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FXAK67 PAJK 202300

Southeast Alaska Forecast Discussion
National Weather Service Juneau AK
300 PM AKDT Tue Aug 20 2019

.SHORT TERM.../Tuesday through Thursday night/ Confidence is
moderate and slowly increasing on the track of a gale force low
headed toward the southern Panhandle this evening and thus wind
directions/speeds for much of the southern Panhandle. The 12Z runs
of the ECMWF and the Canadian and the 18Z runs of the GFS and NAM
have nudged the track of the low to the south and east bringing it
over northern portions of Haida Gwaii through the Dixon Entrance
then over Misty Fjords.

For the rest of this afternoon and into tonight, rain, heavy at
times, will continue to slowly move north through the Panhandle.
The rain shield is expected to stay east of a line from Juneau to
Sitka before making its way into Canada tomorrow. Heaviest
precipitation totals are expected to be in the Southern Panhandle
where an additional 1-1.5" of rain is expected with amounts
greatly decreasing towards the north. Juneau to Sitka will be
right on the line of where the precip ends, there may be a fine
line between areas that pick up a little rainfall and areas who
stay high and dry. Also, since there is a history of instability
with the colder, stratospheric portion of the storm west of the
system, there is a slight chance of thunder this evening for
marine zone 41 and western Prince of Wales tonight.

Have not made too many changes to winds today. Gale force winds
are expected this evening for marine zone 41 just off the coast of
Prince of Wales and in Clarence strait as well. Have winds in
Clarence strait subsiding tonight and going below small craft
levels by Wednesday morning. Gusty winds over 40 mph are are
possible around Ketchikan through late this evening.

Tranquil weather continues across the northern panhandle.
Bumped up temperatures and lowered dew point and RH values for
today across the north as many areas have had enough breaks in the
clouds to warm up into the 60s.

A wetter weather pattern will continue for the rest of the week as
another storm system is expected to impact Southeast Alaskan
Thursday. Rain will begin to push east into Canada on Wednesday as
the current storm system weakens and moves out of the area. Some
scattered showers will still remain across the panhandle
Wednesday afternoon and evening as onshore flow begins to increase
ahead of the next storm system in the gulf.

Models have much better agreement with the system moving in for
Thursday than they did with the storm system from yesterday and
today. An area of low pressure will make its way eastward across
the central gulf on Thursday pushing a front closer to the
region. Rain will overspread much of the panhandle Thursday
afternoon and evening and continue into the nighttime hours.

.LONG TERM.../Friday through Tuesday night/ More typical late
summer or early fall pattern looks to set up from late week
onward. Strengthening and more zonal Pacific jet will guide storms
into the Gulf of Alaska with several rounds of mostly beneficial
rainfall likely through the weekend. Operational guidance is in
decent agreement that a stronger storm system will impact the
Panhandle on Thursday with heavier rainfall and gale force winds
over the outside waters at least. Depending on the track of any
surface waves, breezy to windy conditions are likely over the
inside waters Thursday into Friday as well. Temperatures should be
cooler with the cloud cover and expected rainfall with only minor
diurnal fluctuations.

Given the progressive zonal upper flow, details in any one system
are difficult to hammer out at this time range. Confidence in a
much wetter pattern is high however as we turn the corner from
summer into a more fall-like pattern.


.AJK Watches/Warnings/Advisories...
PUBLIC...Strong Wind until 1 AM AKDT Wednesday for AKZ028.
MARINE...Gale Warning for PKZ036-041.
     Small Craft Advisory for PKZ033-042-043.




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