Alert archive / Utah / Flash Flood Warnings in 2012

Flash Flood Warning 46, NWS Salt Lake City, UT

August 17, 2012Washington County, Utah

NWS Salt Lake City, UT issued this flash flood warning at Aug 17, 2012, 6:34 PM MDT for Washington County, Utah. It was in force for 3 hr. 2 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
Aug 17, 2012, 6:34 PM MDT (00:34 UTC)
Expired
Aug 17, 2012, 9:30 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), 36 km from the middle of the area, began a volume at 00:37 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

TimeReportWhereRemark
Aug 17, 6:37 PM MDTFLASH FLOODZion Np, UTFLASH FLOODING REPORTED IN SPRY CANYON. ROCKS ALSO REPORTED ON THE MAIN ROAD RESULTING FROM HEAVY RAINFALL.
Aug 17, 7:30 PM MDTFLASH FLOODZion Np, UTFLASH FLOODING IN PINE CREEK. NUMEROUS ROCKS ALSO WASHED ON TO HIGHWAY 9 BETWEEN THE SWITCHBACKS AND THE TUNNEL AFFECTING TRAFFIC.

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

The nearest sounding before it

Flgstf/Belemont, AZ (KFGZ), launched 00:00Z, 0.6 hours before the alert went out and 250 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, Flgstf/Belemont, AZ at 00:00Z on 2012-08-18Temperature and dew point through the depth of the atmosphere, with the mixed-layer parcel. CAPE 167 joules per kilogram.LCLLFCEL10008507005003002001001 km2 km3 km6 km9 km12 km-30°-20°-10°0°10°20°30°40°
Temperature in red, dew point in green, the mixed-layer parcel dashed.
HodographHodograph, Flgstf/Belemont, AZ at 00:00Z on 2012-08-18The wind through the lowest 10 kilometers. Zero to 1 km storm-relative helicity -9 square meters per square second.193958Sfc1 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
167 J/kg
Mixed-layer CIN
-75 J/kg
Mixed-layer LCL
1324 m above ground
0-6 km bulk shear
22 kt
0-1 km storm-relative helicity
-9 m²/s²
0-3 km storm-relative helicity
-31 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.

134 
WGUS55 KSLC 180034
FFWSLC
UTC053-180330-
/O.NEW.KSLC.FF.W.0046.120818T0034Z-120818T0330Z/
/00000.0.ER.000000T0000Z.000000T0000Z.000000T0000Z.OO/

BULLETIN - EAS ACTIVATION REQUESTED
FLASH FLOOD WARNING
NATIONAL WEATHER SERVICE SALT LAKE CITY UT
634 PM MDT FRI AUG 17 2012

THE NATIONAL WEATHER SERVICE IN SALT LAKE CITY HAS ISSUED A

* FLASH FLOOD WARNING FOR...
  EAST CENTRAL WASHINGTON COUNTY IN UTAH...SPECIFICALLY SOUTHEASTERN 
  ZION NATIONAL PARK.

* UNTIL 930 PM MDT

* AT 628 PM MDT...NATIONAL WEATHER SERVICE DOPPLER RADAR INDICATED   
  HEAVY RAIN FROM A THUNDERSTORM OVER THE WARNED AREA. DOPPLER       
  ESTIMATED RAINFALL OF .50 TO 1.00 INCHES HAS OCCURRED OVER THIS    
  AREA OVER THE LAST 20 MINUTES. AN ADDITIONAL .25 TO .50 INCHES IS  
  POSSIBLE OVER THE NEXT 30 MINUTES. 

* LOCATIONS IN THE WARNING INCLUDE BUT ARE NOT LIMITED TO ZION       
  NATIONAL PARK...SPECIFICALLY SPRY CANYON...HIDDEN CANYON...PINE    
  CREEK CANYON...WHITE CANYON AND OTHER ADJACENT SLOTS.

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.

&&

LAT...LON 3732 11298 3732 11290 3721 11290 3719 11301

$$

MERRILL
1 follow-up statement
582 
WGUS75 KSLC 180147
FFSSLC

FLASH FLOOD STATEMENT
NATIONAL WEATHER SERVICE SALT LAKE CITY UT
747 PM MDT FRI AUG 17 2012

UTC053-180330-
/O.CON.KSLC.FF.W.0046.000000T0000Z-120818T0330Z/
/00000.0.ER.000000T0000Z.000000T0000Z.000000T0000Z.OO/
WASHINGTON UT-
747 PM MDT FRI AUG 17 2012

...A FLASH FLOOD WARNING REMAINS IN EFFECT UNTIL 930 PM MDT FOR EAST 
CENTRAL WASHINGTON COUNTY...SPECIFICALLY SOUTHEASTERN ZION NATIONAL 
PARK...

AT 737 PM MDT...ZION NATIONAL PARK RANGERS REPORTED ONGOING FLASH 
FLOODING OF BOTH SPRY AND PINE CREEK CANYONS. RAINFALL HAS 
DIMINISHED BUT DOPPLER ESTIMATED ACCUMULATIONS OF UP TO 1.25 INCHES 
OF RAIN FELL FROM EARLIER THUNDERSTORMS. THE ONGOING FLASH FLOODING 
IS EXPECTED TO GRADUALLY DIMINISH THROUGH 930 PM TONIGHT.

ADDITIONALLY...PARK RANGERS REPORTED NUMEROUS ROCKS IMPACTING TRAVEL 
ON STATE HIGHWAY 9 FROM THE SWITCHBACKS UP TO THE TUNNEL. 

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.

&&

LAT...LON 3732 11298 3732 11290 3721 11290 3719 11301

$$

MERRILL

The office that day

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

IssuedProductOfficeCountiesLasted
Aug 17, 7:15 PM MDTFlash Flood WarningSLCWashington3 hr
Aug 18, 2:10 PM MDTRed Flag WarningSLCBeaver, Box Elder, Davis, Iron, Juab, Millard and 5 more34 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; local storm reports from the same archive; the sounding from the Mesonet's radiosonde archive; radar from the NEXRAD Level II archive.