Area Forecast Discussion
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000
FXAK67 PAJK 271354
AFDAJK

Southeast Alaska Forecast Discussion
National Weather Service Juneau AK
554 AM AKDT SAT AUG 27 2016

.SHORT TERM...Longwave upper trof will slowly deepen across the
area through tonight. Several shortwaves will affect the area
through tonight...with one shortwave moving in from the north and
another moving in from the south. The more southern shortwave will
have more of an effect on the area especially tonight. Upper low
will move away from the southern area this morning. Surface low
will slowly develop well southwest of Haida Gwaii and begin to
move northeast tonight. Surface trof over the southern panhandle
will slowly weaken through tonight. High pressure will remain over
northwest Canada through tonight.

Main forecast concerns will be cloud cover...precip
potential...winds...and temps. Early this morning...there was a
band of low clouds along the outer coast southeast of Yakutat.
These clouds will likely drift offshore as low level flow becomes
more offshore today. Clouds associated with the trof over the
south will diminish some through early afternoon...but as flow
aloft becomes more east-southeast late in the day...more clouds
will move back into the far southeast. These clouds will spread
northwest as far as Frederick Sound by late tonight. Patchy high
and mid-level clouds will move southeast out of interior AK into
the northeast gulf ahead of the shortwave moving in from the
north. Some clouds associated with upslope flow on Canadian side
of Coast Mtns have reached the far northeast area...but these
will also diminish as this flow slowly dries out. Looking like
much of the area will see plenty of sunshine today.

Precip potential will be mainly with the southern shortwave and
weak surface trof. There may be a few leftover showers early this
morning near Hyder with exiting upper low. Otherwise...expect some
showers to move in from the east over Hyder as weak vort lobe
moves in late in the day. These showers will spread slowly
northwest and affect the southern third of the area by late
tonight as main shortwave tries to move in. Areal coverage will
remain scattered or less though so keeping POPs at chance levels
or less.

The winds have diminished some over the area especially over the
northern half. Winds over the northern channels are down to 15-20
Kt after reaching 25 KT last night. Think the winds over the
northern area will diminish a bit more through today...then pick
up a bit tonight but stay below SCA levels. Some of the more
east-west channels will probably see some increase in winds this
morning as pressure gradient orientation shifts to favor them a
bit more. But even these areas will diminish again later this
afternoon. Winds in the east-west channels should peak at 15-20
KT. Over the gulf...the 15-20 Kt northwest winds will diminish
slowly through the day over the southern gulf...but the north will
see some outflow from interior passes and channels that could
reach 15-20 KT. The southern channels should have 10-15 KT
northwest winds drop off late this afternoon...then shift around
to a more southeast direction as pressure gradient reorients
itself.

Temps will be somewhat above average over much of the area today
especially over the north. Plenty of sunshine and offshore flow
should push temps well into the 70s over the north...with near 70
around the south.

.LONG TERM...On Sunday surface low pressure will strengthen off
the coast of Haida Gwaii then slowly shift north into the SE gulf.
Meanwhile upper level low pressure will also strengthen in the
same area. This will help to increase the threat of showers across
the southern panhandle and continue offshore flow over the north a
bit longer. Have decreased cloud cover of the northern panhandle
Sunday morning and adjusted high temperatures up some for this
reason.

Another upper level low will move south out of the Yukon on Monday
and merge with the other low over the eastern gulf Monday night.
This will help to spread the chance of showers northward over the
inner channels. Latest model runs have trended stronger with the
surface low and shifted it more NW of the gulf. Shifted the
current forecast in this direction somewhat, but not as strong as
models suggest. Chance of showers remain in the forecast with the
low off shore through Wednesday then on Thursday both the upper
and surface lows shift back to the SE and take majority of the
showers with it. This should allow for another break in the precip
for a day or two. Then models show a front crossing the gulf on
Saturday with some timing differences of when/if rain will arrive.

Used mainly the 00z GFS/ECMWF along with some NAM12 in the shorter
term. Biggest changes were to adjust high temps up on Sunday and
Monday and to shift the low center over the gulf on Tuesday.

&&

.AJK Watches/Warnings/Advisories...
PUBLIC...None.
MARINE...Small Craft Advisory due to Seas for PKZ041-042.
&&

$$

RWT/Ferrin

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