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FXAK67 PAJK 261455

Southeast Alaska Forecast Discussion
National Weather Service Juneau AK
655 AM AKDT Wed Jul 26 2017

.SYNOPSIS...A weak low pressure system west of Haida Gwaii, with
an associated weather front, will continue to slowly weaken and
track northeast over the panhandle today. A ridge of high
pressure will then begin to build into the eastern gulf and over
the panhandle early Thursday into Friday.


.SHORT TERM.../Wednesday through early Friday/...As of 0530am
Wednesday...A large upper level trough with embedded shortwaves
has, to the surprise of no one, made its home in the gulf of
Alaska. However, on the interesting side, water vapor satellite
imagery actually paints a very intriguing picture: a long stream
of moisture being pushed through with the main low of concern over
the panhandle. If we look closer, the source of the moisture can
actually be traced back to the west-central Pacific! Looking at IR
satellite, we can see high clouds along the frontal boundary of
the low that are in line with that plume of moisture. In
addition, the front appears to be wrapping around the low, which
is causing some additional precipitation formation over far
northern portions of the panhandle and some higher clouds there
as well.

For today, patchy fog may occur in some areas of the panhandle
early this morning, since winds will generally be on the lighter
side, and winds should remain light throughout the daytime, save
for areas of Northern Lynn Canal. Expect skies to remain cloudy,
with precipitation predicted over much of the area, especially the
southern portions of the panhandle. For tomorrow, expect the same
pattern with light winds, cloudy skies, and scattered to numerous
showers across the panhandle.

Generally, no significant changes were made to the forecast. PoPs
were blended using the SREF for the first half of the forecast and
SREF and NAM combinations for the latter. The QPF was blended
using the 06Z NAM.

.LONG TERM.../Friday through Tuesday/ As of 1030pm Tuesday...The
new operational models are starting to get a handle on the
synoptic pattern to go along with ensembles. With that being said,
there were some changes for the weekend with more rain across the
forecast area and increased winds over the gulf. It is still too
far out to say how strong the winds will be over the inner
channels, but there were increases to the marine waters ranging
from 15 to 25 kt.

An upper level low is forecast to drift out of the north Pacific
and be over the southeast gulf by Saturday. A surface low
associated with this upper feature will lift a weather front over
the far southern panhandle Friday night and spread precip
northward through Saturday. Southerly winds look to increase from
south to north on Saturday as a ridge builds in behind the front.
The surface low will slowly weaken through Sunday, but rain will
be likely.

Overall, there is about average forecaster confidence for the
weekend into early next week. We used a blend of the 00z GFS and
12z EC along with the new WPC.


.AVIATION...Conditions early today will deteriorate to MVMC over
the northern Panhandle as a weather front progresses northward. At
the same time ongoing rain over the southern Panhandle will
prevent favorable flight conditions through this morning with some
southern locations experiencing low IMC for extended periods of
time today. While chances of rain remain in the forecast for the
southern Panhandle over the next 24hrs, conditions are likely to
improve later this afternoon as the front lifts northward.


.AJK Watches/Warnings/Advisories...




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