FXAK67 PAJK 172350
Southeast Alaska Forecast Discussion
National Weather Service Juneau AK
250 PM AKST Wed Jan 17 2018
.SHORT TERM...Sunny skies shine high above northern communities
while a few bands of light rain have marched northward into the
far southern Panhandle. Meanwhile, large portions of the south-
central Panhandle have little complaints about milky white high
cirrus clouds thickening through the afternoon. The band of light
rain will weaken as it moves northward and perhaps may yield the
possibility of light snow mixed in above Angoon.
The main gale force low well to the south will track northward to
around Haida Gwaii by Friday and weaken as it does so. Thus,
persistent and strong northeast gales over the southeast gulf will
marginally weaken in time during the next couple of days. We must
mention that there is no perfect consensus with the speed and
eventual evolution of the low. The ECMWF pushes north quite a bit
faster and perhaps threatens our dry forecast. This will be
watched. To hedge, we have added a slight chance of rain and/or
rain/snow across the far south on Friday.
The main forecasting issue this afternoon and this evening
continues to be a very decent critical level headed north across
the central Panhandle and perhaps inciting some gusty winds in the
vicinity of Downtown Juneau. At most, we are now looking at gusts
to 40 mph persisting in the evening. But confidence is not great.
And while increasing, the breezes have not been impressive.
Across the south, winds have been gusty in areas that
traditionally are more exposed to outflow winds like Klawock,
Sumner Strait, and Metlakatla. In Metlakatla's case, the period
through Thursday night may be breezy throughout. As the low pulls
north, it will weaken and gradients relax across the Panhandle
Friday, leading to lighter winds region-wide with the exception
of Skagway and potentially Lynn Canal where north winds will
Forecast confidence is good through Thursday with falling
confidence particularly for the southern half on Friday. But no
significant impacts are expected.
.LONG TERM.../Friday through Wednesday as of 10 pm Tuesday/
Models coming into better agreement on the larger scale flow
pattern over the high latitudes. Upper ridge will build over the
Bering Sea Fri-Sun. This will cause an upper trof to dig S into
the W gulf during this time. Still some model differences on what
the upper trof does after Sun, with main issue whether it shifts E
or more to the SW. Still some model differences on what
interactions the upper trof will have with southern stream systems
moving E across the NPAC. This interaction will be the big driver
of weather for early to middle of next week over the area.
Still looking like a cool down is in store for the area during the
first half of the long range, but the stream interaction issue for
latter half of the period will determine how much area might warm
back up. If more southern stream energy is lifted N into the area,
it would allow for a stronger warm up. The initial cool down will
likely take temps to near or slightly below normal. The cool down
should be accompanied by increasing outflow winds as well, but
given lack of a strong sfc high to the N of the area, probably
will not see more than gales with the outflow.
Looking like a generally drier period for the first half of the
long range, although this will depend on where a low near Haida
Gwaii moves during this time. Models have been all over the place
on it, from kicking it E toward SW BC or lifting remnant of system
more to the N and NW as another system tries to undercut it. For
now, staying with drier idea until a better signal on what that
low will do shows up. Later on, upper trof over the gulf will
likely send some showers across the gulf, and southern stream
systems will have their own precip field moving across the NPAC.
If upper trof shifts E, area will see increasing threat for
showers (with mostly snow showers as airmass would be fairly
cool in this scenario). If trof stays further W, this would likely
allow southern stream system to move NE into the area, with a more
stratiform precip shield. Ptype would be tricky as warmer air
would likely move in as well, although the N half could stay cold
enough for snow depending on track of any sfc low that moves into
the E gulf. Overall, do have an increasing threat for precip from
Sun onward as both scenarios would give some precip to the area.
PUBLIC...Strong Wind until 9 PM AKST this evening for AKZ025.
MARINE...Gale Warning for PKZ041.
Small Craft Advisory for PKZ012-013-031-033-035-036-042-043.
Small Craft Advisory due to Seas for PKZ022-051>053.
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