High Wind Warning 3, NWS Juneau, AK

617 
WWAK77 PAJK 090251
NPWAJK

URGENT - WEATHER MESSAGE
National Weather Service Juneau AK
551 PM AKST Sat Jan 8 2022

AKZ025-090400-
/O.EXP.PAJK.HW.W.0003.000000T0000Z-220109T0300Z/
Juneau Borough and Northern Admiralty Island-
Including the city of Juneau
551 PM AKST Sat Jan 8 2022

...HIGH WIND WARNING WILL EXPIRE AT 6 PM AKST THIS EVENING...

Gusty winds in downtown Juneau will continue into the evening but
have fallen well below warning criteria.

$$

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https://weather.gov/ajk

Southeast Alaska Forecast Discussion
National Weather Service Juneau AK
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.
     Strong Wind 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 from noon today to 6 AM AKST Sunday 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.

&&

CM/GFS

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