Gale Warning 60, NWS Juneau, AK

Southeast Alaska Forecast Discussion
National Weather Service Juneau AK
259 PM AKST Fri Feb 24 2017

.SHORT TERM...A marine layer of low clouds developed under the
ridge of high pressure over the gulf early this morning. These
clouds have spread into the coast and as of this afternoon have
pushed into the central inner channels to Juneau. Some places
along the outer coast even had some sprinkles or flurries out of
the marine layer. Due to the clouds, high temperatures have not
reached the mid to upper 30s as expected in places like Yakutat
and Gustavus. This will play a role in determining P-type with the
weather system moving in tonight. The far southern panhandle
remains clear this afternoon and the winds are light, so those
places will see temperatures fall quickly this evening before the
clouds move in.

A low pressure center will develop over the northern gulf near
Yakutat tonight then track SE across the panhandle through
Saturday morning. Models have been in good agreement with this
system the last several days, but forecaster confidence is lower
for P-type and snow amounts since there is some warmer air assoc
with it to start and because it is such a fast mover. Have most
places as a mix of rain and snow, but from Juneau north should see
more snow than rain. Amounts should be on the low end, around 1
inch since the duration will be fairly short, but some places
could see up to 3 inches. Once the precip moves south Saturday
morning, clouds should clear up fairly quickly and end up being a
fairly nice day (despite the north breeze).

Winds ahead of the low have already flipped to the south through
Lynn Canal. Expect those to increase to 20kt this evening as the
pressure packing increases with the low to the NW. There is
potential for some of the central inner channels to reach small
craft level out of the S-SE overnight, but as of right now only
have Cross Sound getting that high on the front end. After the low
moves through, there will be a sharp wind shift to the N with
winds increasing 25-30kt through all of the inside waters. This
was an increase of 5-10kt from the previous forecast. Land areas
will likely notice the sharp wind shift as well, but that will be
before most people wake up for the northern half of the panhandle.

Used mainly the NAM for updates to this forecast package, but most
changes were for local effects.

.LONG TERM...Quiet start to the beginning of the long range period.
Used the 12z NAM/ECMWF for updates to the forecast through day 4
then the latest WPC for the remainder of the forecast.

The northerly winds discussed above will rapidly diminish through
the night Saturday as the pressure gradient weakens. For Sunday,
expect a dry day with generally light winds but weak energy will
move over the area from the north. Increased cloud cover is the
only impact expected from this feature.

Then we turn our attention to what is shaping up to be a very
active weather week from late Monday onward for Southeast Alaska. A
potent northern stream trough will dig into the northern gulf
Monday afternoon. The upper low will cut off and lead to
strengthening surface low pressure in the northeast gulf. This will
set the stage for an overrunning snow event for much of the
panhandle. How this pattern evolves into mid and late week remains
in question as models are struggling with the phasing of the
northern and southern streams resulting in little run to run
consistency. The overall message is this pattern is favorable for
significant snow across portions of the area as well as below
normal temperatures. This timeframe will be closely monitored over
the coming days. Stay tuned...

&&

.AJK Watches/Warnings/Advisories...
PUBLIC...None.
MARINE...Gale Warning for PKZ041-042.
     Small Craft Advisory for PKZ011>013-022-031>036-043-051-052.
&&

Ferrin/TPS

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