Gale Warning 88, NWS Juneau, AK

Southeast Alaska Forecast Discussion
National Weather Service Juneau AK
415 PM AKST Tue Feb 27 2018

.SHORT TERM.../ Tuesday night to Thursday / Weather system coming
into the northeast gulf and northern panhandle was the focus for
todays forecast. There was a blend of the GFS and ECMWF and the
early NAM, for any of the adjustments. . With the low moving up to
the northeast gulf coast looking for northern tier zones to get
2-6 inches though the Haines area to is expected to receive about
5-9 inches of snow. Nearby areas, out to the border on the Haines
Road, and along the Klondike High only expecting 2 to 4 inches of
snow. The Yakutat, Hoonah and Juneau areas should see about 2 to 4
inches as well. Have issued a Winter Weather Advisory for the
coastal area near Cross Sound and a Winter Storm Warning for the
Haines area of Lynn Canal.

Along with this low is band of potential stronger convection so we
are not ruling out the possibility of isolated Thunderstorms
embedded in the shower activity. Mainly of the coastal marine
areas to the coast lines. Am not anticipating it moving inland.

A second wave further south will be moving to the southern Haida
Gwaii area by midday Wednesday and this will sap energy from the
northern system so through Wednesday a stronger outflow of
northerly winds will be picking up and will be seeing drying
conditions through Wednesday night for the panhandle.

Also slowed the cooling down with the north winds out of the
interior more until later Wednesday into Thursday time frame.

.LONG TERM.../Thursday through Tuesday/ As of 10 pm Monday. Dry,
cold, windy weather pattern for the start of the long range
forecast. Strong northerly pressure gradient between low pressure
over Haida Gwaii and high pressure over the Yukon will produce
outflow and northerly winds in the 35 to 40 kt range over the
inner channels. Due to orientation of the gradient not expecting a
Taku wind event for Juneau. Cold arctic airmass with 850 mb temps
in the -15C range will also move over the panhandle due to the
offshore flow. This along with clear skies and radiational cooling
will produce overnight lows in the teens to possible single
digits for the central and northern regions with lows in the 20s
for coastal and southern areas. As the low and Yukon high weaken
and drift to the southeast winds will diminish and temps will
begin to warm slightly. The 500 mb blocking ridge extending from
the N Pacific into the Arctic will last through Saturday keeping
the panhandle dry. Timing of the ridge breaking down is still
uncertain. GFS/Canadian are starting to fall more in line with
allowing a fast moving short wave to over ride a flattening ridge
and bring in next chance of precip Saturday night into Sunday.
Better agreement the ridge will fully break down to more zonal
flow Monday into Tuesday with a return to more moderate
temperatures and wet weather.

With models remaining in good alignment for the early part of the
forecast used only some NAM to nudge up wind speeds. Due to
uncertainty later in the forecast only made minor adjustments
using GFS to increase PoP to slight chance and began to warm
temperatures. If GFS/Canadian/ECMWF start to fall in line as
indicated by newer runs, later forecast will likely need to increase
PoPs Sunday. Forecast confidence is average early on then drops
by the weekend as the ridge breaks down.

&&

.AJK Watches/Warnings/Advisories...
PUBLIC...Winter Weather Advisory from 9 PM this evening to 9 AM AKST
     Wednesday for AKZ022.
     Winter Storm Warning from 9 PM this evening to 9 AM AKST
     Wednesday for AKZ019.
     Strong Wind until 6 PM AKST this evening for AKZ018.
     Strong Wind from Wednesday afternoon through late Wednesday
     night for AKZ018.
MARINE...Gale Warning for PKZ012-013-022-043-051-053.
     Small Craft Advisory for PKZ011-021-031>035-041-042-052.

&&

JWA-Bezenek/PRB

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