Alert archive / Pennsylvania / Mesoscale Discussions in 2012
Mesoscale Discussion 694
The Storm Prediction Center issued this mesoscale discussion at May 4, 2012, 1:26 PM EDT for 7 states. It was in force for 2 hr.
The area
The outline as issued.
The facts
- Issued
- May 4, 2012, 1:26 PM EDT (17:26 UTC)
- Expired
- May 4, 2012, 3:30 PM EDT
- In force
- 2 hr
- Issued by
- the Storm Prediction Center
- Chance of a watch
- 40%
All 97 counties
Kent County, DE, New Castle County, DE, Sussex 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, Dorchester County, 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, Talbot County, MD, Washington County, MD, Atlantic County, NJ, Camden County, NJ, Cape May County, NJ, Cumberland County, NJ, Gloucester County, NJ, Salem County, NJ, Trumbull County, OH, Adams County, PA, Armstrong County, PA, Bedford County, PA, Berks County, PA, Blair County, PA, Bucks County, PA, Butler County, PA, Cambria County, PA, Cameron County, PA, Carbon County, PA, Centre County, PA, Chester County, PA, Clarion County, PA, Clearfield County, PA, Clinton County, PA, Columbia County, PA, Crawford County, PA, Cumberland County, PA, Dauphin County, PA, Delaware County, PA, Elk County, PA, Forest County, PA, Franklin County, PA, Fulton County, PA, Huntingdon County, PA, Indiana County, PA, Jefferson County, PA, Juniata County, PA, Lancaster County, PA, Lawrence County, PA, Lebanon County, PA, Lehigh County, PA, Luzerne County, PA, Lycoming County, PA, McKean County, PA, Mercer County, PA, Mifflin County, PA, Montgomery County, PA, Montour County, PA, Northumberland County, PA, Perry County, PA, Philadelphia County, PA, Potter County, PA, Schuylkill County, PA, Snyder County, PA, Somerset County, PA, Sullivan County, PA, Tioga County, PA, Union County, PA, Venango County, PA, Warren 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, Frederick County, VA, Loudoun County, VA, Prince William County, VA, Berkeley County, WV, Jefferson County, WV, Morgan County, WV
The radar
The State College radar (KCCX), 99 km from the middle of the area, began a volume at 17:27 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, 5.4 hours before the alert went out and 149 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
- 891 J/kg
- Mixed-layer CIN
- -164 J/kg
- Mixed-layer LCL
- 905 m above ground
- 0-6 km bulk shear
- 19 kt
- 0-1 km storm-relative helicity
- 46 m²/s²
- 0-3 km storm-relative helicity
- 136 m²/s²
- Significant tornado parameter
- 0.0
- Supercell composite
- 0.0
The text
As transmitted, in the capitals the NWS used until 2016.
504
ACUS11 KWNS 041726
SWOMCD
SPC MCD 041726
NJZ000-PAZ000-DEZ000-MDZ000-DCZ000-VAZ000-WVZ000-NYZ000-OHZ000-041930-
MESOSCALE DISCUSSION 0694
NWS STORM PREDICTION CENTER NORMAN OK
1226 PM CDT FRI MAY 04 2012
AREAS AFFECTED...FAR NE OHIO...MUCH OF PA...SRN NJ INTO DELMARVA
CONCERNING...SEVERE POTENTIAL...WATCH POSSIBLE
VALID 041726Z - 041930Z
PROBABILITY OF WATCH ISSUANCE...40 PERCENT
SUMMARY...SCATTERED THUNDERSTORM ACTIVITY IS EXPECTED TO INCREASE
THROUGH THE AFTERNOON HOURS. MAINLY UNORGANIZED CLUSTERS OR
PULSE-TYPE STORMS WILL BE CAPABLE OF PRODUCING MARGINALLY SEVERE
HAIL AND STRONG-TO-SEVERE WIND GUSTS. AREA WILL BE MONITORED FOR A
POSSIBLE WW.
DISCUSSION...THUNDERSTORMS WERE DEVELOPING EARLY THIS AFTERNOON FROM
THE NRN CHESAPEAKE INTO CNTRL PA AND NERN OH IN A WARM...MOIST AIR
MASS AHEAD OF A SFC COLD FRONT. THIS COLD FRONT WAS POSITIONED FROM
S-CNTRL NY WWD ACROSS NRN OH. FURTHER S ACROSS CNTRL PA INTO ERN
VA...A SFC TROUGH AND WARM FRONT WAS PROVIDING ADDITIONAL FOCUS FOR
THUNDERSTORM DEVELOPMENT. AS TEMPERATURES HAVE WARMED THROUGH THE
UPPER 70S INTO THE LOW 80S...MLCAPE VALUES ARE APPROACHING 1000 J/KG
AND ARE EXPECTED TO INCREASE TO NEAR 1500-2000 J/KG BY LATER THIS
AFTERNOON. THIS WILL HELP OVERCOME MODEST DEEP LAYER SHEAR OF AROUND
20-30 KT TO SUSTAIN UPDRAFTS. MIDLEVEL LAPSE RATES NEAR 7 C/KM AND
COOL TEMPERATURES ALOFT WILL SUPPORT MARGINALLY SEVERE HAIL AND
STRONG/GUSTY WINDS IN MAINLY DISORGANIZED THUNDERSTORM CLUSTERS.
..LEITMAN/MEAD.. 05/04/2012
...PLEASE SEE WWW.SPC.NOAA.GOV FOR GRAPHIC PRODUCT...
ATTN...WFO...PHI...BGM...AKQ...BUF...CTP...LWX...PBZ...CLE...
LAT...LON 39387441 40067476 40487507 41207575 41717670 42047928
41898031 41688114 41378119 40938042 39637876 38287727
38307598 38807508 39347449 39387441SPC that day
Everything else SPC issued on the same UTC day.
| Issued | Product | Office | Counties | Lasted |
|---|---|---|---|---|
| May 4, 4:16 PM EDT | Mesoscale Discussion | SPC | Clermont | 59 min |
| May 4, 7:52 PM EDT | Mesoscale Discussion | SPC | Adams, Allen, Athens, Auglaize, Belmont, Brown and 49 more | 53 min |
| May 4, 12:19 AM EDT | Mesoscale Discussion | SPC | Bradford, Tioga | 86 min |
Nearby
Mesoscale Discussions in Pennsylvania, 2012Mesoscale Discussions in Maryland, 2012Mesoscale Discussions in Virginia, 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.