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000
FXAK67 PAJK 112320
AFDAJK

Southeast Alaska Forecast Discussion
National Weather Service Juneau AK
320 PM AKDT Thu Apr 11 2024

.SHORT TERM...Satellite and radar imagery reveal clearing skies
across much of the panhandle as a weakening mesolow SW of the
panhandle completes an anticyclonic loop - a result of a
combination of weak steering flow and the influence of the
Fujiwhara effect from a nearby system, and begins moving off to
the S. To the west, upper level cloud cover has begun to
overspread Yakutat, and will continue to push E through the
evening and overnight time frame. While the remaining showers in
the southern panhandle will rapidly diminish through the evening
hours, precipitation will begin to overrun the panhandle from N to
S through late Thursday night into Friday, with Yakutat beginning
Thursday evening.

Aloft, an upper level trough is being ejected E, with ridging
moving in to replace it. The ridging will prove to be short lived,
as a wave ridging along the primary steering pattern will bring
with it a front which will arrive in full force on Friday.
Anticipate small craft conditions across much of the Gulf and some
of the inner channels at times, with windy conditions for some
land-based areas. Snow levels will remain fairly low across much
of the panhandle, especially the N half, driven by lingering
cooler temperatures at 850 mb. As a result, do think that snow
will mix in at times for some locations. With some minor snow
accumulations being possible - especially on Friday night, and
moderate accumulations potentially ocurring along the Klondike
Highway. Fog will be a possibility Thursday night into Friday
morning, mainly for the S half of the area.

The primary changes made to the forecast were to the winds and to
the timing of the front. Wind speeds were increased in many land-
based locations, especially across the N half of the panhandle,
along with some more minor adjustments made to wind speeds in
maritime waters in conjunction with the next approaching system.
The onset of precipitation with the system itself has been slowed
down, as ridging will help keep appreciable PoPs out of the
forecast for longer than previously progged across much of the
area. A few small temperature adjustments were made to high
temperates on Friday (increased across parts of the N panhandle),
and low temperatures Friday night (which were lowered in some
areas).

.LONG TERM.../Saturday through Tuesday/...Relatively quiet mid to
long range forecast with the most active portion front loaded
Saturday morning. Covered mainly by the short term discussion, a
front will make its way through the panhandle Friday into Saturday
morning. By Saturday afternoon, stratiform precipitation will
transition to convective showers as the post frontal environment
pushes into the AOR. As precipitation changes to showers with the
introduction of minor CAA in the 850-700 mb layer, the likelihood
of snow increases. Do not expect any significant snow
accumulations, if any. In fact, as CAA advection moves over the
area with temperatures rising from breaks in clouds, the
atmospheric profile could support ice pellets and graupel. Kept
rain and snow in the forecast to represent the many things
inbetween (except freezing rain).

As time progresses, the trough aloft moves off to the southeast and
a broad ridge replaces it. From this somewhat flat ridge, northerly,
dry winds begin to infiltrate the panhandle with a surface ridge
developing in the Yukon and over the gulf waters. The result is
clearing skies with lighter winds and relatively warmer
temperatures. There is the chance for a marine layer to develop over
the gulf waters, however, current thoughts is that even if one
develops, it will not work its way into the land areas of the AOR
with broad north to northwesterly winds in the gulf. There is the
chance that areas along the NE gulf coast will see some cloud cover
and possibly rain, but this chance was discarded for this forecast
until better confidence can arrive at this solution.

Leaned a bit heavier on the GFS runs as the 12z deterministic GFS
run matches LREF ensemble mean guidance and the EC AIFS and ML 12z
runs on days 4 and 5 onwards. For significant changes to the
forecast, reduced the chance for PoPs significantly on days 4 and 5.
Additionally, kept enhanced southerly winds in Lynn Canal and
Stephens Passage for longer through the early portion of day 3. Lee
side troughing from westerly winds over mountain ranges will likely
help these winds blowing for longer. Beyond day 5 however,
significant model divergence has led to rather low confidence with
no clear trend.

&&

.AVIATION.../Until 00Z Saturday/...Mostly good flight conditions
currently with some windy conditions at the surface across the
panhandle will deteriorate overnight with a frontal band moving
over the area. VFR to MVFR conditions will give way to largely
stratiform MVFR CIG conditions. Rain and snow during the overnight
and morning hours of this system will likely drop VIS briefly at
times overnight for areas along the gulf coast and northern half
of the panhandle. VIS will begin to improve in the late morning
hours with warmer air pushing in, both increasing RH values to
limit any mist potential at the surface and transitioning
precipitation type to rain.

&&

.AJK WATCHES/WARNINGS/ADVISORIES...
PUBLIC...Strong Wind from 1 AM AKDT Friday through Friday afternoon for
     AKZ318.
MARINE...Gale Warning for PKZ652.
     Small Craft Advisory for PKZ012-013-021-022-032-033-642>644-651-
     661>664-671-672.

&&

$$

SHORT TERM...GFS
LONG TERM....NC
AVIATION...NC

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