Flash Flood in California, April 7, 2009

Name: Flash Flood in California, April 7, 2009
Start: 2009-04-07T15:30
End: 2009-04-07T17:30
Location: California

April 7, 2009 · NWS MTR · 1 event in 1 county or zone

A low pressure system cut off from the main flow brought brief heavy rain to central California.

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: 0
Injuries: 0
Property damage: $40,000
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 MTR wrote it up.

A low pressure system cut off from the main flow brought brief heavy rain to central California.

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 San Francisco Bay Area, CA wrote its last area forecast discussion before the first event at Apr 7, 3:15 PM PST, 15 minutes earlier.

Area forecast discussion, Apr 7, 3:15 PM PST, 15 minutes before

AREA FORECAST DISCUSSION
NATIONAL WEATHER SERVICE SAN FRANCISCO BAY AREA CA
415 PM PDT TUE APR 7 2009

.DISCUSSION...AS OF 2:43 PM PDT TUESDAY...FOCUS WITH THIS FORECAST
PACKAGE WILL BE ONGOING SHOWERS AND THEN ANOTHER CHANCE FOR RAIN
LATE IN THE WEEK.

THE MAIN RAIN BAND FROM THIS MORNING HAS PRETTY MUCH PUSHED THROUGH
THE CWA EARLY THIS AFTERNOON. RAINFALL AMOUNTS OVER THE LAST 6 HRS
HAVE BEEN A FEW TENTHS TO ROUGHLY ONE HALF INCH. LOCALLY HIGHER
AMOUNTS TO ALMOST AN INCH HAVE OCCURRED OVER THE COASTAL MT RANGE OF
MONTEREY AND SANTA CRUZ COUNTIES...MINING RIDGE REPORTED 0.86
INCHES. MORE IMPRESSIVELY ARE THE 24 HOUR TEMPERATURE CHANGES WITH
MANY LOCATIONS MUCH COLDER THAN YESTERDAY. FOR INSTANCE...KSTS IS
22 DEGREES COLDER AND NAPA IS A WHOPPING 24 DEGREES COLDER.

SHORT TERM (THIS EVENING-FRIDAY)...
THE UPPER LOW THE BROUGHT RAIN THIS MORNING CONTINUES TO DRIFT
TOWARD THE SAN FRAN COAST THIS AFTERNOON. AS A RESULT...THE AIRMASS
IS BECOMING A LITTLE MORE UNSTABLE OVER THE CWA AS NOTED ON THE SPC
MESOANALYSIS DATA. THEREFORE...EXPECT MORE WIDESPREAD-SCATTERED
SHOWERS WITH AN ISOLATED THUNDERSTORM. RECENT LIGHTNING PLOTS HAVE
NOT INDICATED ANY STRIKES...BUT THE POSSIBILITY STILL REMAINS EVEN
THOUGH IT IS MINOR. IN ADDITION...SMALL HAIL WILL STILL BE POSSIBLE
AS TEMPERATURES ALOFT CONTINUE TO COOL AS SEEN ON AREA PROFILERS.
ONCE THE UPPER LOW DRIFTS INLAND TONIGHT...THE CHANCE FOR PRECIP AND
TSTMS WILL DIMINISH.  BY EARLY WEDNESDAY...THE UPPER LOW IS FORECAST
TO BE INLAND WITH LARGE SCALE SUBSIDENCE IN ITS WAKE WITH A SHORTWAVE
RIDGE BUILDING OVERHEAD. THIS WILL REALLY LOWER THE CHANCES FOR ANY
PRECIP. CURRENT FORECAST WILL CALL FOR DIMINISHING CHANCES OF PRECIP
AFTER MIDNIGHT THROUGH MIDDAY WEDNESDAY. AT THIS TIME...THE SECOND
HALF OF WEDNESDAY INTO EARLY THURSDAY LOOKS TO BE MOSTLY DRY WITH
RIDGING OVERHEAD. NEXT UP WILL BE A RATHER WELL DEFINED AND
PROGRESSIVE COLD FRONT APPROACHING FROM THE NW WEDNESDAY NIGHT. MODEL
GUIDANCE IS COMING INTO BETTER AGREEMENT WITH PLACING AN UPPER LEVEL
TROUGH AND ASSOCIATED SFC COLD FRONT OFF THE NORCAL COAST BY EARLY
THURSDAY. THE FRONT IS FORECAST TO MOVE THROUGH THE CWA THURSDAY INTO
FRIDAY BRINING ANOTHER ROUND OF PRECIP. THE ECMWF AND NAM ARE A
LITTLE STRONGER THAN THE GFS REGARDING STRENGTHEN AND TOTAL QPF. WILL
LEAN MORE TOWARD THE ECMWF AND NAM AND BRING SHOWERS NORTH TO SOUTH
THURSDAY AFTERNOON THROUGH FRIDAY.

LONG TERM (SATURDAY-TUESDAY)...
THE COLD FRONT WILL BE WELL S AND E OF THE CWA BY SATURDAY. BEHIND
THE FRONT WARMING AND DRYING WILL DEVELOP THROUGH MONDAY AS HIGH
PRESSURE BECOMES RE-ESTABLISHED. 850 TEMPERATURES ARE FORECAST TO
WARM A FEW DEGREES EACH DAY WITH MONDAY BEING THE WARMEST. HIGH
PRESSURE WILL WEAKEN ON TUESDAY AS ANOTHER UPPER LEVEL TROUGH MOVES
IN FROM THE NORTH. ATTM...WILL KEEP THE FORECAST DRY WITH THE FINAL
TROUGH...BUT WILL HAVE TO MONITOR THE NEXT SEVERAL MODEL RUNS AND
SEE IF SLT CHC SHOWERS IS NEEDED.

&&

.AVIATION...AS OF 4:15 PM PDT TUESDAY...SPOTTERS HAVE BEEN CALLING
IN WITH REPORTS OF ISOLATED THUNDER. VERY RECENT REPORT FROM CARMEL
VALLEY VILLAGE AREA INDICATES THUNDER CAN BE HEARD. KMRY AND KSNS
HAVE TEMPO FOR THUNDERSTORMS TIL 02Z. ISOLATED THUNDERSTORMS ARE
ALSO DEVELOPING OVER THE EAST BAY AREA. THUNDER WAS REPORTED FROM
OAKLAND AND BERKLEY. OTHERWISE SCATTERED SHOWERS ARE OCCURRING OVER
THE AREA THIS AFTERNOON. AS THE CORE OF THE UPPER LOW MOVES THROUGH
THE AREA ADDITIONAL SHOWERS WILL CONTINUE THROUGH THE EVENING.

&&

.MARINE...AS OF 4:15 PM PDT TUESDAY...MARINE WEATHER STATEMENT
CONTINUES FOR TSTORM AND LIGHTNING POTENTIAL THIS AFTERNOON OVER THE
OCEAN.

.MTR WATCHES/WARNINGS/ADVISORIES...NONE.

PUBLIC FORECAST: MM
AVIATION/MARINE: BJT/CANEPA

NWS ON THE WEB AT WEATHER.GOV/SANFRANCISCO

In the hours before

Local storm report, Apr 7, 2:41 PM PST, 49 minutes before

PRELIMINARY LOCAL STORM REPORT
NATIONAL WEATHER SERVICE SAN FRANCISCO CA
341 PM PDT TUE APR 07 2009

..TIME...   ...EVENT...      ...CITY LOCATION...     ...LAT.LON...
..DATE...   ....MAG....      ..COUNTY LOCATION..ST.. ...SOURCE....
            ..REMARKS..

0338 PM     HAIL             NW LAFAYETTE            37.90N 122.12W
04/07/2009  M0.25 INCH       CONTRA COSTA       CA   TRAINED SPOTTER

0338 PM     HAIL             4 ESE BERKELEY          37.86N 122.23W
04/07/2009  M0.25 INCH       ALAMEDA            CA   TRAINED SPOTTER

&&

ANDERSON

The radar

The San Francisco radar (KMUX), 98 km away, was scanning. The volume nearest the first event began at 23:30 UTC.

Open the radar archive at this moment

Event by event

1 flash flood. Local standard time, as filed.

Flash Flood, Monterey

When: April 7, 3:30 PM PST to 5:30 PM PST
Where: Monterey County, 0.46 mi WNW of Big Sur to 0.99 mi WNW of Big Sur
Cause: Heavy Rain / Burn Area
Property damage: $40,000
Reported by: Law Enforcement
Coordinates: 36.273, -121.807

Heavy rain fell on top of a recently burned forest causing flash flooding and debris flows. More than three feet of mud covered State Route One closing it for several hours. Vehicles parked at the Big Sur Lodge were stuck in mud and debris. One vehicle was even forced into a culvert and buried. At least three separate debris flows were reported along Highway One, all within a 3 mile span.

What these are

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.

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

The same day elsewhere

Every storm in California in 2009 Every state in 2009 This day in weather history Warnings in California, April 2009

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: 166595.