Petersburg, Alaska 7 Day Weather Forecast

Wx Forecast - Wx Discussion - Wx Aviation

434
FXAK67 PAJK 210535
AFDAJK

Southeast Alaska Forecast Discussion
National Weather Service Juneau AK
835 PM AKST Sat Dec 20 2025

.UPDATE...
06z Aviation update

VFR prevails across the majority of the region, with areas along
and south of Sumner Strait holding on to MVFR CIGS and -SHSN.
There is confidence in a second round of MVFR -SN snow early
Sunday morning, mainly along Prince of Wales. After 18z Sunday the
Panhandle will be VFR. Main threat continues to be LLWS for PASI
and the northern TAF sites with winds 2k ft aloft 25-40kt. Strong
cross barrier flow will likely result in mountain wave activity
for the Panhandle, especially for the Gastineau Channel near PAJN.
Winds generally 5-15kt. Stronger winds 25g40kt continue for PAGY.

&&

.PREV DISCUSSION......ISSUED AT ...

SHORT TERM...TONIGHT THROUGH MONDAY...

We are running, on average, some 25 to 35 degrees below what
would be considered normal in climatology for this time of year
across the northern parts of SE Alaska, and 10 to 20 degrees below
normal in the southern areas. Generally, the pattern suggests
undercutting most model guidance inputs a bit more, and the main
changes today was to align the temperature and dewpoint forecasts
closer to what persistence and the pattern would support (no big
changes otherwise). Combined with the wind forecast for what the
wind chill and cold weather impacts would be, this has required
some adjustments today to the Cold Weather Advisory and Extreme
Cold Warning products. In general, the greatest cold weather
impacts are expected to be tonight and again tomorrow night across
much of the northern areas and the eastern zones south to a line
from Port Alexander to Petersburg. Also, expecting the Taku wind
pattern to remain in place for downtown Juneau through Monday, and
the High Wind Warnings for that area (with wind chill impacts)
remain in place. Looking more into the Taku Wind event, strong
cross barrier flow combined with a weak critical level, will allow
for wind gusts of 65 to 75 or greater to reach the surface. We
have seen some gusts up to 50 or 60 mph today, but gust will
become more frequent Sunday morning. The strongest wind gusts are
most likely to occur Sunday afternoon into Sunday evening. This
will mainly affect downtown Juneau, South Douglas, and Thane. The
Juneau airport could see increased winds and gusts, but wind gust
at the airport will remain below 30 mph.

We are watching a weak area of low pressure about 130 miles SW of
Klawock that will rotate around the base of the larger upper
trough tonight, crossing Haida Gwaii tonight. On the north side
of that weak low, we may see a few light snow showers across the
southern-most areas of Prince of Wales Island, Ketchikan and
Metlakatla, but impacts from the snow should remain fairly minor
with any accumulations less than 1 inch. Otherwise, a mostly clear
and cold night across the central and northern areas of SE
Alaska, and this dry/cold pattern continues through Monday until
we start trending towards a bit of a pattern shift midweek (See
long term discussion below). /Garmon

LONG TERM...TUESDAY THROUGH FRIDAY...

For next week, we`ll be watching the potential for a slight shift
in the weather pattern that could bring the next round of snow to
Southeast Alaska along with some marginally warmer temps.

The long range computer models, both deterministic and ensembles,
are trying to put a low pressure center in the northern Gulf of
Alaska in the second half of next week. This would allow for the
flow to switch to a more onshore pattern, or at the very least a
weaker outflow. This would weaken the pressure gradient over area,
allowing for wind speeds to weaken a bit beginning around the
Tuesday/Wednesday time frame. If/when the low continues its journey
eastward, the pressure gradient would tighten up again, allowing for
wind speeds to pick back up for the later days of the week.

As far as snow potential, the EURO and Canadian develop a low in the
northern Gulf as early as Wednesday. Their respective ensembles
mirror this story. The outlier is the GFS. The latest deterministic
run keeps the panhandle dry until late Thursday into Friday. The GFS
ensemble average, however, develops a low Thursday with an averaged
low pressure center remaining in the gulf through the weekend.

For now, moisture amounts are hinting at if the panhandle sees any
snow later next week, it wouldn`t be too much for what is normal in
SE AK until Friday and the weekend.

The 75th percentiles for the EURO and GFS ensembles give the
panhandle less than a tenth of an inch of QPF for Wednesday through
Wednesday night, which would give around 1 to 2 inches of snow at
most. For Thursday into Thursday night, the 75th percentiles are
giving the area around a quarter to just over a half inch of QPF,
with the greater amounts in the GEFS, which would give around 3 to 7
inches of snow over 24 hours. For Friday into Friday night, the 75th
percentiles are giving the area around one to two inches of QPF,
which would give upwards of 12+ inches of snow over 24 hours. The
50th percentiles are giving the area around a half inch to one inch,
which would give around 6 to 12 inches of snow.

So what are the main takeaways off all this data? For starters, the
75th percentile is an upper bound. So the amounts mentioned above
are on the high-end for current estimates. Secondly, snow is
possible as early as Wednesday but majority of the data is pointing
to it not being much much if it does happen. Thursday could be a
wildcard day that is worth watching closely. Friday and next weekend
could be a snowy few days so that will be worth watching closely,
especially with the jump in 75th percentiles from yesterday to
today.

As far as the slightly warmer temps are concerned, there is a
warming trend but most of Southeast is still likely to be below
freezing. Tuesday`s highs will be generally in the single digits to
teens but by Friday, highs could be in the teens in the far north,
20s and 30s elsewhere. For overnight lows, Monday nights forecasted
lows are in the single digits above and below zero with warmer teens
to 20s for Friday night. So warmer but still colder-than-normal.
/Smith

AVIATION.../through Sunday afternoon/...
Mainly VFR conditions with higher winds in the channels and
aloft across the central and northern panhandle. MVFR CIGs and a
slight chance for snow for the far southern panhandle through
tonight, then becoming VFR tomorrow. LLWS was included for PASI
and the northern TAF sites with winds 2k ft aloft 25-40kt. Strong
cross barrier flow will likely result in mountain wave activity,
especially for the Gastineau Channel near PAJN. Few to sct mid to
high level clouds 4-10k ft across the north. Winds generally
5-15kt. Stronger winds 25g40kt continue for PAGY.  /Slagle

MARINE...
Inside Waters: Outflow conditions remain through the weekend, with
gale force winds from the north down Lynn Canal, Glacier Bay,
Stephens Passage, through Icy Strait, and then out of Cross Sound.
This strong east to west gradient will also allow strong breezes
to near gales coming out of the Stikine River into Sumner Strait.

Winds are once again increasing and will continue to increase into
Sunday as outflow strengthens again. This will bring back strong
gales of 40 to 47 kts into Lynn Canal and near Point Couverden.
Eldred Rock and areas around Point Couverden are already seeing
sustained winds back to 40 kts with gusts up to 50 kts. Winds
across other north to south facing channels, Chatham Strait and
Stephens Passage, and out of cross sound, will increase again to
near gales to gale force winds, 28 to 40 kts. Fully developed seas
expected down Lynn Canal and Stephens Passage continue during this
whole outflow period, with the highest seas of 14 to 16 ft.
Widespread freezing spray for many channels will continue, with
heavy freezing spray for Glacier Bay, Lynn Canal, Icy Strait, and
Stephen`s Passage in particular.

Some models are pointing at a weakening pressure gradient mid to
late week next week. This would allow for a break in outflow
conditions with diminishing winds. Behind that couple day break, the
gradient does strengthen once again. We will continue to monitor
this potential break from these strong outflow winds.

Outside: Offshore flow continues, bringing increased gap winds into
the NE Gulf Coast and stronger NE outflow winds coming out of Cross
Sound into the Gulf waters. Outflow gap winds coming off the NE Gulf
coast continue to increase to gale force to strong gales along the
outer coastline, to the east of Yakutat down to Cape Spencer. As
well as increase wind speeds, wave heights once again build to
between 10 and 16 ft Saturday evening into Sunday, with the highest
seas expected in the northern Gulf waters. Sea spray has also
developed over the NE gulf. With cold temperatures, and sea surface
temperatures below 45 degrees F, this sea spray is likely to be
freezing spray.

Outflow winds begin to diminish later Monday into the start of the
week. Then, mid to late week a more organized low pressure system
moves into the gulf once again increasing gulf winds.&&

&&

.AJK WATCHES/WARNINGS/ADVISORIES...
PUBLIC...Cold Weather Advisory until midnight AKST tonight for AKZ317-
     319>322-325>327.
     Extreme Cold Warning from midnight tonight to noon AKST Monday
     for AKZ317-319>322-325>327.
     Extreme Cold Warning until noon AKST Monday for AKZ318.
     Cold Weather Advisory until noon AKST Monday for AKZ323-328-329-
     331.
     Cold Weather Advisory until midnight AKST Sunday night for
     AKZ324.
     Extreme Cold Warning from midnight Sunday night to noon AKST
     Monday for AKZ324.
     High Wind Warning until 9 AM AKST Monday for AKZ325.
     Cold Weather Advisory from midnight tonight to noon AKST Monday
     for AKZ330-332.
MARINE...Heavy Freezing Spray Warning for PKZ011>013-031-032-053-651.
     Heavy Freezing Spray Warning for PKZ021.
     Heavy Freezing Spray Warning for PKZ021-022.
     Heavy Freezing Spray Warning for PKZ022.
     Heavy Freezing Spray Warning for PKZ033.
     Heavy Freezing Spray Warning for PKZ034.
     Heavy Freezing Spray Warning for PKZ034.
     Heavy Freezing Spray Warning for PKZ644.
     Heavy Freezing Spray Warning for PKZ671.
     Storm Warning for PKZ651.
     Gale Warning for PKZ011>013-022-031-032-053-643-644-663-664-671-
     672.
     Small Craft Advisory for PKZ021-033>035-641-642-652-661-662.

&&

$$

SHORT TERM...GARMON/BRUNSEN
LONG TERM...SMITH
AVIATION...AP
MARINE...BRUNSEN

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