn Canal-
329 AM AKDT Wed May 5 2021

...SMALL CRAFT ADVISORY LATE TONIGHT...

.TODAY...Light winds becoming N 15 kt. Seas building to 3 ft. 
.TONIGHT...N wind 15 kt increasing to 25 kt late. Gusts to 40 kt
late. Seas 5 ft. 
.THU...N wind 30 kt diminishing to 20 kt in the afternoon.
Seas 5 ft. 
.THU NIGHT...NW wind 10 kt. Seas 2 ft or less. Rain showers.
.FRI...S wind 15 kt. Seas 3 ft. 
.SAT...S wind 20 kt. Seas 4 ft. 
.SUN...S wind 20 kt. Seas 4 ft. 

$$

PKZ013-060230-
Southern Lynn Canal-
329 AM AKDT Wed May 5 2021

...SMALL CRAFT ADVISORY LATE TONIGHT...

.TODAY...N wind 15 kt. Seas building to 3 ft. 
.TONIGHT...N wind 15 kt increasing to 25 kt late. Seas 5 ft. 
.THU...N wind 30 kt diminishing to 20 kt in the afternoon.
Seas 5 ft. 
.THU NIGHT...SE wind 10 kt. Seas 2 ft or less. 
.FRI...S wind 15 kt. Seas 3 ft. 
.SAT...S wind 20 kt. Seas 4 ft. 
.SUN...S wind 15 kt. Seas 3 ft. 

$$

PKZ021-060230-
Icy Strait-
329 AM AKDT Wed May 5 2021

.TODAY...E wind 10 kt. Seas building to 3 ft in the morning, then
then 2 ft or less in the afternoon. Patchy fog early in the
morning. 
.TONIGHT...E wind 15 kt. Seas building to 3 ft late. 
.THU...E wind 15 kt. Seas 3 ft. 
.THU NIGHT...E wind 10 kt. Seas 2 ft or less. 
.FRI...E wind 10 kt. Seas 2 ft or less. 
.SAT...E wind 15 kt becoming W. Seas 3 ft. 
.SUN...W wind 10 kt. Seas 2 ft or less. 

$$

PKZ022-060230-
Cross Sound-
329 AM AKDT Wed May 5 2021

.TODAY...NE wind 15 kt. Seas 6 ft. S swell early in the morning. 
.TONIGHT...E wind 15 kt. Seas 5 ft. 
.THU...E wind 20 kt. Seas 5 ft. 
.THU NIGHT...E wind 10 kt. Seas 6 ft. 
.FRI...E wind 10 kt. Seas 4 ft. 
.SAT...E wind 10 kt becoming W. Seas 4 ft. 
.SUN...W wind 10 kt. Seas 7 ft. 

$$

PKZ031-060230-
Stephens Passage-
329 AM AKDT Wed May 5 2021

.TODAY...NW wind 15 kt. Seas building to 3 ft. Patchy fog early
in the morning. 
.TONIGHT...N wind 15 kt. Seas 4 ft. 
.THU...N wind 20 kt. Seas 4 ft. Rain showers in the
afternoon. 
.THU NIGHT...SE wind 10 kt. Seas 2 ft or less. 
.FRI...S wind 15 kt. Seas building to 3 ft. 
.SAT...S wind 15 kt. Seas 3 ft. 
.SUN...S wind 10 kt. Seas 2 ft or less. 

$$

PKZ032-060230-
Northern Chatham Strait-
329 AM AKDT Wed May 5 2021

.TODAY...Light winds becoming N 15 kt. Seas building to 3 ft. 
.TONIGHT...N wind 15 kt. Seas 3 ft. 
.THU...N wind 15 kt. Seas 3 ft. Showers in the afternoon. 
.THU NIGHT...S wind 10 kt. Seas 2 ft or less. 
.FRI...S wind 15 kt. Seas building to 3 ft. 
.SAT...S wind 10 kt. Seas 3 ft. 
.SUN...S wind 10 kt. Seas 2 ft or less. 

$$

PKZ033-060230-
Southern Chatham Strait-
329 AM AKDT Wed May 5 2021

.TODAY...N wind 15 kt. Seas building to 3 ft. Near ocean
entrances, seas 6 ft. 
.TONIGHT...N wind 15 kt. Seas 3 ft, except 6 ft near ocean
entrances. 
.THU...NE wind 15 kt. Seas 4 ft, except 9 ft near ocean 
entrances. Showers.
.THU NIGHT...S wind 20 kt. Seas 5 ft, except 10 ft near ocean 
entrances. 
.FRI...S wind 15 kt. Seas 3 ft. 
.SAT...SW wind 10 kt. Seas 3 ft. 
.SUN...S wind 10 kt. Seas 2 ft or less. 

$$

PKZ034-060230-
Frederick Sound-
329 AM AKDT Wed May 5 2021

.TODAY...NE wind 15 kt. Seas building to 3 ft. 
.TONIGHT...NE wind 15 kt. Seas 3 ft. 
.THU...NE wind 20 kt. Seas 4 ft. Rain showers in the
afternoon. 
.THU NIGHT...SW wind 10 kt. Seas 2 ft or less. 
.FRI...S wind 15 kt. Seas building to 3 ft. 
.SAT...S wind 15 kt. Seas 3 ft. 
.SUN...SW wind 10 kt. Seas 2 ft or less. 

$$

PKZ035-060230-
Sumner Strait-
329 AM AKDT Wed May 5 2021

.TODAY...E wind 10 kt. Seas 2 ft or less, except 5 ft near ocean
entrances. 
.TONIGHT...E wind 15 kt. Seas 3 ft, except 5 ft near ocean
entrances. 
.THU...E wind 15 kt. Out of interior passes, gusts to 35 kt
in the morning. Seas 3 ft, except 8 ft near ocean entrances. 
.THU NIGHT...SE wind 15 kt. Seas 3 ft, except 8 ft near
ocean entrances. 
.FRI...S wind 15 kt. Seas 3 ft. 
.SAT...SW wind 10 kt. Seas 3 ft. 
.SUN...S wind 10 kt. Seas 2 ft or less. 

$$

PKZ036-060230-
Clarence Strait-
329 AM AKDT Wed May 5 2021

.TODAY...Light winds becoming N 10 kt. Seas 2 ft or less, except
4 ft near ocean entrances. 
.TONIGHT...E wind 10 kt becoming NW late. Seas building to 4 ft
late. 
.THU...NE wind 20 kt becoming SE in the afternoon. Seas
5 ft. 
.THU NIGHT...SE wind 30 kt. Seas 7 ft. 
.FRI...S wind 20 kt. Seas 5 ft. 
.SAT...S wind 15 kt. Seas 4 ft. 
.SUN...S wind 10 kt. Seas 2 ft or less. 

$$

Southeast Alaska Forecast Discussion
National Weather Service Juneau AK
244 PM AKDT Tue May 4 2021

.SHORT TERM.../Through Thursday/ Disorganized front moving
through the panhandle this afternoon bringing showers of rain to
many areas. Rainfall has not been that heavy though some moderate
showers have shown up at Juneau briefly (dropping around .11
inches in an hour). Little in the way of wind with this front as
well through there are some exceptions. Lynn Canal and Skagway are
the main ones with 20 to 25 kt southerlies blowing through there
this afternoon.

Front is expected to blow through the panhandle early this
evening, followed by gradually diminishing onshore flow. That
onshore flow will keep a chance of showers and clouds going
through most of the night. After midnight however flow gradually
turns offshore which will cause the showers to shut off and breaks
to develop in the cloud cover especially in the north as the low
level boundary layer begins to dry out. The breaks may allow
temperatures to get cool overnight in some areas so left the
mention of patchy fog in for a lot of areas. Frost is also a
possibility as the breaks in cloud cover develop for parts of the
Haines Road, Yakutat, and Hyder where frost advisories have been
issued. All of this is dependent on how fast the breaks develop
so if skies remain overcast temperatures could stay warmer then
expected with less chance of fog or frost.

Focus for Wed night into Thu then shifts to a new low coming up
into the Eastern gulf from the S. The low itself stays offshore,
but at least two frontal bands will try and affect the area. The
first one will likely not have much success due to the still
strong offshore flow across the area other then bringing more mid
to high level cloud cover. Possibility of some rain for the outer
coast Wed night though with outflow not quite as strong there as
further inland.

Second frontal band begins to move into the panhandle Thu
afternoon which will be stronger then the first one. The low will
also have moved far enough north by this point that the offshore
flow will have turned more along shore allowing rain to be more
probable. This rain will then spread northward through Thu night.
Expected rainfall will be light though with only up to a quarter
inch likely. There is also the possibility of some gusty winds
for the southern panhandle (possibility of 40 mph gusts at
Hydaburg) for Thu afternoon as the front comes inland as well.

.LONG TERM.../Thursday through Monday night/...This extended range
forecast begins with some meaningful differences in the upper
levels that get larger with time. When that happens, the
situation does note bode well for model agreement at the surface
and that is, in fact the case today. In general terms, this long
range forecast period begins with a large and negatively tilted
upper trough extending southeast across the Gulf with an upper low
at the bottom of the trough somewhere southwest of Haida Gwaii.
Models cut off the low and weaken the upper trough by late Friday
morning, but details on where this happens are different for each
model. By this coming weekend, low pressure aloft looks like it
will build in from the west across the Gulf and at least one model
merges the original upper low with a trough expanding from the
west. By early next week, model solutions over Southeast Alaska
vary between a strong ridge and a weak upper low across the Gulf
and Southeast Alaska. Not good. At the surface, models are
depicting a significant low somewhere to the south of Haida
Gwaii, or to the west, or to the north. Implications of this are
significant when it comes to the resultant winds over the inner
channels and eastern Gulf. By Friday, solutions vary between a
surface low west of the Dixon Entrance, a broad ridge over the
eastern Gulf and Panhandle, or a front extending east across the
Gulf from a low south of the Alaskan Peninsula. Modeled
precipitation is as disparate amongst the models as the various
other features. Ensembles have been somewhat more consistent,
but are substantially different than the deterministic solutions.
So there's some more "not good".

To quote a popular movie from the early 1980's, "The only winning
move is not to play". In fact, that has been our approach to such
poor deterministic model guidance agreement and such disparate
ensemble guidance. Few if any changes were made to this extended
range forecast and confidence is well below average. -Fritsch

&&

.AJK WATCHES/WARNINGS/ADVISORIES...
PUBLIC...Frost Advisory from 1 AM to 7 AM AKDT Wednesday for AKZ017-019-
     029.
MARINE...Small Craft Advisory for PKZ022-041>043-051>053.

&&

EAL/Fritsch

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