Alert archive / Pennsylvania / Mesoscale Discussions in 2021
Mesoscale Discussion 1520
The Storm Prediction Center issued this mesoscale discussion at Aug 13, 2021, 7:49 PM EDT for 12 counties in Ohio; 19 counties in Pennsylvania; Brooke County, Hancock County, West Virginia. It was in force for 56 min.
The area
The outline as issued.
The facts
- Issued
- Aug 13, 2021, 7:49 PM EDT (23:49 UTC)
- Expired
- Aug 13, 2021, 8:45 PM EDT
- In force
- 56 min
- Issued by
- the Storm Prediction Center
- Concerning
- Severe thunderstorm watch 438
All 33 counties
Carroll County, OH, Columbiana County, OH, Coshocton County, OH, Harrison County, OH, Holmes County, OH, Jefferson County, OH, Licking County, OH, Mahoning County, OH, Portage County, OH, Stark County, OH, Trumbull County, OH, Tuscarawas County, OH, Allegheny County, PA, Armstrong County, PA, Beaver County, PA, Butler County, PA, Cambria County, PA, Clarion County, PA, Crawford County, PA, Elk County, PA, Fayette County, PA, Forest County, PA, Indiana County, PA, Jefferson County, PA, Lawrence County, PA, Mercer County, PA, Somerset County, PA, Venango County, PA, Warren County, PA, Washington County, PA, Westmoreland County, PA, Brooke County, WV, Hancock County, WV
The radar
The Pittsburgh radar (KPBZ), 9 km from the middle of the area, began a volume at 23:50 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 12:00Z, 11.8 hours before the alert went out and 24 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
- 1595 J/kg
- Mixed-layer CIN
- -43 J/kg
- Mixed-layer LCL
- 800 m above ground
- 0-6 km bulk shear
- 26 kt
- 0-1 km storm-relative helicity
- 133 m²/s²
- 0-3 km storm-relative helicity
- 156 m²/s²
- Significant tornado parameter
- 0.0
- Supercell composite
- 0.0
The text
As transmitted.
812
ACUS11 KWNS 132349
SWOMCD
SPC MCD 132349
PAZ000-NYZ000-MDZ000-WVZ000-OHZ000-140045-
Mesoscale Discussion 1520
NWS Storm Prediction Center Norman OK
0649 PM CDT Fri Aug 13 2021
Areas affected...eastern OH...western PA...northern WV
Concerning...Severe Thunderstorm Watch 438...
Valid 132349Z - 140045Z
The severe weather threat for Severe Thunderstorm Watch 438
continues.
SUMMARY...The potential for strong/damaging winds remains, primarily
over northern portions of the watch area.
DISCUSSION...Severe thunderstorms were ongoing at 2345z over
southwestern PA, with strong/occasionally severe storms to the north
of WW 438 over northeast OH/northwest PA. Moderate surface-based
instability and around 30 kts of westerly mid-level flow will
continue to result in a favorable environment in the short term for
a risk of mainly damaging winds. Some uncertainty exists regarding
the coverage of any severe risk north and east of WW 438 with time
given continued nocturnal cooling and influence of prior convection,
however current thinking is that an isolated severe threat may exist
through the evening hours.
The overall risk outside of the current watch is expected to
diminish with time and a downstream watch is not currently
anticipated.
..Bunting.. 08/13/2021
...Please see www.spc.noaa.gov for graphic product...
ATTN...WFO...BUF...CTP...LWX...PBZ...CLE...ILN...
LAT...LON 40178272 41448083 42227931 42117883 41107846 40307871
39667906 39717940 39887982 40158052 40278114 40028257
40178272SPC that day
Everything else SPC issued on the same UTC day.
| Issued | Product | Office | Counties | Lasted |
|---|---|---|---|---|
| Aug 13, 1:13 PM EDT | Mesoscale Discussion | SPC | Adams, Athens, Belmont, Brown, Butler, Clark and 32 more | 2 hr |
| Aug 13, 4:46 PM EDT | Severe Thunderstorm Watch | SPC | Ashland, Athens, Belmont, Carroll, Columbiana, Coshocton and 21 more | 5 hr |
| Aug 12, 10:08 PM EDT | Mesoscale Discussion | SPC | Berks, Bucks, Carbon, Chester, Columbia, Cumberland and 22 more | 67 min |
| Aug 13, 12:33 PM EDT | Mesoscale Discussion | SPC | Adams, Cumberland, Dauphin, Franklin, Fulton, Lancaster and 3 more | 87 min |
| Aug 13, 1:11 PM EDT | Severe Thunderstorm Watch | SPC | Adams, Berks, Chester, Cumberland, Dauphin, Franklin and 6 more | 7 hr |
| Aug 13, 2:48 PM EDT | Mesoscale Discussion | SPC | Bradford, Cameron, Clinton, Lycoming, Potter, Sullivan and 2 more | 87 min |
| Aug 13, 3:29 PM EDT | Severe Thunderstorm Watch | SPC | Bradford, Clinton, Columbia, Lackawanna, Luzerne, Lycoming and 11 more | 7 hr |
| Aug 13, 4:48 PM EDT | Mesoscale Discussion | SPC | Chester | 87 min |
| Aug 13, 7:14 PM EDT | Mesoscale Discussion | SPC | Bradford, Columbia, Lackawanna, Luzerne, Lycoming, Monroe and 9 more | 61 min |
Nearby
Mesoscale Discussions in Pennsylvania, 2021Mesoscale Discussions in Ohio, 2021Mesoscale Discussions in West Virginia, 2021Every mesoscale discussion in 2021
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.