Gale Warning 26, NWS Juneau, AK

Southeast Alaska Forecast Discussion
National Weather Service Juneau AK
1106 AM AKST Sat Jan 8 2022

.UPDATE...With the first front stalling across the southern
Panhandle, critical level has been induced across Salsbury Ridge
east of Downtown Juneau, beginning early this morning, after a few
observations in excess of 50 KT, we elected to go ahead and issue
a high wind warning through 6 PM, as the onset of precipitation
will ease winds. While we considered beginning the winter storm
warning early to account for the high winds and blowing snow, we
decided against trying to message that the snow would not begin as
early.

We are also concerned with some 100 year recurrence intervals of
precipitation and will coordinate with APRFC regarding potential
flooding issues for Monday across the south. While it is not cut
and dry, the fact that we will have such a deep snowpack might
make issues more pronounced than otherwise.

&&

.PREV DISCUSSION......ISSUED AT ...712 AM AKST Sat Jan 8 2022

SHORT TERM.../Through Sunday/

**SIGNIFICANT WINTER STORM TO IMPACT ALL OF SOUTHEAST ALASKA**

Impressive meteorological set up for the incoming winter storm
that could bring record daily snowfall to many locations around
Southeast Alaska. Strong upper jet dynamics exist over the region
already this morning. Enhanced lift from the entrance region of a
110kt jet streak over the Southern Panhandle combined with a
stalled surface boundary have allowed snow showers to break out
across the south this morning. Snowfall accumulations of 1 to 5
inches have fallen already prompting the winter weather hazards to
go into effect much earlier than originally planned. The snow
showers from this morning are actually not associated with the big
system approaching from the south. However on the ground you may
not notice the difference as these snow showers will likely linger
around until the main event begins.

Later this afternoon, the northern and southern branches of the
jet streams phase, allowing for significant amplification of the
storm system approaching in the southern gulf. SE Alaska will be
placed in a prime location for significant lift as a jet couplet
between the right entrance region of the northern jet and the
exit region of an approaching 120 kt southern stream jet streak
move overhead. In the mid levels of the atmosphere, copious
amounts of subtropical moisture will be pumped northward into
Southeast Alaska. Closer to the surface, a deep arctic airmass
has been in place for weeks and will be hard to scour out despite
strong southerly flow. Currently at the Juneau Forecast the
temperature is -15 F as of the writing of this AFD. All of this
combined will set the stage for an extremely impactful winter
storm across the region.

For early Saturday morning, a weak lee side low exists in the
northern gulf with a frontal boundary extending eastward across
the Southern Panhandle. As mentioned above, this has been the
focus for snow shower activity this morning. This weak system will
get absorbed by the main player coming in from the south this
afternoon. Snow showers will persist across the Southern Panhandle
today as one of the main fronts lifts northward toward the
region. With impressive upper dynamics, would not be surprised to
see snowfall rates of 1-2+ inches per hour with any given shower
today. Expect snowfall coverage and intensity to only increase and
begin to push northward by late tonight.

By Sunday precipitation overspreads the entire region as the first
frontal boundary pushes northward and a deep 955 mb surface low
makes its way northward in the western gulf. A much stronger
occluded front approaches the Outer Coast Sunday morning with
strong mid level wind dynamics and much warmer air. This part of
the system will also enhance lift and continue to help pump up
moisture from the south leading to impressive precipitation
rates. Due to warm air approaching, expect areas along the Outer
Coast and South to warm above freezing and switch over to rain.
Further north and inland, the cold airmass will continue to win
out allowing for very heavy snowfall to persist. Snowfall rates
exceeding 2+ inches per hour are likely Sunday especially along
the Coast Mountains to Juneau to Upper Lynn Canal. At the same
time, winds will dramatically increase along the Coast and through
the Southern Panhandle where winds could gust 40 to 50 mph as the
occluded front pushes in. High end gales to low end storms
expected along the Outer Coast at the peak of the event Sunday
morning. Small craft to gale force conditions will persist through
much of the Inner Channels through Sunday. Areas that see strong
wind will likely warm up above freezing faster and therefore
change over to rain. Lower confidence exists in the exact
changeover time from snow to rain along the outer coast. An
earlier changeover would mean significantly lower snowfall
totals, but much higher liquid rain.

Overall the main changes to the forecast this morning were to
increase snowfall for the southern Panhandle due to the weak
frontal boundary. Also increased snowfall amounts for Hyder and
along the Coast Mountains. Allowed the winter weather hazard to
begin for the south due to the heavy snow showers. Increased
snowfall totals for Hyder, as cold air damming and significant
orographic lifting typically allows this area to remain colder
longer and receive much heavier precip than guidance suggests.
Other than that, the forecast remains largely on track with 12 to
30+ inches of snow likely for much of the Panhandle. Lowest
confidence exists in the change over from snow to rain for most
places. There is the possibility some northern areas could stay
snow for the entirety of the event; however model guidance still
disagrees with the northern extent of the "warmer" air.

LONG TERM...(Sunday) A pattern change is expected in the long
term with a warm-up, back-to-back precipitation events, and
strong coastal winds.

A very wet weekend and next week is expected with multiple back-
to- back rounds of subtropical moisture being pushed northwards.
Winter Storm Warnings will be in effect through late Sunday
night.Behind them, precipitation will continue through the week.
As the major system which brought such substantial impacts departs
and is replaced by system after system racing out of the South.
Ensembles and operational runs alike continue to be at odds with
timing, intensity, and location of these systems. All however,
agree that these systems will bring a mixture of rain, snow, and
perhaps even some freezing drizzle to the area.

With this in mind, made few changes to the wind grids-as wind
direction and speed will be largely dependent on the timing and
placement of various systems. Moved temperatures more towards the
NBM, which slightly moderated the warmup, while still keeping it
in forecast-as is supported by anticipated 850 mb heights. Am
confident in continued existence of warmup as the parade of
systems will successfully scour most of the cold air out of the
area, though some areas could switch back to snow during nighttime
periods.

&&

.AJK WATCHES/WARNINGS/ADVISORIES...
PUBLIC...Winter Storm Warning until 6 PM AKST Sunday for AKZ026-028.
     Winter Weather Advisory until 6 AM AKST Sunday for AKZ027.
     Strong Wind late tonight for AKZ027.
     Winter Storm Warning from 6 PM this evening to 9 PM AKST Sunday
     for AKZ020>022-024-025.
     High Wind Warning until 6 PM AKST this evening for AKZ025.
     Strong Wind from 6 PM AKST this evening through late tonight for
     AKZ025.
     Winter Storm Warning from 3 PM this afternoon to noon AKST
     Sunday for AKZ023.
     Winter Storm Warning from 3 PM this afternoon to 6 AM AKST
     Monday for AKZ029.
     Winter Storm Warning from midnight tonight to 6 AM AKST Monday
     for AKZ017>019.
     Strong Wind through late tonight for AKZ018.
     Wind Chill Advisory until midnight AKST tonight for AKZ018.
MARINE...Heavy Freezing Spray Warning for PKZ011.
     Heavy Freezing Spray Warning for PKZ013.
     Heavy Freezing Spray Warning for PKZ032.
     Heavy Freezing Spray Warning for PKZ012-031.
     Gale Warning for PKZ012-013-021-022-031-041>043-051-052-310.
     Small Craft Advisory for PKZ011-032>036-053.

&&

99/99

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

PRELIMINARY LOCAL STORM REPORT
NATIONAL WEATHER SERVICE JUNEAU AK
1055 AM AKST SAT JAN 8 2022

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

0802 AM     NON-TSTM WND GST 1 N DOUGLAS             58.29N 134.39W
01/08/2022  M70 MPH          PKZ031             AK   MESONET

            MESONET STATION JMLA2 AML DOCK JUNEAU.

&&

Special Weather Statement
National Weather Service Juneau AK
233 PM AKST Sat Jan 8 2022

AKZ017>022-024-025-029-091500-
Cape Fairweather to Cape Suckling Coastal Area-
Taiya Inlet and Klondike Highway-Haines Borough and Lynn Canal-
Glacier Bay-Eastern Chichagof Island-
Salisbury Sound to Cape Fairweather Coastal Area-
Eastern Baranof Island and Southern Admiralty Island-
Juneau Borough and Northern Admiralty Island-Misty Fjords-
Including the cities of Yakutat, Skagway, Haines, Gustavus,
Hoonah, Elfin Cove, Pelican, Angoon, Juneau, and Hyder
233 PM AKST Sat Jan 8 2022

...RAIN AND HIGH FREEZING LEVELS TO FOLLOW SIGNIFICANT WEEKEND
WINTER STORM...

There is high confidence in a pattern shift with rain and warmer
temperatures next week following a significant winter storm that
will likely drop more heavy snow across our region. Winter storm
warnings have been issued for heavy snow amounts across Southeast
Alaska. As snow transitions to rain or even heavy rain Sunday
into Monday, conditions will worsen, become very slippery, and
promote ponding. Additional heavy snow on top of already deep
snowpack on roof-tops and other structures, boats, and aircraft
will become heavier as rain-soaked snow challenges load
capability. Rain in higher terrain and higher freezing levels
could also lead to a risk of nuisance flooding into next week.
Finally, we are also concerned that an abrupt rise in temperatures
and freezing levels could mean an increased risk of avalanches
near steep terrain.

While nuisance flooding could occur, no flooding of rivers and
streams is expected.

AKZ023-027-028-091500-
Cape Decision to Salisbury Sound Coastal Area-
Dixon Entrance to Cape Decision Coastal Area-
Southern Inner Channels-
Including the cities of Sitka, Port Alexander, Craig, Klawock,
Ketchikan, and Metlakatla
233 PM AKST Sat Jan 8 2022

...RAIN AND HIGH FREEZING LEVELS AFTER WINTER STORM COULD PROMPT
NUISANCE FLOODING SUNDAY INTO MONDAY...

After a winter storm passes Saturday night, precipitation changes
to rain. With a deep snow pack in many locations across the
southern Panhandle, nuisance flooding could develop in parts of
the southern Panhandle. A flood watch has been posted for the
Ketchikan area as confidence is higher for significant ponding and
yard flooding, given the heavy rain forecasted over the deep snow
pack. Other areas could develop issues as well. Otherwise, surface
conditions will become very slippery. Unplowed areas will become
difficult to pass. In addition, heavy snow loads on roof-tops,
boats, and idle aircraft will be challenged by the heavy rains for
Sunday into Monday. While nuisance flooding could occur, no
flooding of rivers and streams is expected.

AKZ026-091500-
Inner Channels from Kupreanof Island to Etolin Island-
Including the cities of Petersburg, Wrangell, and Kake
233 PM AKST Sat Jan 8 2022

...RAIN AND HIGH FREEZING LEVELS AFTER WINTER STORM COULD PROMPT
NUISANCE FLOODING SUNDAY NIGHT INTO MONDAY...

After a winter storm passes Sunday, precipitation changes to
rain Sunday night. With a deep snow pack in many locations across
the south central Inner Channels, nuisance flooding could develop
in parts of the region. Otherwise, surface conditions will become
very slippery. Unplowed areas will become difficult to pass.
Heavy snow loads on roof- tops, boats, and idle aircraft will be
challenged by the heavy rains for Sunday night into Monday.

While nuisance flooding could occur, no flooding of rivers and
streams is expected.