Alert archive / Virginia / Mesoscale Discussions in 2004

Mesoscale Discussion 754

May 18, 20046 states

The Storm Prediction Center issued this mesoscale discussion at May 18, 2004, 7:49 PM EDT for 6 states. It was in force for 2 hr.

The area

The outline as issued.

The facts

Issued: May 18, 2004, 7:49 PM EDT (23:49 UTC)
Expired: May 18, 2004, 10:15 PM EDT
In force: 2 hr
Issued by: the Storm Prediction Center

All 46 counties

Kent County, DE, New Castle County, DE, Anne Arundel County, MD, Baltimore County, MD, Caroline County, MD, Carroll County, MD, Cecil 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, Washington County, MD, Atlantic County, NJ, Burlington County, NJ, Camden County, NJ, Cumberland County, NJ, Gloucester County, NJ, Salem County, NJ, Chester County, PA, Delaware County, PA, Lancaster County, PA, Montgomery County, PA, Philadelphia County, PA, York County, PA, Arlington County, VA, City of Alexandria, VA, City of Fairfax, VA, City of Falls Church, VA, City of Manassas, VA, City of Manassas Park, VA, City of Winchester, VA, Clarke County, VA, Fairfax County, VA, Fauquier County, VA, Frederick County, VA, Loudoun County, VA, Prince William County, VA, Rappahannock County, VA, Shenandoah County, VA, Warren County, VA, Berkeley County, WV, Jefferson County, WV

The radar

The Sterling radar (KLWX), 93 km from the middle of the area, began a volume at 23:49 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

Phillips Aaf/Abe, MD (KAPG), launched 12:00Z, 11.8 hours before the alert went out and 40 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: 303 J/kg
Mixed-layer CIN: -86 J/kg
Mixed-layer LCL: 937 m above ground
0-6 km bulk shear: 23 kt
0-1 km storm-relative helicity: 103 m²/s²
0-3 km storm-relative helicity: 108 m²/s²
Significant tornado parameter: 0.0
Supercell composite: 1.7

Open this sounding in Storm Lab

The text

As transmitted, in the capitals the NWS used until 2016.

663 
ACUS11 KWNS 182350
SWOMCD
SPC MCD 182349 
NJZ000-PAZ000-DEZ000-MDZ000-DCZ000-VAZ000-WVZ000-190215-

MESOSCALE DISCUSSION 0754
NWS STORM PREDICTION CENTER NORMAN OK
0649 PM CDT TUE MAY 18 2004

AREAS AFFECTED...PORTIONS SERN PA...SRN NJ...DE...NRN MD...NERN
VA...DC

CONCERNING...SEVERE THUNDERSTORM POTENTIAL 

VALID 182349Z - 190215Z

LINE OF TSTMS EXTENDING AT 2330Z FROM MONTGOMERY COUNTY PA SWD TO
HAMPSHIRE COUNTY WV SHOULD MOVE ESEWD ACROSS DISCUSSION AREA THROUGH
ABOUT 3Z.  MAIN THREAT IS GUSTS THAT ARE SUB-SEVERE -- BELOW 50 KT
CRITERIA LEVEL -- BUT STILL CAPABLE OF INTERMITTENT DAMAGE.  WW NOT
EXPECTED.

AVAILABLE INSTABILITY IS NEAR PEAK ATTM.  MODIFIED RUC SOUNDINGS
SUGGEST 1500-2000 J/KG MLCAPE CURRENTLY...WITH APPROXIMATELY 500-700
J/KG DCAPE.  EXPECT DCAPE TO WEAKEN AS SFC COOLING
CONTINUES...HOWEVER LOCALIZED DOWNDRAFTS MAY BRIEFLY PRODUCE
DAMAGING GUSTS.  CAPE ALSO SHOULD DIMINISH GRADUALLY IN INFLOW
LAYER...WITH LOSS OF SFC DIABATIC HEATING.  VERTICAL SHEAR IS WEAK
-- I.E. LESS THAN 20 KT THROUGH 0-6 KM AGL LAYER...WITH GENERALLY
UNIFORM SPEEDS AROUND 20-25 KT THROUGH 300-800 MB LAYER.  WEAK
VERTICAL SHEAR PROFILES SUGGEST LOW POTENTIAL FOR ORGANIZED EVENT.

..EDWARDS.. 05/18/2004

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

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

39187887 40187647 40277558 40047468 39737448 39167476
38827572 38687747 38647858

SPC that day

Everything else SPC issued on the same UTC day.

Issued	Product	Office	Counties	Lasted
May 18, 2:54 PM EDT	Mesoscale Discussion	SPC	New Castle	96 min
May 18, 1:14 PM EDT	Mesoscale Discussion	SPC	Calvert, Charles, Howard, Montgomery, Prince George's, Saint Mary's	2 hr
May 18, 12:54 PM EDT	Mesoscale Discussion	SPC	Allegheny, Armstrong, Beaver, Blair, Butler, Cambria and 22 more	66 min
May 18, 1:04 PM EDT	Mesoscale Discussion	SPC	Bradford, Lackawanna, Luzerne, Sullivan, Susquehanna, Wayne and 1 more	56 min
May 18, 1:45 PM EDT	Severe Thunderstorm Watch	SPC	Allegheny, Armstrong, Beaver, Butler, Clarion, Fayette and 6 more	6 hr
May 18, 1:50 PM EDT	Severe Thunderstorm Watch	SPC	Bradford, Cameron, Elk, Jefferson, McKean, Potter and 2 more	8 hr
May 18, 6:24 PM EDT	Mesoscale Discussion	SPC	Bradford, Cameron, Elk, Jefferson, McKean, Potter and 2 more	2 hr
May 18, 7:09 PM EDT	Mesoscale Discussion	SPC	Allegheny, Armstrong, Beaver, Butler, Fayette, Greene and 3 more	96 min
May 18, 4:02 PM EDT	Mesoscale Discussion	SPC	Brooke, Ohio	118 min

Nearby

Mesoscale Discussions in Virginia, 2004 Mesoscale Discussions in Maryland, 2004 Mesoscale Discussions in New Jersey, 2004 Every mesoscale discussion in 2004

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.