Alert archive / Utah / Mesoscale Discussions in 2012

Mesoscale Discussion 1850

September 1, 2012White Pine County, Nevada; 22 counties in Utah

The Storm Prediction Center issued this mesoscale discussion at Sep 1, 2012, 11:31 AM PDT for White Pine County, Nevada; 22 counties in Utah. It was in force for 119 min.

The area

The outline as issued.

The facts

Issued: Sep 1, 2012, 11:31 AM PDT (18:31 UTC)
Expired: Sep 1, 2012, 1:30 PM PDT
In force: 119 min
Issued by: the Storm Prediction Center
Chance of a watch: 40%

All 23 counties

White Pine County, NV, Beaver County, UT, Box Elder County, UT, Cache County, UT, Carbon County, UT, Davis County, UT, Duchesne County, UT, Emery County, UT, Iron County, UT, Juab County, UT, Millard County, UT, Morgan County, UT, Piute County, UT, Rich County, UT, Salt Lake County, UT, Sanpete County, UT, Sevier County, UT, Summit County, UT, Tooele County, UT, Utah County, UT, Wasatch County, UT, Washington County, UT, Weber County, UT

The radar

The Cedar City radar (KICX), 183 km from the middle of the area, began a volume at 18:31 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 watches that followed

Watches SPC issued over any of the same counties within four hours of this discussion.

Severe Thunderstorm Watch 604Sep 1, 12:00 PM PDT

The nearest sounding before it

Salt Lake City I, UT (KSLC), launched 12:00Z, 6.5 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-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: 158 J/kg
Mixed-layer CIN: -127 J/kg
Mixed-layer LCL: 978 m above ground
0-6 km bulk shear: 44 kt
0-1 km storm-relative helicity: 98 m²/s²
0-3 km storm-relative helicity: 111 m²/s²
Significant tornado parameter: 0.0
Supercell composite: 0.1

Open this sounding in Storm Lab

The text

As transmitted, in the capitals the NWS used until 2016.

735 
ACUS11 KWNS 011831
SWOMCD
SPC MCD 011831 
UTZ000-WYZ000-NVZ000-012030-

MESOSCALE DISCUSSION 1850
NWS STORM PREDICTION CENTER NORMAN OK
0131 PM CDT SAT SEP 01 2012

AREAS AFFECTED...MUCH OF UTAH...NWRN NV

CONCERNING...SEVERE POTENTIAL...WATCH POSSIBLE 

VALID 011831Z - 012030Z

PROBABILITY OF WATCH ISSUANCE...40 PERCENT

SUMMARY...THUNDERSTORM COVERAGE WILL INCREASE THRU THE
AFTERNOON...WITH SUFFICIENT BUOYANCY/SHEAR TO SUPPORT A THREAT OF
SEVERE WIND GUSTS AND PERHAPS SEVERE HAIL. COVERAGE TRENDS WILL
CONTINUE TO BE MONITORED FOR THE POSSIBILITY OF WATCH ISSUANCE.

DISCUSSION...AS OF 18Z...DEEP CONVECTION IS INCREASING ACROSS WRN
UT...WITH TWO STRONG CELLS OVER MILLARD COUNTY SHOWING SOME MIDLEVEL
ROTATION. VIS SATELLITE IMAGERY SHOWS A DEEPENING CU FIELD WITH
ADDITIONAL STORMS BEGINNING TO DEVELOP ACROSS NRN UT AND FAR WRN NV.
THIS ACTIVITY IS OCCURRING IN THE EXIT REGION OF 60-80 KT MID-UPPER
LEVEL JET...WHICH WAS SAMPLED BY THE 12Z VEF SOUNDING. 

TEMPERATURES HAVE WARMED INTO THE 75-80F RANGE ACROSS MUCH OF THE
AREA AS OF 18Z. THE AIRMASS REMAINS RELATIVELY MOIST...WITH
DEWPOINTS GENERALLY IN THE 54-58F RANGE. THESE CONDITIONS ARE
SUPPORTING MODERATE MUCAPE OF 1000-2000 J/KG. MEANWHILE...MODERATE
MIDLEVEL FLOW IS SUPPORTING EFFECTIVE SHEAR OF 35-45 KTS...WHICH IS
SUFFICIENT FOR THE DEVELOPMENT OF ORGANIZED STORM MODES...WITH
BOWING SEGMENTS AND OCCASIONAL SUPERCELLS POSSIBLE.  

AS THE BOUNDARY LAYER WARMS/DEEPENS...THE SEVERE WIND THREAT WILL
INCREASE. IN ADDITION...A SEVERE HAIL THREAT WILL EXIST WITH ANY
SUPERCELL THAT DEVELOPS. IF ORGANIZED CONVECTION CONTINUES TO
INCREASE...SEVERE THUNDERSTORM WATCH ISSUANCE WILL BE POSSIBLE. THE
SEVERE THREAT WILL START TO DECREASE FROM THE SOUTHWEST LATER THIS
AFTERNOON AS MUCH DRIER AIR MOVES IN...BUT THE THREAT MAY PERSIST
INTO THE EVENING FURTHER NORTH ACROSS NRN UT.

..DEAN/CORFIDI.. 09/01/2012

...PLEASE SEE WWW.SPC.NOAA.GOV FOR GRAPHIC PRODUCT...

ATTN...WFO...GJT...SLC...VEF...LKN...

LAT...LON   37611418 38331466 38971488 39611521 40531577 41461458
            41921343 41761140 40760990 40120979 39351019 38831055
            38341110 37521184 37101238 37121351 37611418

SPC that day

Everything else SPC issued on the same UTC day.

Issued	Product	Office	Counties	Lasted
Sep 1, 2:02 PM PDT	Mesoscale Discussion	SPC	Elko, White Pine	88 min
Sep 1, 11:59 AM PDT	Severe Thunderstorm Watch	SPC	Beaver, Box Elder, Cache, Carbon, Davis, Duchesne and 14 more	8 hr
Sep 1, 1:31 PM PDT	Mesoscale Discussion	SPC	Kane, San Juan	89 min
Sep 1, 4:49 PM PDT	Mesoscale Discussion	SPC	Beaver, Box Elder, Cache, Carbon, Davis, Duchesne and 14 more	86 min

Nearby

Mesoscale Discussions in Utah, 2012 Mesoscale Discussions in Nevada, 2012 Every mesoscale discussion 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.