Alert archive / Arkansas / Mesoscale Discussions in 2012

Mesoscale Discussion 2137

December 8, 20128 counties in Arkansas

The Storm Prediction Center issued this mesoscale discussion at Dec 8, 2012, 10:18 PM CST for 8 counties in Arkansas. It was in force for 117 min.

The area

The outline as issued.

The facts

Issued: Dec 8, 2012, 10:18 PM CST (04:18 UTC)
Expired: Dec 9, 2012, 12:15 AM CST
In force: 117 min
Issued by: the Storm Prediction Center
Chance of a watch: 5%

Counties Conway County, AR, Garland County, AR, Logan County, AR, Montgomery County, AR, Perry County, AR, Polk County, AR, Scott County, AR, Yell County, AR

The radar

The Western Arkansas radar (KSRX), 89 km from the middle of the area, began a volume at 04:22 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

Springfield, MO (KSGF), launched 00:00Z, 4.3 hours before the alert went out and 243 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: 0 J/kg
Mixed-layer CIN: No buoyant parcel
Mixed-layer LCL: 460 m above ground
0-6 km bulk shear: 62 kt
0-1 km storm-relative helicity: 346 m²/s²
0-3 km storm-relative helicity: 454 m²/s²
Significant tornado parameter: 0.0
Supercell composite: 0.0

Open this sounding in Storm Lab

The text

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

237 
ACUS11 KWNS 090419
SWOMCD
SPC MCD 090418
ARZ000-OKZ000-090615-

MESOSCALE DISCUSSION 2137
NWS STORM PREDICTION CENTER NORMAN OK
1018 PM CST SAT DEC 08 2012

AREAS AFFECTED...EXTREME SERN OK INTO WRN THROUGH CNTRL AR

CONCERNING...SEVERE POTENTIAL...WATCH UNLIKELY

VALID 090418Z - 090615Z

PROBABILITY OF WATCH ISSUANCE...5 PERCENT

SUMMARY...SLOW BUT GRADUAL INCREASE IN THUNDERSTORM COVERAGE AND
INTENSITIES WILL LIKELY OCCUR INTO THE EARLY MORNING HOURS FROM
EXTREME SERN OK INTO WRN AND CNTRL AR. A FEW STORMS MAY BECOME
CAPABLE OF PRODUCING SMALL TO MARGINALLY SEVERE HAIL. THREAT IS
EXPECTED TO REMAIN TOO MARGINAL FOR WW ISSUANCE.

DISCUSSION...THIS EVENING A QUASI-STATIONARY FRONT EXTENDS FROM
CNTRL AR INTO SERN OK AND NRN TX. VWP DATA SHOW THE LOW LEVEL JET
HAS INCREASED TO 40 KT...AND THE RESULTING THETA-E ADVECTION WILL
CONTRIBUTE TO NWD DESTABILIZATION WITH TIME THROUGH ERN OK AND AR.
OBJECTIVE ANALYSIS INDICATES MUCAPE CURRENTLY FROM 300-500
J/KG...BUT WILL LIKELY INCREASE TO 500-1000 J/KG LATER TONIGHT.
SLIGHTLY ELEVATED STORMS WILL CONTINUE DEVELOPING WITHIN ZONE OF
ISENTROPIC ASCENT ALONG AND NORTH OF THE QUASI-STATIONARY BOUNDARY.
THE INCREASE IN INSTABILITY AND EFFECTIVE CLOUD LAYER SHEAR OF 40+
KT WILL PROMOTE A THREAT FOR UPDRAFT ROTATION AND AT LEAST A MODEST
THREAT FOR HAIL. HOWEVER...WEAK MID LEVEL LAPSE RATES SHOULD
MITIGATE OVERALL LARGE HAIL POTENTIAL.

..DIAL/EDWARDS.. 12/09/2012

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

ATTN...WFO...LZK...SHV...TSA...

LAT...LON   34119390 34159464 35039451 35449391 35409241 34789245
            34119390

SPC that day

Everything else SPC issued on the same UTC day.

Issued	Product	Office	Counties	Lasted
Dec 9, 1:46 AM CST	Mesoscale Discussion	SPC	Crittenden, Cross, Garland, Lee, Lonoke, Monroe and 6 more	2 hr
Dec 9, 12:38 PM CST	Mesoscale Discussion	SPC	Arkansas, Clark, Clay, Cleburne, Cleveland, Conway and 41 more	2 hr
Dec 9, 2:10 PM CST	Tornado Watch	SPC	Arkansas, Clay, Cleburne, Conway, Craighead, Crittenden and 29 more	9 hr
Dec 9, 5:04 PM CST	Mesoscale Discussion	SPC	Clark, Columbia, Dallas, Hempstead, Lafayette, Miller and 2 more	116 min
Dec 9, 5:47 PM CST	Severe Thunderstorm Watch	SPC	Ashley, Bradley, Calhoun, Chicot, Clark, Cleveland and 9 more	6 hr
Dec 9, 5:54 PM CST	Mesoscale Discussion	SPC	Arkansas, Clay, Cleburne, Craighead, Crittenden, Cross and 20 more	96 min

Nearby

Mesoscale Discussions in Arkansas, 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.