Alert archive / Virginia / Mesoscale Discussions in 2012

Mesoscale Discussion 1739

August 10, 20127 states

The Storm Prediction Center issued this mesoscale discussion at Aug 10, 2012, 7:31 PM EDT for 7 states. It was in force for 119 min.

The area

The outline as issued.

The facts

Issued
Aug 10, 2012, 7:31 PM EDT (23:31 UTC)
Expired
Aug 10, 2012, 9:30 PM EDT
In force
119 min
Issued by
the Storm Prediction Center
Chance of a watch
20%
All 109 counties

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, Saint Mary's County, MD, Talbot County, MD, Washington County, MD, Caswell County, NC, Rockingham County, NC, Stokes County, NC, Surry County, NC, Gloucester County, NJ, Salem County, NJ, Adams County, PA, Berks County, PA, Chester County, PA, Cumberland County, PA, Delaware County, PA, Lancaster County, PA, Montgomery County, PA, York County, PA, Albemarle County, VA, Amelia County, VA, Amherst County, VA, Appomattox County, VA, Arlington County, VA, Augusta County, VA, Bedford County, VA, Botetourt County, VA, Buckingham County, VA, Campbell County, VA, Caroline County, VA, Carroll County, VA, Charlotte County, VA, Chesterfield County, VA, City of Alexandria, VA, City of Buena Vista, VA, City of Charlottesville, VA, City of Danville, VA, City of Fairfax, VA, City of Falls Church, VA, City of Fredericksburg, VA, City of Galax, VA, City of Harrisonburg, VA, City of Lexington, VA, City of Lynchburg, VA, City of Manassas, VA, City of Manassas Park, VA, City of Martinsville, VA, City of Radford, VA, City of Richmond, VA, City of Roanoke, VA, City of Salem, VA, City of Staunton, VA, City of Waynesboro, VA, City of Winchester, VA, Clarke County, VA, Culpeper County, VA, Cumberland County, VA, Essex County, VA, Fairfax County, VA, Fauquier County, VA, Floyd County, VA, Fluvanna County, VA, Franklin County, VA, Goochland County, VA, Greene County, VA, Halifax County, VA, Hanover County, VA, Henry County, VA, King George County, VA, King William County, VA, Loudoun County, VA, Louisa County, VA, Lunenburg County, VA, Madison County, VA, Montgomery County, VA, Nelson County, VA, Nottoway County, VA, Orange County, VA, Page County, VA, Patrick County, VA, Pittsylvania County, VA, Powhatan County, VA, Prince Edward County, VA, Prince William County, VA, Rappahannock County, VA, Roanoke County, VA, Rockbridge County, VA, Rockingham County, VA, Shenandoah County, VA, Spotsylvania County, VA, Stafford County, VA, Warren County, VA, Westmoreland County, VA, Berkeley County, WV, Jefferson County, WV

The radar

The Sterling radar (KLWX), 136 km from the middle of the area, began a volume at 23:33 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

Roanoke, VA (KRNK), launched 12:00Z, 11.5 hours before the alert went out and 134 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-pSkew-T log-p diagram, Roanoke, VA at 12:00Z on 2012-08-10Temperature and dew point through the depth of the atmosphere, with the mixed-layer parcel. CAPE 3 joules per kilogram.LCLLFCEL10008507005003002001001 km2 km3 km6 km9 km12 km15 km-30°-20°-10°0°10°20°30°40°
Temperature in red, dew point in green, the mixed-layer parcel dashed.
HodographHodograph, Roanoke, VA at 12:00Z on 2012-08-10The wind through the lowest 10 kilometers. Zero to 1 km storm-relative helicity 99 square meters per square second.19395878Sfc1 km3 km6 km9 kmRMLM
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
3 J/kg
Mixed-layer CIN
-68 J/kg
Mixed-layer LCL
617 m above ground
0-6 km bulk shear
32 kt
0-1 km storm-relative helicity
99 m²/s²
0-3 km storm-relative helicity
100 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.

549 
ACUS11 KWNS 102332
SWOMCD
SPC MCD 102331
PAZ000-NJZ000-DEZ000-MDZ000-VAZ000-DCZ000-WVZ000-NCZ000-110130-

MESOSCALE DISCUSSION 1739
NWS STORM PREDICTION CENTER NORMAN OK
0631 PM CDT FRI AUG 10 2012

AREAS AFFECTED...W CNTRL VA INTO MD AND SERN PA

CONCERNING...SEVERE POTENTIAL...WATCH UNLIKELY

VALID 102331Z - 110130Z

PROBABILITY OF WATCH ISSUANCE...20 PERCENT

SUMMARY...A FEW STORMS MAY PERSIST INTO THE EVENING...WITH LOCALLY
GUSTY WINDS POSSIBLE. A WW IS NOT EXPECTED.

DISCUSSION...A FEW WIDELY SPACED STORMS WERE ONGOING FROM SWRN VA
INTO W CNTRL VA AND SERN PA...IN A ZONE OF MOIST SWLY FLOW AND NEAR
A WEAK LOW PRESSURE TROUGH ALONG THE MOUNTAINS. HEATING WAS MINIMAL
EARLIER TODAY...AND WITH DEWPOINTS INTO THE 68-72 F RANGE IN
PLACE...THE AIR MASS SHOULD BE SLOW TO COOL. THUS...CIN SHOULD BE
NEGLIGIBLE FOR THE NEXT SEVERAL HOURS WITH A CONTINUED THREAT OF
ISOLATED STORMS. LOW TO MIDLEVEL FLOW/SHEAR IS MARGINAL AND
HODOGRAPHS ARE STRAIGHT...WHICH IS RESULTING IN LAX STORM STRUCTURE.
BUT A FEW CELLS MAY PERSIST OVER A SEVERAL COUNTY SWATH WITH
PRECIPITATION LOADING BEING THE DRIVING FACTOR FOR WIND GUSTS.
WIDESPREAD SEVERE WEATHER IS UNLIKELY...BUT AN ISOLATED SEVERE WIND
GUST MAY OCCUR THIS EVENING.

..JEWELL/CORFIDI.. 08/10/2012

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

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

LAT...LON   36267975 36138027 36388099 36858097 37657986 39027843
            40197737 40457592 40257520 39537510 38257646 37187768
            36687843 36267975

SPC that day

Everything else SPC issued on the same UTC day.

IssuedProductOfficeCountiesLasted
Aug 10, 8:21 AM EDTMesoscale DiscussionSPCKent, New Castle, Sussex2 hr
Aug 10, 3:31 PM EDTMesoscale DiscussionSPCCarroll, Frederick, Montgomery, Washington89 min
Aug 10, 12:49 PM EDTMesoscale DiscussionSPCAllegheny, Armstrong, Beaver, Butler, Cameron, Clarion and 16 more86 min
Aug 10, 12:20 PM EDTMesoscale DiscussionSPCBuchanan, Dickenson, Lee, Russell, Scott, Tazewell and 4 more85 min

Nearby

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