Small Craft Advisory 613, NWS Juneau, AK

Southeast Alaska Forecast Discussion
National Weather Service Juneau AK
343 PM AKST Sat Dec 2 2017

.SHORT TERM...Surface ridging is slowly weakening overnight as the
strong weather front moves into the western gulf. This system will
continue to approach the Panhandle, although the low will remain
in the western gulf through the weekend. The front itself will
sweep across the gulf bringing gale force winds over the central
gulf and most of the outside water beginning early Sunday morning.
The inside water will increase to SCA late Sunday night in
Clarence Strait and spread to the other areas from south to north,
excluding the Lynn Canal area. Strongest winds for the inside
waters will be in the north-south oriented areas and near ocean
entrances.

Precipitation has been a mixed bag today with temperatures near
freezing and a shallow warm layer aloft. The southern area
remained dry, with rain along the outside waters up through Sitka.
For the rest of the Panhandle snow fell with amounts ranging from
trace amounts to around 3 inches. Overnight, the central
Panhandle including Yakutat will have mixed rain and snow, then
Sunday the Skagway Haines area will become mixed. The Klondike
highway will remain snow through the weekend.

Temperatures are cooling a bit overnight and then a warming trend
with the approaching system bringing in warmer air by Sunday night.
Temperatures for much of the Panhandle will be nearly steady
overnight Sunday into Monday and completely changing over the
precipitation to rain, with snow levels rising to 1700 feet or
higher.

It was a group effort by the models to get the forecast done
today. The models overall had the same idea for the ridging over
the Panhandle but started to have some disagreement for the timing
and placement of the low in the western gulf by the end of the
weekend. Pressure and winds got a few local changes with wind
directions for tonight. Temperatures were a blend of ECMWF and
GFS. Precipitation had all three models blended to nudge the
forecast, while SREF was the big contributor for QPF.

LONG TERM.../Monday through Saturday as of 9 PM Friday/ Monday
begins with a weather front moving east over the Panhandle. Due to
the seasonably warm temperatures, all low elevation precipitation
associated with this front is expected to be rain. Precipitation
along the Haines and Klondike Highways may be a mix of rain and
snow and entirely snow closer to the border. Behind the front
shower activity diminishes through Monday evening.

Tuesday a low pressure system and its associated weather front
will track north across the Gulf. This will bring another round of
precipitation into the Panhandle on Tuesday; however, the track of
the front remains uncertain. Behind this front a southerly flow
pattern will set up which will continue the seasonably warm
temperatures through late in the week.

Little to no changes made in the extended forecast due to large
model discrepancies. WPC continues to favor an ensemble approach
through the extended forecast. The GFS favors a more westerly
approach for the low pressure system and its front on Tuesday
keeping precipitation more confined to the northern Panhandle and
allowing a brief dry out behind the Sunday and Monday system. The
ECMWF on the other hand is favoring a much more easterly track for
the system bringing the warm front into the southern Panhandle by
early Tuesday morning.

MARINE...A front with band of gale force winds head of it,
including a small barrier jet pocket of Storm force winds near
Cape Suckling Sunday afternoon will impact the marine waters until
the front moves inland Southeast Alaska by Monday. A building
swell behind the main front will increase the seas over the gulf
into the mid teens Sunday night and keep them there to Tuesday,
while it will top in the 20 to 24 foot range over the northern
gulf waters.

&&

.AJK Watches/Warnings/Advisories...
PUBLIC...None.
MARINE...Gale Warning for PKZ043-051-052.
     Small Craft Advisory for PKZ022-036-041-042.
     Small Craft Advisory due to Seas for PKZ053.

&&

KV/Byrd

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