Gale Warning 191, NWS Juneau, AK

Southeast Alaska Forecast Discussion
National Weather Service Juneau AK
303 PM AKDT Thu Oct 11 2018

.SHORT TERM...Current WV Satellite imagery shows an upper
shortwave trough moving across the E Gulf which is helping to
enhance rainfall along a frontal band across the southern
panhandle Thursday afternoon. Showers are developing in the cooler
air aloft associated with this wave over the Gulf and left a
mention of slight chance of TS over E Gulf. Expect the heavier
rain to move out into western BC by late tonight, with isolated to
scattered showers lingering along the coastal mountains and outer
coast overnight.

Model solutions remain in good agreement in the short term
synoptic pattern with a short lived ridge traversing across the
Gulf tonight and over the panhandle Friday. Anticipate areas of
fog to develop late tonight into early Friday with light winds and
some reduced cloud coverage allowing for radiational cooling to
occur. It is possible for the sun to make an appearance Friday in
a few areas before the next weather system arrives. The parent
low in the Bering Sea continues to spin, along with an upper
trough, lifting the next front into the W Gulf. A secondary wave
with low level jet dynamics expected to enhance the gale force
front into the central Gulf early Saturday. Main adjustments to
the inherited forecast was to speed up the initial wave by a few
hours and increase surface winds to near storm force along the
northern Gulf. Confidence is above average in this system bringing
heavy rain to the NE gulf coast and northern panhandle. IVT
forecasts indicate good probability of Atmospheric River
conditions beginning Saturday morning, mainly spread over the
northern half of the panhandle.

.LONG TERM...As of 10pm Wednesday. The extended forecast looks
active with normal temperatures and wet weather. Saturday begins
with our next atmospheric river type front already over the
central/eastern gulf. Models are in agreement that a low will
track north along the front to be over the north-central gulf
mid-day Saturday. Models have also deepened the pressure with the
low, helping to give us more confidence in a period of gale force
winds over the gulf.

Moderate to heavy rain over Yakutat will spread SE over the
northern half of the panhandle through the day. Small craft
advisory winds out of the S-SE will shift over the inner channels
with the front and may have some stronger gusts. There will likely
be a wind shift to the west once the front passes. However, waves
tracking along the front will cause it to oscillate N-S through
Sunday, making it somewhat difficult to pin down where the wind
shifts and heaviest core of rain will be at any given time. One
thing that models are starting to agree more on is that one of the
waves will shift the front back northward Sunday night through
Monday, putting Yakutat back under the fire hose. This would
cause the far southern panhandle to only see a brief/small amount
of rain with this front, which is unfortunate as they have the
most need. Eventually the front should shift back SE before
dissipating, but the likelihood/timing of that is more uncertain.

MOS guidance wanted to warm both max and min temperatures by
several degrees. While 850mb temps are warm due to the atmospheric
rivers transporting the "tropical" airmass over us, do not think
that getting out of the low-mid 50s is likely on a rainy/cloudy
fall day. Today is a good example, fairly similar airmass, but
highs hardly in the 40s. As for the min temperatures, warming them
to have a smaller diurnal range on rainy days seems logical, but
with any breaks in the clouds as the front shifts will likely
cause it to be colder. Have stayed with the status quo for the
most part and opted to not warm temps as much as guidance would
suggest. However, at the beginning of next week when the front
shifts back north, there is a time when the southern panhandle
could be partly cloudy in the afternoon. This would allow for
warmer temps than we have in there. As mentioned above, timing of
when the front wavers is the biggest question, so not ready to
commit to partly cloudy and 60 degrees attm.

&&

.AJK Watches/Warnings/Advisories...
PUBLIC...None.
MARINE...Small Craft Advisory for PKZ022-041>043.
     Small Craft Advisory due to Seas for PKZ051>053.

&&

DDH/Ferrin

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