Small Craft Advisory 324, NWS Juneau, AK

Southeast Alaska Forecast Discussion
National Weather Service Juneau AK
144 PM AKDT Mon Jun 5 2017

.SYNOPSIS...An unseasonably strong low pressure system will
persist over the gulf through the week. Active weather will
prevail as several disturbances rotate around the low bringing
periods of rain and gusty winds to SE AK through the week.

&&

.SHORT TERM...Satellite imagery and surface analysis depict a
984MB low near 53N/148W with associated front pushing into the
outer coast this afternoon. -RA has spread across almost the
entire panhandle as of Mon afternoon with only PAGY and PAYA
being spared attm. Precip will move into PAGY early this
afternoon and into PAYA late afternoon/early evening. Gusty winds
increasing over the S panhandle this afternoon and will expand N
impacting the central panhandle and outer coast as well through
the evening. Precip and winds will diminish overnight before
another perturbation rotating around the low streng thisthens Tue
as it traverses along the remnant front. Models in pretty good
agreement with timing of the mid level energy with this wave, but
differ on how close to the coast it will pass. Feel confident the
outer coast and maybe the S panhandle will get another round of
wind and rain, but less confident on how far N and E the precip
will push as the low pulls the boundary away from the coast again.
Little change to inherited forecast with biggest difference being
stronger winds over the gulf to match model consensus. Given the
lower confidence in precip chances, kept highest PoPs along the
outer coast and changed stratiform wording to convective further N
and E Tue.

.LONG TERM.../Wednesday through Monday/ Upper level pattern is
rather active with two strong upper level lows affecting the
weather over the area through early next week. Upper low number
one will start out Wed near 50N 145W and gradually drift toward
the Pacific NW by Fri night. Upper level flow will gradually
become more and more easterly as this happens with several short
waves joining in to make the forecast more complex. Upper low
number two settles in around the Alaska Peninsula on Sat and stays
more or less in place through early next week. Some of the short
waves wrapping around the low look to make it far enough east to
affect the panhandle for next Sun into Mon but the confidence on
that is rather lacking at the moment.

Lower in the atmosphere the increasing easterly flow aloft will
actually help to dry the panhandle out on Wed as the precip from
the wave on Tue night gets pushed offshore. Wed seems to be the
only dry day we will get as another short wave from the south will
bring another round of rain and maybe some breezy conditions for
Thu. That rain then sticks around into Sat as lingering vorticity
as well as another weak shortwave move through the area. By Sun we
will be transitioning from the first upper low to the affects of
the second as the shortwaves from that begin to enter the area.
Unsure how much of an effect these shortwaves will have on precip
over the area for Sun and beyond as models differ on if they will
even get this far east with any sort of strength. Decided to keep
chance pops for most of the area for Sun and beyond because of the
possibility of this and the low level onshore flow that will be
ongoing into next week.

As for temperatures, a region of high thickness values are
expected to traverse over the region Wed into Thu. That combined
with the drier weather may make Wed the warmest day for the
period with highs possibly getting into the mid to upper 60s.
Warmed up temps for Wed as a result. Thu will likely still be warm
but increased clouds and rain will dampen Thu's highs somewhat.
Cooler but still near normal temps for the rest of the forecast
period.

Forecast models generally in decent agreement with some
differences on short wave timing here and there. Overall used some
GFS and Canadian for updates then transitioned to more WPC for
later periods.

&&

.AVIATION...Low level wind shear of 30 to 40 kt as frontal
boundary and llj moves over the panhandle this afternoon and
evening. Wind shear will diminish this evening but as next wave
moves into the SE gulf Tuesday wind shear will redevelop along
the southern panhandle and coastal areas. VFR to MVFR conditions
from cloud cover and rainfall reduced visibility today with
lowering conditions early this evening. General trend of
improving ceilings and visibility later tonight. With Tuesday
front staying further off shore expect only coastal areas to have
potential to drop to IFR on Tuesday.

&&

.MARINE...Gale force low spinning over the southern gulf is
pushing a front into the outer coast this afternoon. Southerly
gales developing over the offshore waters and Dixon Entrance attm.
Expect winds to rise to gales over Clarence Strait this evening
before diminishing gradually overnight. Ocean entrances for Sumner
and S Chatham will increase to near gales this evening as well.
Cross Sound may see gales develop as well, but kept them at 30 KT
with higher gusts and will have to continue monitoring through the
afternoon and evening. Conditions will improve briefly overnight
as the front stalls along the coast and the parent low drifts
further W. This respite will be short lived as another disturbance
will develop along the boundary and deepen as it moves into the SE
gulf Tue. Models in fairly good agreement with another round of
near gale to gale force winds developing over the SE gulf Tue
morning and propagating N and W through the day.

&&

.AJK Watches/Warnings/Advisories...
PUBLIC...None.
MARINE...Gale Warning for PKZ036-041>043-051-052.
     Small Craft Advisory for PKZ021-022-031>035-053.

&&

BC/PRB/EAL

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