Alert archive / Virginia / Mesoscale Discussions in 2003

Mesoscale Discussion 2321

August 30, 20034 states

The Storm Prediction Center issued this mesoscale discussion at Aug 30, 2003, 11:20 AM EDT for 4 states. It was in force for 3 hr.

The area

The outline as issued.

The facts

Issued: Aug 30, 2003, 11:20 AM EDT (15:20 UTC)
Expired: Aug 30, 2003, 2:15 PM EDT
In force: 3 hr
Issued by: the Storm Prediction Center

All 71 counties

Kent County, DE, New Castle County, DE, Sussex 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, Dorchester County, 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, Saint Mary's County, MD, Somerset County, MD, Talbot County, MD, Wicomico County, MD, Worcester County, MD, Atlantic County, NJ, Cape May County, NJ, Cumberland County, NJ, Gloucester County, NJ, Salem County, NJ, Albemarle County, VA, Arlington County, VA, Buckingham County, VA, Caroline County, VA, City of Alexandria, VA, City of Charlottesville, VA, City of Fairfax, VA, City of Falls Church, VA, City of Fredericksburg, VA, City of Manassas, VA, City of Manassas Park, VA, City of Richmond, VA, Culpeper County, VA, Cumberland County, VA, Essex County, VA, Fairfax County, VA, Fauquier County, VA, Fluvanna County, VA, Goochland County, VA, Greene County, VA, Hanover County, VA, Henrico County, VA, King and Queen County, VA, King George County, VA, King William County, VA, Lancaster County, VA, Loudoun County, VA, Louisa County, VA, Madison County, VA, Middlesex County, VA, New Kent County, VA, Northumberland County, VA, Orange County, VA, Page County, VA, Powhatan County, VA, Prince William County, VA, Rappahannock County, VA, Richmond County, VA, Spotsylvania County, VA, Stafford County, VA, Warren County, VA, Westmoreland County, VA

The radar

The Sterling radar (KLWX), 55 km from the middle of the area, began a volume at 15:23 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 912Aug 30, 1:45 PM EDT

The nearest sounding before it

Washington/Dulle, VA (KIAD), launched 12:00Z, 3.3 hours before the alert went out and 46 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: 245 J/kg
Mixed-layer CIN: -132 J/kg
Mixed-layer LCL: 1261 m above ground
0-6 km bulk shear: 29 kt
0-1 km storm-relative helicity: 68 m²/s²
0-3 km storm-relative helicity: 94 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.

718 
ACUS11 KWNS 301520
SWOMCD
SPC MCD 301520 
NJZ000-PAZ000-DEZ000-MDZ000-VAZ000-DCZ000-WVZ000-301815-

MESOSCALE DISCUSSION 2321
NWS STORM PREDICTION CENTER NORMAN OK
1020 AM CDT SAT AUG 30 2003

AREAS AFFECTED...PORTIONS NJ...DE...EXTREME SERN PA...MUCH OF
MD...DC...NRN VA...EXTREME ERN WV

CONCERNING...SEVERE THUNDERSTORM POTENTIAL...HEAVY RAINFALL 

VALID 301520Z - 301815Z

WIDELY SCATTERED TO SCATTERED TSTMS -- INCLUDING MULTICELL CLUSTERS
-- SHOULD DEVELOP THROUGH 18Z ACROSS MUCH OF COASTAL PLAINS AND
PIEDMONT...FROM SRN DE VALLEY AREA SWWD TO NRN VA.  BANDS OF
ELEVATED CONVECTION MOVING INTO REGION FROM W MAY ALSO BECOME SFC
BASED. A FEW SEVERE GUSTS ARE POSSIBLE...AND SUB-50 KT GUSTS MAY
ALSO PRODUCE SPORADIC DAMAGE.  WW MAY BE REQUIRED.  1630Z
CATEGORICAL OUTLOOK IS BEING UPGRADED TO SLGT RISK FOR MUCH OF THIS
AREA.  ALSO...RAIN RATES 2-3 INCHES/HOUR ARE POSSIBLE...LOCALLY
REACHING 4 INCHES/HOUR IN MOST INTENSE CORES.

SFC ANALYSIS SHOWS COLD FRONT FROM NRN NJ WSWWD ACROSS SRN PA INTO
NRN KY...DRIFTING SWD. PREFRONTAL TROUGH IS ANALYZED FROM SERN MA
ACROSS SRN NJ...TO DE/PA BORDER AREA THEN SWWD ACROSS NRN VA. 
WEAKLY CAPPED PREFRONTAL AIR MASS IS DESTABILIZING RAPIDLY OVER THIS
REGION...WITH STRONG INSOLATION ONGOING AMIDST VERY MOIST
LOW-MIDLEVEL PROFILES. MODIFIED RAOBS AND SHORT-TERM FCST SOUNDINGS
SHOW WEAK LAPSE RATES ABOVE VIGOROUSLY MIXED BOUNDARY LAYER. 
HOWEVER...LARGE TROPOSPHERIC DEPTH AND LOW LEVEL PW COMMONLY 2-2.3
INCHES EACH CONTRIBUTE TO MLCAPE RANGING FROM AROUND 1700 J/KG
AROUND SRN NJ AND DE...TO 2200 J/KG OVER N-CENTRAL VA. ORGANIZATION
OF ACTIVITY WILL BE LIMITED BY WEAK MID-UPPER LEVEL WINDS -- E.G.
10-20 KT ABOVE 400 MB. HOWEVER...30-40 KT 2-3 KM FLOW OBSERVED IN
12Z RAOBS AND CURRENT VWP SHOULD ENHANCE LOW LEVEL SHEAR...SR
INFLOW...PRECIP EFFICIENCY  AND DAMAGING DOWNDRAFT POTENTIAL. 
VERTICAL WIND PROFILE SHOULD BE NEARLY UNIDIRECTIONAL AND WLY.

..EDWARDS.. 08/30/2003

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

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

38977823 39497737 39777637 39867514 39557425 38247511
37417694 37397851 38317886

SPC that day

Everything else SPC issued on the same UTC day.

Issued	Product	Office	Counties	Lasted
Aug 30, 1:45 PM EDT	Severe Thunderstorm Watch	SPC	Kent, New Castle, Sussex	5 hr
Aug 30, 3:11 PM EDT	Mesoscale Discussion	SPC	Kent, New Castle, Sussex	2 hr
Aug 30, 6:29 PM EDT	Mesoscale Discussion	SPC	Sussex	61 min

Nearby

Mesoscale Discussions in Virginia, 2003 Mesoscale Discussions in Maryland, 2003 Mesoscale Discussions in New Jersey, 2003 Every mesoscale discussion in 2003

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.