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FXAK67 PAJK 210140
AFDAJK

Southeast Alaska Forecast Discussion
National Weather Service Juneau AK
440 PM AKST Mon Feb 20 2017

.SHORT TERM...A shortwave trof will move NE across the Hyder area
tonight. A larger shortwave trof will move E into the N gulf
tonight, then elongate SE as the trof moves to the outer coast by
Tue afternoon. A small low will move E across the N gulf late
tonight and Tue. Used blend of the 12z GFS/EC for pressures, but
mainly used GFS for most other parameters. Blended in some SREF
for POPs.

Main forecast concerns are precip potential, cloud cover, and
temps. There is some snow shower activity just SE of the Hyder
zone associated with a shortwave moving NE toward them. Think
they will see a few snow showers reach into that area by early
evening. These snow showers should move out of the Hyder area
around daybreak Tue as shortwave moves away. Larger shortwave
moving into the N gulf will increase shower activity over that
area tonight then these showers should push into the outer coast
toward daybreak Tue. Some of these showers will get into much of
the inner channels Tue afternoon. Keeping highest POPs with these
showers along the outer coast. Precip type will be mainly snow
although some rain could mix in over the far southern areas. Could
see an inch or so of snow along the outer coast, otherwise not
much snowfall is expected.

Broken mid-level clouds over the far S will persist this evening
then push out as shortwave moves away from the area. Thicker and
lower clouds should affect the Hyder area though and hang around
into at least Tue morning. Clouds within cold advection area and
with next shortwave will remain over the E gulf and NE gulf coast
into Tue, with these clouds spreading inland over most of the
remainder of SE AK later tonight and Tue.

Temps should be a bit cooler over most areas due to weak cold
advection tonight, but cloud cover moving into the coast will
help keep temps warmer there. On Tue, with more cloud cover and a
few snow showers around, temps should be several degrees cooler
than they were today.

Otherwise, the most significant wind will be over the central and
parts of the N gulf. Could see up to 25 KT winds especially over
the offshore waters and nearby edge of the coastal waters late
tonight and Tue. Inner channel winds should remain 15 KT or less.

.LONG TERM...General story through the extended forecast has an
upper level ridge over the gulf with weak troughs moving over the
top of it, then progressing SE along the outer coast of the
panhandle. We have one of these passing by Tues evening, Wed
night, Sat, and possibly Monday. Each one of these will have a
weak surface low reflection with showers skirting by along the
coast. Expect winds through the inside waters to flip S-SE ahead
of each wave or be light and variable, then turn back to the
dominant N-NWLY flow behind them.

The Saturday low/trough looks to have the most likely chance of
showers reaching further inland. The upper level flow backs a bit
more onshore with that wave. Temperatures aloft through the week
will be cold enough for majority of showers that pass by to be in
the form of snow, but not expecting much accumulation at this
time.

Between each system the clouds part to allow for fair weather and
some sunshine. Expect normal highs for this time of year, in the
mid 30s for the central/northern panhandle to low 40s across the
south. Partly to mostly clear skies at night will make for a
larger diurnal range with lows also near normal or slightly
below.

Models were in good agreement on the overall pattern with slight
differences on breadth of POP as each wave passes by. Used
primarily the 12z GFS for updates to this forecast package which
also matched well with WPC guidance. Forecast confidence is above
average.

&&

.AJK Watches/Warnings/Advisories...
PUBLIC...None.
MARINE...Small Craft Advisory for PKZ051.
&&

$$

RWT/Ferrin

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