Alert archive / Pennsylvania / Mesoscale Discussions in 2012
Mesoscale Discussion 1925
The Storm Prediction Center issued this mesoscale discussion at Sep 8, 2012, 5:00 AM EDT for Allegany County, Garrett County, Maryland; 26 counties in Pennsylvania; 8 counties in West Virginia. It was in force for 60 min.
The area
The outline as issued.
The facts
- Issued
- Sep 8, 2012, 5:00 AM EDT (09:00 UTC)
- Expired
- Sep 8, 2012, 6:00 AM EDT
- In force
- 60 min
- Issued by
- the Storm Prediction Center
- Chance of a watch
- 40%
All 36 counties
Allegany County, MD, Garrett County, MD, Allegheny County, PA, Armstrong County, PA, Beaver County, PA, Bedford County, PA, Blair County, PA, Butler County, PA, Cambria County, PA, Cameron County, PA, Clarion County, PA, Clearfield County, PA, Crawford County, PA, Elk County, PA, Fayette County, PA, Forest County, PA, Greene County, PA, Huntingdon County, PA, Indiana County, PA, Jefferson County, PA, Lawrence County, PA, McKean County, PA, Mercer County, PA, Somerset County, PA, Venango County, PA, Warren County, PA, Washington County, PA, Westmoreland County, PA, Barbour County, WV, Doddridge County, WV, Harrison County, WV, Marion County, WV, Mineral County, WV, Monongalia County, WV, Preston County, WV, Taylor County, WV
The radar
The Pittsburgh radar (KPBZ), 73 km from the middle of the area, began a volume at 09:01 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
Pittsburgh, PA (KPIT), launched 00:00Z, 9.0 hours before the alert went out and 75 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
- 587 J/kg
- Mixed-layer CIN
- -18 J/kg
- Mixed-layer LCL
- 1511 m above ground
- 0-6 km bulk shear
- 37 kt
- 0-1 km storm-relative helicity
- 21 m²/s²
- 0-3 km storm-relative helicity
- 84 m²/s²
- Significant tornado parameter
- 0.0
- Supercell composite
- 0.8
The text
As transmitted, in the capitals the NWS used until 2016.
775
ACUS11 KWNS 080901
SWOMCD
SPC MCD 080900
PAZ000-MDZ000-NYZ000-WVZ000-081000-
MESOSCALE DISCUSSION 1925
NWS STORM PREDICTION CENTER NORMAN OK
0400 AM CDT SAT SEP 08 2012
AREAS AFFECTED...WRN PA...NRN WV...WRN MD
CONCERNING...SEVERE POTENTIAL...WATCH POSSIBLE
VALID 080900Z - 081000Z
PROBABILITY OF WATCH ISSUANCE...40 PERCENT
SUMMARY...A WIND DAMAGE THREAT MAY EXIST WITH A CONVECTIVE LINE
MOVING INTO WRN PA EARLY THIS MORNING. THE THREAT MAY INCREASE AS
THE LINE MOVES INTO CNTRL PA BUT SHOULD STILL REMAIN RELATIVELY
ISOLATED. WW ISSUANCE WILL BE POSSIBLE DEPENDING UPON HOW THE LINE
ACTS OVER THE NEXT 1 TO 2 HOURS.
DISCUSSION...A FINE LINE OF STRONG THUNDERSTORMS IS ONGOING NEAR THE
PA-OH STATE-LINE AHEAD OF A WELL-DEFINED VORTICITY MAX AND SHORTWAVE
TROUGH EVIDENT ON WATER VAPOR IMAGERY. THE LINE HAS SHOWN SOME
INCREASED ORGANIZATION WITH LIGHTNING INCREASING AND SOME
INTENSIFICATION OF THE ECHOES WITHIN THE LINE. THIS IS LIKELY A
RESULT OF THE STRONG FORCING AND COULD ALSO BE A RESULT OF AN
ENHANCED IN THE LOW-LEVEL JET. AS THE LINE MOVES EWD INTO WRN AND
CNTRL PA...INSTABILITY IS VERY WEAK WITH SBCAPE VALUES AROUND 250
J/KG. IN SPITE OF THIS...THE LINE COULD CONTINUE TO INTENSIFY AS THE
CONVECTION REACHES A SLIGHTLY MORE MOIST BOUNDARY LAYER IN CNTRL PA
WHERE SFC DEWPOINTS ARE IN THE MID TO UPPER 60S F. FOR THIS
REASON...THE LINE WILL NEED TO BE MONITORED CLOSELY AND WW ISSUANCE
CAN NOT BE RULED OUT FOR A WIND DAMAGE THREAT ACROSS PA AND NRN WV
EARLY THIS MORNING.
..BROYLES/MEAD.. 09/08/2012
...PLEASE SEE WWW.SPC.NOAA.GOV FOR GRAPHIC PRODUCT...
ATTN...WFO...BUF...CTP...LWX...PBZ...RLX...CLE...
LAT...LON 42047904 42027980 41898040 41458050 40708036 39248072
39028018 39497868 40537783 41667817 42047904SPC that day
Everything else SPC issued on the same UTC day.
| Issued | Product | Office | Counties | Lasted |
|---|---|---|---|---|
| Sep 8, 11:38 AM EDT | Mesoscale Discussion | SPC | Allegany, Baltimore, Carroll, Frederick, Howard, Montgomery and 2 more | 97 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 | Beaver, Crawford, Erie, Lawrence, Mercer, Venango | 2 hr |
| Sep 8, 8:42 AM EDT | Mesoscale Discussion | SPC | Berks, Bradford, Carbon, Clinton, Columbia, Cumberland and 18 more | 93 min |
| Sep 8, 12:40 PM EDT | Tornado Watch | SPC | Bradford, Lackawanna, Luzerne, Pike, Susquehanna, Wayne and 1 more | 7 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.