Area Forecast Discussion
Issued by NWS
FXAK67 PAJK 212212
Southeast Alaska Forecast Discussion
National Weather Service Juneau AK
212 PM AKDT FRI OCT 21 2016
.SHORT TERM...A gale force low off of Dixon Entrance has caused
numerous showers across the region today and wind gusts of
30-40mph over the southern panhandle. Some isolated lightning
strikes have been detected near the low center, but few and far
between during the day. Instability continues to be favorable for
thunderstorms tonight, so have kept a slight chance in the
forecast over the gulf. A peak in CAPE skirts by the southern
outer coast overnight, so POW Island and Annette Island may hear a
couple rumbles too.
An upper level trough will drop into the NW gulf from the interior
and spawn a new low center and weak surface low tonight. The
upper level low will take over as the parent low and cause the low
over the SE gulf to weaken/broaden over the gulf as it merges with
the new low on Saturday. Showers assoc with the SE low will be
rotated north over the panhandle tonight into Saturday. During
Saturday the upper level low will progress S-SE across the central
gulf and start to turn flow over the panhandle to offshore.
Therefore expect to see showers have more breaks in between
through the afternoon across the north.
The low meandering in the gulf to the north then south again will
cause some wind shifts through the central inner channels. Most
will have NELY winds tonight that will shift to the SE as the low
center moves north. Either way, strongest winds can be expected
through E-W passages. Pressure packing looks to tighten along the
northern gulf coast due to high pressure starting to build in
Canada as the low moves north on Saturday. Have increased winds
out of interior passes including Yakutat Bay and passes to the
east down to Cross Sound.
Used a blend of the 00Z ECMWF, 12Z NAM and GFS to update pressure
today with a shift in the low center. Increased the POP somewhat
with the numerous showers and made the diurnal temperature range
slightly smaller. Forecast confidence is above average.
.LONG TERM...No changes to overall thinking in the extended
forecast period as models remain in good agreement on a dry
offshore flow regime through mid week. The usual outflow locations
such as Skagway and downtown Juneau/Douglas will experience a
period of gusty winds with the potential for gusts of 30-40 mph
Sunday night through Tuesday. Later shifts will be able to fine
tune the wind details as we get closer to this timeframe.
Temperatures during this outflow event are expected to be in the
low to mid 40s during the afternoon. Overnight lows will be highly
variable due to the wind but sheltered areas will fall into the
20s. Model solutions continue to diverge after mid week in
respect to energy ejecting into the gulf and its eventual track.
Utilizing WPC ensemble guidance remained best option after day 4
due to significant model differences. A transition to increased
cloud cover and precipitation chances is still reflected in this
forecast by late next week.
MARINE...Small Craft Advisory for PKZ012-022-033>036-041>043-051-053.
Small Craft Advisory due to Seas for PKZ052.
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