High Wind Warning 12, NWS Juneau, AK

943 
WWAK77 PAJK 072040
NPWAJK

URGENT - WEATHER MESSAGE
National Weather Service Juneau AK
1140 AM AKST Tue Mar 7 2017


AKZ025-072145-
/O.EXP.PAJK.HW.W.0012.000000T0000Z-170307T2100Z/
Juneau Borough and Northern Admiralty Island-
Including the city of Juneau
1140 AM AKST Tue Mar 7 2017

...HIGH WIND WARNING WILL EXPIRE AT NOON AKST TODAY...

Taku winds gusts of 60 mph were reported overnight near Downtown 
Juneau and South Douglas. Wind gusts have begun to lower slightly 
this morning however expect gusts of 40 to 50 mph to last through 
the end of the week.

This will be the final statement on this event.


$$

Southeast Alaska Forecast Discussion
National Weather Service Juneau AK
333 PM AKST Mon Mar 6 2017

.SHORT TERM...Upper level trough has moved over the AK gulf and
will be main feature for some time. A surface low developed early
Monday morning over the eastern AK gulf and is progressing to the
SE. Since the upper level trough has dropped further south the
track of the low now may move further east and south. This would
have the impact of increasing winds over the southeast gulf but
limiting potential precip bands over the far southern panhandle.
Still large model spread, mainly with location of precip bands and
QPF amounts. This is expected due to the extremely unstable
atmosphere, 850-500 mb lapse rates of 8 C/km. Satellite imagery
already showing the convective nature of the low with cold cloud
tops. Cloud shield has moved over the southern panhandle, and snow
showers appear to have begun in Hydaburg. With such a convective
nature snow showers are expected to be heavy at times so still
have the Winter Storm Warnings out for zone 27 and 28. Expect a
very wide range in snow accumulation with respect to amount and
area of coverage. Kept with previous forecast having most snow
over southern Prince of Wales island, but low confidence on exact
location. Outflow winds with gusty conditions for locations such
as Downtown Juneau and Douglas and Skagway due to the tight
northernly gradient between the low moving to the south and cold
arctic high pressure over the Yukon. For Juneau just at the edge
of Taku wind event, good inversion and critical layer but cross
barrier flow just a bit low to get to warning criteria. Lows
tonight may be slightly tempered by cloud cover, but still expect
locations to be in the teens to single digits. Tomorrow's max
temps will be similar to today nearing the mid 20s with increased
solar heating.

Made an adjustment to the position of the low center using a blend
of 12z NAM/ECMWF. Canadian was mostly in line but GFS more of an
outlier today. With uncertainty in pop, QPF and snow, held off on
making adjustments as models that matched for pressure still had
spread on these elements. Forecast confidence is below average.

.LONG TERM...The weather pattern with an upper low positioned
around Dixon Entrance and a ridge over the Bering Sea will deviate
little through the weekend. Below normal temperatures Panhandle-
wide will continue as the southern Panhandle may have periodic
snow showers drawn in from moderate to weak storm systems anchored
near Dixon Entrance and Haida Gwaii. Some solutions suggest that
the snow event for the far south may even need to be extended in
some degree into Wednesday, so we have increased both pop and qpf
here with implications of 1 to 2 inches more. Should the winter
storm forecast verify, we may look at increasing these amounts as
the strong convection described above will likely persist.
Farther north, the wind chill advisory may need extending into the
weekend as blustery conditions will likely persist given tight
gradients.

Likewise, northerly outflow winds will continue into the weekend
for the inside passages. This includes potentially more storms
for northern Lynn Canal and gales for Glacier Bay and gap flow
areas of Stephens Passage. At this time, we left the freezing
spray forecast alone, however, an expansion more deeply into the
gulf and the central and southern Panhandle is not out of the
question.

It is still too early to say when exactly the Bering Sea ridge
retreats west or weakens enough to allow Pacific moisture and
warmer temperatures to advect northward again. Some solutions hint
at this scenario late this weekend. But until we gain more
confidence the current forecast holds for now.

&&

.AVIATION...Visibility restrictions over the far southern
panhandle due to developing snow showers this evening, with
heaviest showers possible later tonight. Due to high variability
in shower timing and location expect conditions to rapidly change
through out the night. Wind shear due to strong outflow and cross
barrier flow will intensify early this evening with a light
decrease over the northern panhandle Tuesday afternoon.

&&

.MARINE...Hazardous conditions for most of the inner channels and
coastal waters. Once again strong northerly winds, high seas, and
strong outflow winds from channeled terrain. Storm force winds
for Northern Lynn Canal last into tomorrow along with Cross Sound
gusts of 60 mph. The combination of cold air and strong winds
producing freezing spray. The southern inner channels have
shifted to the south with the advancing low with speeds increased
this evening.

&&

.AJK Watches/Warnings/Advisories...
PUBLIC...Winter Storm Warning until 3 PM AKST Tuesday for AKZ027.
     Strong Wind through Tuesday afternoon for AKZ018-025.
     Wind Chill Advisory until 3 PM AKST Wednesday for AKZ018.
     Winter Storm Warning from 9 PM this evening to 3 PM AKST Tuesday
     for AKZ028.
MARINE...Heavy Freezing Spray Warning for PKZ013-031.
     Heavy Freezing Spray Warning for PKZ031.
     Heavy Freezing Spray Warning for PKZ011.
     Heavy Freezing Spray Warning for PKZ012.
     Heavy Freezing Spray Warning for PKZ013.
     Heavy Freezing Spray Warning for PKZ053.
     Storm Warning for PKZ012.
     Gale Warning for PKZ011-013-021-022-031-032-034-035-043-051.
     Small Craft Advisory for PKZ033-036-041-042-053.
     Small Craft Advisory due to Seas for PKZ052.
&&

PRB/JWA

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