Alert archive / Virginia / Mesoscale Discussions in 2012

Mesoscale Discussion 964

May 29, 2012Frederick County, Washington County, Maryland; 17 counties in Virginia; 6 counties in West Virginia

The Storm Prediction Center issued this mesoscale discussion at May 29, 2012, 4:22 PM EDT for Frederick County, Washington County, Maryland; 17 counties in Virginia; 6 counties in West Virginia. It was in force for 53 min.

The area

The outline as issued.

The facts

Issued: May 29, 2012, 4:22 PM EDT (20:22 UTC)
Expired: May 29, 2012, 5:15 PM EDT
In force: 53 min
Issued by: the Storm Prediction Center
Chance of a watch: 95%

All 25 counties

Frederick County, MD, Washington County, MD, Augusta County, VA, City of Harrisonburg, VA, City of Staunton, VA, City of Waynesboro, VA, City of Winchester, VA, Clarke County, VA, Fauquier County, VA, Frederick County, VA, Greene County, VA, Highland County, VA, Loudoun County, VA, Madison County, VA, Page County, VA, Rappahannock County, VA, Rockingham County, VA, Shenandoah County, VA, Warren County, VA, Berkeley County, WV, Hampshire County, WV, Hardy County, WV, Jefferson County, WV, Morgan County, WV, Pendleton County, WV

The radar

The Sterling radar (KLWX), 69 km from the middle of the area, began a volume at 20:24 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.

Severe Thunderstorm Watch 316May 29, 4:30 PM EDT

The nearest sounding before it

Washington/Dulle, VA (KIAD), launched 12:00Z, 8.4 hours before the alert went out and 76 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: 601 J/kg
Mixed-layer CIN: -150 J/kg
Mixed-layer LCL: 1156 m above ground
0-6 km bulk shear: 8 kt
0-1 km storm-relative helicity: -68 m²/s²
0-3 km storm-relative helicity: -33 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.

491 
ACUS11 KWNS 292022
SWOMCD
SPC MCD 292022 
MDZ000-VAZ000-WVZ000-292115-

MESOSCALE DISCUSSION 0964
NWS STORM PREDICTION CENTER NORMAN OK
0322 PM CDT TUE MAY 29 2012

AREAS AFFECTED...NRN VA...MD

CONCERNING...SEVERE POTENTIAL...WATCH LIKELY 

VALID 292022Z - 292115Z

PROBABILITY OF WATCH ISSUANCE...95 PERCENT

SUMMARY...STORM INTENSITY HAS BEGUN TO INCREASE SOME ACROSS NRN VA.
STRONGER CELLS MAY BE CAPABLE OF DMGG WINDS AND HAIL. A WW IS BEING
COORDINATED.

DISCUSSION...WITH BROADER HEIGHT FALLS IN ADVANCE OF A GREAT LAKES
UPPER TROUGH...COVERAGE OF THUNDERSTORMS HAS CONTINUED TO INCREASE
ACROSS THE UPPER MID ATLANTIC INTO THE NORTHEAST. THE 18Z IAD
SOUNDING INDICATES AROUND 2500 J/KG SBCAPE HAS DEVELOPED AMIDST A
MOIST AIR MASS AND AMPLE SURFACE HEATING. WINDS ALOFT ARE BEGINNING
TO STRENGTHEN SOME /NOW 30 KTS PER PROFILER DATA/ IN ADVANCE OF THE
UPPER TROUGH...AND MAY SUPPORT SEMI-ORGANIZED CELLS AND SMALL BOWING
SEGMENTS.

..HURLBUT/WEISS.. 05/29/2012

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

ATTN...WFO...LWX...RNK...

LAT...LON   39647726 39257727 38807759 38317817 37947877 37967934
            38357967 39227893 39657847 39647726

SPC that day

Everything else SPC issued on the same UTC day.

Issued	Product	Office	Counties	Lasted
May 29, 4:33 PM EDT	Severe Thunderstorm Watch	SPC	Baltimore, Carroll, Charles, Frederick, Harford, Howard and 4 more	4 hr
May 29, 7:48 PM EDT	Mesoscale Discussion	SPC	Anne Arundel, Charles, Kent, Prince George's	57 min
May 29, 9:48 AM EDT	Mesoscale Discussion	SPC	Brooke, Hancock	87 min
May 29, 10:27 AM EDT	Severe Thunderstorm Watch	SPC	Brooke, Hancock, Marion, Marshall, Monongalia, Ohio and 1 more	5 hr
May 29, 1:25 PM EDT	Mesoscale Discussion	SPC	Brooke, Hancock, Marshall, Ohio	65 min

Nearby

Mesoscale Discussions in Virginia, 2012 Mesoscale Discussions in West Virginia, 2012 Mesoscale Discussions in Maryland, 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.