Gale Warning 36, NWS Juneau, AK

Southeast Alaska Forecast Discussion
National Weather Service Juneau AK
259 PM AKST Fri Jan 24 2020

.SHORT TERM...Active weather pattern continues across Southeast
AK. A deep upper trough over the central gulf will begin to drift
west toward the western gulf Saturday. Southern stream shortwave
will move north over the eastern gulf and across the panhandle
early Saturday through Saturday night. At the surface a cold front
has moved across much of the panhandle and will stall over the far
southeastern area tonight. Current satellite imagery indicates
snow showers rotating around a surface low in the northern gulf
and moving ENE towards the outer coast. The snow showers will
mainly move over northern parts of the panhandle, north from
Sitka to Juneau, then the coverage will drift northwestward
overnight. The front across the southern panhandle will begin to
drift north as a warm front Saturday. A developing low will move N
into the southeast gulf by Saturday morning spreading another
round of precipitation northward across the panhandle Saturday.
The first wave will reach the northern areas by Saturday
afternoon. A secondary wave will follow enhancing precipitation
late Saturday night into Sunday morning.

One of the complexities of this forecast has been the up-and-down
nature of the temperatures over the next few days, which will in
turn derive where and when rain changes to snow and vice-versa.
The current idea is that the central inner channels will begin as
snow Saturday morning before changing over to rain after noon.
The northern inner channels will remain snow Saturday into Sunday
morning. Therefore the more impactful snowfall this weekend will
likely be across parts of the northern channels. Friday night an
winter weather advisory for 3 to 5 inches of snow is expected for
Haines. Then Saturday night there is potential for 7 to 10 inches
of additional snowfall in the Haines and Skagway areas, therefore
a Winter Storm Watch is in effect from Saturday evening through
early Sunday morning. There is also potential for a significant
amount of snowfall in the Juneau area Saturday night so future
shifts will need to decide if any products will need to be
necessary. While models have come into better agreement, the GFS
provided the basis for a few forecast adjustments. Forecast
confidence is moderate to above-average in the short term.

.LONG TERM.../Sunday through Friday/As of 10 PM Thursday/The
picture for the long term continues to look muddy due to large
variations within the various models, but what is clear is that we
will be returning to a stormy pattern in the coming days. Deep
troughing over mainland Alaska and into the Gulf will pool some
rather cold air, which will mainly impact northern panhandle
locations. around this troughing an active jet pattern will send a
series of lows around the trough that will continue to keep flow
southerly should bring warmer temperatures through much of the
panhandle. This southerly flow will also provide ample moisture
for these systems to play with. Given the time of year, and
potential interactions with the arctic air camped out to the
north, p-type issues will likely be the biggest forecast challenge
for next week. North central and northern panhandle locations will
be the ones to watch for potential heavy snowfall as some of these
systems look like they will be pretty good precip makers. For the
southern areas, temperatures look to remain warm enough that
precip type should mainly remain as rain, however still can't rule
out a few snowflakes mixing in if precip is occurring during the
colder parts of the day.

As with any complex set-up, the models really begin to diverge
wildly on specific timings and intensity of any particular storm,
therefore the forecast remains largely unchanged with some
blending to WPC guidance for continuity. The overall message is,
it looks like it will be wet, but it is yet to be determined what
form the precip will take with any real confidence, it just needs
to be noted that the potential is there for at least one or two
storms to bring heavy precipitation and strong winds in the coming
week.

&&

.AJK Watches/Warnings/Advisories...
PUBLIC...Winter Weather Advisory until 6 PM AKST this evening for AKZ025.
     Winter Weather Advisory from 6 PM this evening to 6 AM AKST
     Saturday for AKZ019.
     Winter Storm Warning until 6 PM AKST this evening for AKZ018-019.
     Winter Storm Watch from Saturday evening through late Saturday
     night for AKZ018-019.
MARINE...Small Craft Advisory for PKZ022-036-041>043-051-052.

&&

DDH/JDR

Visit us at http://www.weather.gov/Juneau