Alert archive / Iowa / Mesoscale Discussions in 2012

Mesoscale Discussion 2188

December 20, 20124 counties in Illinois; 16 counties in Iowa; 14 counties in Missouri

The Storm Prediction Center issued this mesoscale discussion at Dec 20, 2012, 7:49 AM CST for 4 counties in Illinois; 16 counties in Iowa; 14 counties in Missouri. It was in force for 4 hr.

The area

The outline as issued.

The facts

Issued: Dec 20, 2012, 7:49 AM CST (13:49 UTC)
Expired: Dec 20, 2012, 11:45 AM CST
In force: 4 hr
Issued by: the Storm Prediction Center

All 34 counties

Appanoose County, IA, Cedar County, IA, Davis County, IA, Des Moines County, IA, Henry County, IA, Jefferson County, IA, Johnson County, IA, Jones County, IA, Keokuk County, IA, Lee County, IA, Louisa County, IA, Muscatine County, IA, Scott County, IA, Van Buren County, IA, Wapello County, IA, Washington County, IA, Hancock County, IL, Henderson County, IL, Mercer County, IL, Rock Island County, IL, Adair County, MO, Chariton County, MO, Clark County, MO, Knox County, MO, Lewis County, MO, Linn County, MO, Macon County, MO, Monroe County, MO, Putnam County, MO, Randolph County, MO, Schuyler County, MO, Scotland County, MO, Shelby County, MO, Sullivan County, MO

The radar

The Quad Cities radar (KDVN), 140 km from the middle of the area, began a volume at 13:53 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

Davenport, (KDVN), launched 12:00Z, 1.8 hours before the alert went out and 145 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: 447 m above ground
0-6 km bulk shear: 93 kt
0-1 km storm-relative helicity: 160 m²/s²
0-3 km storm-relative helicity: 293 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.

092 
ACUS11 KWNS 201349
SWOMCD
SPC MCD 201349 
ILZ000-IAZ000-MOZ000-201745-

MESOSCALE DISCUSSION 2188
NWS STORM PREDICTION CENTER NORMAN OK
0749 AM CST THU DEC 20 2012

AREAS AFFECTED...N-CNTRL/NERN MO...SERN IA...W-CNTRL IL

CONCERNING...BLIZZARD 

VALID 201349Z - 201745Z

SUMMARY...SNOWFALL RATES NEAR 1 IN PER HR ARE FORECAST TO SPREAD
E/NEWD INTO PARTS OF SERN IA AND W-CNTRL IL THROUGH LATE MORNING.
STRENGTHENING WIND SPEEDS WILL ALSO LEAD TO SIGNIFICANT REDUCTIONS
IN VISIBILITIES...CREATING BLIZZARD CONDITIONS BY 18Z.

DISCUSSION...A WELL DEFINED DEEP-LAYER CYCLONE /EVIDENT ON WATER
VAPOR IMAGERY/ WILL CONTINUE SHIFTING E-NEWD...WITH A DRY SLOT
PROTRUDING NWD INTO SERN IA/W-CNTRL IL. 20/12Z KDVN RAOB SAMPLED A
WARM NOSE OF ABOVE FREEZING TEMPERATURES WITHIN THE 900-700 MB
LAYER...WITH MODERATELY STEEP MIDLEVEL LAPSE RATES SUPPORTING
ISOLATED TSTM DEVELOPMENT. WITH TIME...DYNAMIC COOLING AND LOW-LEVEL
CAA SHOULD RESULT IN THE ENTIRE TEMPERATURE PROFILE FALLING BELOW
FREEZING /PRIMARILY AFTER 15Z ACROSS FAR NERN MO/SERN IA/...AND A
SUBSEQUENT CHANGEOVER TO SNOW. ALTHOUGH THE STRONGEST FORCING FOR
ASCENT WILL BE SHIFTING E OF THE HIGHLIGHTED AREA...SNOWFALL RATES
NEAR 1 INCH PER HR WILL STILL BE POSSIBLE...ESPECIALLY WHERE
LOCALIZED CONVECTIVE ENHANCEMENT MAY OCCUR.

ADDITIONALLY...13Z SFC OBS SHOW A 988 MB CENTERED JUST E OF KUIN. AS
THIS SHIFTS ENEWD...TIGHTENING OF THE SFC PRESSURE GRADIENT ALONG
ITS WRN/NWRN PERIPHERY WILL OCCUR AND RESULT IN INCREASING WIND
SPEEDS THROUGH 18Z. 06Z NAM FORECAST MODEL SOUNDINGS SUGGEST WIND
GUSTS AS HIGH AS 50 MPH WILL BE POSSIBLE...WHICH WILL LEAD TO
SIGNIFICANT REDUCTIONS IN VISIBILITIES AND BLIZZARD CONDITIONS.

..ROGERS.. 12/20/2012

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

ATTN...WFO...LSX...DVN...DMX...EAX...

LAT...LON   41429040 40669088 39749172 39509181 39249276 39449323
            39799340 40829308 42119149 42239097 42049059 41429040

SPC that day

Everything else SPC issued on the same UTC day.

Issued	Product	Office	Counties	Lasted
Dec 20, 10:52 AM CST	Mesoscale Discussion	SPC	Adams, Boone, Brown, Bureau, Calhoun, Carroll and 43 more	6 hr
Dec 19, 9:32 PM CST	Mesoscale Discussion	SPC	Adair, Adams, Audubon, Black Hawk, Boone, Bremer and 24 more	5 hr
Dec 20, 3:12 AM CST	Mesoscale Discussion	SPC	Allamakee, Clayton, Winneshiek	4 hr
Dec 19, 7:07 PM CST	Mesoscale Discussion	SPC	Barry, Barton, Cedar, Christian, Dade, Dallas and 15 more	53 min
Dec 19, 7:36 PM CST	Tornado Watch	SPC	Barry, Christian, Douglas, Greene, Jasper, Lawrence and 7 more	6 hr
Dec 19, 10:22 PM CST	Mesoscale Discussion	SPC	Carter, Christian, Dent, Douglas, Howell, Oregon and 8 more	83 min

Nearby

Mesoscale Discussions in Iowa, 2012 Mesoscale Discussions in Missouri, 2012 Mesoscale Discussions in Illinois, 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.