Alert archive / Pennsylvania / Mesoscale Discussions in 2021
Mesoscale Discussion 956
The Storm Prediction Center issued this mesoscale discussion at Jun 13, 2021, 4:56 PM EDT for 31 counties in Pennsylvania. It was in force for 94 min.
The area
The outline as issued.
The facts
- Issued
- Jun 13, 2021, 4:56 PM EDT (20:56 UTC)
- Expired
- Jun 13, 2021, 6:30 PM EDT
- In force
- 94 min
- Issued by
- the Storm Prediction Center
- Concerning
- Severe thunderstorm watch 266
All 31 counties
Blair County, PA, Bradford County, PA, Cambria County, PA, Cameron County, PA, Centre County, PA, Clarion County, PA, Clearfield County, PA, Clinton County, PA, Columbia County, PA, Elk County, PA, Forest County, PA, Huntingdon County, PA, Indiana County, PA, Jefferson County, PA, Juniata County, PA, Lackawanna County, PA, Luzerne County, PA, Lycoming County, PA, McKean County, PA, Mifflin County, PA, Montour County, PA, Northumberland County, PA, Perry County, PA, Potter County, PA, Snyder County, PA, Sullivan County, PA, Susquehanna County, PA, Tioga County, PA, Union County, PA, Warren County, PA, Wyoming County, PA
The radar
The State College radar (KCCX), 52 km from the middle of the area, began a volume at 20:56 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
Buffalo Intl Airport, NY (KBUF), launched 12:00Z, 8.9 hours before the alert went out and 187 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
- 0 J/kg
- Mixed-layer CIN
- No buoyant parcel
- Mixed-layer LCL
- 2252 m above ground
- 0-6 km bulk shear
- 40 kt
- 0-1 km storm-relative helicity
- -7 m²/s²
- 0-3 km storm-relative helicity
- 32 m²/s²
- Significant tornado parameter
- 0.0
- Supercell composite
- 0.0
The text
As transmitted.
470
ACUS11 KWNS 132056
SWOMCD
SPC MCD 132056
PAZ000-NYZ000-132230-
Mesoscale Discussion 0956
NWS Storm Prediction Center Norman OK
0356 PM CDT Sun Jun 13 2021
Areas affected...parts of northern into central Pennsylvania
Concerning...Severe Thunderstorm Watch 266...
Valid 132056Z - 132230Z
The severe weather threat for Severe Thunderstorm Watch 266
continues.
SUMMARY...The severe threat continues across Severe Thunderstorm
Watch 0266. Damaging gusts and large hail remain the primary
threats. The severe threat should persist through sunset.
DISCUSSION...Multicellular clusters and a couple of brief
supercells, evident via KCCX and MRMS mosaic radar data, have
developed across Severe Thunderstorm Watch 0266 with a history of 1
inch diameter hail stones. Given the modest (i.e. 35+ kts) effective
bulk shear and 1000-1500 J/kg MLCAPE in place, multicells and
supercells are expected to persist into the evening hours. Given
15-20 F temperature/dewpoint spreads and 6.5-7.5 C/km low-level
lapse rates, damaging gusts may occur with the more intense
multicellular clusters (especially where cold pool mergers occur)
while the large hail threat will continue with any of the more
sustained supercell structures. By sunset, the boundary layer will
begin to decouple, and the severe threat should gradually diminish
thereafter.
..Squitieri/Grams.. 06/13/2021
...Please see www.spc.noaa.gov for graphic product...
ATTN...WFO...PHI...BGM...BUF...CTP...PBZ...CLE...
LAT...LON 40067786 40247887 40297906 41627961 41707961 41797961
41837961 42007961 42007918 42007692 42007683 42007675
42007548 41487544 41267544 41017573 40067786 40067786
40067786SPC that day
Everything else SPC issued on the same UTC day.
| Issued | Product | Office | Counties | Lasted |
|---|---|---|---|---|
| Jun 13, 12:13 PM EDT | Mesoscale Discussion | SPC | Allegheny, Armstrong, Beaver, Bedford, Butler, Cambria and 8 more | 2 hr |
| Jun 13, 12:50 PM EDT | Severe Thunderstorm Watch | SPC | Allegheny, Armstrong, Beaver, Butler, Clarion, Fayette and 9 more | 7 hr |
| Jun 13, 2:38 PM EDT | Mesoscale Discussion | SPC | Blair, Bradford, Cambria, Cameron, Centre, Clearfield and 20 more | 2 hr |
| Jun 13, 3:26 PM EDT | Mesoscale Discussion | SPC | Allegheny, Armstrong, Beaver, Butler, Clarion, Fayette and 10 more | 94 min |
| Jun 13, 3:26 PM EDT | Severe Thunderstorm Watch | SPC | Blair, Bradford, Cambria, Cameron, Centre, Clearfield and 20 more | 7 hr |
| Jun 13, 7:21 PM EDT | Mesoscale Discussion | SPC | Blair, Bradford, Cambria, Cameron, Carbon, Centre and 20 more | 84 min |
Nearby
Mesoscale Discussions in Pennsylvania, 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.