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449
FXAK67 PAJK 231403
AFDAJK

Southeast Alaska Forecast Discussion
National Weather Service Juneau AK
503 AM AKST Mon Jan 23 2017

.SHORT TERM...A weak low over the far NE gulf will move onshore
near Yakutat Bay this morning. A weak cold front will move across
SE AK today. A strong occluded front will move NE into the eastern
gulf by late tonight.

Main forecast concerns will be precip potential/ptype/amounts and
winds. Precip with the low and weak cold front continues over the
N and most of the outer coast. Am expecting the cold frontal
precip band to move into the S area late this morning or early in
the afternoon. After cold front moves through, the precip will
slowly diminish but a complete dry out is not expected due to
onshore flow in lower levels. Larger area of precip will move into
the E gulf by this evening ahead of the strong occluded front,
then reach the outer coast and parts of the inner channels late
tonight.

Ptype will be tricky. Right now, precip has changed to rain from
PAYA-PAGS-PAOH line southwestward. Think as warmer air moves
further inland, the warmup will not be as strong so precip will
more likely just mix with rain over the remaining N area late this
morning or afternoon. Behind the cold front, airmass appears cold
enough for precip to go back over to mainly snow or a mix along
the coast this afternoon then inland this evening, but the precip
will be more spotty. Then ahead of the occluded front, most places
will start as a mix or snow as the front moves closer to the area.
Have decided to keep the WWA going as is for zones 19,20 and 25
today, and cancelled the WWA for zone 17.

As for precip amounts, most of the N will see about 1-3 inches of
additional snow before precip becomes mixed with rain. Areas
further S will see little or no snow accumulation today as precip
moves in. With the occluded front tonight, the PAYA area could get
2-4 inches of snow by daybreak Tue...with an inch or so possible
tonight along the central coast and N half of the inner channels.

Strongest winds are over the gulf E of the low...with 20-25 KT
winds over the NE gulf. Winds over the inner channels have
diminished some, with most places now 10-20 KT. These winds will
diminish after low jumps inland and front moves through, except
the N channels will see a bit stronger S wind set up late this
afternoon. Much stronger winds will develop ahead of the occluded
front tonight with gales expected over the gulf and 20-30 KT
winds likely by late tonight over most of the inner channels.

.LONG TERM...Period begins with the next in a series of fronts
moving into the N gulf coast early Tue. Satellite TPW indicates
abundant moisture with this system and NAEFS IVT increases to 2-3
standard deviations above normal. Expect heavy precip to move
into AKZ017 Tue and expand eastward into the panhandle overnight
into Wed. Feel this system will be the one to provide sufficient
WAA for precip at sea level to transition to liquid across the
entire panhandle. Haines and Skagway may remain mixed RA/SN
overnight into Wed with no significant accumulations. However,
higher elevations along the Haines and Klondike highways expected
to remain snow with 5-7" accumulations possible through Wed
afternoon. This system will also bring gales to the gulf, a
strong gale barrier jet along the N gulf coast and seas building
to near 20ft over the gulf. Winds will increase along the outer
coast as the front moves onshore and may need wind headlines Tue.
Models in good agreement with another frontal system moving
across the panhandle Thu. Given the continued WAA ahead of this
system, ptype expected to remain liquid at sea level although
moderate snow accumulations will again be possible at higher
elevations along the highways. This active weather pattern will
keep gales prevailing over the gulf along with seas over 12ft
through Fri. Inner channels will remain generally below gale, but
may experience a brief period of gale force winds as fronts move
across the waters.

Operational model solutions continue to diverge significantly
this weekend, but ensembles and WPC support continued active
weather pattern with troughing over the W gulf and deep onshore SW
flow across SE AK through next weekend.

&&

.AJK Watches/Warnings/Advisories...
PUBLIC...Winter Weather Advisory until noon AKST today for AKZ025.
     Winter Weather Advisory until 9 AM AKST this morning for AKZ019-
     020.
MARINE...Gale Warning for PKZ042-043-051-052.
     Small Craft Advisory for PKZ013-021-022-031>034-041.
&&

$$

RWT/BC

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