Small Craft Advisory 464, NWS Juneau, AK

Southeast Alaska Forecast Discussion
National Weather Service Juneau AK
304 PM AKDT Tue Sep 26 2017

.SHORT TERM...Tonight through Thursday...As of 1500 this
afternoon, current WV satellite imagery shows a weak ridge of high
pressure over western Canada, with the ridge axis stretching east
of the SE Alaskan panhandle. A shortwave is currently lifting
across our northern extent, and another shortwave is beginning to
dig out of the parent trough currently positioned over the western
gulf. A substantial plume of moisture is wrapped in with the flow
around the ridge and is being aimed directly at the panhandle,
giving us our atmospheric river event. This onshore flow is
contributing to some substantial accumulation amounts already
across the panhandle, with more expected on the way through
Thursday.

Winds have also been very strong across the area, and we'll
expect winds to remain relatively strong, especially along the
offshore waters where sustained wind speeds may float around 35
knots. This is due to a tight pressure gradient and an additional
weather front that will push through the panhandle late tonight
into Wednesday.

For Thursday, PoPs should begin to diminish throughout the day as
a weak ridge starts to build back into the eastern gulf and the
flow becomes more offshore. Winds should also lighten up once the
pressure gradient weakens.

Generally, the forecast has been pretty consistent, so it didn't
require much change. Any adjustments that were made we tended to
use a combination of the ECMWF and the GFS, as there has been very
good agreement between the two.

.LONG TERM.../Thu night through Tue/ A lot of differences with
models and their ensembles for the weekend and early next week.
Many operational models show a low level ridge over the gulf while
the ensemble means (and latest WPC) have a low. Spread is large
in the ensembles and there has been little run to run consistency.
Given that background, opted to leave current forecast as is.

For Thu night and Fri, cold front should slowly move E of the
area and rain should become showers. Cooler air should move in for
the weekend it appears, but the model differences make for a
difficult temp forecast especially the min temps over the weekend.
All in all, confidence in longer range forecast is very low at
this point.

&&

.AJK Watches/Warnings/Advisories...
PUBLIC...None.
MARINE...Gale Warning for PKZ041>043-051.
     Small Craft Advisory for PKZ012-022-031>033-036-052-053.

&&

Voveris/RWT

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Special Weather Statement
National Weather Service Juneau AK
1211 PM AKDT Tue Sep 26 2017

AKZ017-019>024-026>029-272000-
Cape Fairweather to Cape Suckling Coastal Area-
Haines Borough and Lynn Canal-Glacier Bay-
Eastern Chichagof Island-
Salisbury Sound to Cape Fairweather Coastal Area-
Cape Decision to Salisbury Sound Coastal Area-
Eastern Baranof Island and Southern Admiralty Island-
Inner Channels from Kupreanof Island to Etolin Island-
Dixon Entrance to Cape Decision Coastal Area-
Southern Inner Channels-Misty Fjords-
Including the cities of Yakutat, Haines, Gustavus, Hoonah,
Elfin Cove, Pelican, Sitka, Port Alexander, Angoon, Petersburg,
Wrangell, Kake, Craig, Klawock, Ketchikan, Metlakatla, and Hyder
1211 PM AKDT Tue Sep 26 2017

...HEAVY RAIN EXPECTED WITH THROUGH WEDNESDAY NIGHT ACROSS THE
PANHANDLE...

A front moving through the Panhandle Tuesday is bringing another
round of rain, heavy at times to the area. The heaviest rain
bands will migrate from the southern Panhandle into the northern
and central Panhandle by Tuesday night. Later Wednesday night, the
entire system pushes across the Panhandle. Forecast rainfall
totals ending late Wednesday night are expected to range from 1.5
inches in the southern panhandle to as much as 4 to 5 inches in
the central panhandle, and around 2 inches in the northern inner
channels.

Rivers, lakes, and streams will rise significantly, with smaller
river and streams possibly reaching bankfull. No flooding is
expected for rivers and streams in these areas at this time.

Additional rain is forecast through the end of week, although the
rainfall amounts are not expected to rival the values from the
first part of the week. Rainfall and river stages will continue
to be monitored and additional statements regarding this event may
be issued.

AKZ025-272000-
Juneau Borough and Northern Admiralty Island-
Including the city of Juneau
1211 PM AKDT Tue Sep 26 2017

...SIGNIFICANT RISES EXPECTED ON AREA RIVERS AND STREAMS THROUGH
WEDNESDAY NIGHT...

Bands of rain, heavy at times, are forecast to move into the
Juneau area Tuesday night and will linger into Wednesday night
before beginning to move east. Forecast rainfall totals through
Wednesday night are expected to range from 3 to 5 inches with
most of that falling between Tuesday night and Wednesday night.

Rivers, lakes, and streams will rise significantly during this
time. Montana Creek in particular will likely rise to near or
above minor flood stage of 15.0 feet by Wednesday evening. As of
11 AM Tuesday, Montana creek was at 12.2 feet. The forecast crest
is at 15.7 feet before dropping late Wednesday night. Montana
Creek road could have some water flowing over the low water
crossing Wednesday evening. Jordan Creek is also forecast to rise,
but is only expected to possibly reach bankfull conditions at 9.2
feet late Wednesday night.

Additional rain is forecast through the end of week, although the
rainfall amounts are not expected to rival the values from the
first part of the week. Rainfall and river stages will continue
to be monitored and additional statements regarding this event may
be issued.

AKZ018-272000-
Taiya Inlet and Klondike Highway-
Including the city of Skagway
1211 PM AKDT Tue Sep 26 2017

...SIGNIFICANT RISES EXPECTED ON AREA RIVERS AND STREAMS THROUGH
WEDNESDAY NIGHT...

Bands of rain, heavy at times, are forecast to move into the
Skagway area Tuesday night and will linger into Wednesday night
before beginning to move east. Forecast rainfall totals through
Wednesday night are expected to range from 1 to 2 inches with
most of that falling between Tuesday night and Wednesday night.

Rivers, lakes, and streams will rise significantly during this
time. The Taiya River in particular will likely rise to near
minor flood stage of 15.5 feet by early Tuesday evening before
falling. As of 11 AM Tuesday, the Taiya River was at 13.6 feet.
The Chilkoot Trail could see some water up to ankle deep on
portions of the trail Wednesday night.

Additional rain is forecast through the end of week, although the
rainfall amounts are not expected to rival the values from the
first part of the week. Rainfall and river stages will continue
to be monitored and additional statements regarding this event may
be issued.

Special Weather Statement
National Weather Service Juneau AK
1255 PM AKDT Tue Sep 26 2017

AKZ017-019>024-026>029-272000-
Cape Fairweather to Cape Suckling Coastal Area-
Haines Borough and Lynn Canal-Glacier Bay-
Eastern Chichagof Island-
Salisbury Sound to Cape Fairweather Coastal Area-
Cape Decision to Salisbury Sound Coastal Area-
Eastern Baranof Island and Southern Admiralty Island-
Inner Channels from Kupreanof Island to Etolin Island-
Dixon Entrance to Cape Decision Coastal Area-
Southern Inner Channels-Misty Fjords-
Including the cities of Yakutat, Haines, Gustavus, Hoonah,
Elfin Cove, Pelican, Sitka, Port Alexander, Angoon, Petersburg,
Wrangell, Kake, Craig, Klawock, Ketchikan, Metlakatla, and Hyder
1255 PM AKDT Tue Sep 26 2017

...HEAVY RAIN EXPECTED THROUGH WEDNESDAY NIGHT ACROSS THE
PANHANDLE...

A front moving through the Panhandle Tuesday is bringing another
round of rain, heavy at times to the area. The heaviest rain
bands will migrate from the southern Panhandle into the northern
and central Panhandle by Tuesday night. Later Wednesday night, the
entire system pushes across the Panhandle. Forecast rainfall
totals ending late Wednesday night are expected to range from 1.5
inches in the southern panhandle to as much as 4 to 5 inches in
the central panhandle, and around 2 inches in the northern inner
channels.

Rivers, lakes, and streams will rise significantly, with smaller
river and streams possibly reaching bankfull. No flooding is
expected for rivers and streams in these areas at this time.

Additional rain is forecast through the end of week, although the
rainfall amounts are not expected to rival the values from the
first part of the week. Rainfall and river stages will continue
to be monitored and additional statements regarding this event may
be issued.