Alert archive / Pennsylvania / Mesoscale Discussions in 2011

Mesoscale Discussion 2178

September 14, 20114 states

The Storm Prediction Center issued this mesoscale discussion at Sep 14, 2011, 3:22 PM EDT for 4 states. It was in force for 53 min.

The area

The outline as issued.

The facts

Issued: Sep 14, 2011, 3:22 PM EDT (19:22 UTC)
Expired: Sep 14, 2011, 4:15 PM EDT
In force: 53 min
Issued by: the Storm Prediction Center

All 45 counties

Allegany County, MD, Baltimore County, MD, Carroll County, MD, Frederick County, MD, Garrett County, MD, Harford County, MD, Howard County, MD, Montgomery County, MD, Washington County, MD, Adams County, PA, Bedford County, PA, Berks County, PA, Carbon County, PA, Chester County, PA, Cumberland County, PA, Dauphin County, PA, Franklin County, PA, Fulton County, PA, Juniata County, PA, Lancaster County, PA, Lebanon County, PA, Lehigh County, PA, Perry County, PA, Schuylkill County, PA, Somerset County, PA, York County, PA, City of Winchester, VA, Clarke County, VA, Frederick County, VA, Loudoun County, VA, Shenandoah County, VA, Warren County, VA, Barbour County, WV, Berkeley County, WV, Grant County, WV, Hampshire County, WV, Hardy County, WV, Jefferson County, WV, Mineral County, WV, Morgan County, WV, Preston County, WV, Randolph County, WV, Taylor County, WV, Tucker County, WV, Upshur County, WV

The radar

The Sterling radar (KLWX), 75 km from the middle of the area, began a volume at 19:24 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, 7.4 hours before the alert went out and 80 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: 408 J/kg
Mixed-layer CIN: -181 J/kg
Mixed-layer LCL: 1416 m above ground
0-6 km bulk shear: 14 kt
0-1 km storm-relative helicity: 73 m²/s²
0-3 km storm-relative helicity: 118 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.

656 
ACUS11 KWNS 141922
SWOMCD
SPC MCD 141922 
PAZ000-MDZ000-VAZ000-WVZ000-142015-

MESOSCALE DISCUSSION 2178
NWS STORM PREDICTION CENTER NORMAN OK
0222 PM CDT WED SEP 14 2011

AREAS AFFECTED...ERN WV / MD / SERN PA

CONCERNING...SEVERE POTENTIAL...WATCH UNLIKELY 

VALID 141922Z - 142015Z

STORMS WILL CONTINUE TO DEVELOP AND ONGOING STORMS OVER WV WILL
PROBABLY INTENSIFY FURTHER THIS AFTERNOON.  THE MAIN THREAT WITH
THESE STORMS WILL BE ISOLD WIND DAMAGE.  A SEVERE WW WILL LIKELY NOT
BE NEEDED.

SATELLITE IMAGERY SHOWS A BUILDING CU FIELD OVER THE CNTRL
APPALACHIANS AHEAD OF AN UPSTREAM SHORTWAVE TROUGH DIGGING INTO THE
WRN GREAT LAKES STATES AS IT MOVES TOWARDS THE REGION.  NEUTRAL TO
WEAK HEIGHT RISES ALOFT HAVE PRECLUDED SUBSTANTIAL TSTM COVERAGE SO
FAR.  HOWEVER...STRONG DIABATIC HEATING WITHIN AN APPRECIABLY MOIST
BOUNDARY LAYER IS CONTRIBUTING TO 2000-3000 J/KG SBCAPE.  ALTHOUGH
THE REGION REMAINS ON THE SERN FRINGE OF STRONGER UPPER LEVEL
FLOW...INCREASING WLY 3 KM FLOW ALREADY EVIDENT AT KBGM AND KPBZ
VAD/S /40 KTS/ WILL OVERSPREAD THE NRN PORTION OF THE DISCUSSION
AREA LATER TODAY.  COMBINED WITH STEEP LOW LEVEL LAPSE RATES...THE
NET RESULT MAY BE AN ISOLD WIND DAMAGE RISK WITH THE STRONGER
STORMS...ESPECIALLY IF STORMS CAN CONGEAL INTO ONE OR MORE SMALL
CLUSTERS.  NONETHELESS...THE ABSENCE OF STRONGER FORCING FOR ASCENT
NOT DUE UNTIL LATER THIS EVENING SHOULD ACT TO LIMIT STORM
COVERAGE/INTENSITY--THUS NOT WARRANTING A WW.

..SMITH.. 09/14/2011

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

ATTN...WFO...PHI...BGM...CTP...LWX...PBZ...RLX...

LAT...LON   38727964 38868038 39757990 40887633 40947567 40517543
            40017551 38857732 38667855 38727964

Nearby

Mesoscale Discussions in Pennsylvania, 2011 Mesoscale Discussions in West Virginia, 2011 Mesoscale Discussions in Maryland, 2011 Every mesoscale discussion in 2011

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.