Storms from March provided the necessary moisture to cause a hillside to fail producing a debris flow weeks later.
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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.
The episode as NWS MTR wrote it up.
Storms from March provided the necessary moisture to cause a hillside to fail producing a debris flow weeks later.
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 San Francisco Bay Area, CA wrote its last area forecast discussion before the first event at Apr 30, 10:19 AM PST, 41 minutes earlier.
AREA FORECAST DISCUSSION
NATIONAL WEATHER SERVICE SAN FRANCISCO BAY AREA
1119 AM PDT SAT APR 30 2011
.DISCUSSION...AS OF 9:00 AM PDT SATURDAY...A STRONG NORTHERLY
GRADIENT ALLOWED WINDS IN SOME LOCATIONS TO REMAIN MODERATE
OVERNIGHT KEEPING THE LOWS IN THE 50S FOR NON-WIND SHELTERED
LOCATIONS. THE NORTHERLY GRADIENT WILL DECREASE THROUGH THE DAY...
BUT NOT QUICK ENOUGH RESULTING IN BREEZY CONDITIONS AGAIN TODAY.
A RIDGE HAS BEGUN TO BUILD OVERHEAD USHERING IN A WARMER AIR MASS.
ON THIS MORNING/S KOAK SOUNDING THE LOWER LEVELS HAVE RECOVERED FROM
THE COOLING ASSOCIATED WITH THE TROUGH THAT BRUSHED BY THE AREA
YESTERDAY. TEMPERATURES BELOW 700 MB HAVE WARMED 3 TO 7 DEGREES
CELSIUS OVER YESTERDAY/S READINGS. THIS WARMING WILL CONTINUE
THROUGH NEXT WEEK AS 850 MB TEMPERATURES RISE FROM 4.2 DEGREES THIS
MORNING TO AROUND 12 DEGREES ON SUNDAY AND TO NEARLY 18 DEGREES ON
WEDNESDAY...WHICH IS ABOUT 2 STANDARD DEVIATIONS ABOVE NORMAL. THIS
WILL TRANSLATE INTO ABOVE NORMAL AFTERNOON TEMPERATURES BEGINNING
TOMORROW.
ALTHOUGH A TROUGH MOVES THROUGH THE PACIFIC NORTHWEST ON MONDAY THE
LONG WAVE RIDGE CONTINUES TO BUILD INTO WEDNESDAY. THE RIDGE WILL
HOLD STRONG INTO THURSDAY BEFORE FLATTENING AS ANOTHER TROUGH MOVES
ACROSS THE PACIFIC NORTHWEST. 500 MB HEIGHTS REMAIN ABOVE 576DM
INTO NEXT WEEKEND WITH A WEAK ONSHORE SURFACE FLOW LEADING TO A
COOLING TREND WITH AFTERNOON TEMPERATURES LOWERING BACK TOWARD
NORMAL.
&&
.AVIATION...AS OF 11:15 AM PDT SATURDAY MORNING...VFR CONDITIONS WILL
PREVAIL. HIGH PRESSURE OVER THE AREA WILL KEEP SKIES CLEAR THROUGH
THE FORECAST PERIOD. NORTHERLY WINDS WILL BECOME WESTERLY THIS
AFTERNOON AS ONSHORE PRESSURE GRADIENT INCREASES THROUGH 01Z SUNDAY.
VICINITY OF KSFO...VFR CONDITIONS WILL PREVAIL THROUGH SUNDAY
AFTERNOON. MODERATE WESTERLY WINDS...WITH GUSTS TO 20 KT POSSIBLE
BETWEEN 20Z AND 03Z SUNDAY.
KSFO BRIDGE APPROACH...SIMILAR TO KSFO.
MONTEREY BAY AREA TERMINALS...VFR CONDITIONS THROUGH SUNDAY
MORNING. MODERATE WEST WINDS NEAR 15 KT POSSIBLE THIS AFTERNOON...
ESPECIALLY AT KSNS.
&&
.MTR WATCHES/WARNINGS...
.TDA...SCA...POINT ARENA TO POINT PIEDRAS BLANCAS 10-60 NM.
...SCA...POINT ARENA TO POINT REYES 0-10 NM.
...SCA...PIGEON POINT TO POINT PIEDRAS BLANCAS 0-10 NM.
&&
PUBLIC FORECAST: EVANS
AVIATION/MARINE: RILEYThe national radar mosaic for the moment the first event began.
1 debris flow. Local standard time, as filed.
A hillside near the Watsonville airport gave way weeks after the last heavy rainfall ended. A debris flow occurred at Manfre Road in Freedom and entered a home. The home was destroyed along with everything in it when three feet of mud and debris filled the house.
After NWS Directive 10-1605, the rules offices file Storm Data by.
Every storm in California in 2011Every state in 2011This day in weather historyWarnings in California, April 2011
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: 304116.