Flood in Alaska, September 13, 2016

Name: Flood in Alaska, September 13, 2016
Start: 2016-09-13T03:00
End: 2016-09-13T15:00
Location: Alaska

September 13, 2016 · NWS AJK · 1 event in 1 county or zone

Where it happened

Every event with a place to put it. Tap one for its entry below.

Tornadoes
Tropical storms and surge
Floods
Wind
Hail
Winter weather
Heat and drought
Cold
Fire, smoke and dust
Marine and coastal
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The toll

Deaths: 0
Injuries: 0
Property damage: None recorded
Crop damage: None recorded
Events: 1

Deaths and injuries are direct and indirect together, as the offices filed them. Damage is property and crops in the dollars of the year, not adjusted for inflation, and only where an office estimated it.

What happened

The episode as NWS AJK wrote it up.

An atmospheric river that extended deep into the north Pacific moved over Southeast Alaska on September 12th and 13th. This plume of sub-topical moisture slowly moved through the area Monday afternoon through Tuesday morning with expected rainfall amounts over the northern Lynn Canal region of 1 to 3 inches. Also as the front spread east across the region it increased the freezing levels to be above the ridge tops of six thousand feet. This allowed for increased runoff from snow and ice melt in the Taiya River basin. The combination of the runoff from the snow/ice melt and the heavy rainfall produced moderate flooding along the Chilkoot trail by Tuesday morning.

What forecasters said that day

The local office's own words before the first event, as it sent them, from the Iowa Environmental Mesonet's archive of National Weather Service text.

NWS Juneau, AK wrote its last area forecast discussion before the first event at Sep 12, 2:18 PM AKST, 12 hours 42 minutes earlier.

Area forecast discussion, Sep 12, 2:18 PM AKST, 12 hours 42 minutes before

Southeast Alaska Forecast Discussion
National Weather Service Juneau AK
318 PM AKDT MON SEP 12 2016

.SHORT TERM...Previous forecast remains on track with period of
heavy rain and gusty winds tonight. Impressive rainfall totals in
Yakutat today with hourly rates reaching as high as 0.66 inches.
Between 10 am and 1 pm the Yakutat airport received 1.78 inches of
rain. According to precipitation frequency estimates that happens
once every five years. The atmospheric river that is responsible
for the heavy rain will shift south and east tonight into the
northern and central panhandle. As it does so these areas can
expect a 3-6 hour period of very heavy rainfall. A quick 1-2
inches of rain is expected. The stream of moisture will reach the
southern panhandle late Tuesday morning. Rain chances will remain
high over the northern panhandle on Tuesday with continued onshore
flow and a weak shortwave moving over the area during the
afternoon. However, rainfall will generally be light.

The other big story in the short term will be the wind. Strong low
level flow combined with a tightening pressure gradient will lead
to strong winds developing over the central and northern panhandle
tonight. Southerly gale force winds will also develop over the
inner channels. The strongest winds will be in the Skagway area as
strong 700 mb southwest flow will act to enhance lee side
troughing and the southerly pressure gradient. Additionally, two
shortwaves will move across the area which will provides further
support for high wind gusts up to 60 mph. The high wind watch was
upgraded to a high wind warning through early Tuesday. Gusts up
to 45 mph can be expected for the remainder of the central and
northern panhandle. Winds will gradually diminish Tuesday as the
pressure gradient slackens.

Used hi-res guidance for updates to the previous forecast.

.LONG TERM...Atmospheric river sliding southeast across the region
is forecast to dissipate over the far southern panhandle at the
start of the long term period (Tuesday night). In the wake of the
AR, the surface pressure gradient will remain sufficiently tight
for small craft southerlies over Northern Lynn Canal, with winds
forecast to weaken to 15-20 kt by Wednesday afternoon.

Deep-layer moisture returns to the entire panhandle Wednesday
night, resulting in a rainy period through Thursday night. At the
surface, large spread in MSLP is present in available
deterministic guidance Wednesday and Thursday. Thus, shortwave
surface features were smoothed out of the pressure grids, which
yields persistent southerlies over the gulf in the range of 15-25
kt during much of the long term. Otherwise, model guidance shows a
series of upper distrubances treking across the region from the
weekend through at least the middle of next week, which will
favor periods of rain for SERN AK.

&&

.HYDROLOGY...The burst of heavy rain will lead to steep rises in
area rivers and streams tonight and early Tuesday. A flood watch
has been issued for the Taiya River near Skagway from late tonight
through Tuesday afternoon. See the flood watch statement for
additional information. Other rivers and streams may approach
bankfull, but flooding is not expected at this time.

&&

.AJK Watches/Warnings/Advisories...
PUBLIC...STRONG WIND from 7 PM AKDT this evening through late tonight for
     AKZ025.
     STRONG WIND until 1 AM AKDT Tuesday for AKZ022.
     STRONG WIND from 7 PM this evening to 1 AM AKDT Tuesday for
     AKZ020-021.
     STRONG WIND through late tonight for AKZ019.
     High Wind Warning from 7 PM this evening to 7 AM AKDT Tuesday
     for AKZ018.
     Flood Watch from 10 PM AKDT this evening through Tuesday
     afternoon for AKZ018.
     STRONG WIND until 7 PM AKDT this evening for AKZ018.
     STRONG WIND from Tuesday morning through Tuesday afternoon for
     AKZ018.
     STRONG WIND until 4 PM AKDT this afternoon for AKZ017.
MARINE...Gale Warning for PKZ012-013-021-022-031>034-043-051.
     Small Craft Advisory for PKZ011-035-041-042-052-053.
&&

TPS/Garner

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

In the hours before

Special weather statement, Sep 12, 9:25 PM AKST, 5 hours 35 minutes before

SPECIAL WEATHER STATEMENT
NATIONAL WEATHER SERVICE JUNEAU AK
1025 PM AKDT MON SEP 12 2016

AKZ018>025-130830-
TAIYA INLET AND KLONDIKE HIGHWAY-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-
JUNEAU BOROUGH AND NORTHERN ADMIRALTY ISLAND-
INCLUDING THE CITIES OF...SKAGWAY...HAINES...GUSTAVUS...HOONAH...
ELFIN COVE...PELICAN...SITKA...PORT ALEXANDER...ANGOON...JUNEAU
1025 PM AKDT MON SEP 12 2016

...HEAVY RAIN AND STRONG WIND MONDAY NIGHT...

A QUICK MOVING ATMOSPHERIC RIVER WILL BRING HEAVY RAIN AND STRONG
WIND TO THE NORTHERN AND CENTRAL PANHANDLE THROUGH MONDAY NIGHT.
SOUTHERLY WINDS WITH GUSTS OF 40 TO 50 MPH ARE EXPECTED IN
EXPOSED AREAS.

RAINFALL AMOUNTS OF UP TO 2 INCHES ARE EXPECTED. AS THE FRONT
MOVED THROUGH YAKUTAT RAINFALL RATES WERE 0.2 TO 0.6 INCHES PER
HOUR. THERE WILL BE STEEP RISES ON AREA CREEKS AND STREAMS. MOST
ARE WELL BELOW BANKFULL AND FLOODING IS NOT EXPECTED...HOWEVER
THE TAIYA RIVER NEAR SKAGWAY WILL LIKELY REACH THE FLOOD STAGE OF
16.5 FEET OVERNIGHT. RIVER LEVELS WILL BE MONITORED CLOSELY
DURING THIS EVENT.

FERRIN

Local storm report, Sep 12, 10:29 PM AKST, 4 hours 31 minutes before

PRELIMINARY LOCAL STORM REPORT...CORRECTED
NATIONAL WEATHER SERVICE JUNEAU AK
1129 PM AKDT MON SEP 12 2016

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

0400 PM     HEAVY RAIN       YAKUTAT                 59.54N 139.73W
09/12/2016  M3.46 INCH                          AK   OFFICIAL NWS OBS

            8-HOUR TOTAL

0500 PM     NON-TSTM WND GST 10 W ELFIN COVE         58.19N 136.61W
09/12/2016  M64.00 MPH       PKZ022             AK   OFFICIAL NWS OBS

            CAPE SPENCER GUST

0815 PM     NON-TSTM WND GST PELICAN                 57.95N 136.21W
09/12/2016  E40.00 MPH                          AK   TRAINED SPOTTER

            SOUTHEAST WIND GUSTING TO 40 MPH WITH HEAVY RAIN.

1025 PM     HEAVY RAIN       7 NE GUSTAVUS           58.48N 135.66W
09/12/2016  M0.77 INCH                          AK   MESONET

            1-HOUR RAIN AMOUNT AT GLACIER BAY FUEL DOCK

&&

JWA

The radar

The national radar mosaic for the moment the first event began.

Open the radar archive at this moment

Event by event

1 flood. Local standard time, as filed.

Flood, Taiya Inlet

When: September 13, 3:00 AM AKST to 3:00 PM AKST
Where: Taiya Inlet County, 3.94 mi NNW of Skagway to 13.72 mi NNW of Skagway
Cause: Heavy Rain
Reported by: Park/Forest Service
Coordinates: 59.503, -135.344

The atmospheric river moved across the the panhandle from the northeast gulf coast to the southern panhandle Monday through Tuesday morning. There were two bursts of heavy ran with totals near seal level ranging from three quarters of an inch to just over one inch. There was much more rainfall in the headwaters of the Taiya River with rain amounts from one and half to almost three inches at Chilkoot Pass. The initial bout of rain and high freezing levels produced a two and half foot rise on the Taiya River with the river going over minor flood stage of sixteen point five feet. The river remained just under moderate flood stage through the early morning hours of September 13th from the persistent rainfall. There was another burst of heavy rainfall and the river rose another half foot to go over the moderate flood stage of seventeen feet and crested at seventeen point twenty seven feet around 9 am. The rain tapered off through the late morning and the Taiya River began to slowly recede to be below minor flood stage by Tuesday afternoon. The National Park Service reported that there was significant flooding along the Chilkoot trail with waist deep water at the lower portions of the trail.

What these are

Flood: Flooding that develops more slowly than a flash flood: rivers leaving their banks, or water standing over land for an extended time.

After NWS Directive 10-1605, the rules offices file Storm Data by.

The same day elsewhere

Every storm in Alaska in 2016 Every state in 2016 This day in weather history Warnings in Alaska, September 2016

Sources

NOAA National Centers for Environmental Information, Storm Events Database, compiled from the National Weather Service’s monthly Storm Data. Complete through 2026-06; NCEI adds each month about 75 days after it ends and revises past years a few times a year. Rebuilt 2026-09-24. Each event’s entry at NCEI: 660262.