Alert archive / South Dakota / Mesoscale Discussions in 2011

Mesoscale Discussion 112

February 20, 201135 counties in South Dakota

The Storm Prediction Center issued this mesoscale discussion at Feb 20, 2011, 4:36 AM CST for 35 counties in South Dakota. It was in force for 4 hr.

The area

The outline as issued.

The facts

Issued
Feb 20, 2011, 4:36 AM CST (10:36 UTC)
Expired
Feb 20, 2011, 8:30 AM CST
In force
4 hr
Issued by
the Storm Prediction Center
All 35 counties

Aurora County, SD, Beadle County, SD, Brule County, SD, Buffalo County, SD, Clark County, SD, Codington County, SD, Davison County, SD, Day County, SD, Dewey County, SD, Edmunds County, SD, Faulk County, SD, Haakon County, SD, Hamlin County, SD, Hand County, SD, Hanson County, SD, Hughes County, SD, Hyde County, SD, Jackson County, SD, Jerauld County, SD, Jones County, SD, Kingsbury County, SD, Lake County, SD, Lyman County, SD, McCook County, SD, Meade County, SD, Mellette County, SD, Miner County, SD, Pennington County, SD, Potter County, SD, Sanborn County, SD, Spink County, SD, Stanley County, SD, Sully County, SD, Walworth County, SD, Ziebach County, SD

The radar

The Aberdeen radar (KABR), 169 km from the middle of the area, began a volume at 10:39 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

Aberdeen, SD (KABR), launched 00:00Z, 10.6 hours before the alert went out and 133 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, Aberdeen, SD at 00:00Z on 2011-02-20Temperature and dew point through the depth of the atmosphere, with the mixed-layer parcel. CAPE 0 joules per kilogram.LCL10008507005003002001001 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, Aberdeen, SD at 00:00Z on 2011-02-20The wind through the lowest 10 kilometers. Zero to 1 km storm-relative helicity 142 square meters per square second.1939587897Sfc1 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
0 J/kg
Mixed-layer CIN
No buoyant parcel
Mixed-layer LCL
617 m above ground
0-6 km bulk shear
60 kt
0-1 km storm-relative helicity
142 m²/s²
0-3 km storm-relative helicity
262 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.

199 
ACUS11 KWNS 201037
SWOMCD
SPC MCD 201036
SDZ000-201430-

MESOSCALE DISCUSSION 0112
NWS STORM PREDICTION CENTER NORMAN OK
0436 AM CST SUN FEB 20 2011

AREAS AFFECTED...WRN THROUGH CNTRL AND NERN SD

CONCERNING...WINTER MIXED PRECIPITATION

VALID 201036Z - 201430Z

SNOW IS EXPECTED TO INCREASE IN COVERAGE AND INTENSITY THROUGH THE
MORNING INITIALLY FROM WRN THROUGH CNTRL SD...EVENTUALLY EXPANDING
INTO E-CNTRL AND NERN SD. RATES LOCALLY FROM 1-2 INCHES PER HOUR ARE
EXPECTED. PRECIPITATION MOSTLY IN THE FORM OF FREEZING RAIN AND
SLEET OVER SERN SD SHOULD CHANGE TO SNOW LATER THIS MORNING.

RADAR TRENDS INDICATE SNOW COVERAGE INCREASING FROM WRN THROUGH
CNTRL SD. AREA OF MIXED PRECIPITATION EXPANDING NEWD THROUGH SERN SD
IS ASSOCIATED WITH LEAD VORTICITY MAXIMUM EVIDENT ON RADAR AND RUC
ANALYSIS DATA. IN WAKE OF THE LEAD IMPULSE...EXIT REGION OF A STRONG
UPPER JET LOCATED WITHIN BASE OF WRN U.S. TROUGH IS MOVING NEWD
TOWARD THE CNTRL HIGH PLAINS. LEE CYCLONE WILL DEVELOP EWD ALONG
BAROCLINIC ZONE ACROSS NEB AND WITHIN DIFFLUENT UPPER JET EXIT
REGION...WITH AN ATTENDANT INCREASE IN FRONTOGENETIC FORCING LIKELY
WITHIN DEFORMATION ZONE ACROSS SD. SNOWFALL RATES ARE EXPECTED TO
INCREASE THROUGH THE MORNING...ALONG WITH POTENTIAL FOR BANDED
STRUCTURES AS THIS ZONE OF DEEPER FORCING FOR ASCENT SPREADS EWD
THROUGH SD. INITIAL MIXED PRECIPITATION OVER SERN SD SHOULD BEGIN TO
CHANGE TO SNOW LATER THIS MORNING AS DEEP ASCENT CONTRIBUTES TO
DYNAMIC COOLING THROUGH THE COLUMN. CONVECTIVE ENHANCEMENT WILL
REMAIN LIKELY ACROSS SERN SD THIS MORNING.

..DIAL.. 02/20/2011

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

ATTN...WFO...FSD...ABR...UNR...

LAT...LON   43539688 43549962 43580244 44250369 45300290 45759977
            45289690 43539688

SPC that day

Everything else SPC issued on the same UTC day.

IssuedProductOfficeCountiesLasted
Feb 19, 11:25 PM CSTMesoscale DiscussionSPCAurora, Bon Homme, Brookings, Brule, Buffalo, Charles Mix and 20 more5 hr
Feb 20, 9:17 AM CSTMesoscale DiscussionSPCBeadle, Brookings, Brown, Buffalo, Campbell, Clark and 28 more4 hr

Nearby

Mesoscale Discussions in South Dakota, 2011Every mesoscale discussion in 2011

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.