Area Forecast Discussion
Issued by NWS Juneau, AK

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FXAK67 PAJK 301333
AFDAJK

Southeast Alaska Forecast Discussion
National Weather Service Juneau AK
533 AM AKDT Fri Jul 30 2021

.SHORT TERM.../Friday and Saturday/ Little to no changes made to
the short term forecast as a quiet summertime pattern continues
for Southeast Alaska. High pressure remains over the gulf while an
inverted trough builds over the Panhandle. With 850mb temps
significantly warming to +10 to +15C, expect highs to
progressively get warmer each day. Nudged temperatures into the
mid to upper 70s today and tomorrow, slightly above MOS as highs
have been exceeding model guidance each day this week. It is not
out of the question a few spots could reach the 80 degree mark as
north winds develop at the surface and east southeast flow sets up
aloft leading to downsloping off the higher terrain.

Winds will remain of minimal impact through the period with
little forcing and a weak pressure gradient in place. Afternoon
sea breezes will develop once again this afternoon and evening
with the strongest winds to 15 kt expected around Cross Sound and
Icy Strait, Northern Lynn Canal, and Taiya Inlet.

Only forecast concern is the potential for isolated thunderstorm
development Friday and Saturday afternoon. Southeast flow
increases ahead of an approaching surface low from the south
Friday into Saturday. Aloft, a 50 kt mid level jet streak pushes
into the Southern Panhandle placing the area within the right exit
region of strongest winds. Typically this is an unfavorable area
for precipitation development as the right exit region of the jet
is characterized by upper level convergence and sinking air. This
feature along with a building upper ridge out of the SE will work
to suppress widespread convection Friday and Saturday. However,
due to a hot, unstable airmass at the surface and increasing
moisture flowing northward, there is a slight chance for showers
and thunderstorms during the peak heating of the afternoon Friday
and Saturday. Orographic lifting will be the main lifting
mechanism for storms so expect the higher terrain of the Southern
Panhandle to have the best chance at seeing a storm. CAPE values
500+ j/kg, LIs -1 to -4, 0-6km bulk shear around 35 kt, and dew
points rising into the upper 50s to lower 60s will create
favorable conditions for thunderstorm development. Not expecting
widespread thunderstorm activity; however, there is a possibility
for a thunderstorm or two across a broad swath of the southern and
central panhandle which could produce a few lighting strikes and
brief periods of rain and gusty winds. This being said, most areas
across SE will remain dry.

.LONG TERM.../Sunday through Thursday as of 10 pm Thursday/ Aloft
an upper ridge provides a blocking pattern upstream of SEAK. In
the Gulf, an upper low remains locked in place through mid next
week. The low then becomes displaced to the SE as ridging builds
into the Gulf. At the surface, a low will be stationed SW of the
panhandle with a ridge building into the W Gulf Sunday. The low
will weaken as it becomes cut off by the building ridge. Light
ridging will persist through Monday allowing for drier conditions
and partly cloudy skies. By mid week, guidance supports the ridge
shifting E and lower heights moving into the area. Guidance also
is trying to resolve an easterly wave developing across the
central and northern panhandle mid week as well as a surface low
along the SE gulf coast. These features prompted an increase in
precipitation chances for mid week where rain could be moderate to
locally heavy at times. By the end of next week, the same surface
low looks to remain in the SE gulf where it brings multiple waves
of energy north into the southern panhandle with a drying trend
across the north.

Temperatures will be on the cool down after a period of above
normal temperatures through Sunday. By Monday, temperatures
return to near normal as cloud cover and rain chances increase
through mid week. By the end of the period, a slight warm up with
temperatures climbing back into the 70s is possible as a ridging
pattern sets back up.

&&

.AJK WATCHES/WARNINGS/ADVISORIES...
PUBLIC...Dense Fog Advisory until 10 AM AKDT this morning for AKZ027.
MARINE...None.

&&

$$

CM/CC

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