Area Forecast Discussion
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FXAK67 PAJK 172346
AFDAJK

Southeast Alaska Forecast Discussion
National Weather Service Juneau AK
246 PM AKST Fri Jan 17 2020

.SHORT TERM...Groundhog Day is best enjoyed as a novelty bit of
news on February 2nd, with a trip to Punxsutawny, Pennsylvania at
Phil`s show, or viewing from the couch watching a classic film.
It is not best experienced, repetitively during a random week in
mid- January on a forecast desk. The slam of one short-wave after
another, deciphering mid-level boundaries, cross barrier
gradients, and critical levels is what we have done, repeatedly.
The lull that was speculated today has occurred, but observations
still support extending the warning out, rather than letting the
one of last night expire and issuing another for the true second
event tonight and Saturday. We fully expect an increase in Taku
gust magnitude tonight into early Saturday morning to 75 mph, with
a gradual decline through Saturday night. In other winds the
current state of the High Wind Warning looks good. And in no way
are we expecting a repeat of the ominous scenes townies in the
capital experienced Thursday morning. But expect more disturbing
creaks, window bowing, and pressure waves reverberating through
your homes tonight if you live in Downtown Juneau, Douglas, West
Juneau, and Thane.

We did look at the potential for high winds in Haines late tonight
into Saturday as well. However, given the lack of impacts with the
last event, and the fact that this event should be weaker, we are
cancelling the watch and instead electing to go with gusts a shade
lower than 60 mph.

The best part of this forecaster`s living Groundhog Day
experience is the ending. We shall see if you like it.
Ketchikaners, we see an end to the dry pattern. While we
acknowledge you received snow flurries yesterday afternoon, a
front gathering steam well to the south will interact with the
cold air mass you have been dealing with since just after the New
Year. We expect overrunning snowfall to ensue as early as Saturday
morning with accumulations increasing through the afternoon. We
have been noting significant snowfall possibilities for the south
for some time. But the winds in the north have frankly gotten in
the way of truly focusing on their potential aside from the
differing solutions. We took a careful look at temperatures, low
level thicknesses, QPF possibilities, and have surmised that a
winter weather advisory for a good snow event of 4 to 8 inches is
in order. We do acknowledge that an earlier changeover to rain
late Saturday night could embarrass our totals with something
lower, but this seemed the best solution. One other thing to note
is that models sometimes overestimate QPF in easterly flow, so
this is a concern and prevents our confidence from being high.

Elsewhere we are extending the wind chill advisory for White Pass
through 6 AM Sunday as winds look to last longer and the cold air
will remain entrenched longer for the north.

The snow in Ketchikan will herald the beginning of a weather
pattern change for even the central Panhandle. Even Juneau may see
a little snow late Saturday night into Sunday. But amounts will be
low, as it is not a favorable wind direction for high amounts. But
more southerly flow at all levels will most importantly bring an
end to the cold continental air mass we have endured as of late.
Expect warming temperatures and the rain-snow line creeping
northward next week. More on that in the extended.

.LONG TERM.../Sunday through Friday as of 10 pm Thursday/ Long
range pattern is entering a more progressive phase with initially
a broad upper trough parked over the Bering Sea that will
gradually flatten as the week progresses. At this point, a series
of several short wave troughs will be advancing on the panhandle
from the SW through the week. Generally good agreement from
guidance on this overall pattern. However, timing of each
individual short wave has rather low confidence as each model has
a different idea on how the flattening of the large scale trough
will play out. So forecast confidence for mid to late week is
moderate at the moment.

For the panhandle, the long term will be a time of change as we
claw our way out of the recent cold snap and strong outflow winds
to wetter and warmer conditions. Initially, temperatures across
the panhandle will still be below freezing for many areas, but the
southern panhandle will start to see high temps above freezing as
early as Sun. Deep layer southerly flow will continue the warm air
advection into the panhandle through the week with the central
panhandle warming above freezing as early as Mon and the northern
panhandle following suit by Tue or Wed. The warmer weather is
expected to last through the rest of the week. Ensemble models
support this with some standardized anomaly values for
temperatures above 1 standard deviation above normal for next
week.

As for precipitation in mid week, with temperatures warming above
freezing many areas will likely turn into ice skating rinks as
rain falling on the current snow pack (especially on any snow that
has been compacted by foot or car traffic) turns them into sheets
of ice. This will be somewhat of a lesser problem across the
northern inner channels as even though temps do warm above
freezing, it will not be by much so more of a wintry mix is
possible rather than straight rain.

Given the spread in the timing of the various system coming across
the gulf mid to late week, elected to focus on WPC and NBM for
guidance for the long range.

&&

.AJK Watches/Warnings/Advisories...
PUBLIC...High Wind Warning until midnight AKST Saturday night for AKZ025.
     Strong Wind through Saturday afternoon for AKZ019.
     Strong Wind through Saturday afternoon for AKZ021.
     Strong Wind through late Saturday night for AKZ018.
     Wind Chill Advisory until 6 AM AKST Sunday for AKZ018.
     Winter Weather Advisory from 9 AM Saturday to 6 AM AKST Sunday
     for AKZ028.
MARINE...Heavy Freezing Spray Warning for PKZ031.
     Heavy Freezing Spray Warning for PKZ011.
     Heavy Freezing Spray Warning for PKZ012.
     Heavy Freezing Spray Warning for PKZ013.
     Storm Warning for PKZ012-013.
     Gale Warning for PKZ031-035-041>043.
     Small Craft Advisory for PKZ021-022-032>034-036-051-052.

&&

$$

JWA/EAL

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