Alert archive / Virginia / Mesoscale Discussions in 2012
Mesoscale Discussion 643
The Storm Prediction Center issued this mesoscale discussion at May 1, 2012, 12:43 PM EDT for 19 counties in North Carolina; 48 counties in Virginia; Monroe County, West Virginia. It was in force for 2 hr.
The area
The outline as issued.
The facts
- Issued
- May 1, 2012, 12:43 PM EDT (16:43 UTC)
- Expired
- May 1, 2012, 2:45 PM EDT
- In force
- 2 hr
- Issued by
- the Storm Prediction Center
- Chance of a watch
- 60%
All 68 counties
Alexander County, NC, Alleghany County, NC, Ashe County, NC, Avery County, NC, Burke County, NC, Caldwell County, NC, Caswell County, NC, Forsyth County, NC, Iredell County, NC, McDowell County, NC, Mitchell County, NC, Person County, NC, Rockingham County, NC, Stokes County, NC, Surry County, NC, Watauga County, NC, Wilkes County, NC, Yadkin County, NC, Yancey County, NC, Alleghany County, VA, Amelia County, VA, Amherst County, VA, Appomattox County, VA, Bedford County, VA, Botetourt County, VA, Brunswick County, VA, Buckingham County, VA, Campbell County, VA, Carroll County, VA, Charlotte County, VA, Chesterfield County, VA, City of Buena Vista, VA, City of Colonial Heights, VA, City of Covington, VA, City of Danville, VA, City of Galax, VA, City of Lexington, VA, City of Lynchburg, VA, City of Martinsville, VA, City of Petersburg, VA, City of Radford, VA, City of Richmond, VA, City of Roanoke, VA, City of Salem, VA, Craig County, VA, Cumberland County, VA, Dinwiddie County, VA, Floyd County, VA, Fluvanna County, VA, Franklin County, VA, Giles County, VA, Goochland County, VA, Grayson County, VA, Halifax County, VA, Henry County, VA, Lunenburg County, VA, Mecklenburg County, VA, Montgomery County, VA, Nelson County, VA, Nottoway County, VA, Patrick County, VA, Pittsylvania County, VA, Powhatan County, VA, Prince Edward County, VA, Pulaski County, VA, Roanoke County, VA, Rockbridge County, VA, Monroe County, WV
The radar
The Roanoke radar (KFCX), 40 km from the middle of the area, began a volume at 16:43 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 watches that followed
Watches SPC issued over any of the same counties within four hours of this discussion.
The nearest sounding before it
Greensboro/Hi Pt, NC (KGSO), launched 12:00Z, 4.7 hours before the alert went out and 71 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.
- Mixed-layer CAPE
- 6 J/kg
- Mixed-layer CIN
- -386 J/kg
- Mixed-layer LCL
- 1318 m above ground
- 0-6 km bulk shear
- 28 kt
- 0-1 km storm-relative helicity
- 144 m²/s²
- 0-3 km storm-relative helicity
- 137 m²/s²
- Significant tornado parameter
- 0.0
- Supercell composite
- 0.6
The text
As transmitted, in the capitals the NWS used until 2016.
641
ACUS11 KWNS 011644
SWOMCD
SPC MCD 011643
VAZ000-NCZ000-WVZ000-TNZ000-011845-
MESOSCALE DISCUSSION 0643
NWS STORM PREDICTION CENTER NORMAN OK
1143 AM CDT TUE MAY 01 2012
AREAS AFFECTED...SOUTHERN VA AND NORTHERN/WESTERN NC
CONCERNING...SEVERE POTENTIAL...WATCH POSSIBLE
VALID 011643Z - 011845Z
PROBABILITY OF WATCH ISSUANCE...60 PERCENT
SUMMARY...AT LEAST ISOLATED SEVERE TSTMS CAPABLE OF WIND/HAIL SHOULD
INCREASE THROUGH EARLY/MID AFTERNOON ACROSS PORTIONS OF SOUTHERN VA
AND NORTHERN/WESTERN NC. A CATEGORICAL SLIGHT RISK HAS BEEN ADDED TO
PORTIONS OF THE REGION WITH THE 1630Z DAY 1 OUTLOOK. A SEVERE TSTM
WATCH MAY BE NEEDED THIS AFTERNOON...ESPECIALLY ACROSS SOUTHERN
VA/NORTHERN NC.
DISCUSSION...A SMALL/REMNANT CLUSTER OF TSTMS CONTINUES TO SHIFT
EASTWARD ACROSS FAR WESTERN VA/FAR SOUTHERN WV AS OF 1615Z. IT IS
PLAUSIBLE THAT THIS PERSISTENT CLUSTER/ASSOCIATED WEAK MCV MAY
INFLUENCE SUBSEQUENT DEVELOPMENT INTO PORTIONS OF SOUTHERN VA AS IT
SHIFTS EASTWARD...WHILE THE CU FIELD OTHERWISE CONTINUES TO
EXPAND/MATURE EARLY THIS AFTERNOON OVER THE MOUNTAINS OF VA/NC PER
VISIBLE SATELLITE IMAGERY. GIVEN THE OBSERVED 12Z SOUNDINGS FROM
RNK/GSO AND LOWER 60S F SURFACE DEWPOINTS COINCIDENT WITH AMPLE
INSOLATION/HEATING...INDICATIONS ARE THAT LINGERING BOUNDARY LAYER
INHIBITION WILL QUICKLY ERODE WITH DEVELOPMENT OF MLCAPE ON THE
ORDER OF 1000-2000 J/KG. THE REGION DOES RESIDE ON THE SOUTHERN
EXTENT OF MODERATELY STRONG WESTERLIES ALOFT PER 12Z REGIONAL RAOBS
AND MORE CONTEMPORARY SATELLITE/WSR-88D DERIVED DATA.
THUS...EFFECTIVE SHEAR ON THE ORDER OF 30 KT MAY CONTRIBUTE TO SOME
SUSTAINED/VIGOROUS MAINLY MULTICELLULAR STORMS THIS AFTERNOON...WITH
DAMAGING WINDS/SEVERE HAIL POSSIBLE AT LEAST ON AN ISOLATED BASIS.
..GUYER/MEAD.. 05/01/2012
...PLEASE SEE WWW.SPC.NOAA.GOV FOR GRAPHIC PRODUCT...
ATTN...WFO...AKQ...LWX...RAH...RNK...GSP...MRX...
LAT...LON 36828106 37768052 38087930 37827757 37017729 36657772
36357878 36158000 35418188 35718259 35948242 36318186
36828106SPC that day
Everything else SPC issued on the same UTC day.
| Issued | Product | Office | Counties | Lasted |
|---|---|---|---|---|
| May 1, 3:12 PM EDT | Severe Thunderstorm Watch | SPC | Alamance, Alexander, Bertie, Burke, Caldwell, Caswell and 34 more | 5 hr |
| May 1, 5:49 PM EDT | Mesoscale Discussion | SPC | Beaufort, Bertie, Camden, Chowan, Craven, Currituck and 21 more | 86 min |
| Apr 30, 9:07 PM EDT | Mesoscale Discussion | SPC | Brooke, Cabell, Calhoun, Doddridge, Gilmer, Hancock and 14 more | 53 min |
| May 1, 6:13 PM EDT | Mesoscale Discussion | SPC | Cabell, Jackson, Mason, Pleasants, Putnam, Wirt and 1 more | 62 min |
| May 1, 6:31 PM EDT | Tornado Watch | SPC | Barbour, Braxton, Cabell, Calhoun, Doddridge, Gilmer and 16 more | 5 hr |
Nearby
Mesoscale Discussions in Virginia, 2012Mesoscale Discussions in North Carolina, 2012Mesoscale Discussions in West Virginia, 2012Every 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.