Flood, Denali
- When
- September 21, 10:00 AM AKST to September 23, 5:00 AM AKST
- Where
- Denali County, 0.81 mi E of Denali N.P. to 1.47 mi E of Denali N.P.
- Cause
- Heavy Rain
- Reported by
- Public
- Coordinates
- 63.719, -148.894
Flooding in Alaska, September 21 to 24, 2012
After a few days of heavy rainfall along the south slopes of the Alaska Range that amounted to several inches of rain, the Nenana River flooded at Nenana and Healy. Minor flooding began around 1000AKST on the 21st at Healy.
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
The toll
- Deaths
- 0
- Injuries
- 0
- Property damage
- None recorded
- Crop damage
- None recorded
- Events
- 2
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 AFG wrote it up.
After a few days of heavy rainfall along the south slopes of the Alaska Range that amounted to several inches of rain, the Nenana River flooded at Nenana and Healy. Minor flooding began around 1000AKST on the 21st at Healy. The boat launch was flooded and water was over the bank and rising up the shoulder of the coal hauling road. The Nenana River rose to the highest stage on record when the river crested at 14.9 ft at Healy on the 22nd and a surge of water continued downstream. The crest was protracted as the water levels remained at the crest for nearly 24 hours. This resulted in the flooding of several structures at Denali National Park, and erosion of the southbound lane at MP240 of the Parks Highway. At Nenana, flooding was observed on the 23rd. Up to one foot of water was reported over 10th Avenue west of the railroad tracks. The road to the cemetery was also reported to be flooded. Water filled the drainage ditches and low lying areas on the east side of the city of Nenana. Water levels dropped and the flooding was over by the morning hours of the 24th.
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 Fairbanks, AK wrote its last area forecast discussion before the first event at Sep 21, 1:47 AM AKST, 8 hours 13 minutes earlier.
Area forecast discussion, Sep 21, 1:47 AM AKST, 8 hours 13 minutes before
NORTHERN ALASKA FORECAST DISCUSSION NATIONAL WEATHER SERVICE FAIRBANKS AK 247 AM AKDT FRI SEP 21 2012 .DISCUSSION... LONG WAVE TROUGH REMAINS ENTRENCHED OVER THE BERING SEA WHILE HIGH PRESSURE RIDGE EXTENDS FROM BC NORTHWARD THROUGH THE YUKON AND EASTERN ALASKA. ENERGY CONTINUES TO DRIVE EASTWARD WITH STRONG JET AND SHORTWAVE AND WILL TURN NORTHEAST THIS MORNING AND THEN NORTHWARD THIS AFTERNOON AS SYSTEM MOVES ALONG THE BACK OF UPPER LEVEL RIDGE. A SHORT WAVE OVER THE INTERIOR WILL CONTINUE TO MOVE NORTH AND EAST TODAY. 500 MB WINDS NEAR 75 KTS DIMINISH AS INTERIOR SHORTWAVE MOVES NORTH. ON THE SURFACE A WEAK LOW ASSOCIATED WITH THE UPPER LEVEL SHORTWAVE OVER THE INTERIOR WILL CONTINUE TO MOVE NORTH TODAY. WIDESPREAD RAIN SHOWERS IN THE INTERIOR WILL TAPER OFF TO SCATTERED SHOWERS AS THE LOW CONTINUES TO MOVE NORTH AND EAST. CHINOOK FLOW ALONG THE CENTRAL AND EASTERN ALASKA RANGE WILL DIMINISH THROUGH THE DAY AS THE INTERIOR LOW WEAKENS AND CONTINUES TO MOVE INTO NORTHEAST ALASKA. DENSE FOG ALONG THE CENTRAL NORTH SLOPE WILL DIMINISH THROUGH THE DAY AS THE INTERIOR LOW MOVES ONTO THE EASTERN NORTH SLOPE. NORTH AND NORTHWEST WINDS CONTINUE ALONG THE WEST COAST AS THE INTERIOR LOW MOVES ONTO THE NORTH SLOPE. UNSEASONABLE WARM TEMPERATURES ARE EXPECTED SATURDAY ACROSS THE EASTERN INTERIOR AS UPPER LEVEL RIDGE MOVES WESTWARD. CHINOOK WINDS ARE EXPECTED TO DEVELOP SATURDAY ALONG AND NEAR THE ALASKA RANGE AS A 65 KT CROSS BARRIER FLOW AT 700 MB DEVELOPS AHEAD OF THE SURFACE LOW MOVING NORTH OUT OF THE GULF OF ALASKA. CROSS SECTION ANALYSIS REVEALS MODERATE DOWNWARD MOMENTUM BUT NO CRITICAL LEVEL THEREFORE MINIMAL MOUNTAIN WAVE ENHANCEMENT TO WIND SPEEDS ARE EXPECTED. WINDS ARE NOT EXPECTED TO REACH WARNING CRITERIA HOWEVER ADVISORY LEVEL WINDS ARE EXPECTED IN ZONES 223 225 226 AND ZONE 227 NEAR THE ALASKA RANGE SATURDAY. CONTINUE TO MONITOR LATE SEASON FIRE POTENTIAL SATURDAY AFTERNOON IN ZONES 223 AND 226 AS MIN RH VALUES ARE EXPECTED TO DROP INTO THE LOWER 30S CONCURRENT WITH ADVISORY LEVEL WINDS AND BURNABLE FUELS. MODELS REMAIN IN GOOD AGREEMENT THROUGH EARLY NEXT WEEK WITH THE UPPER LEVEL RIDGE REMAINING OVER WESTERN CANADA AND UPPER LEVEL TROUGH REMAINING OVER THE BERING SEA THROUGH THE WEEKEND. BOTH THE GFS AND ECMWF INDICATE THAT THE WESTERN CANADA RIDGE BREAKS DOWN AND THE BERING SEA TROUGH MOVES EAST OVER ALASKA BY MID WEEK. COASTAL HAZARD POTENTIAL DAYS 3 AND 4...NONE && .HYDROLOGY...NONE && .AFG WATCHES/WARNINGS/ADVISORIES... SMALL CRAFT ADVISORY FOR PKZ245. && CC SEP 12
The radar
The national radar mosaic for the moment the first event began.
Event by event
2 flood. Local standard time, as filed.
Flood, Wrn Tanana Vly Wrn Yukon Vly
- When
- September 21, 10:00 PM AKST to September 24, 7:00 AM AKST
- Where
- Wrn Tanana Vly Wrn Yukon Vly County, Nenana to 19.07 mi W of Nenana
- Cause
- Heavy Rain
- Reported by
- Fire Department/Rescue
- Coordinates
- 64.550, -149.080
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
- Hail and Damaging Winds in Indiana, September 21, 2012
- Hail and Damaging Winds in Ohio, September 21, 2012
- Damaging Wind in Pennsylvania, September 21, 2012
- Hail and Damaging Wind in Illinois, September 21, 2012
- Flood and Hail in Missouri, September 21, 2012
- Waterspout in Lake Michigan, September 21, 2012
- Hail in Missouri, September 21, 2012
- Hail in Michigan, September 21, 2012
- Funnel Cloud in Florida, September 21, 2012
- Damaging Wind in Indiana, September 21, 2012
More
Every storm in Alaska in 2012Every state in 2012This day in weather historyWarnings 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: 407779, 407777.