Flooding and High Wind in Alaska, September 14 to 30, 2012

Name: Flooding and High Wind in Alaska, September 14 to 30, 2012
Start: 2012-09-14T23:30
End: 2012-09-30T23:59
Location: Alaska

September 14 to 30, 2012 · NWS AFC · 10 events in 6 counties and zones

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
Other

Open the live radar over this ground

The toll

Deaths: 1
Injuries: 0
Property damage: $18 million
Crop damage: None recorded
Events: 10

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 AFC wrote it up.

A series of strong, wet storm systems hit Southcentral Alaska in mid-September. Each storm followed nearly the same track along the Alaska Peninsula then along the Bering Sea coast, setting up a strong moist fetch into the Southcentral Alaska. This resulted in widespread flood damage over a large area. Storm total precipitation ranged from 21 to 27 inches along the eastern Kenai Peninsula, while further inland between 6-12 inches of rain fell along the Talkeetna Mountains north to the headwaters of the Nenana River. A large number of roads and bridges were affected; damage to the Alaska Railroad was severe enough to shut down the rail service for several days. Almost 60 homes were either severely damaged or destroyed and over 700 other homes were either affected or sustained minor damage; most of the damage occurred along the Little Susitna River and Willow Creek. State estimates of damage to individual property approached $3.5 million, public infrastructure exceeded $19 million statewide, and the military base in Anchorage sustained an addition $3.5 million in flood damages. There was one fatality associated with the flooding. On September 24, a 51 year old man died while attempting to cross a swollen creek on his ATV.

In addition to flooding, the storms brought strong east and southeast wind to an area from southeast Prince William Sound, to Cordova, through Portage Pass, along Turnagain Arm and along the Anchorage. The first strong storm resulted in wind through the Chugach Mountains with an unofficial peak wind of 120 mph measured by a spotters home weather system in Bear Valley. In the other wind-prone locations, peak wind was generally around 70 to 75 mph, with 90 mph in reported in Portage Valley.

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 Anchorage, AK wrote its last area forecast discussion before the first event at Sep 14, 4:10 PM AKST, 7 hours 20 minutes earlier.

Area forecast discussion, Sep 14, 4:10 PM AKST, 7 hours 20 minutes before

SOUTHCENTRAL AND SOUTHWEST ALASKA FORECAST DISCUSSION
NATIONAL WEATHER SERVICE ANCHORAGE AK
510 PM AKDT FRI SEP 14 2012

.ANALYSIS AND UPPER LEVELS...
ZONAL WEST TO SOUTHWESTERLY FLOW IS IN PLACE OVER MUCH OF SOUTHERN
ALASKA THIS AFTERNOON...WITH SEVERAL EMBEDDED DISTURBANCES PRODUCING
WIDESPREAD RAIN ACROSS PORTIONS OF SOUTHCENTRAL AND SOUTHWEST AK. A
SURFACE LOW IS LOCATED OVER BRISTOL BAY WITH A WEAK OCCLUDED FRONT
EXTENDING INTO THE WESTERN GULF OF ALASKA. FURTHER WEST...A POTENT
UPPER LEVEL LOW IS DIVING SOUTHWARD ACROSS THE BERING SEA.

.MODEL DISCUSSION...
DESPITE SOME DISCREPANCIES IN POSITION AND STRENGTH...MODELS ARE
COMING INTO BETTER AGREEMENT IN HANDLING THE STRONG LOW FORMING IN
THE BERING. GENERAL CONSENSUS SHOWS THE UPPER LOW DROPPING JUST SOUTH
OF THE EASTERN ALEUTIANS AND PHASING WITH A SHORTWAVE MOVING THROUGH
THE NORTHERN PACIFIC BY SATURDAY MORNING. STRONG 140 KT BRANCHES OF
THE JET STREAM WILL DEVELOP ON BOTH SIDES OF THE AMPLIFYING LONGWAVE
TROUGH. IN RESPONSE...MODELS DEVELOP A SURFACE LOW SOUTH OF THE AKPEN
DURING THE DAY ON SATURDAY AND BRING IT INLAND OVER THE SOUTHWEST
MAINLAND ON SUNDAY AS IT RAPIDLY INTENSIFIES.

.SHORT TERM FORECAST...
SOUTHCENTRAL ALASKA...
RAIN AND STRONG WINDS WILL OVERSPREAD MUCH OF SOUTHCENTRAL AK THIS
WEEKEND AS THE POTENT LOW PRESSURE SYSTEM APPROACHES THE SOUTHWEST
COAST. THE ANCHORAGE BOWL WILL BE IMPACTED BY A STRONG WIND EVENT
BEGINNING SATURDAY EVENING AND LASTING THROUGH LATE SUNDAY NIGHT.
STRONG WINDS WILL INITIALLY DEVELOP ALONG TURNAGAIN ARM AND HIGHER
ELEVATIONS ON SATURDAY EVENING AS THE PRESSURE GRADIENT
TIGHTENS...WITH STRONG WINDS THEN SPREADING TO THE LOWER HILLSIDE AND
EAST ANCHORAGE OVERNIGHT SATURDAY AND TO THE REST OF ANCHORAGE DURING
THE DAY ON SUNDAY AS A FRONT MOVES THROUGH THE AREA. STRONG WINDS
WILL ALSO IMPACT MANY AREAS FROM PORTAGE VALLEY ACROSS PRINCE WILLIAM
SOUND AND ALL THE WAY TO CORDOVA SATURDAY NIGHT INTO SUNDAY. WILL
HAVE TO MONITOR COASTAL AREAS OF PRINCE WILLIAM SOUND FOR POTENTIAL
FLOODING AS THE AREA WILL SEE HEAVY RAINFALL SATURDAY NIGHT AND
THROUGH THE DAY ON SUNDAY. FLOOD WATCHES HAVE BEEN ISSUED FOR THESE
AREAS.

SOUTHWEST ALASKA...
RAIN WILL CONTINUE THROUGH THE WEEKEND FOR THE SOUTHWEST MAINLAND AS
THE STRONG BERING LOW APPROACHES. THE SYSTEM WILL MOVE ASHORE IN THE
VICINITY OF BRISTOL BAY DURING THE DAY ON SUNDAY...BRINGING GUSTY
WINDS AS IT PROGRESSES QUICKLY NORTHWARD.

ALEUTIANS/BERING SEA...
RAIN WILL PERSIST INTO TONIGHT FOR THE CENTRAL ALEUTIANS AND THEN
OVERSPREAD THE EASTERN ALEUTIANS ON SATURDAY AS THE LOW CONTINUES TO
DROP SOUTHWARD. THE WESTERN AND CENTRAL PART OF THE CHAIN WILL SEE A
BREAK IN PRECIPITATION AS UPPER LEVEL RIDGING BUILDS IN BEHIND THE
LOW...HOWEVER THIS BREAK WILL BE SHORT LIVED AS THE NEXT SYSTEM
MOVING OFF OF THE KAMCHATKA PENINSULA BRINGS RAIN TO THE WESTERN
BERING ON SATURDAY.

.LONG TERM FORECAST...
MODELS SUGGEST A HIGHLY AMPLIFIED PATTERN IN THE EXTENDED TERM WITH A
LONGWAVE TROUGH OVER THE BERING AND A STRONG RIDGE OVER THE NORTHEAST
PACIFIC...LEAVING THE SOUTHERN MAINLAND IN BROAD SOUTHWESTERLY FLOW
WHICH WOULD FAVOR CONTINUED WIDESPREAD PRECIPITATION.

.AER/ALU...WATCH/WARNING SUMMARY
PUBLIC...HIGH WIND WARNING 101 125 135
         FLOOD WATCH 125 131 135
MARINE...STORM WARNING 120 125
         GALE WARNING 130 132 140 170 176 180
FIRE WEATHER...NONE

CB SEP 12

In the hours before

Special weather statement, Sep 14, 6:45 PM AKST, 4 hours 45 minutes before

SPECIAL WEATHER STATEMENT
NATIONAL WEATHER SERVICE ANCHORAGE AK
745 PM AKDT FRI SEP 14 2012

AKZ101-111-121-125-131-135-145-16000-

...STRONG WINDS AND HEAVY RAINS FOR SOUTHCENTRAL ALASKA...

A STORM OF CONSIDERABLE SIZE AND STRENGTH FOR FALL WILL IMPACT
THE SOUTHERN MAINLAND THIS WEEKEND WITH STRONG WINDS AND HEAVY RAINS.
THE LOW IS FORMING OVER THE NORTH PACIFIC AND IS EXPECTED TO
STRENGTHEN AS IT TRACKS NORTH ACROSS THE ALASKA PENINSULA SATURDAY
AFTERNOON...THEN MOVE INTO MAINLAND BRISTOL BAY NEAR TOGIAK AT PEAK
INTENSITY ON SUNDAY. THE LOW IS THEN EXPECTED TO CONTINUE MOVING
INLAND AND PASS THROUGH THE KUSKOKWIM VALLEY AND SLOWLY BEGIN
WEAKENING SUNDAY NIGHT. AN ASSOCIATED WEATHER FRONT WILL TRACK FROM
THE SOUTHWEST GULF ON SATURDAY TO THE NORTHERN GULF EARLY ON SUNDAY.
THIS FRONT THEN MOVES ONSHORE PRINCE WILLIAM SOUND...THE KENAI
PENINSULA AND POINTS INLAND DURING THE DAY SUNDAY.

STRONG WINDS:

THE SYSTEM WILL FEATURE STRONG WINDS BOTH AHEAD OF AND BEHIND THE
FRONT. TYPICAL CHANNELED AREAS AND THE GULF COAST WILL INITIALLY
BEAR THE BRUNT...BUT WITH FRONTAL PASSAGE EXPECT WINDS TO ENVELOP
HEAVILY POPULATED AND WELL TRAVELED AREAS FROM COOK INLET UP THROUGH
THE MAT-SU VALLEY. TRAVEL IS LIKELY TO BE DIFFICULT AND THERE IS A
HIGHER THAN NORMAL CHANCE OF UPROOTED TREES DUE TO THE SATURATED
GROUND. SIGNIFICANT POWER OUTAGES ARE POSSIBLE.

HEAVY RAIN:

THE SYSTEM WILL BRING WIDESPREAD RAIN TO SOUTHCENTRAL ALASKA. THE
RAIN WILL BE PARTICULARLY HEAVY AT TIMES ALONG THE SOUTHERN TO
EASTERN KENAI PENINSULA AND PRINCE WILLIAM SOUND WHERE GREATER THAN 6
INCHES OF RAIN CAN BE EXPECTED SATURDAY NIGHT INTO SUNDAY NIGHT.
THERE IS AN ELEVATED RISK OF FLOODING ACROSS THESE AREAS AND FLOOD
WATCHES HAVE BEEN ISSUED. PEOPLE WITH INTERESTS NEAR STREAMS AND
RIVERS ARE ADVISED TO REMAIN INFORMED OF THIS SITUATION.

STAY TUNED TO THE NATIONAL WEATHER SERVICE FOR THE LATEST FORECASTS
AND WARNINGS FOR THIS STORM.

MALOY/DIXON

The radar

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

Open the radar archive at this moment

Event by event

7 flood, 3 high wind. Local standard time, as filed.

Flood, Sern P.W. Snd

When: September 14, 11:30 PM AKST to September 22, 8:00 AM AKST
Where: Sern P.W. Snd County, 2.45 mi SE of Cordova to 6.39 mi E of Cordova
Cause: Heavy Rain
Reported by: Official NWS Observations
Coordinates: 60.528, -145.693

High Wind, Anchorage Muni to Bird Creek

When: September 15, 10:00 PM AKST to September 16, 9:00 AM AKST
Where: Anchorage Muni to Bird Creek forecast zone
Measured: 104 kt (120 mph) estimated gust
Reported by: Trained Spotter

Observed on a Davis Weather Monitor 2.

High Wind, Sern P.W. Snd

When: September 16, 12:00 AM AKST to 10:30 AM AKST
Where: Sern P.W. Snd forecast zone
Measured: 70 kt (81 mph) measured gust
Reported by: Official NWS Observations

High Wind, Matanuska Valley

When: September 16, 1:50 AM AKST to 10:00 AM AKST
Where: Matanuska Valley forecast zone
Measured: 61 kt (70 mph) measured gust
Reported by: Official NWS Observations

Flood, Wrn P.W. Snd & Kenai Mtns

When: September 16, 3:00 AM AKST to September 17, 2:00 AM AKST
Where: Wrn P.W. Snd & Kenai Mtns County, 5.95 mi ESE of Seward to 2.26 mi SSW of Seward
Cause: Heavy Rain
Reported by: Official NWS Observations
Coordinates: 60.078, -149.299

Flood, Nern P.W. Snd

When: September 16, 5:00 PM AKST to September 17, 6:00 AM AKST
Where: Nern P.W. Snd County, 5.03 mi SSW of Valdez to 13.82 mi SW of Valdez
Cause: Heavy Rain
Reported by: Official NWS Observations
Coordinates: 61.051, -146.320

Flood, Susitna Valley

When: September 16, 7:00 PM AKST to September 18, 9:00 AM AKST
Where: Susitna Valley County, 27.94 mi SSE of Hayes River to 20.43 mi NNE of Hayes River
Cause: Heavy Rain
Reported by: Official NWS Observations
Coordinates: 61.605, -151.701

Flood, Wrn P.W. Snd & Kenai Mtns

When: September 19, 10:00 AM AKST to September 30, 11:59 PM AKST
Where: Wrn P.W. Snd & Kenai Mtns County, 5.56 mi ESE of Seward to 4.62 mi SSW of Seward
Cause: Heavy Rain
Property damage: $3.3 million
Reported by: Official NWS Observations
Coordinates: 60.076, -149.315

Flood, Susitna Valley

When: September 19, 11:00 AM AKST to September 24, 11:00 AM AKST
Where: Susitna Valley County, 30.44 mi SW of Nancy Lake to 14.69 mi ENE of Hayes River
Cause: Heavy Rain
Deaths: 1 direct, 0 indirect
Property damage: $10 million
Reported by: Official NWS Observations
Coordinates: 61.437, -150.723

The Susitna River at Sunshine crested at 27.66ft on 9/21/12 at 23:00 AKDT. Damages in the Susitna Valley were extensive, with several railroad bridges and smaller roads flooded and washed out. Most of the homes destroyed and damaged were in the Susitna Valley. on 9/24/12 a 51 year old man died while attempting to cross a swollen creek in a remote hunting area.

Flood, Matanuska Valley

When: September 19, 8:00 PM AKST to September 22, 11:00 AM AKST
Where: Matanuska Valley County, 7.29 mi S of Palmer to 11.18 mi SSE of Wasilla
Cause: Heavy Rain
Property damage: $4.8 million
Reported by: Official NWS Observations
Coordinates: 61.496, -149.208

The people who died

As the offices recorded each death: direct deaths were caused by the weather itself, indirect ones by something it set in motion.

Event	Date	Age	Sex	Where	Kind
Flood, Susitna Valley	2012-09-24	51	Male	In Water	Direct

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.
High Wind: Sustained non-thunderstorm winds of 40 mph or more for an hour, or gusts of 58 mph or more.

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

The same day elsewhere

Every storm in Alaska in 2012 Every state in 2012 This day in weather history Warnings in Alaska, September 2012

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: 406776, 404896, 404898, 404897, 406774, 406775, 406777, 406778, 406779, 406780.