Area Forecast Discussion
Issued by NWS Juneau, AK

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FXAK67 PAJK 122247

Southeast Alaska Forecast Discussion
National Weather Service Juneau AK
247 PM AKDT Wed Aug 12 2020

.SHORT TERM.../Wednesday evening through Friday/ Weak low and mid
level onshore flow with an upper trough over the northern
gulf/Southern Alaska has kept clouds around for much of the day.
Isolated showers have popped up over the Panhandle; however most
places will remain dry through the evening. Isolated to scattered
showers will continue into Thursday as a weakening low heads east
towards the Dixon Entrance and weak vort maxes rotate into the
northern Panhandle. The most impactful conditions through Thursday
will be 15 to 20 kt winds in Lynn Canal as higher pressure
remains over the Panhandle keeping the pressure gradient tight up

On Friday, the focus shifts towards a deepening trough in the
western gulf and an elongated low pushing into the central gulf.
A front will extend from the low toward the far southern
Panhandle. The low will move eastward along the front while the
front itself slowly pushes northward into the Central Panhandle by
Friday evening. North of the front, deep offshore flow up to 700mb
will keep the northern Panhandle dry for much of the morning and
afternoon hours. Drying downsloping winds will scour out some
cloud cover and help temperatures rise into the low to mid 60s.
Bumped up high temperatures by 2 to 4 degrees from what was
already in the forecast for points along Icy Strait and northward.
Also increased easterly winds for Cape Spencer and around the
backside of Douglas Friday afternoon as the front pushes northward
and the pressure gradient tightens. SCA conditions likely just
ahead of the advancing front in the gulf and coastal waters
beginning Friday afternoon and continuing on through the evening.
Rain associated with this system will push in from south to north
beginning in the southern Panhandle early Friday morning and
making its way toward Juneau and Icy Strait by late evening.

Models are in pretty good agreement with the overall pattern
despite small discrepancies with placement of the Friday low in
the gulf. Confidence is average in the forecast over the next
couple days.

.LONG TERM.../Friday through next Tuesday/...The extended
forecast is dominated by one low pressure system the lingers over
the south-central gulf through the weekend. This system will keep
periods of rain or showers in the forecast most days, but with
greatest amounts primarily over the southern half of the region.

An E-W jet will be pointed at the Haida Gwaii area early Friday,
then a trough will start digging into the western gulf. A new mid-
level low center forming over the gulf as it progresses eastward
will work to enhance a surface front already moving across the north
Pacific. There is still some uncertainty in the position of the low,
but models are coming into better agreement. Think that there will
be enough offshore flow over the northern panhandle ahead the main
front during the day Friday, so have decreased POP, cloud cover,
and increased high temperatures slightly. For the south, the
moisture plume directed at Haida Gwaii will gradually shift
northward through the day, increasing POP.

As upper level support moves into the region from the west, a triple
point will likely form and enhance rainfall rates as it moves into
the southern panhandle through Friday evening. Expect periods of
heavy rain for the south Saturday and Sunday. Frontal bands will
continue to pass over the area through Sunday in a SE to NW
fashion. If the low center stays as far south as currently
predicted, the Yakutat area will have the lowest chance of rain in
the extended.


.AJK Watches/Warnings/Advisories...




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