Alert archive / Pennsylvania / Mesoscale Discussions in 2021
Mesoscale Discussion 965
The Storm Prediction Center issued this mesoscale discussion at Jun 14, 2021, 1:40 PM EDT for 9 counties in New Jersey; 21 counties in Pennsylvania. It was in force for 3 hr.
The area
The outline as issued.
The facts
- Issued
- Jun 14, 2021, 1:40 PM EDT (17:40 UTC)
- Expired
- Jun 14, 2021, 4:15 PM EDT
- In force
- 3 hr
- Issued by
- the Storm Prediction Center
- Concerning
- Severe potential...watch possible
- Chance of a watch
- 60%
All 30 counties
Burlington County, NJ, Camden County, NJ, Gloucester County, NJ, Hunterdon County, NJ, Mercer County, NJ, Middlesex County, NJ, Morris County, NJ, Somerset County, NJ, Warren County, NJ, Adams County, PA, Berks County, PA, Bucks County, PA, Carbon County, PA, Chester County, PA, Columbia County, PA, Cumberland County, PA, Dauphin County, PA, Delaware County, PA, Lancaster County, PA, Lebanon County, PA, Lehigh County, PA, Luzerne County, PA, Monroe County, PA, Montgomery County, PA, Montour County, PA, Northampton County, PA, Northumberland County, PA, Philadelphia County, PA, Schuylkill County, PA, York County, PA
The watches that followed
Watches SPC issued over any of the same counties within four hours of this discussion.
The nearest sounding before it
Washington/Dulle, VA (KIAD), launched 12:00Z, 5.7 hours before the alert went out and 226 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
- 2 J/kg
- Mixed-layer CIN
- -447 J/kg
- Mixed-layer LCL
- 1007 m above ground
- 0-6 km bulk shear
- 33 kt
- 0-1 km storm-relative helicity
- 31 m²/s²
- 0-3 km storm-relative helicity
- 87 m²/s²
- Significant tornado parameter
- 0.0
- Supercell composite
- 0.0
The text
As transmitted.
496
ACUS11 KWNS 141740
SWOMCD
SPC MCD 141740
NJZ000-PAZ000-DEZ000-142015-
Mesoscale Discussion 0965
NWS Storm Prediction Center Norman OK
1240 PM CDT Mon Jun 14 2021
Areas affected...Portions of central/eastern PA...NJ...and far
northern DE
Concerning...Severe potential...Watch possible
Valid 141740Z - 142015Z
Probability of Watch Issuance...60 percent
SUMMARY...Scattered damaging wind gusts and occasional severe hail
may occur this afternoon as storms move eastward. Watch issuance
will probably be needed.
DISCUSSION...A broken line of storms has developed early this
afternoon along a surface cold front across parts of western/central
PA. A belt of 40-50+ kt mid-level west-southwesterly winds
associated with a shortwave trough will likely foster continued
storm organization given the presence of elongated, nearly straight
hodographs at mid/upper levels. A mainly linear storm mode should
support a continued risk of damaging wind gusts, particularly as
low-level lapse rates continue to steepen ahead of the ongoing
activity via diurnal heating. Some short-term, convection-allowing
model guidance suggests convection may struggle as it crosses the
higher terrain of the Appalachians and encounters a minimum in
boundary-layer instability. But, these storms may tend to intensify
later this afternoon once they encounter a more unstable airmass
characterized by 1000-1500 J/kg MLCAPE and low to mid 60s surface
dewpoints across eastern PA into NJ and vicinity. The timing for a
potential downstream Severe Thunderstorm Watch across
central/eastern PA and NJ remains a bit uncertain given the
possibility that the ongoing storms may weaken some in the
short-term as they move eastward into central PA. Still, a watch
will probably be needed at some point this afternoon.
..Gleason/Grams.. 06/14/2021
...Please see www.spc.noaa.gov for graphic product...
ATTN...WFO...OKX...PHI...BGM...CTP...
LAT...LON 39837750 41377658 41437613 41377523 40997449 40867441
40487428 40047433 39697455 39707534 39757693 39837750SPC that day
Everything else SPC issued on the same UTC day.
| Issued | Product | Office | Counties | Lasted |
|---|---|---|---|---|
| Jun 14, 2:06 PM EDT | Severe Thunderstorm Watch | SPC | Burlington, Camden, Gloucester, Hunterdon, Mercer, Middlesex and 7 more | 9 hr |
| Jun 14, 6:18 PM EDT | Mesoscale Discussion | SPC | Atlantic, Bergen, Burlington, Camden, Cumberland, Essex and 14 more | 117 min |
| Jun 14, 6:41 PM EDT | Mesoscale Discussion | SPC | Cumberland, Gloucester, Salem | 2 hr |
| Jun 14, 7:29 PM EDT | Severe Thunderstorm Watch | SPC | Atlantic, Cape May, Cumberland | 6 hr |
| Jun 14, 11:31 AM EDT | Mesoscale Discussion | SPC | Allegheny, Armstrong, Beaver, Bedford, Blair, Butler and 22 more | 89 min |
| Jun 14, 11:46 AM EDT | Severe Thunderstorm Watch | SPC | Allegheny, Armstrong, Beaver, Bedford, Blair, Butler and 20 more | 6 hr |
| Jun 14, 2:48 PM EDT | Mesoscale Discussion | SPC | Susquehanna | 2 hr |
| Jun 14, 3:25 PM EDT | Mesoscale Discussion | SPC | Fayette, Greene, Somerset, Washington, Westmoreland | 95 min |
Nearby
Mesoscale Discussions in Pennsylvania, 2021Mesoscale Discussions in New Jersey, 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.