Alert archive / Utah / Severe Thunderstorm Warnings in 2021

Severe Thunderstorm Warning 114, NWS Salt Lake City, UT

September 12, 2021Box Elder County, Utah

NWS Salt Lake City, UT issued this severe thunderstorm warning at Sep 12, 2021, 8:23 PM MDT for Box Elder County, Utah. It was in force for 37 min. 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 12, 2021, 8:23 PM MDT (02:23 UTC)
Expired: Sep 12, 2021, 9:00 PM MDT
In force: 37 min
Issued by: NWS Salt Lake City, UT
Area: Storm-based polygon
Hail: 1.0 in
Wind: 60.0 mph

County Box Elder County, UT

The radar

The Salt Lake City radar (KMTX), 83 km from the middle of the area, began a volume at 02:24 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

Elko, NV (KLKN), launched 00:00Z, 2.4 hours before the alert went out and 91 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: 222 J/kg
Mixed-layer CIN: -6 J/kg
Mixed-layer LCL: 2989 m above ground
0-6 km bulk shear: 50 kt
0-1 km storm-relative helicity: -12 m²/s²
0-3 km storm-relative helicity: 71 m²/s²
Significant tornado parameter: 0.0
Supercell composite: -0.1

Open this sounding in Storm Lab

The text

As transmitted.

057 
WUUS55 KSLC 130223
SVRSLC
UTC003-130300-
/O.NEW.KSLC.SV.W.0114.210913T0223Z-210913T0300Z/

BULLETIN - IMMEDIATE BROADCAST REQUESTED
Severe Thunderstorm Warning
National Weather Service Salt Lake City UT
823 PM MDT Sun Sep 12 2021

The National Weather Service in Salt Lake City has issued a

* Severe Thunderstorm Warning for...
  West central Box Elder County in northern Utah...

* Until 900 PM MDT

* At 823 PM MDT, a severe thunderstorm was located 30 miles east of 
  Montello, moving east at 45 mph. An additional strengthening 
  thunderstorm is located across the northern portion of the warned 
  area. 

  HAZARD...60 mph wind gusts and quarter size hail. 

  SOURCE...Radar indicated. 

  IMPACT...Hail damage to vehicles is expected. Expect wind damage 
           to roofs, siding, and trees. 

* Locations impacted include...
  Great Salt Lake North of the Causeway.

This includes Utah Route 30 between mile markers 16 and 28.
 
PRECAUTIONARY/PREPAREDNESS ACTIONS...

For your protection move to an interior room on the lowest floor of a
building.

&&

LAT...LON 4128 11368 4147 11378 4174 11307 4141 11289
TIME...MOT...LOC 0223Z 253DEG 39KT 4139 11362 

HAIL THREAT...RADAR INDICATED
MAX HAIL SIZE...1.00 IN
WIND THREAT...RADAR INDICATED
MAX WIND GUST...60 MPH

$$

CRK

3 follow-up statements

345 
WWUS55 KSLC 130244
SVSSLC

Severe Weather Statement
National Weather Service Salt Lake City UT
844 PM MDT Sun Sep 12 2021

UTC003-130300-
/O.CON.KSLC.SV.W.0114.000000T0000Z-210913T0300Z/
Box Elder UT-
844 PM MDT Sun Sep 12 2021

...A SEVERE THUNDERSTORM WARNING REMAINS IN EFFECT UNTIL 900 PM MDT
FOR WEST CENTRAL BOX ELDER COUNTY...

At 843 PM MDT, a severe thunderstorm was located 25 miles south of
Park Valley, or 46 miles east of Montello, moving east at 45 mph.

HAZARD...60 mph wind gusts and quarter size hail. 

SOURCE...Radar indicated. 

IMPACT...Hail damage to vehicles is expected. Expect wind damage to 
         roofs, siding, and trees. 

Locations impacted include...
Great Salt Lake North of the Causeway.

This includes Utah Route 30 between mile markers 16 and 28.
 
PRECAUTIONARY/PREPAREDNESS ACTIONS...

For your protection move to an interior room on the lowest floor of a
building.

&&

LAT...LON 4128 11368 4147 11378 4174 11307 4141 11289
TIME...MOT...LOC 0243Z 253DEG 39KT 4146 11334 

HAIL THREAT...RADAR INDICATED
MAX HAIL SIZE...1.00 IN
WIND THREAT...RADAR INDICATED
MAX WIND GUST...60 MPH

$$

CRK

535 
WWUS55 KSLC 130247
SVSSLC

Severe Weather Statement
National Weather Service Salt Lake City UT
847 PM MDT Sun Sep 12 2021

UTC003-130300-
/O.CON.KSLC.SV.W.0114.000000T0000Z-210913T0300Z/
Box Elder UT-
847 PM MDT Sun Sep 12 2021

...A SEVERE THUNDERSTORM WARNING REMAINS IN EFFECT UNTIL 900 PM MDT
FOR CENTRAL BOX ELDER COUNTY...

At 847 PM MDT, a severe thunderstorm was located 24 miles south of
Park Valley, or 45 miles southwest of Snowville, moving east at 45
mph.

HAZARD...60 mph wind gusts and quarter size hail. 

SOURCE...Radar indicated. 

IMPACT...Hail damage to vehicles is expected. Expect wind damage to 
         roofs, siding, and trees. 

Locations impacted include...
Great Salt Lake North of the Causeway.

PRECAUTIONARY/PREPAREDNESS ACTIONS...

For your protection move to an interior room on the lowest floor of a
building.

&&

LAT...LON 4133 11340 4155 11356 4174 11307 4141 11289
TIME...MOT...LOC 0247Z 253DEG 39KT 4147 11329 

HAIL THREAT...RADAR INDICATED
MAX HAIL SIZE...1.00 IN
WIND THREAT...RADAR INDICATED
MAX WIND GUST...60 MPH

$$

CRK

031 
WWUS55 KSLC 130258
SVSSLC

Severe Weather Statement
National Weather Service Salt Lake City UT
858 PM MDT Sun Sep 12 2021

UTC003-130308-
/O.EXP.KSLC.SV.W.0114.000000T0000Z-210913T0300Z/
Box Elder UT-
858 PM MDT Sun Sep 12 2021

...THE SEVERE THUNDERSTORM WARNING FOR CENTRAL BOX ELDER COUNTY WILL
EXPIRE AT 900 PM MDT...
                
The storm which prompted the warning has weakened below severe
limits, and no longer poses an immediate threat to life or property.
Therefore, the warning will be allowed to expire.  However small 
hail and gusty winds are still possible with this thunderstorm.  A 
significant weather advisory is now in effect for this storm. 

LAT...LON 4133 11340 4155 11356 4174 11307 4141 11289
TIME...MOT...LOC 0258Z 253DEG 39KT 4150 11317 

$$

CRK

The office that day

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

Issued	Product	Office	Counties	Lasted
Sep 12, 6:46 PM MDT	Special Weather Statement	SLC	Box Elder	44 min
Sep 12, 7:35 PM MDT	Special Weather Statement	SLC		40 min
Sep 12, 8:09 PM MDT	Special Weather Statement	SLC		51 min
Sep 12, 8:57 PM MDT	Special Weather Statement	SLC	Box Elder	48 min
Sep 12, 8:59 PM MDT	Special Weather Statement	SLC	Box Elder	46 min

Nearby

Severe Thunderstorm Warnings in Utah, 2021 Every severe thunderstorm warning in 2021

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.