Alert archive / Pennsylvania / Mesoscale Discussions in 2021
Mesoscale Discussion 1300
The Storm Prediction Center issued this mesoscale discussion at Jul 16, 2021, 5:51 PM EDT for 10 counties in New Jersey; 7 counties in New York; 22 counties in Pennsylvania. It was in force for 114 min.
The area
The outline as issued.
The facts
- Issued
- Jul 16, 2021, 5:51 PM EDT (21:51 UTC)
- Expired
- Jul 16, 2021, 7:45 PM EDT
- In force
- 114 min
- Issued by
- the Storm Prediction Center
- Concerning
- Severe potential...watch unlikely
- Chance of a watch
- 20%
All 39 counties
Bergen County, NJ, Essex County, NJ, Hudson County, NJ, Hunterdon County, NJ, Morris County, NJ, Passaic County, NJ, Somerset County, NJ, Sussex County, NJ, Union County, NJ, Warren County, NJ, Bronx County, NY, New York County, NY, Orange County, NY, Putnam County, NY, Rockland County, NY, Sullivan County, NY, Westchester County, NY, Berks County, PA, Bucks County, PA, Carbon County, PA, Columbia County, PA, Cumberland County, PA, Dauphin County, PA, Juniata County, PA, Lackawanna 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, Perry County, PA, Pike County, PA, Schuylkill County, PA, Snyder County, PA, Wayne County, PA
The radar
The Philadelphia radar (KDIX), 141 km from the middle of the area, began a volume at 21:51 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
Brookhaven, NY (KOKX), launched 12:00Z, 9.9 hours before the alert went out and 236 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
- 1044 J/kg
- Mixed-layer CIN
- -56 J/kg
- Mixed-layer LCL
- 994 m above ground
- 0-6 km bulk shear
- 17 kt
- 0-1 km storm-relative helicity
- 108 m²/s²
- 0-3 km storm-relative helicity
- 105 m²/s²
- Significant tornado parameter
- 0.0
- Supercell composite
- 0.0
The text
As transmitted.
239
ACUS11 KWNS 162152
SWOMCD
SPC MCD 162151
CTZ000-NYZ000-NJZ000-PAZ000-162345-
Mesoscale Discussion 1300
NWS Storm Prediction Center Norman OK
0451 PM CDT Fri Jul 16 2021
Areas affected...portions of central and eastern
Pennsylvania...northern New Jersey...far southeast New York
Concerning...Severe potential...Watch unlikely
Valid 162151Z - 162345Z
Probability of Watch Issuance...20 percent
SUMMARY...A couple damaging wind gusts may accompany the stronger
storms through the remainder of the afternoon. The severe threat is
expected to gradually wane by sunset.
DISCUSSION...MRMS mosaic radar data depicts multicellular clusters
in progress across portions of central PA, with some recent linear
organization noted. These storms are progressing into a well-mixed
boundary layer, characterized by 7+ C/km sfc-3km lapse rates atop 90
F surface temperatures, contributing to 1000-1500 J/kg MLCAPE. Given
the well-mixed boundary layer, efficient downward momentum transport
with some of the stronger storm cores may foster a couple damaging
gusts, though the overall severe threat is expected to remain
relatively sparse given weak vertical shear profiles. By sunset, the
boundary layer will begin to cool/decouple, with the isolated
damaging gust threat gradually diminishing.
..Squitieri/Guyer.. 07/16/2021
...Please see www.spc.noaa.gov for graphic product...
ATTN...WFO...OKX...ALY...PHI...BGM...CTP...
LAT...LON 40267806 40727741 41217662 41507572 41777503 41867431
41647378 41247359 40877365 40577416 40467469 40157538
40067596 40017669 39997749 40267806Nearby
Mesoscale Discussions in Pennsylvania, 2021Mesoscale Discussions in New Jersey, 2021Mesoscale Discussions in New York, 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.