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FXAK67 PAJK 232255

Southeast Alaska Forecast Discussion
National Weather Service Juneau AK
255 PM AKDT Sun Apr 23 2017

.SYNOPSIS...Broad area of low pressure centered along the central
Aleutians impacts the Gulf of Alaska with a trough extending over
gulf to the British Columbia coast. Higher pressure over northern
Canada will weaken as the center moves east towards Hudson Bay.


.SHORT TERM.../ Sunday night to Tuesday night / An old trough
extending over the gulf and Haida Gwaii has clouds and light
rain/showers moving north and west across the southern panhandle
Sunday afternoon. Expect to see the light rain to continue to
work its way northward through the panhandle tonight. It isn`t
until during the early day Monday when the trough has moved north
to the northern gulf that PoP get more than low chance levels.
Winds over the northern coastal marine zones also increase up to
20 kt, as the through approaches.

Another short wave/surface will be developing and increasing in
strength as the feature moves east northeast of the Pacific
towards the Haida Gwaii region later Monday with a closed surface
low pattern go be about 200 nm southwest of the island midday
Tuesday. The operational models are generally agreeing on the
feature although have presently favored the more eastern/weaker
solution pair of the NAM/EC. The low should be curving north into
the southeast gulf west of Prince of Wales Island by early
Wednesday morning. This track and strength seems to be a new path
for the solutions from previous thinking, so blended into the
Wednesday forecast periods.

The new low will spread a new front north into the southern
panhandle and help to dry out the precipitation from the northern
areas Tuesday, and then that front will start to spread the rain

.LONG TERM.../Tuesday morning through Saturday/ Issued 5 am Sunday
- There is not much change in the overall synoptic pattern
through next week. The polar jet will remain over the central
Pacific and this will keep the storm track south of the forecast
area through mid week. There will be a stronger low pressure
system that will lift north out of the north Pacific on Wednesday
and move into the eastern gulf. There are some differences with
the track of this low but the latest few model runs seem to be
picking up on this feature. As the low slowly lifts northeast
through Thursday the threat of precip will increase for the
southern half of the forecast area. The northern areas right now
will see a chance of rain. For late week into the early next
weekend there is increased onshore flow from the southwest and
with that a chance of rain with cloudy skies seems likely.

Wind wise...the inner channels will see relatively light winds
from the north through Wednesday night with weak northernly
pressure gradient. As the low moves into the eastern gulf winds
will increase to 20 kt over marine waters with 15 mph over land
from Fredrick Sound south. The winds will come around to the
south late in the week as a ridge builds over the northern panhandle
as the low moves into Canada on Friday.

Overall there is average forecaster confidence for Tuesday and
Wednesday but lower confidence after that due to the differences
with the low moving out of the north Pacific and spread in the
ensembles. Changes in the long term were modified using the 00z
nam and 12z ec through day 4 then WPC for late in the week into
the weekend.


.AVIATION...We began the periods with vcsh in the southern zones,
and only added change groups where ceilings fluctuated through the
night and into Monday. The northern sites we added evening change
groups as channel breezes fall and then even though vcsh may occur
late tonight, we delayed adding until mvmc conditions arrived
later Monday. No IMC conditions are forecast through the next 24


.MARINE...Winds primarily 20 kt or lest through the part of next
week though will need to watch the low development Tuesday for
the southeast gulf. Seas and swells for the coastal areas 5 to 7
feet tonight and into Monday. A localized buoy is reporting 8
feet, however I suspect those will subside through the evening.


.AJK Watches/Warnings/Advisories...




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