Area Forecast Discussion
Issued by NWS

Home | Current Version | Previous Version | Text Only | Print | Product List | Glossary On
Versions: 1 2 3 4 5 6 7 8 9 10 11 12 13 14 15 16 17 18 19 20 21 22 23 24 25 26
FXAK67 PAJK 231354

Southeast Alaska Forecast Discussion
National Weather Service Juneau AK
554 AM AKDT SUN OCT 23 2016

.SHORT TERM...Rather quiet night across the panhandle as offshore
flow has started to dry out and clear out the panhandle. Most of
the mid to high clouds have cleared out, but a few bands remain,
associated with a weakening disturbance in the northern gulf and
another area over the southern panhandle associated with a low
over Haida Gwaii. Some areas of low clouds and fog are also
sticking around the inner channels this morning due to rather
light flow at low levels and plently of low level moisture from
the showers yesterday. These fog areas should diminish this
morning as they burn off or the strengthening winds blow them

The forecast for the next 24 hours is somewhat complex with
developing outflow for the northern half of the panhandle and the
affects from a weakening low for the southern panhandle. Winds
across the northern panhandle are already starting to increase.
Northern Lynn Canal is already blowing at 30 kt with some of the
other usual outflow areas reporting some gusts as well this
morning. Highest winds for the next 24 hours will be today as
pressure gradients tighten between the building ridge in the
Yukon and the low near Haida Gwaii before they slacken a little
tonight as the low pulls away and weakens. Expecting min gale
force winds for northern Lynn Canal for today with small craft
advisory winds for most of the rest of the northern inner channels
at some point as a result. As for land areas decided not to go for
a strong wind headline for skagway as I don`t think there is
enough cold air coming over the mountain passes yet to get the
winds going strong enough today.

As for the low, it is currently spinning through the southern part
of Haida Gwaii with some bands of high clouds moving over the
southern panhandle. The low will not make much headway into the
area, only getting as far north as the southern part of marine
zone 41. Likewise the rain with this feature will not get very far
north either as the northerly outflow at the surface and easterly
flow aloft tear it apart. The result is only scattered showers
expected for the southern half of the area this afternoon into
tonight with light amounts expected. There is some wind with this
system as well but I am mostly only expecting 20 to 30 kt winds
for marine areas in the southern panhandle and SE gulf and breezy
conditions on land. The southern part of Prince of Wales island
will see the highest winds for this system this afternoon and
evening with gusts possibly reaching 20 to 30 mph.

Short range models were in decent agreement today. Mainly used NAM
and some Hi-Res models for updates to get more details in the
outflow areas. Changes mostly confined to local effects.

.LONG TERM...Overall dry weather pattern in store for the week
with locally windy conditions. At mid levels a quasi stationary
closed low south of Haida Gwaii will fill as high pressure ridge
over the western and central gulf eventually breaks down later in
the week. A broad upper low moves in from the west forming another
closed low over central AK gulf, which then drops to the
southeast. The high pressure ridge ushers in clearing skies and
dry weather while a surface low to the south of the panhandle will
potentially move in some precip bands, especially over the
southern panhandle through the week. Low confidence on any timing
of precip as offshore flow would limit and rainfall and models
have been producing a wide range of solutions. By mid week a
surface low developing along a frontal boundary in the central
gulf brings in next chance for precip, but with the southeast
track this feature could miss the panhandle, thus keeping dry
weather until the weekend. Kept in chance pops until we get a
better handle on the track of these systems.

Main impacts for SE AK will be development of strong northerly and
outflow winds due to pressure gradient between inverted trough
extending over the panhandle and high pressure over the Yukon and
AK gulf. AK gulf outflow winds will be mainly near shore for the
northeastern gulf. Northern inner channels reaching at least gale
force with NAM MOS guidance indicating winds could reach storm
force. Central inner channels impact winds will mainly be easterly
outflow gust. Potential for Taku winds near downtown Juneau and
South Douglas starting late Monday night and into Tuesday
afternoon. Model soundings showing good cross barrier flow,
inversion at 850 mb, and 500 mb critical level. Have issued a
high wind watch for this time frame for gust potential of 60 mph.
Sustained winds will not be as much of an issue in Juneau compared
to the Taku mountain wave gusts.

Cold air aloft with 850 mb temps down into the -8 to -4 C range
over the northern half of the panhandle will drop overnight lows into
the 20s in wind sheltered areas. Downslope winds on the other hand
will produce warmer temps with lows staying in the upper 30s to
low 40s. Late in the week, indications of a warmer airmass moving
in so expecting any precip potential to be mostly rain at lower

For general synoptic patten utilized a blend of GFS/NAM then GFS/
ECWMF and finally kept WPC. Used the NAMDNG5 for winds and wind
gusts as it was picking up the localized features overall. This
model did over do winds some areas, such as the Juneau airport,
so tempered it as much as possible. Forecast confidence is
improved as HiRes models start to resolve the localized features,
but have lower confidence later in the week due to synoptic scale
model spread.


.AJK Watches/Warnings/Advisories...
PUBLIC...High Wind Watch from Monday evening through Tuesday afternoon
     for AKZ025.
MARINE...Gale Warning for PKZ012.
     Small Craft Advisory for PKZ011-013-021-022-031-036-041>043-051.



Visit us at is the U.S. government's official web portal to all federal, state and local government web resources and services.