370
FXAK67 PAJK 181619 AAA
AFDAJK

Southeast Alaska Forecast Discussion...UPDATED
National Weather Service Juneau AK
819 AM AKDT Tue Jun 18 2024

.UPDATE...Just shipped new grids and marine forecasts for fog
along the outer coast from near Yakutat southward along Cross
Sound and to just offshore of Sitka. Visibilities in some areas
are 1/4sm as the Cross Sound FAA Webcam shows. Fog is more patchy
out past 20 miles offshore. Expect the fog to lift somewhat by
mid afternoon before ceilings lower again tonight in the same
areas. W ebcams over the inner channels of SE Alaska show mostly
a low cloud deck around 2500 ft above ground level at several
places with breaks in the cloudcover noted southern Lynn Canal
south through Stephens Passage to Frederick sound and the
Petersburg area.

05/JG

&&

.&&

.PREV DISCUSSION......ISSUED AT 446 AM AKDT TUE JUN 18 2024

.SHORT TERM...High pressure remains over the gulf this morning
allowing for the associated marine layer to expand in coverage
from yesterday morning. This marine layer will continue to persist
and allow for cooler temperatures compared to locations not
affected by the clouds. Some areas will see the marine layer break
up during the daytime hours before the coverage returns during the
overnight hours. Temperatures today look to be a rinse and repeat
of yesterday across the panhandle. With observed temperatures
yesterday not nearly as warm as what was forecasted for the same
time frame, went ahead and lowered todays highs to reflect this
outcome. Cloud cover was also expanded to reflect the increase in
marine layer clouds during the overnight and morning hours across
the panhandle. Overall though, summer will continue to persist for
the panhandle with warm temperatures, afternoon sea breezes, and
little to no rain in the short term forecast.

LONG TERM...Summer continues across SE Alaska through the first
half of the week, though more active weather is on the horizon.
Get out and enjoy it while you can.

A ridge will continue to hover over SE AK through Wednesday, with
the axis slowly moving E over the Gulf and across the area. Dry,
with afternoon sea breezes in the inner channels is the main theme
over the next few days. By Thursday, a weak wave will attempt to
advance through the ridge, bringing with it chances of rain,
though operational guidance is likely overemphasizing PoP chances
with this system. Anticipate fairly minimal QPF totals and wind
impacts, if the system isn`t largely eroded away by the ridge
itself. By the end of the week, an extension of a closed low over
the Aleutians attempts to form into a longwave trough and move
into the Gulf, bringing some onshore flow, cooler temperatures,
and increasing PoPs through the weekend. Think that there is a
good chance that much of the energy will move S of the panhandle,
but still anticipate at least some chances of rain for the area.
Afterwards, some clearing is increasingly likely for the latter
half of Sunday or Monday, though this is not set in stone, with
the GEPS being more pessimistic.

Threats to coastal and gulf waters remain low through Thursday,
with our swells significant deep ocean wave heights remaining
largely under 8ft. With that said, stout 15 to 20 knot northwest
winds along the coast will bring short period wind driven waves to
the west coast of Prince of Wales and into Dixon Entrance.

AVIATION...Marine layer low clouds continue their daily dance in
and out of the inner channels. Lowest conditions this morning are
along the outer coast and in Clarence Strait where ceilings have
dropped to around 900 to 1500 feet. No fog below the cloud deck
has been reported though. These lower conditions have gotten as
far inland as Angoon, Hoonah, Gustavus, and Ketchikan overnight.
Areas farther north and east have seen some clouds but they have
all been above 4000 feet. Expect the low clouds to retreat again
today with all, but the outer coast, Cross Sound, Western Icy
Strait, and possibly Gustavus, becoming VFR by late afternoon. The
clouds will then invade again tonight with a similar area seeing
lower ceilings late, though the area covered could be somewhat
larger then tonight.

MARINE...Marine layer continues to persist over the Inner
channels and outer gulf coast as high pressure remains over the
gulf. The extent of the clouds this morning is greater than
yesterday morning but many areas still remain cloud free. This
trend is expected to continue until the high pressure over the
gulf shifts to the east allowing for a low to move into the
western gulf. Otherwise, diurnal sea breezes are expected to
continue during the daytime hours for locations not affected by
the marine layer.

HYDROLOGY...The Flood advisory for the Chilkat River continues
due to snowmelt from warm temperatures. Flooding conditions are
expected to continue with warmer temperatures persisting across
the Chilkat Valley. Temperatures are expected to decrease by late
week as more clouds return to the area limiting daytime highs.
This should allow for flows on the river to decrease. Otherwise,,
the river is expected to continue to show a diurnal trend in
response to temperatures.

&&

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

&&

$$

Visit us at http://www.weather.gov/Juneau