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FXAK67 PAJK 081917 CCA
AFDAJK

Southeast Alaska Forecast Discussion...UPDATED
National Weather Service Juneau AK
1004 AM AKDT Tue Jul 8 2025

.UPDATE...For the aviation and marine late morning updates.

&&

.AVIATION UPDATE...Still seeing periods of IFR for the central
1/3rd of the Alaska Panhandle this morning where shower and
heavier rain activity closer to the mid/upper level cool pool near
the upper low is situated. We are expecting CIGS and VSBYS to
gradually improve mid to late afternoon as this low shifts east
into British Columbia and the Yukon Territory. Otherwise, expect
some patchy fog and low ceilings tonight but confidence on
IFR/LIFR VSBYS not great...just something to watch for in the 00Z
TAF issuance later today as we analyze what the boundary layer
will look like overnight. /Garmon

.MARINE UPDATE...We did a quick update to bring winds up in Lynn
Canal as well as Stephens Passage where a bit tighter gradient
still exists. Elsewhere forecast seemingly on track. /Garmon

&&

.PREV DISCUSSION...ISSUED AT 539 AM AKDT Tue Jul 8 2025...

SHORT TERM...Numerous showers across the panhandle this morning
with highly variable conditions and rainfall rates. Current radar
imagery outside of Sitka paints this picture well. Most of the
showers across the region appear to be driven by a mid to upper
level low that is over the central panhandle. There is a surface
trough related to this low, but that is over the northern inner
channels and is more of a weakness in the pressure pattern with
light and variable winds under it, for now (see marine section for
more on winds).

Both the surface trough and mid-level low will track eastward
into Canada over the next 12hrs followed by building high
pressure. Before it fully moves out of our area, bands of
vorticity wrapping around the back side of the low are likely to
still cause showers over the portions of the area through the
night but in decreasing spread and strength.

Some sunny breaks are expected today, particularly Yakutat this
morning and elsewhere as showers move out through the afternoon.
Juneau and areas along the Coast Mountains will hold onto showers
and clouds the longest, keeping temperatures from climbing out of
the 50s. Places that do get a sunny break will easily hit 60, but
not too much warmer as the mid-level low brought in a cool
airmass.

LONG TERM...
Key messages:
- A surface ridge allows for a decrease in precipitation Wednesday
  before the next system.
- Another low in the gulf brings moderate to heavy rain toward the
  entire panhandle Thursday into Friday.
- Gale force winds along the NE coast and near Dixon Entrance.

Details: The main impact in the long term forecast remains
focused on the plume of moisture over the panhandle Thursday into
Friday. Ahead of this system, a ridge over the gulf will make for
a slight break in rain. Rain will begin to diminish Tuesday night
into Wednesday. During this time, onshore flow will continue
allowing for short times of light showers. Through Wednesday
afternoon into evening, breaks in the clouds will allow for
additional heating. These breaks of broken to scattered clouds
will mainly occur over the central to southern panhandle.

Early Thursday, a low moves into the western gulf that will send
a warm front toward the panhandle. This low, with the help of an
upper level jet, will also send a plume of increased moisture
toward the panhandle. This plume of moisture will bring widespread
precipitation with times of heavy rain. Confidence in this system
has continued to increase with a rise in IVT values and with more
indications from the Extreme Forecast Index (EFI) tables.
Multiple ensembles are now showing the likelihood of >500 kg/m/s
of integrated water vapor transport moving over the panhandle.
Moderate to heavy rain rates will be occur throughout the
panhandle, with the heaviest rates focused on the southern
panhandle. For most of the southern panhandle, including
Ketchikan, the NBM is indicating a 75% chance of >0.5 inches of
rain in just 6 hrs. Near Port Alexander, there is currently a 45%
chance of >0.75 inches in 6 hours. Overall, in 24 hours, areas
across he panhandle will receive 1 to 2 inches of rain, with
southern Baranof Island and higher elevations receiving up to 3
inches. Currently, no flooding impacts are expected, but increased
snow levels with heavy rain rates can lead to rises in rivers and
creeks to bank full.

This low will also bring gale force winds of 35 to 40 kts toward
the NE gulf with the strongest winds near Kayak Island. Other
areas will see increased winds to strong breezes of 25 to 30 kts
along the outside marine waters. Inner channels winds increase up
to 30 kts with the strongest at ocean entrances and in Clarence
Strait near Dixon Entrance. Land areas in the southern panhandle
will experience wind gusts around 35 to 40 mph, and areas near
Yakutat look to reach gusts up to 30 to 35 mph.

That being said, the active weather continues for SE AK into next
weekend as onshore flow with a few embedded shortwaves keep the
panhandle damp. Stay tuned as we will continue to update the
forecast ahead of this system.

AVIATION...
Wide range of variable flight conditions from IFR up to VFR
across SEAK this morning as a surface trough and mid/upper lvl low
push into the panhandle.

Variable flight conditions and rain showers will continue through
mid morning, with showers becoming more isolated and widespread
improvement to upper-end MVFR to VFR flight conditions prevailing
by 00z this afternoon. By 00z, CIGS raise to AoA 2500ft and visbys
4 to P6SM with likely vsby drops back down to IFR within any
heavier showers impacting TAF sites. Winds should remain around
10kts or less with an isolated gust up to 20kts possible. Windiest
conditions through Tuesday afternoon expected at Skagway, with
sustained winds up to 20kts and gusts up to 30kts. LLWs not a
major concern, but will see broad westerlies develop aloft and
continue through the TAF period, keeping mountain waves across
inner channels in play.

Looking to Tuesday night, expecting flight conditions to
deteriorate once more to MVFR or worse by 09z as surface ridging
pushes over the panhandle, trapping residual surface moisture with
likely lowered CIGS AoB 2500ft and impacted visbys by Wednesday
morning.

MARINE...
Inside waters: As a surface trough over the northern inner
channels shifts off to the east today, high pressure will build in
from the south. This will cause increasing southerly winds, which
have already hit the Midway Island area of Stephen`s Passage and
Point Couverden earlier this morning. The ridge will be quite flat
for the next 24hrs, leading to a general W wind, which means some
of the N-S passage wind directions will want to kink either NW or
SW, or just be variable <10kt. The ridge looks to sharpen over
the eastern gulf on Wednesday, causing NWLY winds to be preferred
on the lee side of the ridge axis (Clarence Strait). Sunny breaks
will enhance sea breeze winds in the afternoon and early evening
both Tuesday and Wednesday.

Outside waters: Generally west winds of around 15 kt and some
higher gusts in showers. Seas remain on the low end with gulf
buoys reporting 4ft combined seas and a S swell with a 15 second
period. Expect seas of 4-6ft to persist until a stronger front
approaches late Wednesday night and winds increase to gale force
(+35kt) by Thursday morning.

&&

.AJK WATCHES/WARNINGS/ADVISORIES...
PUBLIC...None.
MARINE...None.

&&

$$

UPDATE...Garmon
SHORT TERM...Ferrin
LONG TERM....EAB
AVIATION...NM
MARINE...Ferrin

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