Area Forecast Discussion
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FXAK67 PAJK 222247

Southeast Alaska Forecast Discussion
National Weather Service Juneau AK
247 PM AKDT Thu Mar 22 2018

.SHORT TERM.../Thursday night through Friday night/...A low to
the south and high pressure over the Yukon has produced very
strong outflow winds over the Panhandle today. High wind gusts in
excess of 70 mph have been reported today in the downtown Juneau
area as well as Tenakee Springs. Farther north, strong wind gusts
have been recorded all day in Skagway and this afternoon in Elfin
Cove. Storm force winds over northern and southern Lynn Canal
have also been steady all day, with high end gales over northern
Stephens Passage. Gales have been blowing over Cross Sound as
well. Winds have been less intense over the southern half of the
panhandle. High wind warning for Juneau is set to expire at 4pm
today, but strong wind gusts to 55 mph are still in the forecast
and will continue through most, if not all, the night. High end
gale force outflow winds are also forecast for coastal marine
zones 43 and 51 through tonight. A combination of weakening high
pressure over the Yukon tomorrow and the low tracking south will
ease the pressure gradient by tomorrow, so winds will ease up most
places. Exception is Lynn Canal, where small craft winds will
persist through Saturday morning.

Shower activity will be mostly limited to the southern panhandle
and will result from wrap-around precipitation about the low
currently to the southwest of Haida Gwaii. Precip type will be
mostly rain, but a mix of rain and snow is likely late tonight.
Very little accumulation expected near sea level. Higher
elevations, such as the road system on Prince of Wales Island,
may see up to an inch overnight.

Short range forecast winds update using the latest NAM Nest as a
foundation, with some manual edits where the model was clearing
under-doing wind speeds. Temperatures adjusted with a blend of NAM
and GFS MOS. No changes to the PoP forecast. Overall forecast
confidence is average.

.LONG TERM.../Saturday through Wednesday/ Expect a pattern change
to occur in the extended forecast. The extended forecast begins
dry with a weak surface low pressure system over the north central
gulf and a much stronger surface low in the Bering Sea. The low
over the central gulf will have minimal impacts on SE AK; however,
the low in the Bering Sea will send a weather front eastward over
the gulf, bringing wet weather back between Sunday night and
early Monday morning. Initial precipitation may fall in the form
of snow especially over the northern Panhandle. However, warm air
will be advected with this system, which will quickly cause a
changeover to a purely rain system. The exception may be along the
Haines and Klondike Highways where temperatures may stay cool
enough to support snow through the period. This will begin a wet
pattern that persists into the middle next week.

A fair amount of changes were made in the long term. Winds were
increased along the front between Sunday and Monday. Currently no
gale fore winds are forecasted; however, models are trending
intensification of this system. Additionally, models are being
fairly aggressive with precipitation totals associated with the
front, if the trend continues, periods of heavy rain likely to
occur with this system. Temperatures were another area of change.
Started to trend temperatures upward and thus snow levels;
specific detail was paid to the Sunday and Monday timeframe in
order to best disseminate rain and snow. Model agreement is above
average in the long term leading to increased forecast confidence.
Primary guidance was a blend of the ECMWF and GFS through Monday
morning with new WPC guidance used beyond that timeframe.

.AVIATION...Outflow winds and an 850mb jet wrapping around the
Haida Gwaii low will result in moderate turbulence or worse and
LLWS across southeast Alaska through Thursday night and early
Friday morning. Conditions improving significantly by Friday


.AJK Watches/Warnings/Advisories...
PUBLIC...Strong Wind through late tonight for AKZ018-025.
MARINE...Storm Warning for PKZ012-013.
     Gale Warning for PKZ022-032-043-051.
     Small Craft Advisory for PKZ011-021-031-033-034-041-042.




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