976
FXAK67 PAJK 201212
AFDAJK

Southeast Alaska Forecast Discussion
National Weather Service Juneau AK
412 AM AKDT Thu Jun 20 2024

.SHORT TERM...Our period of overall warm and dry weather is slowly
starting to come to an end. High pressure continues to shift to
the east and weaken while a low remains in the gulf. Marine cloud
cover this morning is nowhere near what it was in coverage earlier
this week. Along the outer coast, a marine layer still exists up
to Cape Fairweather but farther offshore, mid and high level
clouds are obscuring satellite imagery of clouds near the surface.
These clouds are expected to continue to move closer to the
panhandle and then inland throughout the day. As the low moves
closer to the coast, winds across the area will start to become
more influenced by this instead of the sea breezes we have been
seeing during the day. Winds are still expected to remain light
across the panhandle with the strongest winds remaining offshore
during this time.


.LONG TERM.../Friday into next week/...The next round of rain and
wind arrive in the panhandle Friday with the rain chances lasting
into the weekend.

We`ll be watching a low tracking east through the gulf towards
Haida Gwaii. The associated front will swing north into the
panhandle. This front will likely (greater than 80% chance) bring
rain to the area, especially in the southern half. Farther north,
confidence is a little lower, so stuck with PoPS around 50 to 70%.
This is due to low confidence in how far north the front, and
organized precip, will go.

In addition to the incoming rain, wind speeds will be elevated
along the front as well. For now, went with marine wind speeds up
to 25 knots along the front in the gulf. Euro ENS and GFS ENS give
greater than 60% chance for wind speeds greater than 20 knots
along the front during this time.

As the front tracks through the inner channels, went with wind
speeds around 15 to 20 knots. This was supported by the latest
NBM, EURO ENS, GFS ENS, and EURO AIFS. Increased winds in Clarence
Strait to up to 20 to 25 knots due to EFI tables highlighting the
wind speeds in the southern inner channels.

Precip will slowly diminish through the weekend and early next
week as the front slowly falls apart, though elevated winds
remain possible.

The forecast for the 25th of June and beyond will prove to be more
optimistic, with frequent breaks between systems, and periods of
clearer skies across the panhandle.

Aloft, the previous low which was ejected E into the Canadian
Interior will be swiftly replaced by another broad area of low
pressure diving into Gulf of AK. The newest low itself isn`t all
that impressive, showing a closed circulation reaching 557
decameters in depth at 500 mb as per operational guidance. The
operational model runs are in broadly good agreement - at least
given how far out they are past initialization - on the bulk of the
associated energy with this system passing S into southern BC and
the Pacific Northwest. However, chances of showers will still linger
across much of the panhandle - associated with the remnants of an
old occluded frontal band from the previous system which the new
low dragged back across the Coast Mountains and into Alaska, and
which will bring some moisture with it despite the impact of
synoptic scale E flow over the Coast Mountains. Anticipate some
breaks in the clouds between these showers, which could result in
fog formation for some areas during the early morning hours of the
25th and the 26th. As ridging builds over the Gulf in the wake of
the (now) departing low on the 26th, expect those breaks to
become the predominant weather pattern, though some showers may
linger.

The synoptic scale pattern on the 26th - a ridge over the Gulf
bringing NW flow across the panhandle, could encourage the
development of a marine layer across the outer coastal waters
overnight. This brings with it the potential for cooler temperatures
for outer coastal communities during the daytime on the 26th and the
27th should the marine layer be able to advance though at this time
forecasting the extent of low level stratus coverage remains a
challenge. For the remainder of the panhandle, widespread warm
weather will return in force the 26th, the 27th, and potentially the
28th as diurnal heating thanks to the midnight sun takes hold. While
some showers could form with the heat of the day, am not
anticipating anything significant and think that current guidance
is overestimating chances of precip during this time frame. There
are some indications that another system will approach the
panhandle the 28th or the 29th, but this far out, operational and
ensemble guidance alike trend towards being too aggressive in
breaking down ridging, and so anticipate that this system will
likely be delayed beyond what current guidance is indicating; if
it reaches SE AK at all.

&&

.AVIATION...

Marine layer is working its way up the southern panhandle once
again this morning with IFR CIGS between 600-900ft near PAKT and
PAKW. Will see gradually improving CIGS across the southern
panhandle to general VFR flight conditions by the afternoon as
high level clouds move in overhead. For the northern panhandle,
expect predominate VFR flight conditions through today. A weak
front in the northern Gulf of Alaska will spread BKN to OVC skies
across the area with CIGS AoA 5000 ft. A stronger reinforcing low
moves into the eastern Gulf by Friday early morning, increasing
shower potential after 09z for the northern panhandle. Winds
should remain 10kts or less expect for PAGY, where sustained
winds up to 15kts will be possible after 23z.

&&

.MARINE...As high pressure moves to the east, a low will continue
to take control of the gulf. This will bring small craft
conditions to the offshore areas as winds and seas are expected to
increase. Headed into the weekend, a second low is expected to
move up from the south and west bringing more elevated winds and
seas to the area.

&&

.HYDROLOGY...Minor flooding continues along the Chilkat as warm
daytime and overnight temperatures have continued to allow for
more snow and ice melt. These conditions are expected to continue
into the start of the weekend before more clouds and cooler
temperatures will help to reduce how warm we have been getting.
Elsewhere, other river and stream basins have been responding to
the warmer temperatures by showing increased flows.

&&

.AJK WATCHES/WARNINGS/ADVISORIES...
PUBLIC...None.
MARINE...Small Craft Advisory for PKZ663-664-671-672.

&&

$$

SHORT TERM...SF
LONG TERM....GJS/GFS
AVIATION...NM

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