Alert archive / Utah / Flash Flood Warnings in 2017

Flash Flood Warning 40, NWS Salt Lake City, UT

August 12, 2017Iron County, Utah

NWS Salt Lake City, UT issued this flash flood warning at Aug 12, 2017, 11:49 AM MDT for Iron 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
Aug 12, 2017, 11:49 AM MDT (17:49 UTC)
Expired
Aug 12, 2017, 2:45 PM MDT
In force
3 hr
Issued by
NWS Salt Lake City, UT
Area
Storm-based polygon
Flood severity
None

County Iron County, UT

The radar

The Cedar City radar (KICX), 21 km from the middle of the area, began a volume at 17:49 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, 5.8 hours before the alert went out and 287 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 2017-08-12Temperature and dew point through the depth of the atmosphere, with the mixed-layer parcel. CAPE 845 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 2017-08-12The wind through the lowest 10 kilometers. Zero to 1 km storm-relative helicity 21 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
845 J/kg
Mixed-layer CIN
-148 J/kg
Mixed-layer LCL
2429 m above ground
0-6 km bulk shear
32 kt
0-1 km storm-relative helicity
21 m²/s²
0-3 km storm-relative helicity
13 m²/s²
Significant tornado parameter
0.0
Supercell composite
-0.0

Open this sounding in Storm Lab

The text

As transmitted.

409 
WGUS55 KSLC 121749
FFWSLC
UTC021-122045-
/O.NEW.KSLC.FF.W.0040.170812T1749Z-170812T2045Z/
/00000.0.ER.000000T0000Z.000000T0000Z.000000T0000Z.OO/

BULLETIN - EAS ACTIVATION REQUESTED
Flash Flood Warning
National Weather Service Salt Lake City UT
1149 AM MDT SAT AUG 12 2017

The National Weather Service in Salt Lake City has issued a

* Flash Flood Warning for...
  East central Iron County in southern Utah...

* Until 245 PM MDT
    
* At 1147 AM MDT, Doppler radar indicated a thunderstorm producing 
  heavy rain over the Brian Head burn scar.  This warning includes 
  the Parowan Creek Drainage as well as Benson, Center, Bowery 
  Creeks and Soda Spring and associated drainages. This warning 
  includes SR-143 from near Brian Head to Parowan.

* Some locations that will experience flooding include...
  Parowan and Brian Head. 

Excessive rainfall over the Brain Head burn scar will result in 
debris flow. The debris flow can consist of rock, mud, vegetation 
and other loose materials.

PRECAUTIONARY/PREPAREDNESS ACTIONS...

If a debris flow has occurred it is important to realize that the
runout area remains very dangerous. Additional debris flows may occur
within minutes of the original flow. Please remain vigilant and be
prepared to take swift action.

&&

LAT...LON 3778 11272 3767 11282 3768 11289 3783 11283
      3783 11290 3785 11283

$$

CRK
2 follow-up statements
179 
WGUS75 KSLC 121917
FFSSLC

Flash Flood Statement
National Weather Service Salt Lake City UT
117 PM MDT SAT AUG 12 2017

UTC021-122045-
/O.CON.KSLC.FF.W.0040.000000T0000Z-170812T2045Z/
/00000.0.ER.000000T0000Z.000000T0000Z.000000T0000Z.OO/
Iron UT-
117 PM MDT SAT AUG 12 2017

...THE FLASH FLOOD WARNING REMAINS IN EFFECT UNTIL 245 PM MDT FOR
EAST CENTRAL IRON COUNTY...

Heavy rainfall has fallen over western portions of the Brian Head 
burn scar. A debris flow is imminent for the Parowan Creek drainage 
as well Benson, Center, Bowery Creeks and Soda Spring and associated 
drainages. This warning includes SR-143 from near Brian Head to 
Parowan as well as the city of Parowan.

Some locations that will experience flooding include...
Parowan and Brian Head. 

PRECAUTIONARY/PREPAREDNESS ACTIONS...

If a debris flow has occurred it is important to realize that the
runout area remains very dangerous. Additional debris flows may occur
within minutes of the original flow. Please remain vigilant and be
prepared to take swift action.

&&

LAT...LON 3778 11272 3767 11282 3768 11289 3783 11283
      3783 11290 3785 11283

$$

CRK
513 
WGUS75 KSLC 122051
FFSSLC

Flash Flood Statement
National Weather Service Salt Lake City UT
251 PM MDT SAT AUG 12 2017

UTC021-122100-
/O.EXP.KSLC.FF.W.0040.000000T0000Z-170812T2045Z/
/00000.0.ER.000000T0000Z.000000T0000Z.000000T0000Z.OO/
Iron UT-
251 PM MDT SAT AUG 12 2017

...THE FLASH FLOOD WARNING FOR EAST CENTRAL IRON COUNTY HAS
EXPIRED...

Heavy rainfall has ended across the western portion of the Brian 
Head burn scar. Debris may be present on SR-143 through the evening 
and travelers through this area are urged to maintain awareness. 

LAT...LON 3778 11272 3767 11282 3768 11289 3783 11283
      3783 11290 3785 11283

$$

CRK

The office that day

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

IssuedProductOfficeCountiesLasted
Aug 12, 12:23 PM MDTFlash Flood WarningSLCGarfield3 hr
Aug 12, 12:44 PM MDTSpecial Weather StatementSLC46 min
Aug 12, 2:47 PM MDTFire Weather WatchSLCWashington24 hr
Aug 12, 3:15 PM MDTSevere Thunderstorm WarningSLCKane, San Juan30 min
Aug 12, 3:52 PM MDTSpecial Weather StatementSLCDuchesne38 min
Aug 12, 3:54 PM MDTSpecial Weather StatementSLC51 min
Aug 12, 4:20 PM MDTSpecial Weather StatementSLCBox Elder40 min

Nearby

Flash Flood Warnings in Utah, 2017Every flash flood warning in 2017

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.