Alert archive / California / Flash Flood Watches in 2012

Flash Flood Watch 2, NWS San Francisco Bay Area, CA

December 23, 2012Marin County, Napa County, Sonoma County, California

NWS San Francisco Bay Area, CA issued this flash flood watch at Dec 23, 2012, 9:31 AM PST for Marin County, Napa County, Sonoma County, California. It was in force for 5 hr.

The area

The counties it named.

The facts

Issued
Dec 23, 2012, 9:31 AM PST (17:31 UTC)
Expired
Dec 23, 2012, 3:00 PM PST
In force
5 hr
Issued by
NWS San Francisco Bay Area, CA
Flood severity
None

Counties Marin County, CA, Napa County, CA, Sonoma County, CA

The radar

The Sacramento radar (KDAX), 88 km from the middle of the area, began a volume at 17:33 UTC, the scan nearest the moment this went out.

Open the radar archive at this moment

The archived warnings, watches and discussions in force at that minute are drawn over the scan, this one among them.

The nearest sounding before it

Oakland, CA (KOAK), launched 12:00Z, 5.5 hours before the alert went out and 81 km from the middle of its area. This is the routine balloon launch nearest before it, the air the forecaster had in hand, not a measurement taken for the alert.

Skew-T log-pSkew-T log-p diagram, Oakland, CA at 12:00Z on 2012-12-23Temperature and dew point through the depth of the atmosphere, with the mixed-layer parcel. CAPE 5 joules per kilogram.LCLLFCEL10008507005003002001001 km2 km3 km6 km9 km12 km15 km-30°-20°-10°10°20°30°40°
Temperature in red, dew point in green, the mixed-layer parcel dashed.
HodographHodograph, Oakland, CA at 12:00Z on 2012-12-23The wind through the lowest 10 kilometers. Zero to 1 km storm-relative helicity 178 square meters per square second.1939587897Sfc1 km3 km6 km9 kmRMLM
The wind turning with height, colored by layer: ground to 1 km, 1 to 3 km, 3 to 6 km, 6 to 10 km.
Mixed-layer CAPE
5 J/kg
Mixed-layer CIN
-19 J/kg
Mixed-layer LCL
833 m above ground
0-6 km bulk shear
62 kt
0-1 km storm-relative helicity
178 m²/s²
0-3 km storm-relative helicity
210 m²/s²
Significant tornado parameter
0.0
Supercell composite
0.0

Open this sounding in Storm Lab

The text

As transmitted, in the capitals the NWS used until 2016.

124 
WGUS66 KMTR 231731
FFAMTR

URGENT - IMMEDIATE BROADCAST REQUESTED
FLOOD WATCH
NATIONAL WEATHER SERVICE SAN FRANCISCO BAY AREA
931 AM PST SUN DEC 23 2012

DEFAULT OVERVIEW SECTION
CAZ506-232100-
/O.NEW.KMTR.FF.A.0002.121223T1731Z-121223T2100Z/
/00000.0.ER.000000T0000Z.000000T0000Z.000000T0000Z.OO/
NORTH BAY INTERIOR VALLEYS-
931 AM PST SUN DEC 23 2012

...FLASH FLOOD WATCH IN EFFECT UNTIL 1 PM PST THIS AFTERNOON...

THE NATIONAL WEATHER SERVICE SAN FRANCISCO BAY AREA HAS ISSUED
A

* FLASH FLOOD WATCH FOR A PORTION OF CALIFORNIA...INCLUDING THE
  FOLLOWING AREA...SONOMA VALLEY AND SONOMA CREEK AREA.

* UNTIL 1 PM PST THIS AFTERNOON

* STAGE ON SONOMA CREEK AT AGUA CALIENTE HAS REACHED NEARLY 18
  FEET AS OF 8:45 PST AND THE CREEK CONTINUES TO RISE RAPIDLY IN
  RESPONSE TO A BAND OF INTENSE RAINFALL CURRENTLY MOVING THROUGH
  THE AREA.


PRECAUTIONARY/PREPAREDNESS ACTIONS...

A FLASH FLOOD WATCH MEANS THAT CONDITIONS MAY DEVELOP THAT LEAD
TO FLASH FLOODING. FLASH FLOODING IS A VERY DANGEROUS SITUATION.

YOU SHOULD MONITOR LATER FORECASTS AND BE PREPARED TO TAKE ACTION
SHOULD FLASH FLOOD WARNINGS BE ISSUED.

&&

$$

STRUDLEY
3 follow-up statements
329 
WGUS66 KMTR 231905
FFAMTR

URGENT - IMMEDIATE BROADCAST REQUESTED
FLOOD WATCH
NATIONAL WEATHER SERVICE SAN FRANCISCO BAY AREA
1105 AM PST SUN DEC 23 2012

DEFAULT OVERVIEW SECTION
CAZ506-232200-
/O.EXT.KMTR.FF.A.0002.000000T0000Z-121223T2200Z/
/00000.0.ER.000000T0000Z.000000T0000Z.000000T0000Z.OO/
NORTH BAY INTERIOR VALLEYS-
1105 AM PST SUN DEC 23 2012

...FLASH FLOOD WATCH NOW IN EFFECT UNTIL 2 PM PST THIS
AFTERNOON...

THE FLASH FLOOD WATCH IS NOW IN EFFECT FOR

* A PORTION OF CALIFORNIA...INCLUDING THE FOLLOWING AREA...NORTH 
  BAY INTERIOR VALLEYS.

* UNTIL 2 PM PST THIS AFTERNOON

* STAGE ON SONOMA CREEK AT AGUA CALIENTE HAS REACHED NEARLY 18 
  FEET AS OF 8:45 PST AND THE CREEK CONTINUES TO RISE RAPIDLY IN 
  RESPONSE TO A BAND OF INTENSE RAINFALL CURRENTLY MOVING 
  THROUGH THE AREA. 

* THE FLASH FLOOD WARNING HAS BEEN EXTENDED TO INCLUDE THE NAPA
  VALLEY REGION. SOME SMALL CREEKS IN THE AREA THAT FEED NAPA
  CREEK AND THE NAPA RIVER ARE APPROACHING MONITOR OR FLOOD
  STAGES. THE FRONT IS EXPECTED TO MOVE THROUGH THE AREA OVER THE
  NEXT SEVERAL HOURS SO CONTINUED RISE IN STAGE MAY OCCUR OVER THE
  NEXT SEVERAL HOURS.


PRECAUTIONARY/PREPAREDNESS ACTIONS...

A FLASH FLOOD WATCH MEANS THAT CONDITIONS MAY DEVELOP THAT LEAD
TO FLASH FLOODING. FLASH FLOODING IS A VERY DANGEROUS SITUATION.

YOU SHOULD MONITOR LATER FORECASTS AND BE PREPARED TO TAKE ACTION
SHOULD FLASH FLOOD WARNINGS BE ISSUED.

&&

$$

STRUDLEY
091 
WGUS66 KMTR 232116
FFAMTR

URGENT - IMMEDIATE BROADCAST REQUESTED
FLOOD WATCH
NATIONAL WEATHER SERVICE SAN FRANCISCO BAY AREA
116 PM PST SUN DEC 23 2012

DEFAULT OVERVIEW SECTION
CAZ505-232300-
/O.EXB.KMTR.FF.A.0002.000000T0000Z-121223T2300Z/
/00000.0.ER.000000T0000Z.000000T0000Z.000000T0000Z.OO/
COASTAL NORTH BAY...INCLUDING POINT REYES NATIONAL SEASHORE-
116 PM PST SUN DEC 23 2012

...FLASH FLOOD WATCH IN EFFECT UNTIL 3 PM PST THIS AFTERNOON...

THE NATIONAL WEATHER SERVICE SAN FRANCISCO BAY AREA HAS
EXPANDED THE

* FLASH FLOOD WATCH TO INCLUDE A PORTION OF CALIFORNIA...
  INCLUDING THE FOLLOWING AREA...SOUTHERN MARIN COUNTY.

* UNTIL 3 PM PST THIS AFTERNOON

* THE FLASH FLOOD WARNING HAS BEEN EXTENDED TO INCLUDE THE COASTAL
  WATERSHEDS OF SOUTHERN MARIN COUNTY. IN PARTICULAR, CORTE MADERA
  CREEK AT ROSS IS APPROACHING FLOOD STAGE AND THE FRONT HAS NOT
  COMPLETELY MOVED THROUGH THE AREA YET. CORTE MADERA CREEK AND
  OTHER ASSOCIATED DRAINAGES NEARBY MAY APPROACH OR GO ABOVE FLOOD
  STAGE. HOWEVER, THE FRONT IS EXPECTED TO PASS QUICKLY, SO THE
  DURATION AND MAGNITUDE OF FLOODING, IF IT OCCURS, SHOULD BE MINOR. 

PRECAUTIONARY/PREPAREDNESS ACTIONS...

A FLASH FLOOD WATCH MEANS THAT CONDITIONS MAY DEVELOP THAT LEAD
TO FLASH FLOODING. FLASH FLOODING IS A VERY DANGEROUS SITUATION.

YOU SHOULD MONITOR LATER FORECASTS AND BE PREPARED TO TAKE ACTION
SHOULD FLASH FLOOD WARNINGS BE ISSUED.

&&

$$

CAZ506-232300-
/O.EXT.KMTR.FF.A.0002.000000T0000Z-121223T2300Z/
/00000.0.ER.000000T0000Z.000000T0000Z.000000T0000Z.OO/
NORTH BAY INTERIOR VALLEYS-
116 PM PST SUN DEC 23 2012

...FLASH FLOOD WATCH NOW IN EFFECT UNTIL 3 PM PST THIS
AFTERNOON...

THE FLASH FLOOD WATCH IS NOW IN EFFECT FOR

* A PORTION OF CALIFORNIA...INCLUDING THE FOLLOWING AREA...NORTH 
  BAY INTERIOR VALLEYS.

* UNTIL 3 PM PST THIS AFTERNOON

* STAGE ON SONOMA CREEK AT AGUA CALIENTE HAS REACHED NEARLY 18 
  FEET AS OF 8:45 PST AND THE CREEK CONTINUES TO RISE RAPIDLY IN 
  RESPONSE TO A BAND OF INTENSE RAINFALL CURRENTLY MOVING 
  THROUGH THE AREA. 

* THE FLASH FLOOD WARNING HAS BEEN EXTENDED TO INCLUDE THE NAPA 
  VALLEY REGION. SOME SMALL CREEKS IN THE AREA THAT FEED NAPA 
  CREEK AND THE NAPA RIVER ARE APPROACHING MONITOR OR FLOOD 
  STAGES. THE FRONT IS EXPECTED TO MOVE THROUGH THE AREA OVER 
  THE NEXT SEVERAL HOURS SO CONTINUED RISE IN STAGE MAY OCCUR 
  OVER THE NEXT SEVERAL HOURS. 

PRECAUTIONARY/PREPAREDNESS ACTIONS...

A FLASH FLOOD WATCH MEANS THAT CONDITIONS MAY DEVELOP THAT LEAD
TO FLASH FLOODING. FLASH FLOODING IS A VERY DANGEROUS SITUATION.

YOU SHOULD MONITOR LATER FORECASTS AND BE PREPARED TO TAKE ACTION
SHOULD FLASH FLOOD WARNINGS BE ISSUED.

&&

$$

STRUDLEY
217 
WGUS66 KMTR 232312
FFAMTR

URGENT - IMMEDIATE BROADCAST REQUESTED
FLOOD WATCH
NATIONAL WEATHER SERVICE SAN FRANCISCO BAY AREA
312 PM PST SUN DEC 23 2012

DEFAULT OVERVIEW SECTION
CAZ505-506-240015-
/O.EXP.KMTR.FF.A.0002.000000T0000Z-121223T2300Z/
/00000.0.ER.000000T0000Z.000000T0000Z.000000T0000Z.OO/
COASTAL NORTH BAY...INCLUDING POINT REYES NATIONAL SEASHORE-
NORTH BAY INTERIOR VALLEYS-
312 PM PST SUN DEC 23 2012

...FLASH FLOOD WATCH HAS EXPIRED...

THE FLASH FLOOD WATCH FOR A PORTION OF CALIFORNIA HAS EXPIRED.

$$

CAZ529-240300-
/O.NEW.KMTR.FF.A.0003.121223T2312Z-121224T0300Z/
/00000.0.ER.000000T0000Z.000000T0000Z.000000T0000Z.OO/
NORTHERN MONTEREY BAY-
312 PM PST SUN DEC 23 2012

...FLASH FLOOD WATCH IN EFFECT UNTIL 7 PM PST THIS EVENING...

THE NATIONAL WEATHER SERVICE SAN FRANCISCO BAY AREA HAS ISSUED
A

* FLASH FLOOD WATCH FOR A PORTION OF CALIFORNIA...INCLUDING THE
  FOLLOWING AREA...LOWER SOQUEL CREEK AND APTOS CREEK
  SYSTEMS...INCLUDING TRIBUTARY CREEKS.

* UNTIL 7 PM PST THIS EVENING

* MANY LOCAL STREAM GAGES HAVE INDICATED VERY RAPID RISES IN STAGE
  OVER THE PAST HOUR...INCLUDING THE GAGE ON SOQUEL CREEK AT
  BRIDGE STREET...WHICH HAS GONE ABOVE MONITORING STAGE.
  MONITORING STAGE IS AT 11 AND A HALF FEET. FLOOD STAGE IS AT
  14.5 FEET. ADDITIONAL RAINFALL AND RUNOFF MAY CREATE DANGEROUS
  CONDITIONS LOCALLY. SOME CREEKS IN THE APTOS CREEK BASIN MAY
  ALSO BE FLOODING..SO CAUTION IS ADVISED.


PRECAUTIONARY/PREPAREDNESS ACTIONS...

A FLASH FLOOD WATCH MEANS THAT CONDITIONS MAY DEVELOP THAT LEAD
TO FLASH FLOODING. FLASH FLOODING IS A VERY DANGEROUS SITUATION.

YOU SHOULD MONITOR LATER FORECASTS AND BE PREPARED TO TAKE ACTION
SHOULD FLASH FLOOD WARNINGS BE ISSUED.

&&

$$

STRUDLEY

The office that day

Everything else NWS San Francisco Bay Area, CA issued on the same UTC day.

IssuedProductOfficeCountiesLasted
Dec 23, 8:55 AM PSTFlash Flood WarningMTRSonoma4 hr
Dec 23, 1:41 PM PSTFlash Flood WarningMTRSonoma3 hr
Dec 23, 2:17 PM PSTRiver Flood WarningMTRNapa8 hr
Dec 23, 2:17 PM PSTRiver Flood WarningMTRNapa11 hr
Dec 23, 2:33 PM PSTSmall Craft Advisory for Hazardous SeasMTR15 hr
Dec 23, 2:38 PM PSTFlash Flood WarningMTRSanta Cruz5 hr
Dec 23, 3:12 PM PSTFlash Flood WatchMTRSanta Cruz4 hr

Nearby

Flash Flood Watches in California, 2012Every flash flood watch in 2012

Sources

The product and its follow-ups from the Iowa Environmental Mesonet's archive of National Weather Service and Storm Prediction Center text; the sounding from the Mesonet's radiosonde archive; radar from the NEXRAD Level II archive.