Gale Warning 263, NWS Juneau, AK

Southeast Alaska Forecast Discussion
National Weather Service Juneau AK
256 PM AKST Mon Nov 16 2020

.SHORT TERM..../Monday evening through Tuesday night/ Active
weather in the short term with an outflow event across the north
and a low moving up from the south.

The outflow event for the northern Panhandle remains on track
over the next few days with minimal changes made to the overall
forecast. Went ahead and upgraded the High Wind Watch to a High
Wind Warning for Downtown Juneau and Douglas as MTNWV guidance and
cross sections continue to indicate favorable conditions for
mountain wave development. Expecting Taku winds to begin Tuesday
morning and last through Wednesday morning with the strongest
winds expected Tuesday evening. Frequent gusts to 70 mph are
likely during this time frame. Due to the increase in winds,
expect Downtown Juneau and Douglas to remain quite a bit "warmer"
than wind sheltered areas towards the valley.

Canceled the High Wind Watch for Skagway as current thinking is
that they will stay just below high wind criteria. Despite the
strong PAGY to PAJN pressure gradient producing storm force winds
in Lynn Canal, the inversion just above the surface may keep the
strongest winds from going down the valley and reaching Skagway.
Capped wind gusts to 55 mph in Skagway during this time frame. There
is moderate confidence in this wind forecast for Skagway, however
this will need to be watched closely during the next day or so as
a warning may be needed if winds appear to be stronger than
forecast.

Across the south, the big story for the short term will be the
first accumulating snowfall of the season. This evening, a
northerly pressure gradient remains in place keeping colder air
locked in near the surface. Winds aloft are expected to turn
northerly tonight as a low approaches the southern BC coast.
Model guidance has improved regarding the timing and track of this
system. The low is expected to track northward through Hecate
Strait and into the Dixon Entrance by Wednesday morning, then
meander around the SE gulf and weaken.

Precipitation will spread into Misty Fjords and the far southern
Panhandle from the SE Tuesday evening then spread further north
and west Tuesday night. There is some uncertainty regarding QPF
with this system as guidance has been going lower with precip
amounts with each run. The lower totals are most likely due to
the drying northerly winds near the surface, which will also help
keep the cold air locked in place. Due to a persistent northerly
gradient and the lack of warm air advection with this system (850
mb temps remaining around -6C to -8C), kept temps below guidance
for the southern Panhandle with highs only in the low to mid 30s
Tuesday and Wednesday. Currently expecting 1 to 3 inches of snow
around Ketchikan and Prince of Wales Island Tuesday evening
through Wednesday afternoon. Decided not to issue a Winter Weather
Advisory at this time due to the continuing trend of lower precip
amounts. Instead, issued a Special Weather Statement regarding the
first accumulating snow of the season for Ketchikan, Metlakatla,
and portions of POW island.

.LONG TERM.../Wednesday through Monday as of 10 pm Sunday/
Northerly outflow winds decrease on Wednesday as pattern changes
occurs with a low tracking into the SE AK Gulf from Dixon
Entrance. This low weakens with little in the way of northward
progression then tracks back to the southeast. Towards the end of
the week a trough moves into the NE Gulf from the west swinging a
front across the AK Gulf. No impactful weather associated with
this front. For the weekend indications of a deeper low moving
into the NE Gulf and stronger front tracking across the AK Gulf
and impacting the Panhandle.

Increased outflow winds for Wednesday, especially for the
northern regions due to gradient between the SE Gulf low and high
pressure remaining over Western Canada. Also kept temps lower for
same locations due to the cold outflow remaining. Still fair
operational model spread for this low, especially with respect to
how far north precipitation bands will go. There is better
agreement that the southern locations will see some snow and then
begin to mix with rain as flow shifts more southerly and warmer
air advects in.

For the long range synoptic pattern ensembles have been mainly
consistent with overall idea but fair amount of spread on details.
Both NAEFS and ENS standardized anomalies indicate weekend
precipitation and warmer mid and low level temps and increase in
gulf winds but nothing to indicate any highly impactful events.
EFI tells a similar story. So weekend outlook is a typical late
fall system with gale force winds likely and with southerly flow a
change from snow to a mix or all rain. Precipitation type will
depend highly on how much of the cold air that is established
early in the week remains.

Besides the increase in winds for Wednesday and a decrease in PoP
with the late week front not much change done. Forecast confidence
through the end of the week is average even with the uncertainty
of the SE Gulf low. Late week confidence is lower, even with more
certainty of the weekend low moving in but with less certainty on
strength and position.

&&

.AJK WATCHES/WARNINGS/ADVISORIES...
PUBLIC...High Wind Warning from 6 AM Tuesday to 9 AM AKST Wednesday for
     AKZ025.
     Strong Wind from Tuesday morning through late Tuesday night for
     AKZ019.
     Strong Wind from 9 PM AKST this evening through late Tuesday
     night for AKZ018.
MARINE...Storm Warning for PKZ012-013.
     Gale Warning for PKZ022-031>034-041>043-051.
     Small Craft Advisory for PKZ011-021-035-036.

&&

CM/PRB

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