Name: Debris Flow in California, May 25, 2006
Start: 2006-05-25T18:00
End: 2006-05-25T23:59
Location: California

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 HNX wrote it up.

Although Highway 140 WSW of El Portal opened early on May 25th after a rock-catching fence had been built to hold rock movement from earlier in the month, a major landslide occurred late in the day on the 25th and has dumped a massive amount of rock onto the road. This slide reached dimensions of 600 feet wide, 600 feet long, and 300 feet deep on May 25th. The road will not be able to be used in that area for the foreseeable future and bridges will be built over the Merced River to circumnavigate the slide. The loss in tourism revenue to the area around Mariposa is estimated to be in excess of $4 Million by the end of June 2006.

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 Hanford, CA wrote its last area forecast discussion before the first event at May 25, 12:30 PM PST, 5 hours 30 minutes earlier.

Area forecast discussion, May 25, 12:30 PM PST, 5 hours 30 minutes before

AREA FORECAST DISCUSSION
NATIONAL WEATHER SERVICE SAN JOAQUIN VALLEY - HANFORD CA
130 PM PDT THU MAY 25 2006

...UNSEASONABLY COOL WEATHER IN STORE FOR CENTRAL CA THIS WEEKEND...

SHORT TERM...FOR THE CENTRAL CALIFORNIA INTERIOR...WATER VAPOR LOOP
INDICATES A LONGWAVE TROUGH OVER THE WESTERN US WITH A DEEP UPPER
LEVEL LOW SPINNING ABOUT 48N/136W. MODELS IN GOOD AGREEMENT WITH
DROPPING THE LOW TOWARD THE PAC NW OVER THE NEXT 24 HOURS. WESTERLY
FLOW WILL INCREASE IN RESPONSE AND WILL INCREASE ON-SHORE PRESSURE
GRADIENTS ACROSS THE AREA. WINDS WILL BEGIN TO INTENSIFY TOMORROW
AFTERNOON AND WILL LIKELY REACH WIND ADVISORY CRITERIA LEVELS
THROUGHOUT THE WIND FAVORED AREAS OF KERN COUNTY. WILL ISSUE A WIND
ADVISORY FOR ZNS 95, 98, AND 99 WITH THE FORECAST PACKAGE FROM 2 PM
FRIDAY TO 8 AM SATURDAY. ITS WORTH MENTIONING THAT ON-SHORE
PRESSURE GRADIENTS ACTUALLY MAX OUT SATURDAY AFTERNOON, AS DOES
UPPER LEVEL WIND SUPPORT. THINKING WINDS WILL CONTINUE TO BLOW WITH
TENACITY THROUGH THE DAY SATURDAY, AND THUS THE W. ADV WILL LIKELY
NEED TO EITHER BE EXTENDED OR RE-ISSUED AT SOME POINT. TEMPERATURES
MAY COOL A FEW DEGREES TOMORROW, BUT THE SIGNIFICANT COOLING WILL
TAKE PLACE THIS WEEKEND WHEN THE UPPER LEVEL LOW DIVES INTO THE
GREAT BASIN, DRAGGING A STRONG COLD FRONT ACROSS THE AREA.
BASED ON THICKNESS VALUES AND 850MB TEMPS, SURFACE MAX TS COULD
STRUGGLE TO REACH 70 DEGREES IN THE SJV ON SATURDAY. I BROUGHT
FORECAST TEMPERATURES DOWN THIS WEEKEND, BUT PERHAPS NOT ENOUGH.
GENERALLY TROUGHINESS CONTINUES INTO SUNDAY, SO NOT EXPECTING MUCH
OF A WARM-UP IF ANY AT ALL. WITH ALL THE RELATIVELY ACTIVE WEATHER
EXPECTED THROUGH THE WEEKEND, ONE KEY COMPONENT MISSING IN THE
EQUATION IS MOISTURE. AS A RESULT, MOSTLY SUNNY SKIES AND DRY
CONDITIONS WILL CONTINUE ALTHOUGH THERE WILL BE SOME AFTERNOON
CUMULUS BUILD-UPS OVER THE SIERRA WITH THE MAIN TROUGH PASSAGE THIS
WEEKEND.

.LONG TERM...SUNDAY NIGHT THROUGH THURSDAY...MODELS ARE IN GOOD
AGREEMENT IN SLOWLY MOVING THE UPPER LOW EAST OF THE AREA ON MONDAY
AND THIS SHOULD ALLOW FOR A SLOW WARMING TREND TO BEGIN. DAY TO DAY
WARMING WILL BE SLIGHT AS THE MEAN TROUGH POSITION WILL REMAIN OVER
THE WEST COAST. THIS PATTERN WILL KEEP TEMPERATURES BELOW NORMAL AND
THE WINDS BLOWING IN THE KERN COUNTY MOUNTAINS AND DESERTS EACH
DAY. BY THURSDAY, THERE IS SOME DISAGREEMENT BETWEEN THE GFS AND
EUROPEAN MODELS, AS THE EURO BUILDS A RIDGE OVER CALIFORNIA AS IT
DEVELOPS A LOW OUT AROUND 140W. THE GFS MODEL ON THE OTHER HAND
KEEPS THE TROUGH OVER THE AREA AND SHOWS LITTLE CHANGE IN THE
PATTERN. IN THE GRIDS, HAVE INDICATED THE SLOW WARMING AND THEN ON
THURSDAY HAVE BUMPED UP TEMPERATURES CONSIDERABLY MORE.

&&

.AVIATION...VFR CONDITIONS WILL PREVAIL UNDER MAINLY CLEAR SKIES.
FOR MORE DETAILS...PLEASE REFER TO TAFS FOR KMCE..KFAT AND KBFL.

&&

.HNX WATCHES/WARNINGS/ADVISORIES...WIND ADVISORY FROM 2 PM FRIDAY TO
8 AM PDT SATURDAY FOR THE KERN MOUNTAINS AND DESERT.

&&

MYERS/DUDLEY

Event by event

1 debris flow. Local standard time, as filed.

Debris Flow, S Sierra Foothills

When: May 25, 6:00 PM PST to 11:59 PM PST
Where: S Sierra Foothills forecast zone
Reported by: PARK/FOREST SERVICE

What these are

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.

The same day elsewhere

More

Every storm in California in 2006 Every state in 2006 This day in weather history Warnings in California, May 2006

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: 5509848.