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FXAK67 PAJK 191310
AFDAJK

Southeast Alaska Forecast Discussion
National Weather Service Juneau AK
510 AM AKDT Thu Jul 19 2018

.SHORT TERM...Satellite imagery and surface analysis indicate
upper low moving E across Haida Gwaii early this morning with
ridge building over the gulf. Some clearing overnight
combined with saturated BL from recent rains has resulted in some
patchy fog development early this morning. Heaviest fog has been
in PAPG and PAWG with visibilities below 1SM. Expect fog to
dissipate by mid morning. Energy wrapping around the upper low
will maintain shower activity across the panhandle today.
Increased instability near the low along with some energy wrapping
around will increase chances of TSTM development over BC that
could migrate WWd into Misty Fjords area so added mention of SChc
TSTM this afternoon/evening. Otherwise, showers will diminish from
N-S today as the ridge influence increases across the region. As
the ridge begins to take hold NWly winds will increase. Nudged
temps towards NBM resulting in temps into the mid 60s today and
into the low to mid 70s Fri except along the outer coast. Stratus
evident over the gulf will advect E-SE into the weekend and will
likely limit warming potential along the gulf coast.

.LONG TERM.../Thursday through next Tuesday/ The main change
to the forecast resulted from a more eastward positioned ridge
axis over the eastern gulf instead of the central gulf. Perhaps
the ridge breaks into the Panhandle sometime early to mid next
week, but solutions differ, and all we can rely on is ensemble
clustering at this point. New model runs continue to suggest
frontal action becomes more organized to our west but confidence
is not high enough to go with any more than a slight chance of
rain by mid-week.

As a result of this, we continued the trend of raising
temperatures early next week, and now extend 70 degrees to the
Panhandle interior through at least Monday. We even warmed
temperatures a degree or two through the already advertised toasty
weekend.

Winds needed little change except to introduce southeasterlies
over the gulf on the west side of the ridge axis. We would not be
shocked at some point to see small craft westerlies develop at
ocean entrances should the interior heat and chilly gulf stratus
provide solid pressure gradient support. But otherwise, we expect
winds to be mainly on the lighter side.

We used an ensemble of mainline models for the gulf winds Saturday
and relied on increasing influence of WPC thereafter. No changes
to the weekend`s dry forecast and our conservative approach keeps
most of the Panhandle PoP free through most of Tuesday. Forecast
confidence is good through the weekend, and diminishes early to
mid next week.

&&

.HYDROLOGY...As of 4 AM Thursday...Suicide Basin continues to
release water into Mendenhall Lake. Webcam imagery indicates
Suicide Basin continues to drain and at 3 AM Mendenhall Lake was
at 8.39 feet and rising. Flood stage at the lake is 9.0 feet.
There is the potential for flooding to begin by late Thursday
morning, and it is expected to reach a near record peak stage of
around 12 feet Thursday night into early Friday morning. Water
levels should fall rapidly after it crests. However, there is
uncertainty in the initial glacial lake volume, which may result
in varying crest height and timing.

Once the lake stage reaches 9.1 feet, water will cover West
Glacier Spur Road between Skater`s Cabin and the West Glacier
Trailhead. Also, water will flow into the Mendenhall Lake
campground. Once the lake stage reaches 10.9 feet, View Drive will
be flooded and impassible with significant flooding to some homes
in the area.

&&

.AJK Watches/Warnings/Advisories...
PUBLIC...Flood Watch from this afternoon through Friday afternoon for
     AKZ025.
MARINE...Small Craft Advisory for PKZ041.

&&

$$

BC/JWA

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