Alert archive / Virginia / Mesoscale Discussions in 2012
Mesoscale Discussion 1735
The Storm Prediction Center issued this mesoscale discussion at Aug 10, 2012, 3:31 PM EDT for 4 states. It was in force for 89 min.
The area
The outline as issued.
The facts
- Issued
- Aug 10, 2012, 3:31 PM EDT (19:31 UTC)
- Expired
- Aug 10, 2012, 5:00 PM EDT
- In force
- 89 min
- Issued by
- the Storm Prediction Center
- Chance of a watch
- 40%
All 50 counties
Carroll County, MD, Frederick County, MD, Montgomery County, MD, Washington County, MD, Adams County, PA, Cumberland County, PA, Franklin County, PA, Fulton County, PA, Huntingdon County, PA, Juniata County, PA, Mifflin County, PA, Perry County, PA, Albemarle County, VA, Amherst County, VA, Appomattox County, VA, Augusta County, VA, Buckingham County, VA, City of Buena Vista, VA, City of Charlottesville, VA, City of Fairfax, VA, City of Harrisonburg, VA, City of Lexington, VA, City of Manassas, VA, City of Manassas Park, VA, City of Staunton, VA, City of Waynesboro, VA, City of Winchester, VA, Clarke County, VA, Culpeper County, VA, Fairfax County, VA, Fauquier County, VA, Fluvanna County, VA, Frederick County, VA, Greene County, VA, Loudoun County, VA, Madison County, VA, Nelson County, VA, Orange County, VA, Page County, VA, Prince William County, VA, Rappahannock County, VA, Rockbridge County, VA, Rockingham County, VA, Shenandoah County, VA, Stafford County, VA, Warren County, VA, Berkeley County, WV, Hampshire County, WV, Jefferson County, WV, Morgan County, WV
The radar
The Sterling radar (KLWX), 71 km from the middle of the area, began a volume at 19:30 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
Washington/Dulle, VA (KIAD), launched 12:00Z, 7.5 hours before the alert went out and 79 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.
- Mixed-layer CAPE
- 279 J/kg
- Mixed-layer CIN
- -40 J/kg
- Mixed-layer LCL
- 652 m above ground
- 0-6 km bulk shear
- 35 kt
- 0-1 km storm-relative helicity
- 8 m²/s²
- 0-3 km storm-relative helicity
- 105 m²/s²
- Significant tornado parameter
- -0.0
- Supercell composite
- -0.2
The text
As transmitted, in the capitals the NWS used until 2016.
409
ACUS11 KWNS 101932
SWOMCD
SPC MCD 101931
PAZ000-MDZ000-VAZ000-WVZ000-102100-
MESOSCALE DISCUSSION 1735
NWS STORM PREDICTION CENTER NORMAN OK
0231 PM CDT FRI AUG 10 2012
AREAS AFFECTED...PARTS OF WRN/NRN VA...WRN AND CNTRL MD...S CNTRL PA
CONCERNING...SEVERE POTENTIAL...WATCH POSSIBLE
VALID 101931Z - 102100Z
PROBABILITY OF WATCH ISSUANCE...40 PERCENT
SUMMARY...THE NEED FOR A WATCH IS STILL NOT CERTAIN...BUT TRENDS ARE
BEING MONITORED FOR THE POSSIBILITY OF AN INCREASING SEVERE THREAT
THAT COULD REQUIRE A WW WITHIN THE NEXT 1 TO 2 HOURS.
DISCUSSION...MID/UPPER FORCING FOR UPWARD VERTICAL MOTION TO SUPPORT
CONVECTIVE DEVELOPMENT REMAINS A BIT UNCLEAR...BUT UPPER FLOW ACROSS
AND TO THE LEE OF THE ALLEGHENY MOUNTAINS IS DIFLUENT...TO THE EAST
OF THE QUASI-STATIONARY GREAT LAKES CYCLONE. AND LOW-LEVEL LAPSE
RATES ARE BECOMING FAIRLY STEEP WITHIN AT LEAST A NARROW CORRIDOR OF
STRONGER HEATING TO THE LEE OF THE HIGHER TERRAIN. GIVEN THE
CONTINUING PRESENCE OF SURFACE DEW POINTS IN THE UPPER 60S TO NEAR
70F ACROSS THIS REGION...BOUNDARY LAYER CAPE COULD BECOME MODERATELY
LARGE WITH AT LEAST WEAK MID-LEVEL COOLING...WHICH APPEARS
POSSIBLE...BUT IS NOT CERTAIN LATE THIS AFTERNOON. GIVEN THE CLOSE
PROXIMITY OF THE 40-50 KT CYCLONIC 500 MB JET STREAK NOSING
NORTHEASTWARD ACROSS THE UPPER OHIO VALLEY...SCATTERED STRONG/SEVERE
STORM DEVELOPMENT DOES NOT APPEAR OUT OF THE QUESTION BETWEEN NOW
AND 22-23Z. ALTHOUGH LOW-LEVEL FLOW AND SHEAR LIKELY WILL REMAIN
FAIRLY WEAK...ORGANIZED CONVECTIVE DEVELOPMENT...INCLUDING ISOLATED
SUPERCELLS...MAY PROVIDE A RISK FOR SEVERE WIND GUSTS AND HAIL.
..KERR/CORFIDI.. 08/10/2012
...PLEASE SEE WWW.SPC.NOAA.GOV FOR GRAPHIC PRODUCT...
ATTN...WFO...AKQ...CTP...LWX...RNK...
LAT...LON 37787951 38627892 39317876 39797849 40817801 40987763
40607681 39547699 38467735 37217894 37787951SPC that day
Everything else SPC issued on the same UTC day.
| Issued | Product | Office | Counties | Lasted |
|---|---|---|---|---|
| Aug 10, 8:21 AM EDT | Mesoscale Discussion | SPC | Caroline, Cecil, Dorchester, Kent, Queen Anne's, Somerset and 3 more | 2 hr |
| Aug 10, 7:31 PM EDT | Mesoscale Discussion | SPC | Anne Arundel, Baltimore, Calvert, Caroline, Carroll, Cecil and 12 more | 119 min |
| Aug 10, 12:49 PM EDT | Mesoscale Discussion | SPC | Allegheny, Armstrong, Beaver, Butler, Cameron, Clarion and 16 more | 86 min |
| Aug 10, 12:20 PM EDT | Mesoscale Discussion | SPC | Buchanan, Dickenson, Lee, Russell, Scott, Tazewell and 4 more | 85 min |
Nearby
Mesoscale Discussions in Virginia, 2012Mesoscale Discussions in Pennsylvania, 2012Mesoscale Discussions in Maryland, 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.