Alert archive / Pennsylvania / Mesoscale Discussions in 2011

Mesoscale Discussion 899

May 23, 20114 states

The Storm Prediction Center issued this mesoscale discussion at May 23, 2011, 4:40 PM EDT for 4 states. It was in force for 95 min.

The area

The outline as issued.

The facts

Issued
May 23, 2011, 4:40 PM EDT (20:40 UTC)
Expired
May 23, 2011, 6:15 PM EDT
In force
95 min
Issued by
the Storm Prediction Center
All 59 counties

Anne Arundel County, MD, Baltimore County, MD, Calvert 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, Washington County, MD, Adams County, PA, Berks County, PA, Bradford County, PA, Carbon County, PA, Chester County, PA, Columbia County, PA, Cumberland County, PA, Dauphin County, PA, Franklin County, PA, Juniata County, PA, Lackawanna County, PA, Lancaster County, PA, Lebanon County, PA, Lehigh County, PA, Luzerne County, PA, Lycoming County, PA, Mifflin County, PA, Montour County, PA, Northumberland County, PA, Perry County, PA, Schuylkill County, PA, Snyder County, PA, Sullivan County, PA, Susquehanna County, PA, Tioga County, PA, Union County, PA, Wyoming 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, Clarke County, VA, Culpeper County, VA, Fairfax County, VA, Fauquier County, VA, Loudoun County, VA, Prince William County, VA, Rappahannock County, VA, Stafford County, VA, Berkeley County, WV, Jefferson County, WV

The radar

The State College radar (KCCX), 118 km from the middle of the area, began a volume at 20:40 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

Phillips Aaf/Abe, MD (KAPG), launched 12:00Z, 8.7 hours before the alert went out and 114 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, Phillips Aaf/Abe, MD at 12:00Z on 2011-05-23Temperature and dew point through the depth of the atmosphere, with the mixed-layer parcel. CAPE 0 joules per kilogram.LCL10008507005003002001001 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, Phillips Aaf/Abe, MD at 12:00Z on 2011-05-23The wind through the lowest 10 kilometers. Zero to 1 km storm-relative helicity -35 square meters per square second.193958Sfc1 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
0 J/kg
Mixed-layer CIN
No buoyant parcel
Mixed-layer LCL
530 m above ground
0-6 km bulk shear
31 kt
0-1 km storm-relative helicity
-35 m²/s²
0-3 km storm-relative helicity
11 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.

542 
ACUS11 KWNS 232040
SWOMCD
SPC MCD 232040 
PAZ000-NYZ000-DEZ000-MDZ000-DCZ000-VAZ000-WVZ000-232215-

MESOSCALE DISCUSSION 0899
NWS STORM PREDICTION CENTER NORMAN OK
0340 PM CDT MON MAY 23 2011

AREAS AFFECTED...CNTRL/ERN PA/MD...NRN VA

CONCERNING...SEVERE THUNDERSTORM WATCH 338...

VALID 232040Z - 232215Z

THE SEVERE WEATHER THREAT FOR SEVERE THUNDERSTORM WATCH 338
CONTINUES.

WW 338 IS SCHEDULED TO EXPIRE AT 22Z. GIVEN THE LIKELIHOOD OF AN
ISOLATED SEVERE THREAT PERSISTING BEYOND THIS TIME FRAME...A
REPLACEMENT WW WILL BE COORDINATED BETWEEN 21-22Z ALONG AND E OF
ONGOING BROKEN LINE OF TSTMS FROM CNTRL PA INTO NRN VA.

AS OF 2030Z...A BROKEN LINE OF TSTMS WAS LOCATED ALONG A CONFLUENCE
AXIS FROM CLINTON COUNTY PA TO MADISON COUNTY VA. DESPITE SOME
RECENT WEAKENING NOTED IN RADAR REFLECTIVITY ON THE SRN EXTENT OF
TSTM CELLS IN NRN VA...ENVIRONMENT ALONG AND EAST OF THE CONFLUENCE
AXIS REMAINS WEAKLY UNSTABLE ACROSS PA TO MODERATELY UNSTABLE SWD
INTO NRN VA. EFFECTIVE SHEAR AROUND 40 KT WILL SUPPORT ORGANIZED
UPDRAFTS PRIMARILY PRODUCING DAMAGING WINDS AND SEVERE HAIL.

..GRAMS.. 05/23/2011

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

ATTN...WFO...PHI...BGM...CTP...LWX...

LAT...LON   41127764 41787735 42117708 42127616 41977563 41037538
            39777558 39117596 38537644 38347784 38467830 38597827
            41127764

SPC that day

Everything else SPC issued on the same UTC day.

IssuedProductOfficeCountiesLasted
May 23, 10:33 AM EDTMesoscale DiscussionSPCAllegany, Baltimore, Carroll, Frederick, Garrett, Howard and 4 more87 min
May 23, 10:48 AM EDTSevere Thunderstorm WatchSPCAllegany, Anne Arundel, Baltimore, Calvert, Carroll, Charles and 8 more9 hr
May 23, 2:33 PM EDTMesoscale DiscussionSPCAllegany, Carroll, Charles, Frederick, Howard, Montgomery and 1 more87 min
May 23, 8:25 AM EDTMesoscale DiscussionSPCCrawford, Erie65 min
May 22, 9:02 PM EDTMesoscale DiscussionSPCCarroll, Craig, Floyd, Giles, Montgomery, Patrick and 5 more58 min
May 23, 3:16 PM EDTSevere Thunderstorm WatchSPCAlleghany, Amelia, Amherst, Appomattox, Bath, Bedford and 78 more7 hr
May 23, 7:02 PM EDTMesoscale DiscussionSPCAmelia, Appomattox, Brunswick, Buckingham, Campbell, Charles City and 40 more58 min
May 23, 7:20 PM EDTMesoscale DiscussionSPCBoone, Brooke, Cabell, Calhoun, Doddridge, Jackson and 16 more85 min

Nearby

Mesoscale Discussions in Pennsylvania, 2011Mesoscale Discussions in Maryland, 2011Mesoscale Discussions in Virginia, 2011Every 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.