Alert archive / Nebraska / Mesoscale Discussions in 2012

Mesoscale Discussion 1633

July 28, 201230 counties in Nebraska

The Storm Prediction Center issued this mesoscale discussion at Jul 28, 2012, 1:49 PM CDT for 30 counties in Nebraska. It was in force for 56 min.

The area

The outline as issued.

The facts

Issued: Jul 28, 2012, 1:49 PM CDT (18:49 UTC)
Expired: Jul 28, 2012, 2:45 PM CDT
In force: 56 min
Issued by: the Storm Prediction Center
Chance of a watch: 60%

All 30 counties

Adams County, NE, Antelope County, NE, Boone County, NE, Buffalo County, NE, Clay County, NE, Custer County, NE, Dawson County, NE, Franklin County, NE, Garfield County, NE, Greeley County, NE, Hall County, NE, Hamilton County, NE, Harlan County, NE, Holt County, NE, Howard County, NE, Kearney County, NE, Loup County, NE, Madison County, NE, Merrick County, NE, Nance County, NE, Phelps County, NE, Pierce County, NE, Platte County, NE, Polk County, NE, Rock County, NE, Sherman County, NE, Valley County, NE, Webster County, NE, Wheeler County, NE, York County, NE

The radar

The Grand Island radar (KUEX), 129 km from the middle of the area, began a volume at 18:47 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

N. Platte/Lee Bi, NE (KLBF), launched 12:00Z, 6.8 hours before the alert went out and 166 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: 98 J/kg
Mixed-layer CIN: -392 J/kg
Mixed-layer LCL: 2134 m above ground
0-6 km bulk shear: 24 kt
0-1 km storm-relative helicity: 144 m²/s²
0-3 km storm-relative helicity: 187 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.

259 
ACUS11 KWNS 281850
SWOMCD
SPC MCD 281849
NEZ000-281945-

MESOSCALE DISCUSSION 1633
NWS STORM PREDICTION CENTER NORMAN OK
0149 PM CDT SAT JUL 28 2012

AREAS AFFECTED...PORTIONS CNTRL/ERN NEB

CONCERNING...SEVERE POTENTIAL...WATCH POSSIBLE

VALID 281849Z - 281945Z

PROBABILITY OF WATCH ISSUANCE...60 PERCENT

SUMMARY...DMGG WIND AND HAIL THREAT IS EXPECTED TO INCREASE THIS
AFTERNOON ACROSS PARTS OF CNTRL/ERN NEB...ASSOCIATED WITH DEEPENING
CONVECTION ALONG A NEWD MOVING WEAK WARM FRONT. ADDITIONAL
DEVELOPMENT IS POSSIBLE FARTHER N ASSOCIATED WITH AN UPPER IMPULSE.
CONVECTIVE TRENDS ARE BEING MONITORED FOR A POSSIBLE WW.

DISCUSSION...CU FIELD HAS INCREASED WITHIN THE PAST HR ALONG A NEWD
MOVING WARM FRONT...WHICH WAS SITUATED FROM 30 S LBF TO 25 N SLN AS
OF 18Z. THIS AREA IS ALONG THE SRN FRINGE OF SCT MID/UPPER LEVEL
CLOUD COVER...AND HAS HEATED UP TO NEAR 100 F ALONG/S OF THE WARM
FRONT. DEEP BOUNDARY LAYER MIXING HAS ERODED MOST CINH...AND SHOULD
RESULT IN CONVECTIVE INITIATION WITHIN THE NEXT 1-2 HRS...WITH
MLCAPE VALUES APPROACHING 1000 J/KG. 18Z SFC OBS/PROFILER DATA SHOW
BOUNDARY LAYER FLOW IS SLIGHTLY MORE BACKED AHEAD OF THE WARM FRONT
THAN INDICATED BY MOST MODEL GUIDANCE...BUT IS EXPECTED TO VEER
TOWARDS THE S/SSW WITH TIME AS THE WARM FRONT CONTINUES ADVANCING
NEWD AND WEAK SFC CYCLOGENESIS OCCURS OVER N-CNTRL/NERN NEB.
NONETHELESS...MODERATE MIDLEVEL WLYS WILL YIELD SUFFICIENT EFFECTIVE
SHEAR VALUES /30-40 MPH/ TO SUPPORT MULTICELL AND OCCASIONAL
SUPERCELL STRUCTURES. THE HOT/WELL-MIXED BOUNDARY LAYER COMBINED
WITH STEEP MIDLEVEL LAPSE RATES WILL SUPPORT BOTH A THREAT FOR DMGG
WINDS AND LARGE HAIL.

FARTHER N...THICK CLOUD COVER HAS STIFLED DIABATIC HEATING THUS FAR.
HOWEVER...INCREASING DEEP-LAYER ASCENT ASSOCIATED WITH AN UPPER
IMPULSE OVER ERN/CNTRL SD...ALONG WITH INCREASING LOW-LEVEL
CONVERGENCE INVOF AFOREMENTIONED DEEPENING SFC LOW AND NEWD
ADVANCING WARM FRONT...COULD RESULT IN ADDITIONAL CONVECTIVE
DEVELOPMENT BY LATE AFTERNOON.

..ROGERS/CORFIDI.. 07/28/2012

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

ATTN...WFO...OAX...GID...LBF...

LAT...LON   42529756 41459721 40249787 40019853 40079940 40599983
            41340002 42189992 42619899 42639847 42529756

SPC that day

Everything else SPC issued on the same UTC day.

Issued	Product	Office	Counties	Lasted
Jul 28, 6:02 PM CDT	Severe Thunderstorm Watch	SPC	Adams, Buffalo, Clay, Custer, Dawson, Fillmore and 21 more	4 hr

Nearby

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.