Gale Warning 73, NWS Juneau, AK

Southeast Alaska Forecast Discussion
National Weather Service Juneau AK
538 AM AKST Thu Feb 22 2024

.SHORT TERM...A front arrives in the panhandle beginning Wednesday
night, bringing with it rain, wind, and for a few locations,
accumulating snow.

By Thursday, anticipate widespread rain across the panhandle,
alongside small craft and gale force conditions across the inner
channels and outer coastal waters. Between 1 and 2 inches of rain
could fall across much of the area before the system departs by
late Thursday night. Alongside the rain, windy conditions are
expected across parts of the area - including Juneau and Skagway.
The windy conditions in Skagway will combine with sufficiently
cool temperatures to generate snow for higher elevations. Higher
snow ratios associated with CAA will quickly lead to whiteout
conditions near White Pass.

On the tail end of this frontal band, stronger cold air advection
around -8 to -10 C will cause atmospheric profile supporting for
snow. While most of the moisture will be sapped away from the mid
levels, leaving sporadic showers, the precipitation type will be
snow. This cold air advection will also likely yield rather steep
lapse rates combined with lower dewpoints, meaning that while
snow may be falling, surface temperatures may still be above
freezing, even up to 38-40 degrees F. Highest likelihood for these
snow showers (still only around 40%) appears to be the Yakutat
area.

.LONG TERM.../Friday through Wednesday/...Pattern changes for the
mid and long range forecast. Initial colder air moves in behind a
strong front Friday into Saturday. This is followed by drier
break Sunday into Monday as cold air becomes established and
northerly outflow winds increase. More front moves in next week,
but uncertain on details for that time frame. Friday: The previous
days front continues to track east while shearing apart. Will
have breaks between precip bands as we start to see temps drop.
850 mb temps already trending into the -8 to -10 C range. Any snow
accumulation for this time will be minor. For Saturday the next
front not showing as organized precip bands as previous days.
Still looking good for gale force winds over the gulf and inner
channels pickup to small craft as the front moves in. At this time
expecting snow amounts for Saturday in the 3 to 6 inch range for
the NE Gulf coast and Icy Strait corridor. Now looking at lower
QPF amounts with probability of 6 hour liquid accumulation above
0.25 inches less than 30%. For snow accumulation good probability
of 1 inch over 6 hours but again dropping to 40% for amounts above
2 inches. Model soundings indicate dendritic growth zone not
ideal saturation. Also this is not the typical pattern for airmass
change for SE AK. Normally for snow events is cold air in place
with a warmer airmass switching snow over the a mix or all rain.
This time we're starting rain and shifting to a mix then all snow.
By the time the cold air is established along the entire air
column the precip rates will likely be diminishing. After the
front pressure gradient shifts and we're now into cold northerly
outflow winds with lows in the teens. Next low/front moves in
Tuesday and that has been chance for precip being mostly snow
since cold air will have set in. Still questions on position and
timing of how fast the Friday night to Saturday low moves
southeast along the eastern gulf, which impacts how long the front
will remain over the area. Better alignment for Sunday into
Monday and then expect a low next week, but again not solid on the
details.

&&

.AVIATION.../12z issuance/...A band of moisture will track north
to south through the day today. As it does, flying conditions will
lower to mainly MVFR conditions with occasional low-end MVFR at
times. Once the band of rain clears your area, weather conditions
will improve rapidly to VFR. That being said, leftover onshore
flow will keep showers in the area, so times of high-end MVFR are
possible late in the forecast period.

&&

.AJK WATCHES/WARNINGS/ADVISORIES...
PUBLIC...Blizzard Warning from 9 AM this morning to 9 PM AKST this
     evening for AKZ318.
     Strong Wind from 9 AM this morning to 3 PM AKST this afternoon
     for AKZ319.
     Strong Wind from 3 PM AKST this afternoon through this evening
     for AKZ323.
     Strong Wind from noon AKST today through this afternoon for
     AKZ325-327.
     Strong Wind late tonight for AKZ328-330-332.
MARINE...Gale Warning for PKZ012.
     Small Craft Advisory for PKZ011-013-022-031>036-053-641>644-651-
     652-661>664-671-672.

&&

SHORT TERM...NC
LONG TERM....PRB
AVIATION...GJS

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

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