Alert archive / Arizona / Mesoscale Discussions in 2021

Mesoscale Discussion 1517

August 13, 20216 counties in Arizona

The Storm Prediction Center issued this mesoscale discussion at Aug 13, 2021, 3:56 PM MST for 6 counties in Arizona. It was in force for 64 min.

The area

The outline as issued.

The facts

Issued
Aug 13, 2021, 3:56 PM MST (22:56 UTC)
Expired
Aug 13, 2021, 5:00 PM MST
In force
64 min
Issued by
the Storm Prediction Center
Concerning
Severe potential...watch possible
Chance of a watch
40%

Counties Cochise County, AZ, Graham County, AZ, Maricopa County, AZ, Pima County, AZ, Pinal County, AZ, Santa Cruz County, AZ

The radar

The Tucson radar (KEMX), 69 km from the middle of the area, began a volume at 22:58 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.

The nearest sounding before it

Tuscon, AZ (KTUS), launched 12:00Z, 10.9 hours before the alert went out and 36 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, Tuscon, AZ at 12:00Z on 2021-08-13Temperature and dew point through the depth of the atmosphere, with the mixed-layer parcel. CAPE 544 joules per kilogram.LCLLFCEL10008507005003002001001 km2 km3 km6 km9 km12 km15 km-30°-20°-10°0°10°20°30°40°
Temperature in red, dew point in green, the mixed-layer parcel dashed.
HodographHodograph, Tuscon, AZ at 12:00Z on 2021-08-13The wind through the lowest 10 kilometers. Zero to 1 km storm-relative helicity -36 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
544 J/kg
Mixed-layer CIN
-46 J/kg
Mixed-layer LCL
1049 m above ground
0-6 km bulk shear
1 kt
0-1 km storm-relative helicity
-36 m²/s²
0-3 km storm-relative helicity
-1 m²/s²
Significant tornado parameter
0.0
Supercell composite
0.0

Open this sounding in Storm Lab

The text

As transmitted.

207 
ACUS11 KWNS 132257
SWOMCD
SPC MCD 132256 
AZZ000-140000-

Mesoscale Discussion 1517
NWS Storm Prediction Center Norman OK
0556 PM CDT Fri Aug 13 2021

Areas affected...southern AZ

Concerning...Severe potential...Watch possible 

Valid 132256Z - 140000Z

Probability of Watch Issuance...40 percent

SUMMARY...Thunderstorms over the higher terrain are expected to
increase in coverage and move southwest into the lower elevations
this evening.  Damaging winds will be the primary severe risk.

DISCUSSION...Isolated strong/severe thunderstorms over the higher
terrain of eastern AZ are likely to increase in coverage this
evening as merging outflows contribute to additional updrafts with
time.  Moderate MLCAPE and 25-30 kts of northeasterly flow at 3 km
(per KFSX VAD) will result in southwest-moving clusters capable of
severe wind gusts as storms move off of the higher terrain and into
the lower elevations.  Some question remains concerning the overall
coverage of the severe threat, however the potential exists for
coverage to warrant watch issuance.  Convective trends will continue
to be monitored closely, and a watch is possible prior to 01z.

..Bunting/Goss.. 08/13/2021

...Please see www.spc.noaa.gov for graphic product...

ATTN...WFO...TWC...FGZ...PSR...

LAT...LON   31610984 31461052 31661175 32841316 33791286 33891116
            33531033 32680950 31820929 31610984

Nearby

Mesoscale Discussions in Arizona, 2021Every mesoscale discussion 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.