Alert archive / Virginia / Mesoscale Discussions in 2012

Mesoscale Discussion 1441

July 9, 20125 counties in Maryland; 27 counties in Virginia; Jefferson County, West Virginia

The Storm Prediction Center issued this mesoscale discussion at Jul 9, 2012, 12:09 AM EDT for 5 counties in Maryland; 27 counties in Virginia; Jefferson County, West Virginia. It was in force for 96 min.

The area

The outline as issued.

The facts

Issued: Jul 9, 2012, 12:09 AM EDT (04:09 UTC)
Expired: Jul 9, 2012, 1:45 AM EDT
In force: 96 min
Issued by: the Storm Prediction Center
Chance of a watch: 5%

All 33 counties

Calvert County, MD, Charles County, MD, Montgomery County, MD, Prince George's County, MD, Saint Mary's County, MD, Arlington County, VA, Caroline County, VA, City of Alexandria, 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 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, Shenandoah County, VA, Spotsylvania County, VA, Stafford County, VA, Warren County, VA, Westmoreland County, VA, Jefferson County, WV

The radar

The Sterling radar (KLWX), 39 km from the middle of the area, began a volume at 04:11 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 00:00Z, 4.2 hours before the alert went out and 39 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: 0 m above ground
0-6 km bulk shear: 38 kt
0-1 km storm-relative helicity: 1 m²/s²
0-3 km storm-relative helicity: 27 m²/s²
Significant tornado parameter: 0.0
Supercell composite: -0.3

Open this sounding in Storm Lab

The text

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

180 
ACUS11 KWNS 090410
SWOMCD
SPC MCD 090409
VAZ000-MDZ000-DCZ000-WVZ000-090545-

MESOSCALE DISCUSSION 1441
NWS STORM PREDICTION CENTER NORMAN OK
1109 PM CDT SUN JUL 08 2012

AREAS AFFECTED...NRN VA...DC...WRN SHORE OF MD

CONCERNING...SEVERE POTENTIAL...WATCH UNLIKELY

VALID 090409Z - 090545Z

PROBABILITY OF WATCH ISSUANCE...5 PERCENT

SUMMARY...MARGINAL/LOCALIZED SEVERE POTENTIAL WITH SCATTERED TSTMS
THAT ARE NOT EXPECTED TO INTENSIFY SUBSTANTIALLY.

DISCUSSION...WITHIN A FAVORABLE RIGHT ENTRANCE REGION OF A 110 KT
UPPER-LEVEL JET STREAK OVER NEW ENGLAND AND WEAK MID-LEVEL HEIGHT
FALLS ON THE GLANCING INFLUENCE OF AN IMPULSE OVER SRN ONTARIO...A
CLUSTER OF TSTMS HAS FORMED DURING THE PAST COUPLE OF HOURS IN ERN
WV/NRN VA. MODERATE ELEVATED BUOYANCY IN MODIFIED 00Z IAD RAOB
AMIDST AROUND 30 KT EFFECTIVE SHEAR COULD SUPPORT A RISK FOR
MARGINALLY SEVERE HAIL. NEARLY UNIDIRECTIONAL DEEP-LAYER WLY FLOW
MAY YIELD SPLITTING CELLS...BUT OVERALL STORM STRUCTURES WITHIN A
CLUSTER TYPE MODE SHOULD NOT BE PARTICULARLY CONDUCIVE TO SUSTAINING
ROTATING UPDRAFTS.

..GRAMS/CORFIDI.. 07/09/2012

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

ATTN...WFO...AKQ...LWX...

LAT...LON   39167867 39377766 39217694 38917644 38287637 37997654
            37977700 38107800 38297849 38547878 39167867

SPC that day

Everything else SPC issued on the same UTC day.

Issued	Product	Office	Counties	Lasted
Jul 9, 3:19 PM EDT	Severe Thunderstorm Watch	SPC	Talbot	4 hr
Jul 9, 1:36 PM EDT	Mesoscale Discussion	SPC	Albemarle, Amelia, Amherst, Appomattox, Bedford, Botetourt and 44 more	54 min
Jul 9, 2:59 PM EDT	Severe Thunderstorm Watch	SPC	Amelia, Brunswick, Chesterfield, Cumberland, Dinwiddie, Greensville and 21 more	7 hr
Jul 9, 4:48 PM EDT	Mesoscale Discussion	SPC	Appomattox, Brunswick, Charlotte, Dinwiddie, Greensville, Isle of Wight and 10 more	87 min
Jul 9, 5:53 PM EDT	Mesoscale Discussion	SPC	Carroll, Floyd, Franklin, Grayson, Halifax, Henry and 5 more	97 min
Jul 9, 7:17 PM EDT	Mesoscale Discussion	SPC	Brunswick, Greensville, Isle of Wight, Southampton, Surry, Sussex and 4 more	88 min

Nearby

Mesoscale Discussions in Virginia, 2012 Mesoscale Discussions in Maryland, 2012 Mesoscale Discussions in West Virginia, 2012 Every 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.