Alert archive / Utah / Flash Flood Warnings in 2017

Flash Flood Warning 37, NWS Salt Lake City, UT

August 5, 2017Iron County, Utah

NWS Salt Lake City, UT issued this flash flood warning at Aug 5, 2017, 6:18 PM 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 5, 2017, 6:18 PM MDT (00:18 UTC)
Expired
Aug 5, 2017, 9:15 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), 19 km from the middle of the area, began a volume at 00:18 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 00:00Z, 0.3 hours before the alert went out and 285 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 00:00Z on 2017-08-06Temperature and dew point through the depth of the atmosphere, with the mixed-layer parcel. CAPE 635 joules per kilogram.LCLEL10008507005003002001001 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 00:00Z on 2017-08-06The wind through the lowest 10 kilometers. Zero to 1 km storm-relative helicity 26 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
635 J/kg
Mixed-layer CIN
-26 J/kg
Mixed-layer LCL
2674 m above ground
0-6 km bulk shear
17 kt
0-1 km storm-relative helicity
26 m²/s²
0-3 km storm-relative helicity
46 m²/s²
Significant tornado parameter
0.0
Supercell composite
1.1

Open this sounding in Storm Lab

The text

As transmitted.

233 
WGUS55 KSLC 060018
FFWSLC
UTC021-060315-
/O.NEW.KSLC.FF.W.0037.170806T0018Z-170806T0315Z/
/00000.0.ER.000000T0000Z.000000T0000Z.000000T0000Z.OO/

BULLETIN - EAS ACTIVATION REQUESTED
Flash Flood Warning
National Weather Service Salt Lake City UT
618 PM MDT SAT AUG 5 2017

The National Weather Service in Salt Lake City has issued a

* Flash Flood Warning for...
  Southeastern Iron County in southern Utah...

* Until 915 PM MDT
    
* At 615 PM MDT, Doppler radar indicated a thunderstorm producing 
  heavy rain over the western Brian Head burnscar specifically the 
  Parowan Creek drainage. Up to one inch of rain has already fallen. 
  Flash flooding is expected to begin shortly.

* Excessive rainfall over the Brian Head burn scar will result in 
  debris flow moving through the Parowan Creek drainage, including 
  SR-143. 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 3781 11285 3781 11280 3768 11281 3768 11288

$$

NC
1 follow-up statement
952 
WGUS75 KSLC 060149
FFSSLC

Flash Flood Statement
National Weather Service Salt Lake City UT
749 PM MDT SAT AUG 5 2017

UTC021-060315-
/O.CON.KSLC.FF.W.0037.000000T0000Z-170806T0315Z/
/00000.0.ER.000000T0000Z.000000T0000Z.000000T0000Z.OO/
Iron UT-
749 PM MDT SAT AUG 5 2017

...THE FLASH FLOOD WARNING REMAINS IN EFFECT UNTIL 915 PM MDT FOR
SOUTHEASTERN IRON COUNTY...

At 744 PM MDT, Doppler radar indicated that the thunderstorms 
producing heavy rain have moved out of the warned area. However the 
warning remains in effect due to the fact that flash flooding may be 
ongoing as a result 1-2 inches of rain that have previously fallen 
on the area.  

Some locations that will experience flooding include...
Parowan Creek, the southwestern part of the Brian Head burn scar, 
and parts of SR-143.

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 3781 11285 3781 11280 3768 11281 3768 11288

$$

NC

The office that day

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

IssuedProductOfficeCountiesLasted
Aug 5, 7:24 PM MDTFlash Flood WarningSLCKane5 hr
Aug 6, 3:24 PM MDTFlash Flood WarningSLCIron3 hr

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.