842
FXAK67 PAJK 121401
AFDAJK

Southeast Alaska Forecast Discussion
National Weather Service Juneau AK
601 AM AKDT Wed Aug 12 2026

.SYNOPSIS...

Key Messages:

- Suicide Basin is releasing. Major flood stage on Mendenhall Lake
  and River expected to be reached Wednesday night.

- Warming trend for the week with highs in the 70s. Lower 80s
  will be possible, especially across interior locations across
  the south and far northern interior for mid to late week.

- The warm and dry conditions will bring elevated threat for fire
  starts across much of SE AK. A few small fires have been
  observed already over the past week.

&&

.SHORT TERM...Ridge of high pressure will build over the Gulf
through today, lingering through the rest of the week to the west of
the panhandle. Warm temperatures and dry weather is expected to
continue across the panhandle today through the end of the week,
with the warmest temperatures expected Thursday and Friday after the
ridging strengthens over the Gulf as westerly flow transitions to a
northwesterly offshore flow. Some marine layer clouds will still
develop in the Gulf with this ridge placement, however any low
stratus clouds are expected to stay just offshore and along the
outer coast.

The majority of the panhandle will see clearing skies
with the offshore flow, and by the end of the week most of the
panhandle is expected to see warmer temperatures with highs reaching
mid to high 70s Thursday and Friday. Inland areas along the Klondike
and Haines Highways may see high temperatures in the high 70s to low
80s through the end of the week with these clear skies. The southern
panhandle is also expected to see temperatures reach near 80 into
the low 80s Thursday and Friday, with areas further from the water
having potential to see daytime highs in the mid 80s.

There still is potential for some convective activity in the SE
corner of the panhandle Thursday and Friday afternoon/evening, with
the instability present and overall setup suggesting a very low
chance for easterly thunderstorms moving into the area. The moisture
still is not ideal however, and any development is likely to be
isolated over the SE panhandle and along the coastal range. Some
model guidance shows 60-70% RH at the low/mid levels with a bit of
westerly component to lower level winds to bring moisture into the
area, but confidence is still lacking as to if these ingredients
align for thunderstorm development.

.LONG TERM...Primary focus continues to be on warm/dry through the
end of the week along with the uncertainty of equatorial
tropical storms and subsequent moisture transport into the N/Pac.
Starting off, for the end of the week clusters still show strong
agreement in a ridge dominating the western seaboard, limiting
major surface lows from moving into the Gulf and serving as the
source for abnormally warm temperatures aloft. LREF 850mb
temperature histograms have shifted to more normal distribution,
translating to increased confidence for 12C to 14C at 5000ft by
Thur/Fri. For folks at sea level, this means warm temperatures,
with afternoon highs likely in the mid-70s to mid-80s, depending
on where you are in the Panhandle. Thunderstorms might make an
appearance Thur/Fri across the central and southern area; however,
this will ultimately depend on where the ridge axis sets up and a
shortwave moving down from Canada along the coast range,
something to watch.

Moving through the weekend guidance breaks down the ridge
suggesting cooler temperatures and some moisture; however,
guidance continues to break down the ridge too soon. Thinking we
hold on to warmer temperatures into Saturday, with cooler
temperatures and moisture arriving by late Sunday and/or start of
next week. With that said, there are a variety of outcomes in
various ensemble system solutions; current forecast Monday
afternoon sticks with troughing setting up in the Gulf and an
increase in clouds and light rain.

For the maritime environment, anticipate northwest winds to
continue along the coast, with daily sea breezes moving through
the inside, peak afternoon speeds likely moderate to fresh
breezes. By Sunday/Monday northwest winds along the coast give way
to southerlies as a series of lows moves into the Gulf. Will need
to watch for the potential for fresh to strong breezes along the
northern coast.

&&

.AVIATION...Main aviation issues today remain where low cloud
cover is and is not. This morning the low cloud are along the
outer coast from around Sitka northwestward and expanding inland
to eastern Icy Strait and Peril Strait with ceilings down to 1400
ft. The channels of western Prince of Wales also has areas of
fog/low clouds with klawock seeing vis down to 3/4 mile and
ceilings down to 200 ft. Everywhere else in the panhandle is
seeing VFR conditions this morning with light winds. Today the low
clouds and any fog are expected to diminish this morning with VFR
conditions becoming more widespread. Yakutat and Cross Sound might
be the only exceptions with cloud ceilings down to 2000 ft
persisting for a good part of the day possibly. Highest winds will
be with afternoon sea breezes that will likely reach 15 to
possibly 20 kt at most this afternoon and evening. Into tonight,
offshore flow will be increasing so low clouds (down to IFR or
MVFR) may just be relegated to the outer coast from Baranof
Island northward (with some possibly around Craig and Klawock)
with other areas remaining VFR.

&&

.MARINE...
Outside: Marine forecast remains on track. High pressure over the
Gulf will strengthen and shift eastward, tightening the gradient
over the eastern Gulf. Gentle to moderate northwest breezes will
become fresh for the outer coastal waters from near Cape Spencer
down to Dixon Entrance. Wave heights of 3 to 4 ft will increase
to 4 to 6 ft by midweek and remain through the end of the week.
Winds will diminish by the weekend as the high weakens. Main
marine concern for outer and coastal waters will be nightly return
of marine layer, with fog and low stratus impacting visibility.

Inside: High pressure out in the Gulf is expected to linger
through the week, with light to gentle W/NW-ly winds overnight
shifting to a NW-ly moderate to fresh breeze for the inner
channels by this afternoon. Localized wind shifts due to sea
breezes are possible, alongside elevated gusts to 15-20 kt, but
overall wind direction is expected to be from the NW. Strongest
inner channel winds up to 15 to 20 kts are expected for the
afternoon and evening hours. Winds across the inner channels will
also diminish Thursday and Friday as the ridge begins weakening,
however N-ly winds of 15 to 20 kt are expected for northern Lynn
Canal from a tightened N-S gradient remaining across the northern
panhandle the end of the week.

&&

.FIRE WEATHER...High pressure continues to sit over the area with
no real signal of a pattern change likely until the upcoming
weekend. With the persistent dry weather, we have started to see
temperatures rise into the 70s with some pockets of 80s for the
inland areas with warm temperatures expected to continue through
the week. Looking at the past few days, relative humidities have
fallen down to the 30s to 40s for some areas during the daytime
hours with rebounding during the overnight hours into the 90s.
With the continued lack of rain, fine fuels such as grasses will
continue to dry. Models continue to suggest the potential for
isolated thunderstorms along the Panhandle border with Canada as
well as the SE panhandle on Thursday and Friday. However, due to
the lack of low/mid level moisture the chance of thunderstorms is
only around 15% or less.

Overall, expecting the dry and warm trend to continue through the
week with fire weather conditions continuing to develop, the main
variable to watch for will be daytime winds. As of now, expecting
the worst fire weather conditions to be Thursday and Friday
afternoon, however given the persistent pattern can`t rule out
this extending further into the weekend.

&&

.HYDROLOGY.../Flood Warning in Effect/

Mendenhall Lake gauge levels, along with USGS imagery from
Suicide Basin and water levels within the basin, indicate that
a glacial lake outburst flood is ongoing into Mendenhall Lake and
River.

As of 5am AKDT, the Mendenhall River is at 5.2 ft and rising. It
usually takes around 2 days from when the basin release starts to
when you see the highest water levels. Water levels on the
Mendenhall Lake and River will rise through Wednesday as the
release continues, with a forecast crest between 16.1 to 16.6 feet
expected early Thursday morning. Compared to previous years this
is slightly below last year`s high water mark, and above the high
water marks of 2023 and 2024.

Visit weather.gov/ajk/SuicideBasin for the latest updates on the
Glacial Lake Outburst Flood for Mendenhall Lake and River. The
weather.gov/ajk/SuicideBasin web page is currently updated every
two hours by the NWS Juneau office and as we move further into the
event, this cadence will increase to hourly updates.

&&

.AJK WATCHES/WARNINGS/ADVISORIES...
PUBLIC...Heat Advisory from noon today to 7 PM AKDT Thursday for AKZ318-
     319.
     Heat Advisory from noon Thursday to 7 PM AKDT Friday for AKZ328-
     330>332.
MARINE...None.

&&

$$

SHORT TERM...Contino
LONG TERM...BAS
AVIATION...EAL
MARINE...Contino
HYDROLOGY...NM

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