Alert archive / California / Flash Flood Warnings in 2016

Flash Flood Warning 16, NWS San Francisco Bay Area, CA

December 15, 2016Marin County, Sonoma County, California

NWS San Francisco Bay Area, CA issued this flash flood warning at Dec 15, 2016, 12:57 PM PST for Marin County, Sonoma County, California. It was in force for 4 hr. 9 reports came from inside the area while it was in force.

The area

The outline as issued, with what was reported inside it.

The facts

Issued: Dec 15, 2016, 12:57 PM PST (20:57 UTC)
Expired: Dec 15, 2016, 5:00 PM PST
In force: 4 hr
Issued by: NWS San Francisco Bay Area, CA
Area: Storm-based polygon
Flood severity: None

Counties Marin County, CA, Sonoma County, CA

The radar

The Sacramento radar (KDAX), 92 km from the middle of the area, began a volume at 20:58 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.

What was reported inside it

Time	Report	Where	Remark
Dec 15, 1:28 PM PST	FLOOD	5 E Petaluma, CA	NORTHBOUND 121 CLOSED DUE TO FLOODING. JCT RTE 116/121 ARNOLD DR/FREMONT DR. TO SCHELLVILLE RD./EIGHT ST.
Dec 15, 2:04 PM PST	FLASH FLOOD	4 Ese Rohnert Park, CA	ROADWAY BEING WASHED AWAY AT LICHAU/COLD SPRINGS RD NEAR COPELAND CREEK.
Dec 15, 2:42 PM PST	FLASH FLOOD	2 W Sonoma, CA	FLASH FLOODING ON ROADWAY AT FOWLER CREED RD
Dec 15, 3:18 PM PST	FLASH FLOOD	1 S Sonoma, CA	ROADWAYS FLOODED AND BLOCKING TRAFFIC AT 20000 BROADWAY NEAR SONOMA VALLEY HIGH SCHOOL
Dec 15, 3:32 PM PST	FLASH FLOOD	4 Wnw Rohnert Park, CA	CAR STUCK IN FLOODING AT MEADOW LN/LLANO RD INTERSECTION
Dec 15, 4:12 PM PST	FLASH FLOOD	8 Ne Novato, CA	3 VEHICLES STRANDED IN FLASH FLOOD AT SR121/SEARS POINT RACEWAY. BOTH DIRECTIONS OF ROAD FLOODED.
Dec 15, 4:22 PM PST	FLASH FLOOD	3 Ssw Sonoma, CA	ROADWAY FLOODING AT ARNOLD DR / STAGE GULD RD
Dec 15, 4:23 PM PST	FLASH FLOOD	3 Ssw Sonoma, CA	ROADWAY FLOODING AT WATMAUGH RD / SR116
Dec 15, 4:26 PM PST	FLASH FLOOD	5 Wnw Rohnert Park, CA	ROADWAY FLOODING AT TODD RD / OLD GRAVENSTEIN HIGHWAY

Local storm reports filed while the alert was in force, from inside its polygon or its counties.

The nearest sounding before it

Oakland, CA (KOAK), launched 12:00Z, 9.0 hours before the alert went out and 84 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-p

Temperature in red, dew point in green, the mixed-layer parcel dashed.

Hodograph

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: 1 J/kg
Mixed-layer CIN: No buoyant parcel
Mixed-layer LCL: 767 m above ground
0-6 km bulk shear: 50 kt
0-1 km storm-relative helicity: 276 m²/s²
0-3 km storm-relative helicity: 311 m²/s²
Significant tornado parameter: 0.0
Supercell composite: 0.0

Open this sounding in Storm Lab

The text

As transmitted.

321 
WGUS56 KMTR 152057
FFWMTR
CAC041-097-160100-
/O.NEW.KMTR.FF.W.0016.161215T2057Z-161216T0100Z/
/00000.0.ER.000000T0000Z.000000T0000Z.000000T0000Z.OO/

BULLETIN - EAS ACTIVATION REQUESTED
Flash Flood Warning
National Weather Service San Francisco CA
1257 PM PST THU DEC 15 2016

The National Weather Service in The San Francisco Bay Area has issued
a

* Flash Flood Warning for...
  Southeastern Sonoma County in northern California...
  Northern Marin County in northern California...

* Until 500 PM PST

* At 1253 PM PST, gauge reports indicated heavy rain falling across
  the warned area and creek gauges rising above flood stage. Flash
  flooding is already occurring.

Automated stream gages have reported water levels rising above flood
stage on Willow Brook in Penngrove Park in Petaluma, Sonoma Creek at
Agua Caliente, Copeland Creek in Rohnert Park, Colgan Creek near
Sebastopol, and other creeks in the lower Laguna de Santa Rosa west
of the City of Santa Rosa.  There have also been reports of flooding
in other lowland valley settings in southern Sonoma County and
northern Marin County, as well as roadway flooding.

PRECAUTIONARY/PREPAREDNESS ACTIONS...

Turn around, don't drown when encountering flooded roads. Most flood
deaths occur in vehicles.

In hilly terrain there are hundreds of low water crossings which are
potentially dangerous in heavy rain. Do not attempt to cross flooded
roads. Find an alternate route.

A Flash Flood Warning means that flooding is imminent or occurring.
If you are in the warned area move to higher ground immediately.
Residents living along streams and creeks should take immediate
precautions to protect life and property.

&&

LAT...LON 3857 12265 3841 12249 3817 12239 3814 12248
      3818 12275 3825 12297 3838 12308 3847 12292
      3856 12280

$$

MWS

1 follow-up statement

259 
WGUS76 KMTR 160053
FFSMTR

Flash Flood Statement
National Weather Service San Francisco CA
453 PM PST THU DEC 15 2016

CAC041-097-160103-
/O.EXP.KMTR.FF.W.0016.000000T0000Z-161216T0100Z/
/00000.0.ER.000000T0000Z.000000T0000Z.000000T0000Z.OO/
Sonoma CA-Marin CA-
453 PM PST THU DEC 15 2016

...THE FLASH FLOOD WARNING FOR SOUTHEASTERN SONOMA AND NORTHERN MARIN
COUNTIES WILL EXPIRE AT 500 PM PST...

Flooding is no longer expected to pose a threat. Please continue to
heed any remaining road closures.

LAT...LON 3857 12265 3841 12249 3817 12239 3814 12248
      3818 12275 3825 12297 3838 12308 3847 12292
      3856 12280

$$

MWS

The office that day

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

Issued	Product	Office	Counties	Lasted
Dec 14, 6:07 PM PST	Areal Flood Advisory	MTR	Marin, Napa, Sonoma	12 hr
Dec 15, 3:06 AM PST	Small Craft Advisory	MTR		3 days
Dec 15, 3:40 AM PST	Wind Advisory	MTR	Alameda, Contra Costa, Marin, Monterey, San Benito, San Mateo and 3 more	21 hr
Dec 15, 10:24 AM PST	Areal Flood Advisory	MTR	Marin, Napa, Sonoma	6 hr
Dec 15, 3:12 PM PST	Areal Flood Advisory	MTR	Alameda, Contra Costa	4 hr
Dec 15, 3:16 PM PST	Areal Flood Advisory	MTR	City and County of San Francisco, San Mateo	4 hr
Dec 15, 3:38 PM PST	Flash Flood Warning	MTR	Napa	3 hr

Nearby

Flash Flood Warnings in California, 2016 Every flash flood warning in 2016

Sources

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