Area Forecast Discussion
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FXAK67 PAJK 212330

Southeast Alaska Forecast Discussion
National Weather Service Juneau AK
230 PM AKST Mon Jan 21 2019

.SHORT TERM.../Through Tuesday night/...A gale force low will
approach the southern outer coast late tonight, then stall in the
vicinity of Cape Decision on Tuesday. Associated front will spread
precipitation in over the southern half of the panhandle through
the night even as precipitation diminishes over the northern half.
What is left of this front will move north along the windward side
of the coast mountains Tuesday and Tuesday night while weakening.
Precipitation type will be in the form of rain where precipitation
is most likely and forecast to be heaviest. Later tonight, the
rain/snow line should migrate south from Berner`s Bay to Frederick
Sound before moving back north again tomorrow. Saw some freezing
rain in the Yakutat area earlier today and have included a chance
of this returning tonight before PoP diminishes by morning.

High end gale force winds connected with this low will result in
strong wind gusts for zones 27 and 28 this evening. Southern
marine zones will see 45 kts out of the southeast this evening
with an abrupt shift to the southwest from Cape Ommaney south as
the center of circulation closes the coast.
Southerly/southeasterly gale force winds are also forecast for
portions of Chatham and Sumner Straits as well as Clarence Strait.

Used a blend of GFS and NAM for updates to pressure, wind, PoP,
and QPF. Adjustments to temperatures from both NAM and GFS MOS.
Biggest changes to temperatures were to decrease overnight lows near
the Haines border and White Pass by 12 to 18 degrees to get them
close to what they were last night since no change in airmass is
expected tonight. Overall forecast confidence is average.

.LONG TERM.../Wednesday through Monday as of 10 pm
Saturday/...Highly amplified longwave pattern to develop over the
Gulf of Alaska and western North America Wednesday, lasting
through the weekend. There is good agreement between ensemble
guidance and to some extent their operational counterparts on the
development of enhanced mid and upper level ridging along with
west coast of North America with deep upstream troughing over the
Bering Sea. This will spell a period of warm and wet weather for
SE AK Wednesday night through the early part of the weekend.
Guidance has not resolved the details of the individual systems
ejecting northward into the Gulf out of the longwave trough to the
west. Thus, while the forecast calls for warm and wet conditions
in general, the details as to when the heaviest precipitation and
the strongest winds will occur is still to be determined.

For later in the weekend into early next week, there are some
indications that the whole longwave pattern will begin to
retrograde, with the strongest moisture transport shifting west of
SE AK. A few of the operational solutions even close off a upper
high over the Gulf by Monday which could lead to very stable and
potentially foggy conditions. While this remains to be seen, think
with the retrograding longwave pattern, at least some drying can
be expected by late weekend with some modest cooling possible.


.AJK Watches/Warnings/Advisories...
PUBLIC...Strong Wind from 6 PM this evening to midnight AKST tonight for
MARINE...Gale Warning for PKZ033-035-036-041>043.
     Small Craft Advisory for PKZ012-013-021-022-051-052.
     Small Craft Advisory due to Seas for PKZ053.




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