Storm Warning 1, NWS Juneau, AK

Southeast Alaska Forecast Discussion
National Weather Service Juneau AK
641 AM AKST Sun Jan 5 2025

.SHORT TERM...Snow has arrived across SE AK Through the overnight
hours, a band of accumulating snow has swept across the panhandle.
For most areas, accumulations have proven to be fairly marginal,
with strong warm air advection aloft leading to either a
changeover to rain, or to sleet or other forms of precipitation.

The exception to this is the Icy Strait Corridor Northward. Juneau
and Gustavus have seen colder air remain entrenched, with
accumulating snow falling across both areas as of the time of
writing. Strong warm air advection - driven in part by an LLJ
sweeping across - will help lead to a changeover to rain for the
Icy Strait Corridor through the afternoon or evening hours on
Sunday. Snowfall totals will be dependent on how soon this
changeover to rain occurs. A later changeover would likely lead to
significantly greater snow amounts.

The far northern panhandle will likely see cold air remain
entrenched for the greatest period of time - and with it, the
greatest snowfall amounts. Warm air will eventually reach Skagway
and Haines proper by late Sunday night into Monday morning, but
lingering cooler air along the Haines and Klondike Highways will
lead to continuing accumulation in areas at elevation. The Icy
Strait Corridor will likely see snow accumulations of up to 6
inches. Depending on how quickly the warm air advection reaches
these areas, the potential does exist for greater amounts. For the
Haines and Skagway areas, there is the additional question of how
much QPF actually falls. While 7-15 inches is currently in the
forecast, amounts may be lower than anticipated for some areas
should there ultimately be less QPF.

WInd-wise, northerly outflow winds will continue subsiding through
the morning hours as the pressure gradient slackens. A relative
lull in the winds for many locations will be replaced by
strengthening southerly flow through Sunday night.

.LONG TERM...A big pattern change is upon us as multiple systems are
set to push through the region from the south bringing
precipitation, wind, and warming temperatures. Little to no changes
were made to the inherited long range forecast.

On Monday, the upper level jet will see a surge of winds and
moisture, developing into an Atmospheric River type of stationary
front. The moisture plume will initially be directed at the central
gulf coast (Yakutat) then waver eastward over the panhandle for
Monday night into Tuesday. The warm air directed from the tropics
will cause snow levels to rise further as well, though high
elevation highways, particularly the Klondike, will likely see snow
stick around a bit longer after towns at sea level are expected to
have switched over to rain by Monday morning. Rainfall amounts
Monday through Tuesday look to be 3-4 inches around Yakutat and 1-3
inches elsewhere.

Still on track for conditions to deteriorate as our first storm
force low positions itself south of Kodiak Monday, driving a broad
fetch of severe gale to storm force winds across the majority of the
gulf. Wave models have continued to underperform this threat, slowly
shifting significant heights higher over the previous week’s model
runs. Expecting at least 28 to 32ft southerly fresh seas peaking
Monday, with a maximum along Cape Edgecumbe west towards Cape
Suckling. With that said, a stout jet of 75 to 85 knots near 5000ft
has the potential to mix down to the surface, driving even higher
seas than model guidance is suggesting. If this were to occur
heights closer to 35ft are likely. Either way, impressive total wave
energy associated with Monday’s storm.

Models remain in fairly good agreement on a distinct 12-18 hour
break Tuesday night into Wednesday before the next surge of moisture
and wind arrives for Thursday. This next system will further enhance
warming across the panhandle and usher in rising snow levels leading
to increased snowmelt runoff. A hydrologic outlook has been
issued to discuss the potential impacts from these two potent
heavy precipitation events over the coming week. For more
information, see the Hydrology section below.

&&

.AVIATION.../Until 12Z Monday/...For around PAGY / Northern Lynn
Canal, strong northerly outflow winds decrease and then flip to the
south as the warm front pushes through from south to north today,
which will allow warmer air to advect in, increasing lower level
temperatures, and allowing the snow to changeover to all liquid,
helping to increase visibilities a bit from mainly the MVFR/IFR
range for areas experiencing frozen precipitation to primarily
within the MVFR range. After the point of the warm front moving
through, ceilings may still dip into the IFR range, at times, but
will still primarily hover around the MVFR range. LLWS of around 35
to 50 kt to out of a SE direction for PAYA and around 25 kt out of a
S direction for PASI was added starting at 06Z for PAYA and 09Z for
PASI.

&&

.MARINE...Northerly flow rapidly diminishes through the day on
Sunday across the panhandle, with southerly flow taking its place
by Sunday night for many maritime locations. A storm force low
moves into the western gulf late Sunday into Monday. Winds along
the central and northern gulf will quickly increase to
southeasterly gales. As the low gets closer, these gales will move
toward the coast with storm force winds in the gulf and along the
far northern coast. With consistent southeasterly winds, seas can
build to 30 to 35 ft later Monday into Tuesday.

&&

.HYDROLOGY...Pair of atmospheric rivers inbound early part of the
week based on increasing confidence of the mid and long range
models. First feature for Tuesday has a small chance of flooding
issues. It does however prime the region, and start the snowmelt
process. The second feature will take advantage of the prep, and
increased snow levels and rain to add more snow melt into the
rivers and streams.

&&

.AJK WATCHES/WARNINGS/ADVISORIES...
PUBLIC...Winter Storm Warning until 6 AM AKST early this morning for
     AKZ317.
     Extreme Cold Warning until 6 AM AKST early this morning for
     AKZ318.
     Winter Storm Warning until noon AKST Monday for AKZ318-319.
     Winter Weather Advisory until midnight AKST tonight for AKZ320-
     325.
MARINE...Gale Warning for PKZ053-643-644-651-652-664-671-672.
     Small Craft Advisory for PKZ012-022-032-641-642-661>663.

&&

SHORT TERM...GFS
LONG TERM....STJ
AVIATION...JLC
MARINE...EAB/GFS
HYDROLOGY...Bezenek

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

Preliminary Local Storm Report
National Weather Service Juneau AK
204 PM AKST Sun Jan 5 2025

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

0135 PM     Snow             4 W Auke Bay            58.41N 134.76W
01/05/2025  M3.3 Inch        Juneau             AK   Public

            Since 1:20pm yesterday, 1/4/25, we have had
            3.25in of snowfall. Currently, we have a
            steady snowfall, no wind and 30deg.

&&

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