Alert archive / Pennsylvania / Mesoscale Discussions in 2012
Mesoscale Discussion 921
The Storm Prediction Center issued this mesoscale discussion at May 27, 2012, 1:41 PM EDT for 5 states. It was in force for 64 min.
The area
The outline as issued.
The facts
- Issued
- May 27, 2012, 1:41 PM EDT (17:41 UTC)
- Expired
- May 27, 2012, 2:45 PM EDT
- In force
- 64 min
- Issued by
- the Storm Prediction Center
- Chance of a watch
- 20%
All 36 counties
Allegany County, MD, Garrett County, MD, Washington County, MD, Jefferson County, OH, Allegheny County, PA, Bedford County, PA, Blair County, PA, Cambria County, PA, Cumberland County, PA, Fayette County, PA, Franklin County, PA, Fulton County, PA, Greene County, PA, Huntingdon County, PA, Indiana County, PA, Juniata County, PA, Mifflin County, PA, Perry County, PA, Somerset County, PA, Washington County, PA, Westmoreland County, PA, Frederick County, VA, Berkeley County, WV, Brooke County, WV, Grant County, WV, Hampshire County, WV, Hancock County, WV, Hardy County, WV, Marion County, WV, Mineral County, WV, Monongalia County, WV, Morgan County, WV, Ohio County, WV, Preston County, WV, Taylor County, WV, Tucker County, WV
The radar
The Pittsburgh radar (KPBZ), 121 km from the middle of the area, began a volume at 17:44 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
Pittsburgh, PA (KPIT), launched 12:00Z, 5.7 hours before the alert went out and 105 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
- 993 J/kg
- Mixed-layer CIN
- -88 J/kg
- Mixed-layer LCL
- 1085 m above ground
- 0-6 km bulk shear
- 16 kt
- 0-1 km storm-relative helicity
- 46 m²/s²
- 0-3 km storm-relative helicity
- 47 m²/s²
- Significant tornado parameter
- 0.0
- Supercell composite
- 0.0
The text
As transmitted, in the capitals the NWS used until 2016.
811
ACUS11 KWNS 271742
SWOMCD
SPC MCD 271741
PAZ000-MDZ000-WVZ000-VAZ000-OHZ000-271845-
MESOSCALE DISCUSSION 0921
NWS STORM PREDICTION CENTER NORMAN OK
1241 PM CDT SUN MAY 27 2012
AREAS AFFECTED...SWRN/S CNTRL PA...ERN OH...ERN PANHANDLE OF
WV...WRN MD
CONCERNING...SEVERE POTENTIAL...WATCH UNLIKELY
VALID 271741Z - 271845Z
PROBABILITY OF WATCH ISSUANCE...20 PERCENT
SUMMARY...PULSE SEVERE STORMS CAPABLE OF DMGG WINDS...HAIL...AND
HEAVY RAINFALL WILL BECOME POSSIBLE THIS AFTERNOON.
DISCUSSION...CONVECTIVE INITIATION HAS OCCURRED INVOF THE
ALLEGHENIES AND A STATIONARY FRONT ACROSS PORTIONS OF SRN PA AND WRN
MD. COVERAGE WILL LIKELY INCREASE BY MID AFTERNOON WITH THE APPROACH
OF A CONVECTIVELY INDUCED VORT MAX OVER SRN ONTARIO. WITH AN
UNCAPPED AND MODERATELY UNSTABLE AIR MASS...MORE VIGOROUS UPDRAFTS
MAY OCCUR COINCIDENT WITH THE APPROACHING UPPER WAVE. HAIL IS
POSSIBLE WITH THE STRONGER CORES AND DMGG WINDS /LOCALLY ENHANCED BY
STEEPENING LOW-LEVEL LAPSE RATES/ MAY OCCUR WITH COLLAPSING STORMS.
HOWEVER...WITH THE STRONGER DEEP-LAYER SHEAR REMAINING TO THE N OF
THE AREA...CONVECTION WILL GENERALLY BE SOMEWHAT DISORGANIZED AND
BRIEF IN NATURE. HEAVY RAINFALL IS PROBABLE GIVEN SLOW STORM MOTION
AND WELL ABOVE NORMAL PWAT VALUES.
..HURLBUT/CARBIN.. 05/27/2012
...PLEASE SEE WWW.SPC.NOAA.GOV FOR GRAPHIC PRODUCT...
ATTN...WFO...CTP...LWX...PBZ...RLX...
LAT...LON 40627996 40747800 40647711 40187700 39527768 39087847
38667916 38807963 39338009 40108083 40578077 40627996SPC that day
Everything else SPC issued on the same UTC day.
| Issued | Product | Office | Counties | Lasted |
|---|---|---|---|---|
| May 27, 6:34 PM EDT | Mesoscale Discussion | SPC | Allegany, Baltimore, Carroll, Frederick, Garrett, Howard and 3 more | 56 min |
| May 27, 12:56 PM EDT | Mesoscale Discussion | SPC | Ashtabula, Geauga, Lake, Mahoning, Trumbull | 64 min |
| May 27, 1:33 PM EDT | Severe Thunderstorm Watch | SPC | Ashtabula, Carroll, Columbiana, Cuyahoga, Geauga, Harrison and 8 more | 5 hr |
| May 27, 4:12 PM EDT | Mesoscale Discussion | SPC | Allegheny, Armstrong, Beaver, Blair, Butler, Cambria and 18 more | 63 min |
| May 27, 5:21 PM EDT | Severe Thunderstorm Watch | SPC | Adams, Bedford, Blair, Cambria, Centre, Clearfield and 21 more | 4 hr |
Nearby
Mesoscale Discussions in Pennsylvania, 2012Mesoscale Discussions in West Virginia, 2012Mesoscale Discussions in Maryland, 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.