Winter Storm in Alaska, February 24 to 26, 2021

Southeast Alaska Forecast Discussion
National Weather Service Juneau AK
545 AM AKST Wed Feb 24 2021

.SHORT TERM...Our next weather system approaches the panhandle.
Satellite imagery shows a surface low developing in the western
Gulf with a long fetch of moisture being transport up from the
Pacific. Aloft, a shortwave trough associated with the surface
low pivots towards the panhandle. As this system continues to
push east, widespread precipitation and winds will increase
through the morning. Temperatures overnight have been steady in
the low to mid 30s. This morning, most areas will be cool enough
at the onset of precipitation to see some snow or at least a mix.
As winds increase, a southerly push ahead of the low will warm
temperatures enough for a change to rain. As the low deepens,
winds pick up substantially bringing widepread strong wind
headlines and high wind gusts up to 65 mph for the southern
coastal areas. Further north, the transition to rain is still
expected but exact timing could vary depending on when winds begin
to increase. Newest model guidance suggest a bit slower arrival
time with the low tracking towards Sitka before pivoting to the
south and moving along the southern coast through late Wednesday
night. This may cause current forecast arrival time to be a little
on the fast side but small enough, forecast changes were forgone.

With this system, rain could be heavy at times across the
central and southern panhandle. 24 hour precipitation totals
nearing 1.50 inches are likely with lesser amounts to the north.
As the low tracks further south Wednesday night, southerly winds
will flip to the north and begin weakening. A change over to snow
is expected as northerly flow allows for temperatures to cool.
Areas across the north can expect to see the change over the
quickest while the central panhandle sees a change over this
evening and into tonight. Minor accumulations between 1 to 3
inches are expected with highest amounts across the far north.
Thursday, a broad area of low pressure over the northeast gulf
coast will promote shower activity across the panhandle. By
Thursday evening, precipitation will exit allowing for a brief
break on Friday.

.LONG TERM.../Friday through Wednesday night/...An active weather
pattern continues into the long term with at least two systems
expected to impact Southeast Alaska through early next week.

The period begins with weak ridging building over the Gulf on
Friday leading to WNW flow over Southeast Alaska. Showers will be
diminishing in the morning becoming mainly dry for most of the
area by the afternoon. Drier air moving in aloft should even lead
to breaks in the clouds during the day. Unfortunately, the quiet
weather won't last long as the next weather maker moves by
Saturday morning.

Precipitation moves back into the region as a low moves into the
NW gulf swinging a front into the Panhandle Saturday morning.
Good upper level dynamics will be associated with this front as a
SW-NE oriented jet pumps in subtropical moisture. The NAEFs and
EC Situational Awareness Tables already show IVT values and PW 2
to 3 standard deviations above normal for this time period. There
is potential for heavy rain across the region this weekend as
there are signals an atmospheric river will develop with this
front. P-type should be predominantly rain with the northerly
track of the low and persistent southerly flow into the Panhandle;
however precip may begin initially as snow before low level cold
air is scoured out. Snow levels will rise significantly as this
system pushes in with levels as high as 3,000 - 4000 ft across the
central and southern Panhandle on Saturday. Current thinking is
that a total of 1 - 2.5 inches of liquid will fall from Saturday
morning through Sunday evening. A brief break in the heavier
precipitation is expected Sunday night through Monday as the
system departs and a zonal onshore flow pattern sets up.

Models and ensembles continue the active weather pattern into
early next week as there is good agreement another system will
move into the northern gulf by Tuesday. This system may be very
similar to the previous one with good upper level dynamics and
subtropical connections. Details regarding these systems will be
fine tuned in the coming days. Overall confidence remains high in
an active pattern continuing across the region. Focused on the
weekend system for any changes to the forecast.

&&

.AJK WATCHES/WARNINGS/ADVISORIES...
PUBLIC...Strong Wind from 9 AM AKST this morning through this evening for
     AKZ026.
     High Wind Warning from noon today to 6 PM AKST this evening for
     AKZ023-027.
     Strong Wind from 3 PM AKST this afternoon through this evening
     for AKZ024.
     Strong Wind from 3 PM AKST this afternoon through this evening
     for AKZ021-022-025.
     High Wind Warning from 3 PM this afternoon to 9 PM AKST this
     evening for AKZ028.
MARINE...Storm Warning for PKZ041>043-051.
     Gale Warning for PKZ021-022-031>036-052.
     Small Craft Advisory for PKZ011>013-053.

&&

CC/CM

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