Alaska, 2015Flash Flood and Debris Flow in Alaska, August 18 to 19, 2015
August 18 to 19, 2015 · NWS AJK · 4 events in 3 counties and zones
A strong front moved through the Panhandle on the morning of Tuesday August 18th. This system had abundant amount of moisture associated with the cold front as the system originated from the North Pacific and was able to tap into tropical moisture.
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
- Deaths
- 6
- Injuries
- 0
- Property damage
- $3.4 million
- Crop damage
- None recorded
- Events
- 4
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.
A strong front moved through the Panhandle on the morning of Tuesday August 18th. This system had abundant amount of moisture associated with the cold front as the system originated from the North Pacific and was able to tap into tropical moisture. The front produced very heavy precipitation along coastal locations and prolonged moderate rain further inland. The heavy rain produced flooding over the Sitka area and in the Taiya River basin along the Chilkoot trail near Skagway. The strong winds that accompanied the front along with the very high rain fall rates caused several landslides along the central outer coast with three fatalities in Sitka. As the front moved through the inner channels there was a brief strong wind that occurred near Skagway.
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 Aug 17, 2:58 PM AKST, 9 hours 55 minutes earlier.
Area forecast discussion, Aug 17, 2:58 PM AKST, 9 hours 55 minutes before
SOUTHEAST ALASKA FORECAST DISCUSSION
NATIONAL WEATHER SERVICE JUNEAU AK
358 PM AKDT MON AUG 17 2015
.SHORT TERM...STRONG WINDS AND HEAVY RAIN FOR THE NORTHERN HALF OF
THE PANHANDLE THROUGH TUESDAY DAYTIME.
THE SHORT TERM FORECAST PERIOD IS VERY ACTIVE FOR SOUTHEAST
ALASKA. AN INTENSIFYING LOW NEAR KODIAK ISLAND IS TRACKING
NORTHEASTWARD INTO PRINCE WILLIAM SOUND OVERNIGHT, THEN JUMPING
INLAND INTO SOUTHEAST MAINLAND ALASKA AND THEN INTO SOUTHERN
YUKON. MEANWHILE, A STRONG RIDGE OF HIGH PRESSURE IS MAINTAINING
ITS CONTROL OVER THE NORTH PACIFIC OCEAN. THE LOW IS EXPECTED TO
DROP DOWN TO 993 MB OVER YUKON, WHILE PRESSURE WILL BE AROUND
1020 MB OVER THE SOUTHERN END OF THE PANHANDLE. THE COMBINED
SYSTEM IS CREATING AN ANOMALOUSLY STRONG SOUTHERLY PRESSURE
GRADIENT OVER SOUTHEAST ALASKA. THIS WILL GENERATE SIGNIFICANT
WINDS ACROSS THE NORTHERN HALF OF THE PANHANDLE.
STRONG WIND GUSTS EXCEEDING 40 MPH ARE EXPECTED IN AREAS
INCLUDING YAKUTAT, ELFIN COVE, GUSTAVUS, HOONAH, HAINES, SKAGWAY,
JUNEAU, AND SITKA OVERNIGHT TONIGHT INTO TUESDAY MORNING. FOR
SKAGWAY, DO EXPECT WIND GUSTS UP TO 65 MPH AND THUS CONTINUE TO
HAVE THE HIGH WIND WARNING FOR THEM. ALSO INTRODUCE 50 KT
SUSTAINED WINDS WITH 10 FEET WAVE HEIGHT FOR NORTHERN LYNN CANAL.
GALE FORCE WINDS WILL BE FOUND IN LYNN CANAL, CROSS SOUND, ICY
STRAIT, GLACIER BAY, STEPHENS PASSAGE, AND CHATHAM STRAIT TONIGHT
INTO TUESDAY. WINDS WILL START TO DIMINISH AT THE END OF THE SHORT
TERM FORECAST PERIOD TUESDAY AFTERNOON.
HEAVY RAIN IS ANOTHER BIG STORY MAKER FOR THE SHORT TERM FORECAST
PERIOD. 2 TO 4 INCHES OF RAIN EXPECTED IN PARTS OF NORTHERN
PANHANDLE. 4 TO 6 INCHES ALONG THE COAST FROM NORTH OF SITKA TO
YAKUTAT...HIGHEST RAINFALL AMOUNTS OVER THE UPSLOPE AREA OF
MOUNTAINS. RAINFALL RATE AS HIGH AS 1 INCH PER HOUR WILL TAKE
PLACE OVERNIGHT TONIGHT. FOR AREAS SUCH AS YAKUTAT, THIS WILL BE A
2 TO 5 YEAR RAIN EVENT. KEEP THE FLOOD WATCH FROM YAKUTAT TO AREAS
AS FAR SOUTH AS SITKA AND ANGOON. THE FLOOD WATCH FOR CENTRAL
PANHANDLE (PETERSBURG, WRANGELL, AND KAKE) WAS CANCELLED AS QPF
AMOUNTS ARE NOT AS HIGH AS ANTICIPATED. PLEASE REFER TO FLOOD
WATCH STATEMENT FOR MORE INFORMATION. THE SITUATION ON HEAVY RAIN
WILL BE MONITORED CLOSELY AND THE STATEMENT WILL BE UPDATED THIS
EVENING.
CHANGES ARE MINOR TODAY. REFRESH THE INHERITED GRIDS WITH NAM
MODEL AS IT IS THE MOST SKILLFUL IN PREDICTING THE PRESSURE
GRADIENT OVER SOUTHEAST ALASKA. FOR RAINFALL AMOUNTS, UTILIZE
GUIDANCE FROM RIVER FORECAST CENTER. FORECAST CONFIDENCE ON THE
HEAVY RAIN AND STRONG WIND IS ABOVE AVERAGE.
.LONG TERM...THE RAIN EVENT FROM SHORT TERM WILL JUST BE STARTING
TO SETTLE DOWN AS WE GET INTO TUE NIGHT AND WED. THE ATMOSPHERIC
RIVER WILL HAVE WEAKENED NOTICEABLE BY TUE EVENING AND WILL BE
MOVING TO THE SE OUT OF THE PANHANDLE AND INTO COASTAL BRITISH
COLUMBIA. RAIN/SHOWERS WILL STILL BE PRESENT IN THE CONTINUED
WESTERLY FLOW BUT WITH THE MAIN MOISTURE PLUME MOVING OUT OF THE
AREA AMOUNTS WILL NOT BE AS GREAT. WINDS LIKEWISE WILL BE ON THE
DOWNWARD TREND AS PRESSURE GRADIENTS ACROSS THE GULF CONTINUE TO
WEAKEN IN THE WAKE OF THE MAIN PARENT LOW MOVING NE INTO CANADA.
20 TO 30 KT WINDS ACROSS THE GULF WILL BE THE RULE OF TUE EVENING
BUT WILL GRADUALLY DIMINISH TO 20 KT BY WED EVENING.
FOR THE REST OF THE LONG RANGE, UPPER LEVEL PATTERN REMAINS
RATHER PROGRESSIVE WITH A RATHER FLAT RIDGE OVER THE WESTERN GULF
THROUGH LATE WEEK. THIS RIDGE WILL HAVE ONE WEAK SHORT WAVE TROUGH
MOVE THROUGH IT ON THU BEFORE IT IS SHOVED OUT OF THE WAY BY A
STRONGER SHORT WAVE TROUGH FOR NEXT WEEKEND. FROM HERE THE PATTERN
TRENDS TOWARD A HIGHER AMPLITUDE PATTERN AS THE TROUGH SLOWS DOWN
OVER THE GULF WHILE A RIDGE BUILDS OVER THE EASTERN ALEUTIANS AND
ALASKA PENINSULA.
AT THE SURFACE THE TREND IS FOR CONTINUED WET WEATHER FOR MOST OF
THE LONG RANGE PERIOD. TUE NIGHT INTO WED FEATURES CONTINUED
ONSHORE FLOW WITH A WEAK UPPER TROUGH MOVING THROUGH THU BUT NO
ATMOSPHERIC RIVER SO RAIN WILL CONTINUE THROUGH AT LEAST THU BUT
ANY HEAVY RAINFALL IS NOT EXPECTED. THU NIGHT INTO FRI MIGHT BE
THE ONLY DRY PERIOD OUT OF THE WEEK AS THE WEAK RIDGE OVER THE
GULF BUILDS UP ENOUGH TO TURN FLOW MORE NW AND N. IT MIGHT BE
ENOUGH FOR SOME SUN TO PEAK THROUGH THE CLOUDS. AS SUCH HAVE PUT
SOME MOSTLY CLOUDY SKIES WITH SOME AREAS OF PARTLY CLOUDY HERE AND
THERE FOR THU NIGHT INTO FRI.
INTO THE WEEKEND, THE NEXT STRONGER TROUGH WILL BE ENTERING THE
GULF. MODELS ARE HAVING SOME DIFFICULTIES AS TO THE STRENGTH OF
THE SURFACE FEATURE AS WELL AS TIMING. THE GFS IS THE ON THE
WEAKER SIDE WITH A 1004 MB LOW IN THE CENTRAL GULF FRI NIGHT. THE
ECMWF AND CANADIAN MEANWHILE ARE SUGGESTING AROUND 991 MB AND 994
MB RESPECTIVELY WITH SMALL CRAFT WINDS ACROSS MOST OF THE SOUTHERN
HALF OF THE GULF. OF THE THREE THE ECMWF HAS SO FAR SEEN THE BEST
CONSISTENCY BETWEEN INDIVIDUAL RUNS SO DECIDED TO LEAN IN THAT
DIRECTION AS WELL AS THE WPC (FAVORED THE ECMWF WITH SOME EMPHASIS
ON ITS ENSEMBLE MEANS) FOR THE WEEKEND. IN ANY CASE, THE WEEKEND
IS LOOKING WET FOR A GOOD PORTION OF THE PANHANDLE WITH POSSIBLY
SOME GUSTY WINDS ALONG SOME OF THE INNER CHANNELS AND OUTER COAST.
&&
.AJK WATCHES/WARNINGS/ADVISORIES...
PUBLIC...FLOOD WATCH FROM 7 PM AKDT THIS EVENING THROUGH TUESDAY EVENING
FOR AKZ017>025.
STRONG WIND FROM 10 PM AKDT THIS EVENING THROUGH TUESDAY
AFTERNOON FOR AKZ022-025.
STRONG WIND FROM 1 AM AKDT TUESDAY THROUGH TUESDAY MORNING FOR
AKZ020-021-023.
STRONG WIND FROM 1 AM AKDT TUESDAY THROUGH TUESDAY EVENING FOR
AKZ019.
HIGH WIND WARNING FROM 4 AM TO 7 PM AKDT TUESDAY FOR AKZ018.
STRONG WIND FROM 10 PM AKDT THIS EVENING THROUGH LATE TONIGHT
FOR AKZ018.
MARINE...STORM WARNING FOR PKZ012.
GALE WARNING FOR PKZ011-013-021-022-031-032-043-051.
SMALL CRAFT ADVISORY FOR PKZ033>036-041-042-052-053.
&&
RCL/EAL
VISIT US AT HTTP://WWW.WEATHER.GOV/JUNEAUIn the hours before
Special weather statement, Aug 17, 8:02 PM AKST, 4 hours 51 minutes before
SPECIAL WEATHER STATEMENT
NATIONAL WEATHER SERVICE JUNEAU AK
902 PM AKDT MON AUG 17 2015
AKZ017>024-026-181300-
CAPE FAIRWEATHER TO CAPE SUCKLING COASTAL AREA-
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-
INNER CHANNELS FROM KUPREANOF ISLAND TO ETOLIN ISLAND-
INCLUDING THE CITIES OF...YAKUTAT...SKAGWAY...HAINES...GUSTAVUS...
HOONAH...ELFIN COVE...PELICAN...SITKA...PORT ALEXANDER...ANGOON...
PETERSBURG...WRANGELL...KAKE 902 PM AKDT MON AUG 17 2015
...HEAVY RAIN WILL CAUSE RIVERS...CREEKS...AND STREAMS TO RISE BY
TUESDAY...
HEAVY RAIN WILL SPREAD FROM THE YAKUTAT AREA ACROSS THE NORTHERN
AND CENTRAL PANHANDLE THROUGH TUESDAY AFTERNOON. RAINFALL TOTALS
WILL RANGE FROM 4 TO 6 INCHES ALONG THE NORTHEAST GULF COAST...TO
1 TO 3 INCHES OVER THE REMAINDER OF THE NORTHERN PANHANDLE. AS A
RESULT...AREA RIVERS...CREEKS...AND STREAMS WILL RISE...AND
APPROACH A CREST NEAR MINOR FLOOD STAGE DURING TUESDAY...AND THEN
FALL BY WEDNESDAY MORNING.
THIS STATEMENT WILL BE UPDATED BY 5 AM TUESDAY MORNING OR SOONER
IF CONDITIONS WARRANT.
Event by event
1 high wind, 1 flood, 1 flash flood, 1 debris flow. Local standard time, as filed.
High Wind, Taiya Inlet and Klondike Highway
- When
- August 18, 12:53 AM AKST to 6:53 AM AKST
- Where
- Taiya Inlet and Klondike Highway forecast zone
- Measured
- 52 kt (60 mph) measured gust
- Reported by
- ASOS
Skagway Airport observed 55 MPH gusts during the morning of August 18th. Nearby marine observations had gusts in excess of 65 mph.
Flood, Taiya Inlet
- When
- August 18, 3:00 AM AKST to August 19, 3:00 AM AKST
- Where
- Taiya Inlet County, 3.27 mi NNW of Skagway to 3.92 mi N of Skagway
- Cause
- Heavy Rain
- Reported by
- River/Stream Gage
- Coordinates
- 59.493, -135.339
Heavy rain moved over the area through the day on the 18th and the Taiya River began to rise significantly through the day as the moist weather front moved over Southeast Alaska. The freezing levels were very high and ample amount of moist as the front had sub-tropical characteristics. The river crested in the afternoon at a stage of seventeen point twenty seven feet. This was just over moderate flood stage of seventeen feet and it flooded the Chilkoot trail with knee to thigh deep water in places. The river was below minor flood stage by the early morning of the 19th.
Flash Flood, Sitka Coastal
- When
- August 18, 9:00 AM AKST to 11:00 AM AKST
- Where
- Sitka Coastal County, 4.03 mi NNW of Sitka to 4.18 mi ENE of Sitka
- Cause
- Heavy Rain
- Deaths
- 3 direct, 0 indirect
- Property damage
- $1.7 million
- Reported by
- Emergency Manager
- Coordinates
- 57.099, -135.387
A strong cold front with sub-tropical moisture moved into the eastern gulf and moved over the coastal areas of Southeast Alaska. As the front approached the coastal area of Sitka very high rain rates were being reported across the area in the early morning hours which lasted less than 6 hours. In three hours the Sitka airport reported one point seven inches which was a 25 year rainfall intensity return period. The Sitka Magnetic Observatory Climate Reference Station (CRN), which is closer to steep terrain, reported two point zero one inches was a 45 year rainfall intensity return period. Along with the very high rain rates there was also very strong winds of thirty-three mile per hour with much high wind gusts at higher elevations. The combination of the heavy rain and strong winds caused catastrophic debris flows across the Sitka area on the morning of August 18th. Multiple roads were blocked along with homes damaged or destroyed and there was 3 fatalities in Cramer Ave slide. A state of emergency was declared and as one point seven million dollars worth of damage was done.
Debris Flow, Sitka Coastal
- When
- August 18, 9:00 AM AKST to 11:00 AM AKST
- Where
- Sitka Coastal County, 3.97 mi NNW of Sitka to 4.18 mi ENE of Sitka
- Cause
- Heavy Rain
- Deaths
- 3 direct, 0 indirect
- Property damage
- $1.7 million
- Reported by
- Emergency Manager
- Coordinates
- 57.099, -135.385
A strong cold front with sub-tropical moisture moved into the eastern gulf and moved over the coastal areas of Southeast Alaska. As the front approached the coastal area of Sitka very high rain rates were being reported across the area in the early morning hours which lasted less than 6 hours. In three hours the Sitka airport reported one point seven inches which was a 25 year rainfall intensity return period. The Sitka Magnetic Observatory Climate Reference Station (CRN), which is closer to steep terrain, reported two point zero one inches was a 45 year rainfall intensity return period. Along with the very high rain rates there was also very strong winds of thirty-three mile per hour with much high wind gusts at higher elevations. The combination of the heavy rain and strong winds caused catastrophic debris flows across the Sitka area on the morning of August 18th. Multiple roads were blocked along with homes damaged or destroyed and there was 3 fatalities in Cramer Ave slide. A state of emergency was declared and as one point seven million dollars worth of damage was done.
- High Wind
- Sustained non-thunderstorm winds of 40 mph or more for an hour, or gusts of 58 mph or more.
- Flood
- Flooding that develops more slowly than a flash flood: rivers leaving their banks, or water standing over land for an extended time.
- Flash Flood
- Flooding that begins within six hours of the rain that causes it, or of a dam or levee failure or ice jam release, often with deadly speed.
- Debris Flow
- A fast-moving slurry of mud, rock and debris, usually on a slope soaked by heavy rain or stripped by a fire.
After NWS Directive 10-1605, the rules offices file Storm Data by.
- Tornadoes in Wisconsin, August 18, 2015$156,000 · EF1 · 4 events
- Tornadoes and Flash Flood in Illinois, August 18 to 19, 2015$360,000 · EF0 · 8 events
- Damaging Winds in New York, August 18, 2015$235,000 · 61 kt wind · 7 events
- Tornado and Hail in Illinois, August 18, 2015$162,000 · EF0 · 10 events
- Flash Flood in New York, August 18, 2015$100,000 · 1 event
- Flash Flood in New Hampshire, August 18, 2015$100,000 · 1 event
- Damaging Winds in New York, August 18, 2015$85,000 · 55 kt wind · 4 events
- Hail and Damaging Wind in New Mexico, August 18, 2015$27,000 · 2.75 in hail · 13 events
- Hail and Damaging Winds in Texas, August 18 to 19, 20151.75 in hail · 27 events
- Flash Flood and Flood in North Carolina, August 18 to 19, 2015$15,000 · 2 events
- Hail and Damaging Winds in Kansas, August 18, 20151 in hail · 9 events
- Drought in Texas, August 18 to 31, 20156 events
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: 595642, 600436, 595640, 611642.