Alert archive / Utah / Flash Flood Warnings in 2012

Flash Flood Warning 66, NWS Salt Lake City, UT

September 11, 2012Washington County, Utah

NWS Salt Lake City, UT issued this flash flood warning at Sep 11, 2012, 1:45 PM MDT for Washington County, Utah. It was in force for 3 hr. No storm report in the archive falls inside the area while it was in force.

The area

The outline as issued.

The facts

Issued
Sep 11, 2012, 1:45 PM MDT (19:45 UTC)
Expired
Sep 11, 2012, 4:45 PM MDT
In force
3 hr
Issued by
NWS Salt Lake City, UT
Area
Storm-based polygon
Flood severity
None

County Washington County, UT

The radar

The Cedar City radar (KICX), 87 km from the middle of the area, began a volume at 19:48 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

Las Vegas, NV (KVEF), launched 12:00Z, 7.8 hours before the alert went out and 188 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, Las Vegas, NV at 12:00Z on 2012-09-11Temperature and dew point through the depth of the atmosphere, with the mixed-layer parcel. CAPE 2 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, Las Vegas, NV at 12:00Z on 2012-09-11The wind through the lowest 10 kilometers. Zero to 1 km storm-relative helicity 17 square meters per square second.1939Sfc1 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
2 J/kg
Mixed-layer CIN
-171 J/kg
Mixed-layer LCL
1725 m above ground
0-6 km bulk shear
9 kt
0-1 km storm-relative helicity
17 m²/s²
0-3 km storm-relative helicity
37 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.

781 
WGUS55 KSLC 111945
FFWSLC
UTC053-112245-
/O.NEW.KSLC.FF.W.0066.120911T1945Z-120911T2245Z/
/00000.0.ER.000000T0000Z.000000T0000Z.000000T0000Z.OO/

BULLETIN - EAS ACTIVATION REQUESTED
FLASH FLOOD WARNING
NATIONAL WEATHER SERVICE SALT LAKE CITY UT
145 PM MDT TUE SEP 11 2012

THE NATIONAL WEATHER SERVICE IN SALT LAKE CITY HAS ISSUED A

* FLASH FLOOD WARNING FOR...
  SOUTH CENTRAL WASHINGTON COUNTY IN UTAH

* UNTIL 445 PM MDT

* AT 135 PM MDT...LOCAL LAW ENFORCEMENT REPORTED THAT THE LAUB DIKE 
IN SANTA CLARA HAS FAILED AND FLOODING WAS REPORTED IN PORTIONS OF 
THE COMMUNITY. 

* LOCATIONS IN THE WARNING INCLUDE BUT ARE NOT LIMITED TO SANTA CLARA

PRECAUTIONARY/PREPAREDNESS ACTIONS...

DO NOT DRIVE YOUR VEHICLE INTO AREAS WHERE THE WATER COVERS THE
ROADWAY. THE WATER DEPTH MAY BE TOO GREAT TO ALLOW YOUR CAR TO CROSS 
SAFELY. TURN AROUND AND DONT DROWN. 

&&

LAT...LON 3714 11367 3715 11363 3707 11359 3711 11367

$$

PW
2 follow-up statements
191 
WGUS75 KSLC 112038
FFSSLC

FLASH FLOOD STATEMENT
NATIONAL WEATHER SERVICE SALT LAKE CITY UT
238 PM MDT TUE SEP 11 2012

UTC053-112245-
/O.CON.KSLC.FF.W.0066.000000T0000Z-120911T2245Z/
/00000.0.ER.000000T0000Z.000000T0000Z.000000T0000Z.OO/
WASHINGTON UT-
238 PM MDT TUE SEP 11 2012

...A FLASH FLOOD WARNING REMAINS IN EFFECT UNTIL 445 PM MDT FOR SOUTH
CENTRAL WASHINGTON COUNTY...

AT 223 PM MDT...FLOODING FROM THE RETENTION POND BEHIND LAUB DIKE IN 
SANTA CLARA IS BEGINNING TO ABATE. THE POND IS NOW EMPTY AND THE 
WATER HAS MOVED DOWNSTREAM TOWARDS THE SANTA CLARA RIVER. FLOODING 
WAS REPORTED SOUTH OF SNOW CANYON HIGH SCHOOL. 

THE SANTA CLARA RIVER WILL CONTINUE TO RUN AT VERY HIGH LEVELS 
THROUGH AT LEAST 400 PM DOWNSTREAM FROM SANTA CLARA TO WHERE IT 
JOINS THE VIRGIN RIVER NEAR BLOOMINGTON. 

LOCATIONS IN THE WARNING INCLUDE BUT ARE NOT LIMITED TO SANTA CLARA

PRECAUTIONARY/PREPAREDNESS ACTIONS...

DO NOT DRIVE YOUR VEHICLE INTO AREAS WHERE THE WATER COVERS THE
ROADWAY. THE WATER DEPTH MAY BE TOO GREAT TO ALLOW YOUR CAR TO CROSS 
SAFELY. TURN AROUND AND DONT DROWN. 

&&

LAT...LON 3714 11367 3715 11363 3707 11359 3711 11367

$$

PW
142 
WGUS75 KSLC 112241
FFSSLC

FLASH FLOOD STATEMENT
NATIONAL WEATHER SERVICE SALT LAKE CITY UT
441 PM MDT TUE SEP 11 2012

UTC053-112251-
/O.EXP.KSLC.FF.W.0066.000000T0000Z-120911T2245Z/
/00000.0.ER.000000T0000Z.000000T0000Z.000000T0000Z.OO/
WASHINGTON UT-
441 PM MDT TUE SEP 11 2012

...THE FLASH FLOOD WARNING WILL EXPIRE AT 445 PM MDT FOR SOUTH
CENTRAL WASHINGTON COUNTY...

FLOODING IN SANTA CLARA HAS ENDED AND THE FLASH FLOOD WARNING IS 
BEING ALLOWED TO EXPIRE. 

LAT...LON 3714 11367 3715 11363 3707 11359 3711 11367

$$

PW

The office that day

Everything else NWS Salt Lake City, UT issued on the same UTC day.

IssuedProductOfficeCountiesLasted
Sep 10, 6:08 PM MDTSpecial Weather StatementSLCTooele22 min
Sep 11, 10:52 AM MDTAreal Flood WarningSLCWashington8 hr
Sep 11, 12:20 PM MDTAreal Flood WarningSLCKane4 hr
Sep 11, 12:27 PM MDTFlash Flood WarningSLCWayne4 hr
Sep 11, 4:20 PM MDTFlash Flood WarningSLCWayne3 hr

Nearby

Flash Flood Warnings in Utah, 2012Every flash flood warning 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.