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FXAK67 PAJK 212242
AFDAJK

Southeast Alaska Forecast Discussion
National Weather Service Juneau AK
242 PM AKDT Sun Apr 21 2019

.SYNOPSIS...One front attempting to exit the panhandle this
evening with front a little slow to spread east over the coast
mountains. A quick moving strongly developing wave in the
northeast Pacific that is beginning to curve north into the
Eastern Gulf of Alaska.

&&

.SHORT TERM...The first front will get pushed through the area by
Monday morning. The gusty winds from the first front have
essentially lessened with only gusts to 40 mph in the far southern
panhandle. The next low is rapidly deepening to a depth of 980 mb
by Monday morning west of the Cape Suckling then the low will
reform inland in southern Yukon Territory. Assisting the low and
frontal strength is strong low level jet of 60 to 70 kt flowing
across the panhandle to the northeast gulf as the low tracks
northward.

The new front will start to impact the southern
panhandle Sunday evening around 10 pm increasing wind gusts to 60
mph or higher prompting the high wind warning that has been
issued. The warnings fill in going north through the panhandle to
be over the northern sections in the morning with the Lynn Canal
area lingering into the afternoon timeframe. The gusts to 60 mph
plus will extend through the rest of the panhandle. The strong
gusty winds should last 3 to 6 hours as they go northward. The
strength and position of the low is forming sort of a double dose
of wind. After the front with east to southeast winds go past a
strong burst of southwest winds will moving into the coastal
regions off the gulf of Alaska This is where some of the strong
winds are coming from for the coastal zones.

Behind the monday front a secondary trough just ahead of cold pool
aloft sweeps in with a band of organize showers.  Some of the
showers could be enhance so the shower could be heavy. Also near the
front edge of the colder air pool there may be sufficient mid level
lift to spawn an isolated Thunderstorms. Have kept the location of
them in the northern gulf coastal waters to the northern offshore
area. The heavier shower activity will likely move through the
southern panhandle on Tuesday, leaving a westerly onshore flow
pattern across the gulf and into the panhandle.

As if the wind, heavy showers, and thunder potential was not enough
the cold pool moving across the gulf will cooling temperatures and
lowering snow levels.  The Yakutat area could potentially see
accumulations Monday night in a mix or straight snow shower
event. The mix/snow will move across the northern panhandle
Tuesday/Tuesday evening. Snowfall looks to limited to the northern
third of the panhandle although could stretch down in a mix to
the northern half of the central panhandle.

.LONG TERM.../Tuesday through Sunday/ As of 10 pm Saturday. Upper
level trough over Western Alaska that has been feeding storms into
the panhandle is finally showing signs of breaking down mid to
late week. It starts with an arctic high digging into the northern
part of the trough eventually cutting it off into an upper low.
Said low then drifts E across the gulf late week, ending up over
BC by next Sunday. Though how fast it does this has not been pined
down yet. Forecast confidence is moderate through the long range
as there are several weak short waves mixed into this pattern that
are complicating the forecast. Favored WPC for any needed updates
today.

At the surface, several short waves are moving through the area
through late week, but none are anywhere near as strong as the Sun
and Mon systems. The only short wave of note is at the beginning
of the long range on Tue that will be bringing more showers and
some gusty winds to the area. Nothing significant, mostly 20 to
30 kt winds for most areas and more organized showers but these
should be brief lasting only through about mid day Tue. Rest of
the long range features continued damp conditions as more weak
waves move through. The panhandle shows signs of beginning to dry
out by next weekend from NW to SE as the upper low moves out.

Another concern for the long range is the cooler air mass that
will be moving through Tue into Fri with the coolest conditions
expected for Tue and Wed. 850 mb temps forecast to drop down into
the -7 to -8C range at that time. Snow levels will likely lower
to a few hundred feet across the area. Some areas in the north
(like Yakutat, Haines, Gustavus, Hoonah, Skagway, and Juneau) may
see their rain showers change over to a mix or all snow,
particularly at night. No significant accumulations are expected
at this time, but an inch or two here and there is not out of the
questions.

&&

.AVIATION...Fairly widespread ceilings under 3000 feet Sunday
evening with locally gusty winds in the southern panhandle early
with some turbulence and local wind shear. As the next system
spreads north tonight and into the northern panhandle Monday
morning. Rain will lower ceilings and reduce visibility so IFR
condition will increase overnight to early Tuesday. Along with the
rain, strong winds, wind shear, and moderate to severe turbulence
near airports, except Yakutat will have lighter winds and less
shear. Later in the afternoon after the low moves north and jumps
inland, a hard shift in winds to Southwest will impact outer
coastal airports.

&&

.MARINE...Gale to Storm force winds Sunday night into Monday with
the strong developing system. The eastern gulf may see a small
pocket of gale force winds in the northeast gulf late Monday to
early Tuesday ahead of the trough with the band of semi organized
showers.

&&

.HYDROLOGY...Incoming rain fall will raise stream and river levels
but is not expected to threaten any flooding issues.

&&

.AJK Watches/Warnings/Advisories...
PUBLIC...High Wind Warning from 1 AM to 7 AM AKDT Monday for AKZ026.
     High Wind Warning from 10 PM this evening to 7 AM AKDT Monday
     for AKZ027-028.
     High Wind Warning from 4 AM to 10 AM AKDT Monday for AKZ024.
     High Wind Warning from 7 AM to 1 PM AKDT Monday for AKZ021-025.
     High Wind Warning from 10 AM to 4 PM AKDT Monday for AKZ020-022.
     High Wind Warning from 8 AM to 2 PM AKDT Monday for AKZ023.
     High Wind Warning from 11 AM to 7 PM AKDT Monday for AKZ018-019.
MARINE...Storm Warning for PKZ012-013-021-022-036-042-043.
     Gale Warning for PKZ011-031>035-041-051>053.

&&

$$

Bezenek/EAL

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