796
FXAK67 PAJK 250002
AFDAJK

Southeast Alaska Forecast Discussion
National Weather Service Juneau AK
302 PM AKST Sun Nov 24 2024

.SHORT TERM...Looks like snow is back on the menu with an upper
level trough descending down from the northern Bering Sea. An
associated weak low at the surface will develop Monday along the
NE Gulf Coast and become stationary. On the onset of low
development, SW flow aloft will hit the Yakutat area with some
snow, prompting a winter weather advisory. As the low becomes more
stationary Monday afternoon and evening, pressure gradients in the
northern inner channels will favor northerly winds from the stout
high pressure in place near Whitehorse in Canada. The result is a
pattern very reminiscent of heavy snow for the Icy Strait area
and, if moisture was more abundant, significant snow
accumulation. Unfortunately, relative humidities for ice only look
to extend up to around 700 mb, which is enough for snow but not
enough for significant snow. 850 mb winds from the SW flowing over
a reinforcing stable layer from northerly winds down Lynn Canal
will remain persistent for more than 24 hours. Currently, just
north of Icy Strait, somewhat impressive frontogenesis at 850-700
mb looks to stick around, driving heavier snowfall. Unfortunately,
for those snow lovers, maximum omega, around -30 ubar/s at -5
degrees C, with minimal lift in the dendritic growth zone. At this
point, most moisture is in the lower levels of the atmosphere
with relative humidities above 700 mb being increasingly
uncertain. Additionally, windier conditions in Icy Strait looks to
inhibit snow accumulations for land areas due to mixing at the
surface. Wetbulb temperatures look to lift above 32 degrees for
Pelican, Hoonah, and Gustavus, limiting snow accumulation.

Overall, this setup looks to stick around for a long period of
time. While snow totals in Juneau look significant in a vacuum,
actual snow accumulation in any given 12 hour period looks to be
up to 4 inches for multiple days.

.LONG TERM...Heading into the long term period, we continue with the
unsettled weather for the panhandle. High pressure looks to
remain over the Yukon while an area of weak low pressure looks to
remain in the Gulf of Alaska. With this setup, cold air from
Canada will still be moving into the panhandle while there is the
potential that the low in the Gulf brings moisture to the area.
Temperatures for the panhandle are expected to warm up slightly
during the middle of the week before the return of the colder air
aloft. This colder air will bring surface temperatures down as
well as keeping what precipitation that does fall as snow. While
there is not any significant amounts of snow currently forecasted
for the long term, cold temperatures will allow for the snow to
stick to the ground and remain. As we head into the latter half of
the week, there looks to be a better chance of seeing snow right
around Thanksgiving. This will need to be watched as it gets
closer to see if it could bring significant snow to the area.
After Thanksgiving, the pattern looks to remain unsettled and
ensemble guidance continues to struggle on a clear outcome.
Guidance from CPC issued on Friday suggests that the area will
likely see temperatures and precipitation around near- normal for
the extended forecast.

&&

.AVIATION...Quiet aviation weather through Monday morning for
most of the panhandle as outflow winds are diminishing. The
exceptions are Skagway and Taku Inlet where gusty outflow
continues and Yakutat where snow will be coming back into the
forecast starting Monday morning. The remaining outflow is
expected to gradually diminish through Monday with the associated
turbulence that comes with it. As for the precipitation, the NE
gulf coast will see it first as early as Monday morning. Icy
Strait/Cross Sound may see it by Monday afternoon. Expect ceilings
and vis to start dropping to MVFR conditions with possible IFR
due to snow. The rest of the panhandle will likely see precip
moving in Monday night with the associated drop in vis and
ceilings.

&&

.MARINE...Light pressure gradients from an incoming weak surface
low look to keep wind speeds and wave heights low for the next
few days. The bigger question is wind direction rather than speed,
as competing air masses near Icy Strait Corridor could lead to
erratic wind directions. Broadly speaking, Lynn Canal is to
remain mostly northerly, and areas south of Icy Strait are to
remain mostly easterly to southeasterly, with speeds around a
moderate breeze and a small chance around 30% to be a fresh
breeze. Areas around Point Couverden may have higher wave heights
or wind magnitudes than advertised, due to converging winds
Monday.

&&

.AJK WATCHES/WARNINGS/ADVISORIES...
PUBLIC...Winter Weather Advisory from 6 AM to 6 PM AKST Monday for AKZ317.
     Winter Weather Advisory from 6 PM Monday to 3 AM AKST Wednesday
     for AKZ325.
MARINE...None.

&&

$$

SHORT TERM...NC
LONG TERM....SF
AVIATION...EAL
MARINE...NC

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