Area Forecast Discussion
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FXAK67 PAJK 260008 CCA
AFDAJK

Southeast Alaska Forecast Discussion...CORRECTED
National Weather Service Juneau AK
408 PM AKDT Tue Jul 25 2017

.SHORT TERM...The models remain in relatively good agreement with
the approaching low pressure area. Small nuances in how much rain
will fall and a few degrees up or down between the NAM/GFS/ECWMF.

Forecast is on track and so the changes were mainly on a
microscale. The heaviest precipitation will fall over the southern
Panhandle. A large swath of clouds seen on satellite is extending
from over Haida Gwaii and reaching the Coast Mountain range as far
up as near Endicott Arm. The rain has been light to start with
this afternoon and should increase as the night goes on. The area
of rain will spread northward and barely reaching Skagway/Haines
and Yakutat area by Wednesday morning.

Winds remain and will remain 15 kt or less through Wednesday,
increasing slightly in the north-south orientated passes in the
southern Panhandle. Wind directions will be changing as the low
pressure moves through the area.

With the low moving into the area, the low stratus layer that has
plagued the area has started to break up. Yakutat could see some
patchy fog late tonight/early Wednesday morning.

.LONG TERM.../Thursday through Monday/ As of 1030pm Monday...The
remnant trough from the low pressure discussed above will continue
the showers over the region on Thursday, namely over the southern
panhandle during the first half of the day. On Friday, a weak
ridge of high pressure settles over the central panhandle causing
light winds.

Another low pressure system tracking across the S. Gulf/N. Pacific
looks to approach the southern panhandle on Saturday. However,
available long range models have pretty big differences on low
placement and strength with each other and from model run to run.
The Canadian keeps the low much further west through the weekend,
the GFS brings it up into the eastern gulf on Saturday while the
ECMWF is between the 2 and delays the onset of precipitation
until later in the day. Overall having the surface and upper
level low approach from the south to start should allow for a
lower chance of precip over the northern panhandle Friday night
into Saturday. Have decreased POP slightly to account for this,
but also increased the chances over the southern panhandle. Waves
of upper level vorticity look to pinwheel around the parent low
aloft going into the start of next week and is likely why model
surface lows are being dominant at different times/locations.
Despite this expect the potential for showers to remain in the
forecast, spreading across the area from south to north over the
weekend.

Due to model differences, only made relatively minor adjustments to
the extended forecast. Forecast confidence is average.

&&

.AJK Watches/Warnings/Advisories...
PUBLIC...None.
MARINE...None.

&&

$$

KV/Ferrin

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