Alert archive / Virginia / Mesoscale Discussions in 2011

Mesoscale Discussion 549

April 24, 20116 states

The Storm Prediction Center issued this mesoscale discussion at Apr 24, 2011, 2:12 PM EDT for 6 states. It was in force for 93 min.

The area

The outline as issued.

The facts

Issued: Apr 24, 2011, 2:12 PM EDT (18:12 UTC)
Expired: Apr 24, 2011, 3:45 PM EDT
In force: 93 min
Issued by: the Storm Prediction Center

All 73 counties

Kent County, DE, New Castle County, DE, Anne Arundel County, MD, Baltimore County, MD, Calvert County, MD, Caroline County, MD, Carroll County, MD, Cecil County, MD, Charles County, MD, City of Baltimore, MD, Frederick County, MD, Harford County, MD, Howard County, MD, Kent County, MD, Montgomery County, MD, Prince George's County, MD, Queen Anne's County, MD, Talbot County, MD, Washington County, MD, Burlington County, NJ, Camden County, NJ, Gloucester County, NJ, Hunterdon County, NJ, Mercer County, NJ, Salem County, NJ, Warren County, NJ, Adams County, PA, Berks County, PA, Bucks County, PA, Chester County, PA, Cumberland County, PA, Dauphin County, PA, Delaware County, PA, Franklin County, PA, Lancaster County, PA, Lebanon County, PA, Lehigh County, PA, Montgomery County, PA, Northampton County, PA, Philadelphia County, PA, Schuylkill County, PA, York County, PA, Arlington County, VA, City of Alexandria, VA, City of Fairfax, VA, City of Falls Church, VA, City of Fredericksburg, VA, City of Harrisonburg, VA, City of Manassas, VA, City of Manassas Park, VA, City of Winchester, VA, Clarke County, VA, Culpeper County, VA, Fairfax County, VA, Fauquier County, VA, Frederick County, VA, Greene County, VA, King George County, VA, Loudoun County, VA, Madison County, VA, Orange County, VA, Page County, VA, Prince William County, VA, Rappahannock County, VA, Rockingham County, VA, Shenandoah County, VA, Stafford County, VA, Warren County, VA, Berkeley County, WV, Hampshire County, WV, Hardy County, WV, Jefferson County, WV, Morgan County, WV

The radar

The Sterling radar (KLWX), 110 km from the middle of the area, began a volume at 18:14 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 195Apr 24, 3:40 PM EDT

The nearest sounding before it

Washington/Dulle, VA (KIAD), launched 12:00Z, 6.2 hours before the alert went out and 107 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: 1135 m above ground
0-6 km bulk shear: 42 kt
0-1 km storm-relative helicity: -16 m²/s²
0-3 km storm-relative helicity: 32 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.

018 
ACUS11 KWNS 241812
SWOMCD
SPC MCD 241812 
NJZ000-PAZ000-DEZ000-MDZ000-VAZ000-DCZ000-WVZ000-241945-

MESOSCALE DISCUSSION 0549
NWS STORM PREDICTION CENTER NORMAN OK
0112 PM CDT SUN APR 24 2011

AREAS AFFECTED...SERN PA...NJ...DE...MD...NRN VA...WASHINGTON DC

CONCERNING...SEVERE POTENTIAL...WATCH POSSIBLE 

VALID 241812Z - 241945Z

PORTIONS OF SERN PA...NJ...DE...MD...NRN VA...AND WASHINGTON DC ARE
BEING MONITORED FOR THUNDERSTORM INITIATION AND SUBSEQUENT INCREASE
IN SVR WEATHER POTENTIAL/POSSIBLE WW ISSUANCE THIS AFTERNOON.

MESOANALYSIS INDICATES A COLD FRONT WAS LOCATED FROM SERN NY WSW
ACROSS CNTRL/SRN PA AND INTO THE OH VALLEY REGION AT 18Z.
TEMPERATURES S OF THE FRONT ARE WARMING INTO THE 70S AND 80S...WHICH
IS AIDING IN STEEPENING LOW-LEVEL LAPSE RATES AND BOUNDARY LAYER
DESTABILIZATION. IN ADDITION...AXIS OF LOW 60S DEWPOINTS EXTENDS NWD
INTO THE MID ATLANTIC REGION...WHICH IS AIDING IN WEAK TO MODERATE
INSTABILITY...WITH MLCAPE VALUES EXPECTED TO PEAK AROUND 500-1500
J/KG DURING THE AFTERNOON. THOUGH UPPER-LEVEL SUPPORT FOR ADDITIONAL
AIRMASS DESTABILIZATION IS GENERALLY LACKING...COMBINATION OF
CONTINUED SURFACE HEATING...CONVERGENCE/ASCENT ALONG THE COLD
FRONT...AND VERTICAL MOTION FIELDS ASSOCIATED WITH APPROACHING MCV
OVER SERN OH/NRN WV MAY AID IN THUNDERSTORM INITIATION DURING THE
NEXT FEW HOURS. VWP WIND PROFILES AND RUC FORECAST SOUNDINGS
INDICATE THAT VERTICAL WIND SHEAR IS FAVORABLE FOR BOTH SUPERCELLS
AND FAST MOVING LINE SEGMENTS. THE PRIMARY THREAT ASSOCIATED WITH
ANY SVR STORM ACTIVITY WILL LIKELY BE DAMAGING WINDS...THOUGH
ISOLATED LARGE HAIL AND A TORNADO CANNOT BE RULED OUT.

..GARNER.. 04/24/2011

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

ATTN...WFO...PHI...AKQ...CTP...LWX...

LAT...LON   40827630 41067471 39877463 38607589 38207721 38227960
            39917811 40827630

SPC that day

Everything else SPC issued on the same UTC day.

Issued	Product	Office	Counties	Lasted
Apr 24, 3:40 PM EDT	Severe Thunderstorm Watch	SPC	Kent, New Castle, Sussex	5 hr
Apr 24, 6:10 PM EDT	Mesoscale Discussion	SPC	Kent, New Castle	65 min
Apr 23, 8:16 PM EDT	Mesoscale Discussion	SPC	Garrett	59 min

Nearby

Mesoscale Discussions in Virginia, 2011 Mesoscale Discussions in Maryland, 2011 Mesoscale Discussions in Pennsylvania, 2011 Every mesoscale discussion in 2011

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.