Area Forecast Discussion
Issued by NWS
FXAK67 PAJK 292345
Southeast Alaska Forecast Discussion
National Weather Service Juneau AK
345 PM AKDT MON AUG 29 2016
.SHORT TERM...Low pressure west of the Dixon Entrance continue to
spin in place, rotating showers north over the panhandle.
Northward progress of these showers has been slow, but steady
through the day, as has the increasing cloud cover. Shower
activity over the far northern inner channels started well ahead
of more southerly locations, beginning in Haines and Skagway early
this morning. Some showers registered as heavy over the southern
inner channels, but those rain rates should lessen overnight
tonight eve as areal coverage expands to fill in all of the
panhandle south of Cape Fairweather with scattered to numerous
shower by late tonight. Little change in this aspect of the
forecast through tomorrow until late in the day, when showers
should start letting up over the central inner channels.
Winds continue to be an issue in the short range, but not so much
from the low west of the Dixon Entrance. Rather, the big wind
maker is the very strong northerly pressure gradient cause by the
interaction of very strong high pressure centered over the
Beaufort Sea and ridging south across the eastern interior and
western Yukon. Outflow winds vicinity Alsek River will remain very
strong through the short term. Elsewhere, small craft northerlies
to 30 kts over Lynn Canal with gusty conditions in Haines and
Skagway are expected. Another area to watch will be downtown
Juneau tomorrow afternoon, where northeasterly downslope winds are
expected to gusts to 35 mph.
Used a blend of GFS and NAM for the tonight period and GFS/ECMWF
for the tomorrow period for pressures. Used a blend of NAM12 and
high resolution NAM as a foundation for winds. PoP and QPF from
NAMDNG5. Temps tweaked primarily using GFS MOS. Overall forecast
confidence is average.
.LONG TERM...The low aloft persists southwest of Haida Gwaii into
Wednesday before being moved into the BC coast north of Vancouver
Island Thursday morning. After the low moves inland expect the
mid level flow across southeast Alaska to be a light northerly
while the lower level flow under 5000 feet will be variable with a
trough extending across the panhandle to the northern gulf.
A weak ridge is expected to move eastward across the Gulf of
Alaska Thursday and Friday while a weather system will develop and
move out of the northern pacific and into the panhandle region
late Saturday/Sunday depending on model solutions. Based on the
ensembles solution from WPC today will hold the main preciptiation
off until Sunday for the time being.
Showers moving northwards from the south look to get to about as
far north as Icy Strait although north of there a few showers may
manage so move over the coastal range into northern lynn canal.
Winds to remain strong and gusty across Lynn Canal and into
Stephens Passage to the Wednesday before they settle
down, although they will may not be as strong overnight.
.AVIATION...Very rough flying day over southeast Alaska today with
more moderate turbulence and low level wind shear expected for the
next 24 hours. Multiple PIREPS today indicating light to moderate
turbulence with severe turbulence being reported as low as 2000
feet by light GA over Lynn Canal and up to FL400 by a 747.
Generally VMC with periods of MVMC due primarily to CIGS. Be
careful out there.
MARINE...Small Craft Advisory for PKZ012-022-036-043-051.
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