542
FXAK67 PAJK 171309
AFDAJK

Southeast Alaska Forecast Discussion
National Weather Service Juneau AK
509 AM AKDT Tue Sep 17 2024

.SHORT TERM...A lull in the active weather pattern on Tuesday
begins drawing to a close Tuesday night as another front moves
into SE AK.

Satellite and radar imagery as of the time of writing (12z) show
clearing skies across most of the panhandle as a low which is
still bringing chances of rain to the southern half of the area
departs through the morning hours.

In the place of the departing low, ridging will briefly rebuild as
energy races downstream of an approaching system. The ridge won`t
be very impressive, with 500 mb decameter heights struggling to
get above 654 decameters through the day. This will contribute to
widespread clearing skies across the area. The weak ridge will be
displaced Tuesday night as another system approaches from the
west. Northerly flow will prevail for most locations through the
daytime hours, though flow will veer to the S Tuesday night as
the system approaches. Winds and chances of rain will increase
Tuesday night into Wednesday as the system arrives. For additional
details, see the long term forecast discussion.

.LONG TERM.../Wednesday through Sunday/...This extended range
forecast period sees Southeast Alaska situated on the north side
of the upper level jet stream with periods of upper level zonal
flow punctuated by pronounced upper level troughs. The single
exception to this will be on Friday when an upper ridge transits
the area from west to east. What this means: No less than three
lows pressure centers will transit across the Gulf of Alaska and
Southeast Alaska over the next five days with the only meaningful
chance of dry weather occurring on Friday when the upper level
ridge passes overhead. Model divergence gets rather large on
Friday going into Saturday with regard to a low over the far
southeast Gulf. Details on how strong and precisely where it will
make its closest approach to the southern outer coast are lacking
big time. Fortunately we have several days to pin down this
potentially storm force low. As is often the case, GFS is offering
the strongest solution. If the worst case GFS solution pans out,
potential exists for the first high wind warning of this Autumn
season for the southern outer coast. Stay tuned.

&&

.AVIATION...Patchy fog and low clouds north and east of Kupreanof
Island is creating a few areas of IFR conditions this morning as
higher level clouds have cleared out. Areas farther south are
still dealing with higher overcast so those areas are seeing VFR
or MVFR conditions due to a lack of low clouds or fog developing.
Once the morning fog dissipates today most areas should be VFR
through the evening hours. An incoming front late Tue night into
Wed will start to bring ceilings and vis down to MVFR or lower due
to precipitation. Winds will also be increasing especially in the
northern Lynn Canal area. Some light turbulence and low level
wind shear may be possibly into Wed as the front moves in.

&&

.MARINE...Wind speeds largely remain on the lower side until
Tuesday night across most of the area. By late Tuesday night, the
next front will move in from the west, causing wind speeds to
increase. 20 to 25 knots in the gulf with 10 to 20 knots in the
inner channels. The exception for the inner channels is Lynn Canal
where wind speeds will increase to 20 to 30 kts by late Tuesday
night with elevated winds lasting into Wednesday.

&&

.AJK WATCHES/WARNINGS/ADVISORIES...
PUBLIC...Strong Wind late tonight for AKZ318.
MARINE...Small Craft Advisory for PKZ012-013-641-661-662-671-672.

&&

$$

SHORT TERM...GFS
LONG TERM....Fritsch
AVIATION...EAL
MARINE...GJS/GFS

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