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FXAK67 PAJK 301807 AAA
AFDAJK

Southeast Alaska Forecast Discussion...UPDATED
National Weather Service Juneau AK
1007 AM AKDT Mon Jun 30 2025

.UPDATE...For aviation 18Z product release and for hydrology
section for Taku River Glacier Lake Dam Outburst Flood release.

&&

.Aviation Update...Low pressure centered about 100 nm west of
Haida Guaii is moving north and weakening today. To the east of
the low the occlusion/warm front is also making slow progress
north across the central Alaska Panhandle today with heaviest
rains and lowest ceilings from Sitka to Petersburg. The rains will
work their way north today into the Gustavus and Juneau areas but
are expected to diminish as the front moves north toward Haines
and Sitka. For the southern Panhandle we expect mostly low
ceilings to IFR through late today into tonight however with
heavier rains diminishing. Elsewhere mostly IFR through tonight
into Tuesday morning with light rain and low ceilings, except for
Yakutat where we bring in MVFR toward 09Z.

&&

.Hydrology Update...Observations indicate Lake No Lake that drains
into the Taku River is releasing off the glacier this morning. We
have issued a Special Weather Statement highlighting main impacts
expected with this...mainly just below minor flood stage with
debris in the water being the main impact to expect. Crest on the
Taku is expected late tomorrow morning.

&&

.Previous Discussion...Issued at 636 AM AKDT Mon Jun 30 2025...

.SHORT TERM.../Through Monday Night/...Although there`s still some
relative uncertainty about the exact path of Monday`s weather
system, whether the surface low will stay offshore near Sitka or
move inland before dissipating, the overall outcome remains the
same. A warm front bringing precipitation will move through the
Panhandle on Monday, delivering moderate to heavy rain from the
southern Panhandle up to around Petersburg.

An upper-level shortwave will enhance lift due to divergence ahead
of the wave and vorticity advection along the trough. Combined
with strong warm air advection near 850 mb, this will increase
upward motion through Monday morning. The upper-level trough is
expected to reach northern Lynn Canal by the afternoon, but
mountain-induced shearing in the Inner Channels will keep low-
level advection limited to the southern Panhandle.

As a result, areas like Ketchikan, Metlakatla, and southern Prince of
Wales Island may see rainfall rates of 0.15 to 0.20 inches per
hour. Flooding is not expected due to the fast-moving nature of
the heaviest rainfall, though brief periods of reduced visibility
from heavy rain are possible.

Earlier concerns about gusty winds following the warm front, due
to dry air at 700-500 mb, have eased. Cold air advection appears
to be separate from the dry air, which reduces lapse rates and
available instability (CAPE). As a result, gusty winds are no
longer anticipated, since there are no strong forcing mechanisms
in place.

.LONG TERM...

Continued colder than normal temperatures, widespread overcast cloud
cover, and precipitation look to continue for the panhandle
through Tuesday, though more breaks in the cloud deck and less
rain could be in store for the latter half of the week, including
the Fourth of July. A cold upper level low will remain stationary
through July 3rd, before being ejected E into British Columbia,
only to be swiftly replaced by another cold upper level low moving
in from the W. While there is fairly solid confidence in the
larger synoptic scale pattern over the state during this timeframe
as a result, the same cannot be said for smaller scale details. In
particular, the various upper level troughs moving around the
first 500 mb low, have much less confidence on timing, strength,
and placement, as does the potential for a weak ridge in the lower
levels to try and build in during the latter half of the week.
What is known into next week is chances for rain will broadly
remain in the forecast, though the potential for fewer showers
July 3rd through the end of the week will exist.

Highest confidence is in the Monday/Tuesday system. A low will
stall and decay into an open trough off the coast of the AK
through the day on Tuesday before the remnants meander into the
panhandle and disintegrate entirely on Wednesday. During this
time, expect wave of showers to rotate around the decaying low,
moving into the panhandle and delivering rounds of rainfall to
much of the area. By Tuesday night, shower coverage will be
diminishing as the remnant trough continues to weaken.

Beyond Tuesday, confidence rapidly diminishes, but what can be
said is that cloud cover will linger and chances of rain showers
will continue, albeit diminished from what was previously
anticipated. Operational guidance indicates the potential for an
easterly wave moving across the northern half of the panhandle on
Wednesday. Alongside the easterly wave, chances for showers will
linger through the latter half of the week, but in the lull
between the former upper level low (which will be ejected
Wednesday), and the arrival of the next upper level low,
confidence has begun to grow that weak low level ridging will
attempt to build in. Should this ridging be sufficiently strong,
shower coverage will diminish across the area, and some
occasional breaks (and marginally warmer weather) are possible
Wednesday through the end of the week.

&&

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

&&

$$

SHORT TERM...99
LONG TERM....99

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