769
FXAK67 PAJK 162353
AFDAJK

Southeast Alaska Forecast Discussion
National Weather Service Juneau AK
353 PM AKDT Tue Jul 16 2024

.SHORT TERM.../Through wed night/ Active short range period today
as a new moderate atmospheric river takes aim at the central and
northern panhandle starting tonight and lasting into Wednesday.
Rainfall totals look to range from around 1.5 to 3 inches with
higher totals in isolated and high elevation areas over a 24 hour
period. Area of highest confidence for moderate to heavy rainfall
is from around Gustavus and Hoonah eastward to Petersburg. Some
uncertainly on where the eastern and western edges of the heavy
rainfall will be, especially the western edge. General trends over
the last 24 hours have edged the rainfall slightly further west
then where they were depicted yesterday which put Hoonah and
Gustavus right on the western edge. The eastern edge is
complicated by the eastward movement of the moisture plume
Wednesday into Wed night which will spread at least a brief period
of rain across the southern panhandle Wed night which could drop
up to 1 to 1.5 inches of rainfall there. The moisture plume is
then expected to be exiting the panhandle by late Wed night. The
target for the highest rainfall is the Juneau area.

Wind wise, expect elevated winds for most of the inner channels
starting tonight and lasting into Wed. Most inner channels will
likely see a brief period of 25 kt small craft wind conditions at
some point through Wed afternoon. Highest winds will likely be
late tonight for the south and Wed morning/mid day for the central
and northern panhandle. Northern Lynn and Skagway winds will last
the longest possibly lasting into late Wednesday night before
diminishing.

.LONG TERM.../Thursday through Tuesday/...
Overview: A relatively quite weather period is likely for SE AK. A
number of breaks are in the mid to long range, not exactly dry but
not the intense rainfall and stronger winds we have been seeing.

Mid level low with trough extended into the AK Gulf moves eastward
then drops to the south into the weekend. As part of a blocking
pattern, to the west a ridge then another low, this mid level
pattern will shift in position somewhat by likely not change until
late next week. For Thursday remnants of the Wednesday front will be
over the southern region keeping rain going. Points north of
Frederick Sound not have higher chances of rain breaks that day.
With the 500 mb low in place flow pattern will move a low extending
from a deeper system over the far SW Gulf northward into the SE Gulf
by Friday. For now winds around the low expected to be in the 20 kt
range with lighter winds to the north. Light to moderate rainfall
amounts move in with the system with most models keeping precip over
the south with diminishing rates as the low moves northward. GFS
tracks furthest north with highest winds and pop. By late Saturday
this low will have dissipated, but the main low remains in place
into next week and thus can keep pushing precip bands over the
panhandle. The southerly flow and weather breaks will let day time
highs pick back up into the upper 60s to low 70s. With the run to
run inconsistencies seen that past few days not fully jumping on any
one solution so overall keeping with SE AK climatology: mostly
cloudy chance of rain.

&&

.AVIATION.../Until 00Z Thursday/...Generally expect continued
lowering of CIGs and VSBYs into the MVFR / IFR category range
into Wednesday morning as the next frontal system moves through
the Alaskan Panhandle region. Those conditions will begin to
improve toward Wednesday afternoon. SFC winds may become a bit
gusty as the front pushes through from this evening into the
morning over some locations. LLWS values of up to around
magnitudes of 30 to 40 knots are possible out of a southeasterly
direction along with the passage of that front, as well.

&&

MARINE...Highest winds and seas in the marine areas will be
mainly confined to the extreme SE Gulf waters and across most of
the inner channels Tonight into Wednesday. Highest expected winds
will top out at 25 to 30 kt small craft criteria winds especially
in Clarence Strait. Seas will top out at 10 ft late tonight for
the extreme SE gulf waters. Inner channel seas will likely be
around 5 to 6 ft at the highest with higher seas in areas of long
fetch.

&&

.HYDROLOGY...Rivers and streams are running high with Auke Lake in
Juneau still hovering around minor flood stage and the Chilkat
River still over minor flood stage from the previous event. The
forecasted rain amounts of 1.5 to 3 inches for the area from
Tuesday night through late Wednesday afternoon and the saturated
soils will cause rivers and streams to rise rapidly. There is good
ensemble agreement on this heavy rain event with 50 to 70% chance
the area will see the forecasted rain amounts and these values
are very anomalous for this time of year. With that said there are
flood advisories out for the Chilkat River area, Taiya River area
and the Mendenhall valley area for minor flooding through
Thursday morning. Flooding is expected to develop through
Wednesday afternoon and persist into the evening time frame. A
flood watch is still in affect for the full Juneau borough as
other non gauge rivers/streams that may flow out of their banks.
For other areas outside of the flood advisories, there is a
special weather statement out for significant river rises but not
flood is expected for those areas. Some of the large rivers may
stay above flood stage longer due to the lag in draining all the
rainfall runoff and melted ice.



&&

.AJK WATCHES/WARNINGS/ADVISORIES...
PUBLIC...Flood Watch from 7 PM AKDT this evening through late Wednesday
     night for AKZ325.
MARINE...Small Craft Advisory for PKZ011>013-021-022-031>036-641-642-644-
     661-662.

&&

$$

SHORT TERM...EAL
LONG TERM....PRB
AVIATION...JLC

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