Heavy Snow and High Wind in Alaska, January 20, 2023

Southeast Alaska Forecast Discussion
National Weather Service Juneau AK
358 AM AKST Fri Jan 20 2023

.SHORT TERM...A storm force low moves into the central portion of
the AK Gulf today and tracks northward towards Prince William
Sound through Friday night. The associated storm force front
crosses over the eastern gulf with increasing gulf winds, seas
building towards 30 ft, and inner channel winds increasing to
gale force. Overland wind gust should only reach 50 mph as the
front passes, but will monitor for possible higher gusts. Non
diurnal temperature trend into Saturday as temps this morning were
in the low to mid 40s and should stay steady or rise slightly as
the front advances. As the low center reaches the NE Gulf cold air
will move in with temps then dropping in the early morning and
then through the day. Heaviest precip expected to occur late this
morning and into the evening. Warm air aloft and at the surface
keeps precip as rain for all locations except upper elevations
and the winter weather advisory continuing for White Pass into
early Saturday morning with 4 to 7 inches of accumulation.
Expecting more of a mix of rain and snow with CAA behind the front
late tonight, however due to warmer surface temps any
snow accumulation should be at most an inch or two. New model
runs backed off on PoP for tonight as the low center pulled
further to the west, which along with lower QPF gave better
consensus on limiting snow totals. Still some models having
precip more showery in nature and with increased rates and snow
melt cooling can not rule out training of cells and higher snow
totals.

GFS/NAM were in good agreement with position of the low which was
further west than previous forecast. GFS depicted a stronger
front, but for now held off on those higher winds. However did
follow the GFS/NAM QPF forecast and lowered totals for tonight
along the central and coastal panhandle.

.LONG TERM...Period begins with winds and precip continuing across
the region as another low pushes N through the central gulf
pushing another frontal band through the panhandle. This will
bring another round of precip and winds to the region. Precip
will be generally liquid over the region except for the Haines and
Klondike highways where another round of 3-6 inches of snowfall
Fri night into Sat. CAA over the inner channels may be sufficient
to bring accumulating snow near sea level to the Juneau and the
Icy Strait corridor. Given model spread in boundary layer thermal
profiles, confidence is below average on how the rain/snow line
will meander so kept mention of up to 2 inches snowfall over this
region. Conditions will ease Sat night as a short wave ridge moves
across the region. This respite will be brief however as long
wave trough remaining anchored over the W gulf will continue to
direct a series of storms across the region through mid next week.

&&

.AVIATION...Marginal VFR conditions across Southeast Alaska due to
reduced CIGS and VSBY in widespread precipitation. Areas of IFR
conditions for both CIGS and VSBY as well. No significant changes
expected over the next 24 hours. Widespread turbulence and LLWS as
well with low level jet strength with SSW winds of 70 kts as low
as 5000 ft. Conditions improving in the respect by Saturday
morning except for the northeast gulf coast, which will see
worsening conditions over the next 24 hours.

&&

.MARINE...Southerly storm force winds to 50 kts will become
southeasterly as the region of strongest winds moves north along
the extreme eastern Gulf. Combined seas 10 ft this morning,
building to as high as 29 ft by this afternoon before beginning
to subside overnight. On the inside, gales of 35 to 40 kts
beginning over the southern inner channels this morning and
spreading north through Friday night.

&&

.AJK WATCHES/WARNINGS/ADVISORIES...
PUBLIC...Strong Wind from this afternoon through late tonight for AKZ317-
     319-323.
     Winter Weather Advisory from noon today to 6 AM AKST Saturday
     for AKZ318.
     Strong Wind from this evening through late tonight for AKZ318.
     Strong Wind this evening for AKZ320-322.
     Strong Wind from 9 AM AKST this morning through this evening for
     AKZ327.
     Strong Wind from 9 AM AKST this morning through late tonight for
     AKZ328.
     Strong Wind from 9 AM AKST this morning through this evening for
     AKZ330-332.
MARINE...Storm Warning for PKZ042-043-051-052.
     Gale Warning for PKZ011>013-021-022-031>036-041.
     Small Craft Advisory for PKZ053.

&&

SHORT TERM...PRB
LONG TERM....BC
AVIATION...Fritsch

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