Area Forecast Discussion
Issued by NWS
FXAK67 PAJK 242304
Southeast Alaska Forecast Discussion
National Weather Service Juneau AK
304 PM AKDT Mon Apr 24 2017
.SYNOPSIS...A weather front across the northern gulf will lift
north across northern Southeast Alaska tonight. A ridge of high
pressure across the Panhandle will weaken and move east by Tuesday
morning. A gale force low will approach the eastern gulf Tuesday.
.SHORT TERM...Weak lift in onshore flow has resulted in very light
shower activity or sprinkles across parts of Southeast Alaska
today, but rates and organization to rain bands appear to be
increasing as vorticity advects northward into tonight. Still the
main thrust of rain showers will be into the northeast and eastern
gulf coast with only a chance of measurable precipitation
spreading inland. Farther south, ridging behind the front will
begin to suppress clouds with possible clearing into Tuesday
morning. We have added some patchy fog mainly across the southern
and central Panhandle late tonight early Tuesday morning.
Confidence is higher for fog in the south.
Tuesday a developing system in the North Pacific will swing
northeastward into the eastern gulf by late Tuesday. While
agreement exists for a low, differences in track and position
emerge as early as Tuesday afternoon which lowers confidence in
some details of the forecast. A more easterly track toward Dixon
Entrance like the ECMWF will slow rain`s arrival into the southern
Panhandle. A westerly track would increase the rain`s efficiency
of driving northward across the Panhandle. Thus, the chance of
rain for the north may become bona fide light rain earlier.
We have kept the stronger winds across Prince of Wales Island but
reduced them for many areas across the northern Panhandle as
gradients will be small. Winds will increase along the coast, but
we do not anticipate gusts above 30 miles per hour from Sitka
northward late Tuesday.
From Wednesday into Wednesday night, model differences were
smaller as all agree the low will remain in the eastern gulf, thus
edits were more sparse during this time.
We used 12Z ECMWF/NAM for guidance especially from Monday night
into early Wednesday. Temperatures were warmed a few degrees over
the north Tuesday to account for ridging and sunnier skies ahead
of the system approaching from the south.
.LONG TERM.../Wednesday night through Sunday/ The low will slowly
lift north but will remain south of Sitka through Wednesday night
before weakening and lifting east into the inner channels. Rain
will remain a high threat south of the low but north it will be on
the drier side. After the low moves into Canada there will be a
period of onshore flow but towards the weekend it looks like the
northern half of the forecast area could be dry with a low moving
over Dixon Entrance. The southern areas will see a higher threat
for precip over the weekend being closer to the low and near an
area of deformation.
There is average forecaster confidence through the long term
period. The overall trend in the models is to have bits of energy
from the jet lift north into the gulf but overall most of the
weather systems will be south of the area. For any changes done to
the forecast the 00z nam, and 00z gfs was used through Thursday
and then WPC after that.
.AVIATION...Predominately VFR conditions today with areas of lower
clouds along the southern panhandle, western Baranof island as
well as the northeast gulf into the Yakutat region of MVR for
ceilings...although Yakutat has lowered to 800 feet this
afternoon. Light winds up 15 kt for most of the areas...although a
few higher winds and gusts near the showers as they track
.MARINE...The front moving north across the northeast gulf tonight
will briefly send winds to 25 kt in zone 52 tonight. We have kept
the gale force easterlies in the southeastern gulf coast for the
system approaching from the south late Tuesday as well as the
small craft for Clarence Strait. Winds to the north were lightened
through much of the period slightly.
PUBLIC...Strong Wind from Tuesday afternoon through Tuesday evening for
MARINE...Gale Warning for PKZ041.
Small Craft Advisory for PKZ036-042-052.
Small Craft Advisory due to Seas for PKZ043.
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