Alert archive / Pennsylvania / Mesoscale Discussions in 2012

Mesoscale Discussion 1027

June 3, 20127 states

The Storm Prediction Center issued this mesoscale discussion at Jun 3, 2012, 1:37 PM EDT for 7 states. It was in force for 2 hr.

The area

The outline as issued.

The facts

Issued: Jun 3, 2012, 1:37 PM EDT (17:37 UTC)
Expired: Jun 3, 2012, 4:00 PM EDT
In force: 2 hr
Issued by: the Storm Prediction Center
Chance of a watch: 5%

All 106 counties

Kent County, DE, New Castle County, DE, Allegany County, MD, 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, Garrett County, MD, Harford County, MD, Howard County, MD, Kent County, MD, Montgomery County, MD, Prince George's County, MD, Queen Anne's County, MD, Talbot County, MD, Washington County, MD, Atlantic County, NJ, Bergen County, NJ, Burlington County, NJ, Camden County, NJ, Cape May County, NJ, Cumberland County, NJ, Essex County, NJ, Gloucester County, NJ, Hudson County, NJ, Hunterdon County, NJ, Mercer County, NJ, Middlesex County, NJ, Monmouth County, NJ, Morris County, NJ, Ocean County, NJ, Passaic County, NJ, Salem County, NJ, Somerset County, NJ, Sussex County, NJ, Union County, NJ, Warren County, NJ, Bronx County, NY, Kings County, NY, New York County, NY, Orange County, NY, Queens County, NY, Richmond County, NY, Rockland County, NY, Adams County, PA, Bedford County, PA, Berks County, PA, Blair County, PA, Bucks County, PA, Cambria County, PA, Carbon County, PA, Chester County, PA, Cumberland County, PA, Dauphin County, PA, Delaware County, PA, Fayette County, PA, Franklin County, PA, Fulton County, PA, Huntingdon County, PA, Juniata County, PA, Lancaster County, PA, Lebanon County, PA, Lehigh County, PA, Monroe County, PA, Montgomery County, PA, Northampton County, PA, Perry County, PA, Philadelphia County, PA, Pike County, PA, Schuylkill County, PA, Somerset County, PA, Westmoreland 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, Page County, VA, Prince William County, VA, Rappahannock County, VA, Shenandoah County, VA, Warren County, VA, Berkeley County, WV, Grant County, WV, Hampshire County, WV, Hardy County, WV, Jefferson County, WV, Marion County, WV, Mineral County, WV, Monongalia County, WV, Morgan County, WV, Preston County, WV, Tucker County, WV

The radar

The Sterling radar (KLWX), 117 km from the middle of the area, began a volume at 17:40 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, 5.6 hours before the alert went out and 119 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: 1755 m above ground
0-6 km bulk shear: 35 kt
0-1 km storm-relative helicity: 101 m²/s²
0-3 km storm-relative helicity: 123 m²/s²
Significant tornado parameter: 0.0
Supercell composite: 0.0

Open this sounding in Storm Lab

The text

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

082 
ACUS11 KWNS 031738
SWOMCD
SPC MCD 031737
NYZ000-NJZ000-PAZ000-DEZ000-MDZ000-DCZ000-VAZ000-WVZ000-032000-

MESOSCALE DISCUSSION 1027
NWS STORM PREDICTION CENTER NORMAN OK
1237 PM CDT SUN JUN 03 2012

AREAS AFFECTED...CNTRL/SRN/ERN PA...NERN WV...NRN VA...MUCH OF
MD/DE...THE DISTRICT OF COLUMBIA...NJ...SERN NY

CONCERNING...SEVERE POTENTIAL...WATCH UNLIKELY

VALID 031737Z - 032000Z

PROBABILITY OF WATCH ISSUANCE...5 PERCENT

SUMMARY...STORMS MAY CONTAIN GUSTY WINDS AND SMALL HAIL THIS
AFTERNOON...AND A MARGINALLY SVR STORM WILL ALSO BE POSSIBLE. THE
ISSUANCE OF A WW IS UNLIKELY.

DISCUSSION...A LOW-LEVEL BAROCLINIC ZONE ACCOMPANYING A DIFFERENTIAL
HEATING BOUNDARY ARCS FROM CNTRL/SRN PA INTO SERN NY OVER THE SRN
FRINGES OF THE EXPANSIVE MULTI-LAYERED CLOUD DECK SURROUNDING BROAD
CYCLONIC FLOW ACROSS THE NERN STATES. THIS ZONE WILL BE THE FOCUS
FOR CONVECTIVE INITIATION THROUGH THE AFTERNOON...AS LOW-LEVEL LAPSE
RATES CONTINUE TO STEEPEN ON THE WARM SIDE OF THE BOUNDARY -- I.E.
0-3-KM AGL LAPSE RATES ALREADY REACHING 8-9 C/KM OWING TO STRONG
INSOLATION. CONVECTION MAY ALSO DEVELOP IN RESPONSE TO OROGRAPHIC
ASCENT INVOF HIGHER TERRAIN. STORMS WILL BE STEERED ESEWD GIVEN
30-35 KT OF MID-LEVEL WNWLY FLOW OVER THE SWRN PERIPHERY OF THE
BROAD CYCLONIC ENVELOPE. THE STEEP LAPSE RATES COMBINED WITH SFC
DEWPOINTS IN THE UPPER 40S TO THE LOWER 50S WILL YIELD SBCAPE VALUES
NEARING 1000 J/KG IN SOME AREAS...WHICH MAY SUPPORT A FEW VIGOROUS
UPDRAFTS CAPABLE OF PRODUCING SMALL HAIL AND GUSTY WINDS. GIVEN THE
STRENGTH OF THE MID-LEVEL FLOW SUPPORTING MODEST DEEP SHEAR...AND
COLD MID-LEVEL TEMPERATURES -- I.E. AROUND -20C AT 500 MB PER 12Z
RAOBS -- THE STRONGEST STORMS MAY PRODUCE COPIOUS AMOUNTS OF SMALL
HAIL AND POSSIBLY AN ISOLATED INSTANCE OF MARGINALLY SVR HAIL. ONE
OR TWO LINE SEGMENTS MAY CONTAIN MARGINALLY SVR WIND GUSTS.
HOWEVER...STORM STRENGTH WILL GREATLY BE MITIGATED BY THE ABSENCE OF
RICHER LOW-LEVEL MOISTURE / STRONGER BUOYANCY. STORMS WILL DECREASE
IN NUMBER/INTENSITY THIS EVENING AS NOCTURNAL STABILIZATION
COMMENCES.

..COHEN/CARBIN.. 06/03/2012

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

ATTN...WFO...OKX...ALY...PHI...BGM...AKQ...CTP...LWX...PBZ...
RLX...

LAT...LON   40627985 40577663 41987395 40707374 39007474 38357689
            38687907 39568035 40627985

Nearby

Mesoscale Discussions in Pennsylvania, 2012 Mesoscale Discussions in New Jersey, 2012 Mesoscale Discussions in Maryland, 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.