Winter Storm Warning 3, NWS Juneau, AK

Southeast Alaska Forecast Discussion
National Weather Service Juneau AK
526 AM AKST Sat Jan 20 2024

.SHORT TERM...Satellite imagery and surface analysis shows high
pressure over Yukon with low pressure over the SW gulf with a
decaying front pushing N through the panhandle early this morning.
This boundary is the focus from some light snow across the central
panhandle with light accumulations expected. Little dynamics to
push the boundary much further N today so expect precip chances to
diminish through this afternoon. Strong PGF persists over the N
with gales continuing over Lynn Canal through Sat. The high wind
warning for Skagway was cancelled as wind gusts have topped out
50-55mph. Guidance shows gradient relaxing slightly this morning
into the afternoon before increasing again tonight into Sunday as
another low approaches from the S. This low will take another
jab at the arctic airmass entrenched over the region and
expanding precip chances northward overnight.

.LONG TERM...Main story for the midweek is the pattern change for
the entire panhandle this weekend. Ensemble guidance is
suggesting that outflow winds will be coming to an end and
temperatures will be on a constant rise through the weekend. This
is thanks in part to several frontal waves moving up the panhandle
from a parent low near the Alaskan Peninsula beginning Saturday.
Cold air and northerly outflow will hold off much of the precip in
the central and northern panhandle Saturday before a stronger
frontal wave moves up the panhandle Sunday. Prior to this wave,
850 mb temperatures look to warm substantially across the southern
panhandle to 0 degrees Celsius. Therefore, much of the
precipitation falling across the southern panhandle will fall as
rain except at elevation over PoW Island. Then on Sunday, the
southerly wave will push northward, changing any remaining areas
to rain as it moves north. Then, it looks like cold air will stall
the front. Along this front from Icy Strait northward, a band of
snow will follow. Unfortunately, how much warm air will push
northward, how much cold air will be in place to prevent the front
from moving northward, how much moisture will actually be present
after pushing through the cold, dry air, and where the boundary
will stall are all questions which will effect accumulating snow
totals. At this time, ensemble guidance seems to indicate that a
80% chance of at least 0.25 inches of QPF is expected for the
Juneau area and similar percentages for the Icy Strait corridor of
at least 0.20 inches of QPF. Combine that with the relatively low
snow ratios of around 12:1 diminishing down to 8:1 means that
around 5 - 8 inches is expected. Therefore, this prompted a winter
storm watch for the Icy Strait corridor and Juneau on Sunday.
Less moisture is expected to reach up near Haines, but snow ratios
are expected to be higher. Therefore, 3 - 5 inches are also
expected for Haines. The main trend compared to yesterday is the
increase in QPF across the Icy Strait corridor, and the band
remaining somewhat stationary for the heavier precipitation. With
the heavier precip, it may lean toward precip type staying as snow
for longer through Sunday night, particularly for the Juneau
area.

What is high confidence is we will be on the warming trend into next
week with temperatures becoming above normal instead of the below
normal temperatures that the panhandle has been experiencing. Along
with the warming trend, more rain is in the forecast as an active
pattern fully takes hold. One thing to note is LREF grand ensemble
seems to indicate a possibly potent system moving in late next week.
At this time, the Anchorage area appears to take the brunt of the
impacts, however, more will become clear with time. Stay tuned for
more information.

&&

.AVIATION...Over the northern areas, VFR continues. Persistent and
heightened northerly winds continue to influence the majority of
the north-to-south-oriented channels. Sitka east towards PAPG and
south, anticipate a wave of snow progressing eastward through the
morning bringing MVFR and IFR briefly under heavier bouts of
snow. Precipitation will briefly end late Saturday afternoon,
giving way to a more pronounced frontal system positioning itself
near Dixon Entrance by late Saturday evening. As the front
advances northward overnight, expect widespread precipitation
across the south, resulting in borderline MVFR/IFR CIGS.

&&

.AJK WATCHES/WARNINGS/ADVISORIES...
PUBLIC...Wind Chill Advisory until 6 AM AKST Sunday for AKZ318.
     Strong Wind through late tonight for AKZ318.
     Winter Storm Watch from Sunday afternoon through late Sunday
     night for AKZ320>322-325.
MARINE...Gale Warning for PKZ012-013-022-031-643-644-651-664.
     Small Craft Advisory for PKZ021-032>034-053-641-642-652-661>663-
     671-672.

&&

SHORT TERM...BC
LONG TERM....NC
AVIATION...AP

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

Preliminary Local Storm Report
National Weather Service Juneau AK
526 AM AKST Sat Jan 20 2024

..TIME...   ...EVENT...      ...CITY LOCATION...     ...LAT.LON...
..DATE...   ....MAG....      ..COUNTY LOCATION..ST.. ...SOURCE....
            ..REMARKS..

0248 AM     Non-Tstm Wnd Gst 1 WSW Skagway           59.45N 135.33W
01/20/2024  M61 MPH          PKZ012             AK   ASOS

            ASOS station PAGY Skagway Airport.

&&