Small Craft Advisory 638, NWS Juneau, AK

689 
FZAK53 PAJK 211234
CWFYAK

Marine Forecast for Yakutat Bay
National Weather Service Juneau AK
334 AM AKST Tue Dec 21 2021

Coastal Waters Forecast for Yakutat Bay

Wind forecasts reflect the predominant speed and direction
expected. Sea forecasts represent the average of the highest
one-third of the combined windwave and swell height.

PKZ053-220645-
Yakutat Bay-
334 AM AKST Tue Dec 21 2021

...SMALL CRAFT ADVISORY THIS AFTERNOON THROUGH THIS EVENING...

.TODAY...E wind 15 kt becoming NE 25 kt in the afternoon. Seas
7 ft. Snow early in the morning. 
.TONIGHT...NE wind 25 kt diminishing to 15 kt late. Seas 7 ft.
Freezing spray. 
.WED...NE wind 25 kt. Seas 5 ft. Freezing spray in the
morning. 
.WED NIGHT...NE wind 20 kt. Seas 5 ft. Freezing spray. 
.THU...NE wind 20 kt. Seas 5 ft. 
.FRI...NE wind 20 kt. Seas 4 ft. 
.SAT...NE wind 15 kt. Seas 3 ft. 

$$

428 
FZAK53 PAJK 220033
CWFYAK

Marine Forecast for Yakutat Bay
National Weather Service Juneau AK
333 PM AKST Tue Dec 21 2021

Coastal Waters Forecast for Yakutat Bay

Wind forecasts reflect the predominant speed and direction
expected. Sea forecasts represent the average of the highest
one-third of the combined windwave and swell height.

PKZ053-221845-
Yakutat Bay-
333 PM AKST Tue Dec 21 2021

.TONIGHT...NE wind 15 kt. Seas 7 ft. Freezing spray. 
.WED...NE wind 20 kt. Seas 5 ft. Freezing spray in the
morning. 
.WED NIGHT...NE wind 20 kt. Seas 4 ft. Freezing spray late.
.THU...NE wind 20 kt. Seas 7 ft. S swell. Freezing spray. 
.THU NIGHT...NE wind 20 kt. Seas 8 ft. SW swell. 
.FRI...NE wind 20 kt. Seas 4 ft. 
.SAT...NE wind 20 kt. Seas 4 ft. 
.SUN...E wind 20 kt. Seas 4 ft. 

$$

Southeast Alaska Forecast Discussion
National Weather Service Juneau AK
721 AM AKST Mon Dec 20 2021

.SHORT TERM...The upper level jet will continue to have a
positively tilted ridge that goes from the Aleutians, up into the
arctic, then down across the panhandle (N-NWLY flow). Another
brisk morning today under mostly clear skies, but high clouds are
already starting to move in across the north. Expect a slow/steady
increase in temperatures through the next 24 hours, but with most
places staying below freezing.

The jet becomes amplified on Tuesday with a NWLY jet streak that
crosses the Anchorage area, then into the northern Gulf of Alaska.
Jet streak dynamics will help to spin up a surface low which then
tracks SE with the jet through Tuesday night. At the mid levels
(500mb), the jet streak is quite strong (110-120+ knots) and moves
south a bit faster. Precip will move in Monday evening, but
initially the column isn't saturated in the dendritic growth zone,
aka not many ice crystals in the clouds. Therefore, a chance of
freezing drizzle remains in the forecast for most of the region at
the onset, but only a light glaze is anticipated. If the freezing
drizzle/rain becomes more prevalent, more parts of the panhandle
may be added to the list of advisories/warnings, but at this point
the expected snow totals are driving those.
Yakutat/Haines/Skagway look to get about 3 inches out of this
storm, so they have been left out of any statements for now. As
the low progresses SE, snowfall rates pick up with greatest
amounts falling during the Tuesday morning commute.
Petersburg/Wrangell areas ended up with the greatest snowfall at
about 10 inches. Please see the latest forecast/statement for
details in your area.

As the low tracks away to the south through Tuesday night, skies
will clear fairly quickly. Winds will increase out of the north
as well, particularly through the northern Lynn Canal region and
other interior passes. Light to moderate freezing spray becomes
more likely as temperatures drop under clear skies late Tuesday
night.

.LONG TERM.../Monday through Thursday night/...the mid range
forecast begins with clear, cold, quiet weather around the
panhandle. But Monday is looking like a transition day to a quick
hit of snow on Tuesday.

Clouds are expected to increase late Monday. And the pressure
gradient over the panhandle should lighten up so winds should
decrease as well. High temps look to be in the 20s for most of the
area, 30s are possible along the outer coast.

An area of low pressure is projected to move southeast through
the gulf through Tuesday so the snow would track southeast through
the panhandle. It would begin in the Yakutat area late Monday and
track southeast, exiting through the southern panhandle Tuesday
night. Just ahead of the low, 850mb temps are projected to get
near -4C in the central and southern panhandle, so rain/snow
mixing was allowed to stay in the forecast but confidence is low
due to surface temps only get a few degrees above 32 before
cooling back to the 20s Tuesday night.

The 24 hour QPF amounts for Tuesday through Tuesday night range
from near a tenth of an inch in the northern inner channels to
about a half inch in the central inner channels. This idea is
backed up by the model ensemble outputs. 24 hour QPF probabilities
of more than 0.10” was greater than 70 to 80% and probabilities
of more than 0.50” rose to around 30-60%. So if typical SE AK
snow ratios play out, overall snowfall amounts shouldn’t be too
high. Went with a comfortable one to four inch range, but locally
higher amounts are still possible. Once this event gets closer,
forecaster confidence will increase with use of hi-res models in
addition to ensemble probabilities.

Inner channel wind forecast was, overall, left to ride due to
expected strong outflow winds. Outside waters were touched up to
try to incorporate the details in speed and direction as the low
passes. Overall, still expecting gale forecast winds in outside
waters as low passes on Tuesday.

Models solutions late in the week in general agreement in deep Nly
flow through the atmosphere with strong signals of below normal
temps expected heading into next weekend.

&&

.AJK WATCHES/WARNINGS/ADVISORIES...
PUBLIC...Winter Storm Warning from 7 PM this evening to 7 PM AKST Tuesday
     for AKZ026.
     Winter Weather Advisory from 9 PM this evening to 9 PM AKST
     Tuesday for AKZ027-029.
     Winter Weather Advisory from 7 PM this evening to 4 PM AKST
     Tuesday for AKZ024.
     Winter Storm Warning from 6 PM this evening to noon AKST Tuesday
     for AKZ025.
     Winter Weather Advisory from 6 PM this evening to noon AKST
     Tuesday for AKZ020>022.
     Winter Storm Warning from 9 PM this evening to 9 PM AKST Tuesday
     for AKZ028.
MARINE...Small Craft Advisory for PKZ041>043.

&&

Ferrin/JLC

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