680
FXAK67 PAJK 271346
AFDAJK

Southeast Alaska Forecast Discussion
National Weather Service Juneau AK
546 AM AKDT Sat Apr 27 2024

.SHORT TERM...Rain begins returning to the panhandle as a system
moves in, bringing chances of precip through the weekend, though
the upcoming week will see increasing chances of drier weather
past Monday.

Satellite and radar imagery depict cloud cover moving back into
the panhandle from S to N, with a low level cloud deck moving
through the S panhandle as of the time of writing. This will cap
high temperatures in the southern panhandle, though initially
clear skies in the N half of the area will enable high
temperatures to climb into the upper 50s for this area before
increasing cloud cover brings an end to the warm weather.

Aloft, a broad trough in the upper levels stretches from the
western Bering Sea to Haida Gwaii as of the time of writing. While
the primary upper level low is located in the vicinity of the
Aleutian Islands, the low`s corresponding fronts are occluding,
and cyclogenesis has begun on the opposite side of the Gulf of AK.
Aided by divergence aloft on the lee side of the upper level
trough the surface reflection of this newly developing low will
move north past Haida Gwaii and into the Eastern Gulf through
Saturday and Sunday. Past this point, the interaction between the
two lows (Fujiwhara Effect), will see the low currently near the
Aleutians, by this point substantially weaker, race off to the SE,
with the currently developing low retrograding around its own
axis before heading back S.

Before the developing low departs however, it will bring rain
across SE AK. Frontogenesis along the E flank of the developing
low will see an initial push of showers into the southern half of
the panhandle through Saturday morning, before the primary
frontal band itself advances N through the panhandle, reaching
into the Icy Strait Corridor northward Saturday night. While
there has been some question on how much precipitation will
actually manage to make its way through the dry air which has been
entrenching itself in SE AK, moisture transport is looking
increasingly likely be sufficient to overcome this limitation.
Still think that precip totals will be fairly limited, with the
greatest QPF totals still progged for the southern panhandle, but
almost all of the area will likely see at least some precip -
though it is possible that the current totals for Skagway and
Haines could be on the generous side. The exception will be
Yakutat, which will likely see precip stay more on the low side
with this particular system.

Maritime winds will see strong small craft conditions across the
southern gulf which will successfully push into the southern inner
channels through Saturday. Otherwise, the winds in many of the
inner channels will be caught between two competing forces -
pressure gradient force encouraging N flow, and synoptic flow
encouraging S flow. At this time, think that barring the southern
channels, N flow will largely win out until the primary frontal
band arrives, which should - for a time - be able to overcome the
pressure gradient force and bring a surge of S winds into the
other inner channels. For additional details, see the marine
discussion.

Primary changes made to the forecast were to refine the timing of
the frontal band associated with the developing low, as well as
wind directions in the inner channels as the pressure gradient
force and synoptic scale flow pattern contrast each other.
Increased QPF across the Icy Strait Corridor somewhat as the
system arrives, though still do not expect anything too
substantial from this system.

.LONG TERM.../Sunday through Tuesday night/...A triple point low
will have developed over the eastern Gulf of Alaska and on an
existing frontal boundary by Sunday. The small craft intensity surface
winds circulating about this low will have already peaked by that
time and precipitation associated with the front will be focused
primarily over the southern half of the Panhandle with rain likely
as far north as Tenakee Springs and Angoon. The low itself will
pinwheel over the southeastern Gulf before ejecting southeast and
out of the forecast area late Sunday night or early Monday. As
this happens, shower activity will diminish from north to South,
leaving scattered to isolated shower activity through Monday night
and a high probability of dry weather and diminishing cloud cover
for Tuesday. The pressure gradient over the inner channels will be
quite weak, so winds will be minimal once the low tracks off to
the southeast. Daytime highs ranging from the upper 50s to lower
60s, but overnight lows are still getting down close to or
slightly below freezing.


&&

.AVIATION...Conditions this morning are a split depending on your
location in the panhandle. Most locations across the northern
panhandle are reporting VFR conditions with the exception of
Yakutat which is reporting half mile and fog this morning at the
time of writing. Meanwhile, the southern panhandle is slowly being
enveloped by an advancing low cloud deck that is dropping
conditions down to MVFR and IFR. This layer is expected to expand
north during the day bringing lower CIGs to more areas throughout
the day. LLWS is expected to increase across the southern
panhandle towards the latter half of the TAF period as winds
across the area increase.

&&

.MARINE...
Winds increase a low moves in, with 25 to 30 knot winds lifting
into the southern waters Saturday. South of Cross Sound and
Frederick Strait, expect 8 to 15 ft developing seas, with the
highest significant heights south of Cape Decision and west coast
of Prince of Wales.

Seas become a fresh southwest swell Sunday, with significant
heights diminishing through Monday.

&&

.AJK WATCHES/WARNINGS/ADVISORIES...
PUBLIC...None.
MARINE...Small Craft Advisory for PKZ035-036-641>643-661>664.

&&

$$

SHORT TERM...GFS
LONG TERM....Fritsch
AVIATION...SF
MARINE...AP

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