Alert archive / Arkansas / Mesoscale Discussions in 2012

Mesoscale Discussion 311

March 20, 201210 counties in Arkansas

The Storm Prediction Center issued this mesoscale discussion at Mar 20, 2012, 9:27 PM CDT for 10 counties in Arkansas. It was in force for 33 min.

The area

The outline as issued.

The facts

Issued: Mar 20, 2012, 9:27 PM CDT (02:27 UTC)
Expired: Mar 20, 2012, 10:00 PM CDT
In force: 33 min
Issued by: the Storm Prediction Center

Counties Arkansas County, AR, Desha County, AR, Independence County, AR, Jackson County, AR, Lawrence County, AR, Monroe County, AR, Prairie County, AR, Sharp County, AR, White County, AR, Woodruff County, AR

The radar

The Little Rock radar (KLZK), 65 km from the middle of the area, began a volume at 02:29 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

Little Rock, AR (KLZK), launched 00:00Z, 2.5 hours before the alert went out and 146 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: 52 J/kg
Mixed-layer CIN: -37 J/kg
Mixed-layer LCL: 453 m above ground
0-6 km bulk shear: 47 kt
0-1 km storm-relative helicity: 74 m²/s²
0-3 km storm-relative helicity: 197 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.

951 
ACUS11 KWNS 210228
SWOMCD
SPC MCD 210227
ARZ000-MSZ000-210300-

MESOSCALE DISCUSSION 0311
NWS STORM PREDICTION CENTER NORMAN OK
0927 PM CDT TUE MAR 20 2012

AREAS AFFECTED...ERN AR

CONCERNING...TORNADO WATCH 93...

VALID 210227Z - 210300Z

THE SEVERE WEATHER THREAT FOR TORNADO WATCH 93 CONTINUES.

WW 93 WILL BE CANCELLED BEFORE ITS EXPIRATION TIME OF 03Z. TREND HAS
BEEN FOR STORMS OVER AR TO DECREASE IN INTENSITY...AND THREAT
APPEARS TOO MARGINAL TO WARRANT ANOTHER WW ISSUANCE AT THIS TIME.

BROKEN BAND OF STORMS CONTINUES LIFTING NWD THROUGH ERN AR. THE
THERMODYNAMIC ENVIRONMENT IS VERY MARGINAL WITH MUCAPE AOB 500
J/KG...AND THE BOUNDARY LAYER HAS ALSO STABILIZED SOMEWHAT WITH THE
ONSET OF NOCTURNAL COOLING AS TEMPERATURES FALL INTO THE LOW-MID
60S. A 50 KT LLJ WILL SHIFT NWD THROUGH AR OVERNIGHT MAINTAINING
LARGE HODOGRAPHS. DESPITE THE FAVORABLE LOW LEVEL
SHEAR...INSTABILITY APPEARS TOO LIMITED TO MAINTAIN A WW AT THIS
TIME.

STORMS HAVE INTENSIFIED OVER NRN LA...AND SOME POTENTIAL MAY EXIST
FOR THIS ACTIVITY TO LIFT NWD INTO SRN AR LATER THIS EVENING AT
WHICH TIME THE SEVERE THREAT WILL BE RE-EVALUATED.

..DIAL.. 03/21/2012

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

ATTN...WFO...MEG...JAN...LZK...

LAT...LON   33569166 34529178 35899195 36419168 36139104 33779109
            33569166

SPC that day

Everything else SPC issued on the same UTC day.

Issued	Product	Office	Counties	Lasted
Mar 20, 10:59 PM CDT	Tornado Watch	SPC	Union	7 hr
Mar 21, 2:17 AM CDT	Mesoscale Discussion	SPC	Ashley	118 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.