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818
FXAK67 PAJK 242143
AFDAJK

Southeast Alaska Forecast Discussion
National Weather Service Juneau AK
143 PM AKDT Tue Apr 24 2018

.SHORT TERM...Wet, cold, and windy is the story of the day. Shower
activity has diminished (minus a few locations across the
panhandle), as an upper-level shortwave moves eastward. Most of
this precipitation will shear apart into the evening hours. The
next weather front in the central panhandle is currently tracking
eastward across the central Gulf, to impact the northern panhandle
tonight.

Minimal changes to pressure were needed, with most adjustments
done between the Wednesday and Wednesday night period using a
GFS/EC blend. Mostly local edits were made in the wind grids:
increasing winds in the Skagway/White Pass area, wind directions
that had already shifted, and decreasing some of the marine winds.
Skagway and White Pass could see gusts up to 50 mph with some
locally higher gusts possible. The NAMnest was not picking up on
this pattern, however, standard deviations were showing values 5-6
above normal in the 700 mb wind field.

There will be a warming trend towards the end of the week with
guidance suggesting 60 degree temps over the southern panhandle.
At this point, models are showing a warm "blob" near 8 C (~46 F)
at the 850 mb level. We went towards trending of increasing
temperatures, especially over the southern panhandle.

Not many changes were necessary to POP, except for expanding the
coverage. QPF values were bumped up to account for Thursday`s
water vapor transport. Fog could become a concern late tonight as
some southern panhandle locations start to clear out. Model
agreement looks great through tomorrow night, but will trend
upwards if we see any indication in upcoming model runs.

.LONG TERM.../Thursday through Tuesday as of 10 pm Monday/
Slowed the eastward movement of the occluded front early in the
period (daytime Thu), but it should dissipate by Thu evening. Used
18z GFS to handle the 12z Thu-06z Fri time frame. Still some
questions about potential systems moving into the area over the
weekend, with GFS most bullish with precip threat and GEM/EC both
fairly dry over the area. Decided to stay the course for the Fri
to Sun period to allow the models a chance to sort out the
details better. Did bring in latest WPC for 12z Mon onward, which
pushed the sfc ridge further S over the gulf than previous
forecast had it.

For Thu into Thu night, kept in the higher POPs over the N half of
the area, but the precip should diminish from the NW through the
daytime hours. Am expecting Thu night to be mainly dry with high
pressure building across the area from the SW.

For Fri-Sun, sticking with low POP forecast for now, but later
shifts will need to monitor this time frame for potential precip
threats, especially Sat-Sun. Even Mon-Tue seem to be tricky as the
model differences persist during early next week. Forecast
confidence for the Sat-Tue time frame is low at this point.

&&

.AJK Watches/Warnings/Advisories...
PUBLIC...Strong Wind through Wednesday afternoon for AKZ018.
     Strong Wind late tonight for AKZ017.
MARINE...Gale Warning for PKZ012-051-052.
     Small Craft Advisory for PKZ013-021-022-042-043-053.
     Small Craft Advisory due to Seas for PKZ041.

&&

$$

SS/RWT

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