Alert archive / Pennsylvania / Mesoscale Discussions in 2012
Mesoscale Discussion 1928
The Storm Prediction Center issued this mesoscale discussion at Sep 8, 2012, 11:38 AM EDT for 5 states. It was in force for 97 min.
The area
The outline as issued.
The facts
- Issued
- Sep 8, 2012, 11:38 AM EDT (15:38 UTC)
- Expired
- Sep 8, 2012, 1:15 PM EDT
- In force
- 97 min
- Issued by
- the Storm Prediction Center
All 94 counties
Allegany County, MD, Baltimore County, MD, Carroll County, MD, City of Baltimore, MD, Frederick County, MD, Howard County, MD, Montgomery County, MD, Washington County, MD, Albany County, NY, Broome County, NY, Chemung County, NY, Chenango County, NY, Cortland County, NY, Delaware County, NY, Fulton County, NY, Greene County, NY, Hamilton County, NY, Herkimer County, NY, Lewis County, NY, Madison County, NY, Montgomery County, NY, Oneida County, NY, Onondaga County, NY, Oswego County, NY, Otsego County, NY, Saratoga County, NY, Schenectady County, NY, Schoharie County, NY, Sullivan County, NY, Tioga County, NY, Tompkins County, NY, Warren County, NY, Adams County, PA, Bedford County, PA, Berks County, PA, Bradford County, PA, Carbon County, PA, Centre County, PA, Clinton County, PA, Columbia County, PA, Cumberland County, PA, Dauphin County, PA, Franklin County, PA, Fulton County, PA, Huntingdon 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, Monroe County, PA, Montour County, PA, Northumberland County, PA, Perry County, PA, Pike County, PA, Schuylkill County, PA, Snyder County, PA, Sullivan County, PA, Susquehanna County, PA, Tioga County, PA, Union County, PA, Wayne 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 Harrisonburg, 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, Loudoun County, VA, Madison County, VA, Page County, VA, Prince William County, VA, Rappahannock County, VA, Rockingham County, VA, Shenandoah County, VA, Warren County, VA, Berkeley County, WV, Hampshire County, WV, Hardy County, WV, Jefferson County, WV, Morgan County, WV
The radar
The Binghamton radar (KBGM), 74 km from the middle of the area, began a volume at 15:40 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 watches that followed
Watches SPC issued over any of the same counties within four hours of this discussion.
The nearest sounding before it
Albany, NY (KALY), launched 12:00Z, 3.6 hours before the alert went out and 240 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
- 113 J/kg
- Mixed-layer CIN
- -168 J/kg
- Mixed-layer LCL
- 869 m above ground
- 0-6 km bulk shear
- 43 kt
- 0-1 km storm-relative helicity
- 294 m²/s²
- 0-3 km storm-relative helicity
- 397 m²/s²
- Significant tornado parameter
- 0.0
- Supercell composite
- 0.8
The text
As transmitted, in the capitals the NWS used until 2016.
477
ACUS11 KWNS 081538
SWOMCD
SPC MCD 081538
NYZ000-PAZ000-MDZ000-DCZ000-VAZ000-WVZ000-081715-
MESOSCALE DISCUSSION 1928
NWS STORM PREDICTION CENTER NORMAN OK
1038 AM CDT SAT SEP 08 2012
AREAS AFFECTED...PARTS OF THE NRN/CNTRL APPALACHIANS
CONCERNING...SEVERE THUNDERSTORM WATCH 634...
VALID 081538Z - 081715Z
THE SEVERE WEATHER THREAT FOR SEVERE THUNDERSTORM WATCH 634
CONTINUES.
SUMMARY...DAMAGING WIND THREAT SHOULD PERSIST WITHIN WW 634 ALONG A
THIN FRONTAL SQUALL LINE CURRENTLY IN SWRN NY. ALONG WITH THE SRN
EXTENT OF THE LINE IN WRN PA AND WV...THIS QLCS SHOULD INTENSIFY
RAPIDLY AS IT REACHES THE INSTABILITY AXIS FROM NRN VA TO CNTRL NY
IN THE EARLY AFTERNOON...WITH A SUBSTANTIAL INCREASE IN THE DAMAGING
WIND THREAT EXPECTED. A DOWNSTREAM TORNADO WATCH IS ANTICIPATED FOR
WFO BTV/ALY/BGM AND A SEVERE THUNDERSTORM WATCH IS EXPECTED FOR
CTP/LWX/PHI.
DISCUSSION...A NARROW BUT LONG BAND OF ENHANCED REFLECTIVITY WITHOUT
CG DETECTED LIGHTNING EXTENDED FROM SWRN NY TO ERN KY AS OF
1530Z...ALONG THE SURFACE COLD FRONT. AN 80-100 MILE GAP REMAINS
BETWEEN THIS AND THE LEADING EDGE OF MORE ROBUST SURFACE HEATING
WHERE 15Z TEMPERATURES HAD RISEN THROUGH THE 70S AND LOWER 80S. AS
THE FRONT MERGES WITH THIS INSTABILITY AXIS...A SUBSTANTIAL INCREASE
IN CONVECTIVE INTENSITY IS ANTICIPATED. LOW/DEEP-LAYER SHEAR WILL BE
STRONGEST WITH NRN EXTENT...WHILE STRONGER HEATING WITH SRN EXTENT
SHOULD PROMOTE RELATIVELY GREATER BUOYANCY. THIS SETUP APPEARS TO BE
SUPPORTIVE FOR THE ADVERTISED POTENTIAL OF SCATTERED TO NUMEROUS
DAMAGING WIND EVENTS. A FEW EMBEDDED QLCS TORNADOES ALSO APPEAR
PROBABLE ACROSS CNTRL/ERN NY.
..GRAMS.. 09/08/2012
...PLEASE SEE WWW.SPC.NOAA.GOV FOR GRAPHIC PRODUCT...
ATTN...WFO...BTV...ALY...PHI...BGM...BUF...CTP...LWX...
LAT...LON 44207583 44357519 44107392 43587349 42307406 39397642
38317767 38227840 38497933 39837876 42027707 44207583SPC that day
Everything else SPC issued on the same UTC day.
| Issued | Product | Office | Counties | Lasted |
|---|---|---|---|---|
| Sep 8, 5:00 AM EDT | Mesoscale Discussion | SPC | Allegany, Garrett | 60 min |
| Sep 8, 12:15 PM EDT | Severe Thunderstorm Watch | SPC | Allegany, Anne Arundel, Baltimore, Calvert, Caroline, Carroll and 13 more | 9 hr |
| Sep 8, 1:48 PM EDT | Severe Thunderstorm Watch | SPC | Dorchester, Somerset, Wicomico, Worcester | 7 hr |
| Sep 8, 2:12 PM EDT | Mesoscale Discussion | SPC | Anne Arundel, Baltimore, Calvert, Caroline, Carroll, Cecil and 9 more | 93 min |
| Sep 8, 3:25 PM EDT | Mesoscale Discussion | SPC | Saint Mary's, Somerset | 65 min |
| Sep 8, 4:22 PM EDT | Mesoscale Discussion | SPC | Anne Arundel, Calvert, Caroline, Cecil, Charles, Dorchester and 6 more | 53 min |
| Sep 8, 12:57 AM EDT | Mesoscale Discussion | SPC | Chautauqua | 2 hr |
| Sep 8, 8:42 AM EDT | Mesoscale Discussion | SPC | Broome, Cayuga, Chemung, Chenango, Cortland, Herkimer and 13 more | 93 min |
| Sep 8, 10:03 AM EDT | Severe Thunderstorm Watch | SPC | Allegany, Cattaraugus, Cayuga, Chemung, Franklin, Genesee and 16 more | 5 hr |
| Sep 8, 10:39 AM EDT | Mesoscale Discussion | SPC | Albany, Bronx, Columbia, Dutchess, Greene, Kings and 14 more | 2 hr |
| Sep 8, 11:18 AM EDT | Tornado Watch | SPC | Bronx, Dutchess, Kings, Nassau, New York, Orange and 6 more | 10 hr |
| Sep 8, 12:40 PM EDT | Tornado Watch | SPC | Albany, Broome, Chenango, Clinton, Columbia, Cortland and 22 more | 7 hr |
| Sep 8, 1:30 PM EDT | Mesoscale Discussion | SPC | Bronx, Dutchess, Kings, Nassau, New York, Putnam and 3 more | 60 min |
| Sep 8, 2:46 PM EDT | Mesoscale Discussion | SPC | Albany, Clinton, Columbia, Delaware, Dutchess, Essex and 14 more | 59 min |
| Sep 8, 3:55 PM EDT | Mesoscale Discussion | SPC | Columbia, Rensselaer, Washington | 65 min |
| Sep 8, 6:17 PM EDT | Mesoscale Discussion | SPC | Suffolk | 58 min |
| Sep 8, 12:20 PM EDT | Mesoscale Discussion | SPC | Amherst, Appomattox, Bedford, Botetourt, Buckingham, Campbell and 22 more | 115 min |
| Sep 8, 7:10 PM EDT | Mesoscale Discussion | SPC | Greensville, Isle of Wight, Prince George, Southampton, Surry, Sussex and 3 more | 65 min |
Nearby
Mesoscale Discussions in Pennsylvania, 2012Mesoscale Discussions in New York, 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.