Alert archive / South Dakota / Mesoscale Discussions in 2012

Mesoscale Discussion 2108

November 10, 2012Dawes County, Sioux County, Nebraska; 4 counties in North Dakota; 11 counties in South Dakota

The Storm Prediction Center issued this mesoscale discussion at Nov 10, 2012, 11:11 AM MST for Dawes County, Sioux County, Nebraska; 4 counties in North Dakota; 11 counties in South Dakota. It was in force for 4 hr.

The area

The outline as issued.

The facts

Issued: Nov 10, 2012, 11:11 AM MST (18:11 UTC)
Expired: Nov 10, 2012, 3:15 PM MST
In force: 4 hr
Issued by: the Storm Prediction Center

Counties Emmons County, ND, Grant County, ND, Morton County, ND, Sioux County, ND, Dawes County, NE, Sioux County, NE, Corson County, SD, Custer County, SD, Dewey County, SD, Fall River County, SD, Haakon County, SD, Jackson County, SD, Meade County, SD, Oglala Lakota County, SD, Pennington County, SD, Perkins County, SD, Ziebach County, SD

The radar

The Rapid City radar (KUDX), 65 km from the middle of the area, began a volume at 18:10 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

Rapid City, SD (KUNR), launched 12:00Z, 6.2 hours before the alert went out and 72 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: 3 J/kg
Mixed-layer CIN: 0 J/kg
Mixed-layer LCL: 520 m above ground
0-6 km bulk shear: 66 kt
0-1 km storm-relative helicity: -25 m²/s²
0-3 km storm-relative helicity: 27 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.

765 
ACUS11 KWNS 101812
SWOMCD
SPC MCD 101811
NDZ000-SDZ000-NEZ000-WYZ000-102215-

MESOSCALE DISCUSSION 2108
NWS STORM PREDICTION CENTER NORMAN OK
1211 PM CST SAT NOV 10 2012

AREAS AFFECTED...WRN SD...S-CNTRL ND...FAR NWRN NEB

CONCERNING...HEAVY SNOW

VALID 101811Z - 102215Z

SUMMARY...BAND OF MODERATE TO OCCASIONALLY HEAVY SNOWFALL IS
EXPECTED TO PERSIST AS IT MOVES EWD ACROSS WRN SD...S-CNTRL ND AND
FAR NWRN NEB. SNOWFALL RATES IN EXCESS OF 1 INCH/HR ARE LIKELY WITH
THE POSSIBILITY OF BRIEF PERIODS OF 2 INCHES/HR.

DISCUSSION...SURFACE ANALYSIS DEPICTS A BROAD AREA OF LOW PRESSURE
EXTENDING FROM SWRN CO NEWD INTO ERN SD/FAR WRN MN. TWO SURFACE LOWS
ARE LOCATED WITHIN THIS BROAD AREA...ONE CENTERED OVER SWRN CO AND
THE OTHER OVER E-CNTRL SD. RECENT RADAR IMAGERY AND SURFACE
OBSERVATIONS INDICATE PERIODS OF MODERATE/HEAVY SNOW WITHIN A BAND
ORIENTED SW TO NE ACROSS WRN SD. ALSO OF NOTE...THE MODEL GUIDANCE
WAS TOO SLOW WITH THE ONSET OF THIS BAND.

SURFACE THETA-E FIELDS SHOW A WARM AIR ADVECTION NOSE FROM CNTRL IA
NWWD INTO CNTRL SD. THIS TRAJECTORY FAVORS ADDITIONAL MOIST
ADVECTION INTO THE REGION. STRONG FRONTOGENESIS IS ONGOING ACROSS
CNTRL NEB WITH THE FAR NORTHERN PORTION OF THE AGEOSTROPHIC
CIRCULATION LIKELY PHASING WITH LARGE SCALE LIFT ASSOCIATED WITH THE
EXIT REGION OF A STRONG JET STREAK /CURRENTLY EXTENDING FROM NWRN NM
NEWD INTO WRN NEB/. THESE DYNAMICS SHOULD FAVOR THE CONTINUATION OF
THE SNOW BAND WITH THE POTENTIAL FOR SOME INTENSIFICATION AS IT
MOVES EWD. SNOWFALL RATES IN EXCESS OF 1 INCH/HOUR WITH BRIEF
PERIODS OF 2 INCHES/HOUR ARE ANTICIPATED.

..MOSIER.. 11/10/2012

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

ATTN...WFO...ABR...BIS...LBF...UNR...CYS...

LAT...LON   46660232 46840183 46870147 46930057 46699991 46149997
            45520016 44340092 43370174 42770231 42430321 42360359
            42390383 42670400 43010407 43330395 43540384 43840359
            44130331 44720299 44960288 46080251 46660232

SPC that day

Everything else SPC issued on the same UTC day.

Issued	Product	Office	Counties	Lasted
Nov 10, 12:53 PM MST	Mesoscale Discussion	SPC	Adams, Burt, Butler, Clay, Colfax, Cuming and 22 more	2 hr
Nov 10, 2:36 PM MST	Severe Thunderstorm Watch	SPC	Adams, Burt, Butler, Cass, Clay, Colfax and 28 more	7 hr
Nov 10, 4:10 PM MST	Mesoscale Discussion	SPC	Boyd, Cherry, Keya Paha	5 hr
Nov 9, 5:17 PM MST	Mesoscale Discussion	SPC	Adams, Benson, Billings, Bottineau, Bowman, Burke and 21 more	4 hr

Nearby

Mesoscale Discussions in South Dakota, 2012 Mesoscale Discussions in North Dakota, 2012 Mesoscale Discussions in Nebraska, 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.