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307
FXAK67 PAJK 192231
AFDAJK

Southeast Alaska Forecast Discussion
National Weather Service Juneau AK
231 PM AKDT Tue Jun 19 2018

.SHORT TERM.../Through Thursday night/ Upper high over the far SE
corner of the area will drift slowly E through Thu. A couple of
shortwave trofs will move N through the area tonight through Thu.
A weak occluded front will move NE into the central gulf by Thu.
The high pressure ridge over the eastern gulf and SE AK will
weaken slowly through Thu. Models were in decent agreement on the
main features, although they did have some important differences
with possible small low pressure areas along the front for Thu.
Ended up using a blend of the 12z GFS/NAM through 12z Thu, then
decided to leave the remainder of the period mostly as is.

For tonight and Wed morning, will have diminishing precip threat
across the N gulf early tonight as remnant of front dissipates
there. Still a lot of marine layer clouds over the gulf, and some
of these will move back onshore along the outer coast tonight.
There will also be a band of high level clouds that moves N
through the area tonight as weak shortwave moves through.
Strongest winds will be along the SE gulf and a couple inner
channel areas that will have thermally enhanced W wind. Looking at
20-25 KT winds for Cross Sound and 15-20 KT for Icy Strait to
start tonight, but those should decrease late in the night as
lower level temps cool off area wide and thermal contrast
diminishes. Over the SE gulf, 15-20 KT NW winds will occur
especially closer to the outer coast. Will be watching for a wind
shift from NW to S-SE over the far S inner channel area tonight
as a thermal low drifts N of that area and some low level ridging
moves in. Could be a 15+ Kt burst of wind as the wind shift moves
through, but this would only last for an hour or less.

For Wed afternoon and Wed night, another shortwave will move N
into the southern area, and this may spark some showers and TSTMS
over the Hyder area by early afternoon. Most of the activity will
be to their E where warmer lower level temps will be. Temps will
be somewhat cooler over the S Wed as the low level SE push
continues. The N will still be on the warm side though, with most
areas getting well into the 70s. There may be some high level
clouds that move N across the area during this time. Marine layer
clouds will hang tough over the eastern gulf, and these may affect
the central and northern outer coast especially at night.

For Thu and Thu night, looking cooler and cloudier as upper ridge
continues to move away and the low level ridge over the eastern
gulf flattens some. Also, the next weak occluded front will move
into the central gulf. There is potential for some showers to
form over the area in the afternoon and continue into the evening,
but models differ on this so POPS were kept at chance levels or
less. Could be more wind over the inner channels Thu and Thu night as
southerly gradient increases, but not expecting wind to reach SCA
levels attm.

.LONG TERM.../Friday through Tuesday/...The long term forecast
will see precip chances increasing through the weekend. Friday,
the high pressure ridge that has been in place over the eastern
gulf will weaken some as a couple upper level short-waves/surface
trough pass through from the SW. There are still differences in
timing for these and potential showers, but most models are
converging on most of Friday attm. As the trough(s) move through
some of the central inside waters will see winds shift NW to SW
for a period then likely back.

A low pressure system will approach the southern gulf from the SW
on Saturday. Models have come into better agreement on the south
track of the low, but still differ some on how quickly assoc rain
reaches the coast. At this time rain is looking most likely for
the southern panhandle later Saturday and most of Sunday. The
northern panhandle should see less rain due to offshore flow, but
will likely have a cloudy day with much cooler temperatures than
that start of the week.

The ridge in the gulf looks to re-build as the low pressure moves
east into Canada. This should help to decrease the precip threat
Monday, but models are holding on to it longer along the Coast
Mountains. Used a blend of models to help with the timing of the
troughs and low pressure system over the weekend to find a middle
ground.

&&

.AJK Watches/Warnings/Advisories...
PUBLIC...None.
MARINE...Small Craft Advisory for PKZ022.
     Small Craft Advisory due to Seas for PKZ041>043-051>053.

&&

$$

RWT/Ferrin

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