Alert archive / New Jersey / Mesoscale Discussions in 2021
Mesoscale Discussion 848
The Storm Prediction Center issued this mesoscale discussion at Jun 4, 2021, 2:26 PM EDT for 5 states. It was in force for 94 min.
The area
The outline as issued.
The facts
- Issued
- Jun 4, 2021, 2:26 PM EDT (18:26 UTC)
- Expired
- Jun 4, 2021, 4:00 PM EDT
- In force
- 94 min
- Issued by
- the Storm Prediction Center
- Concerning
- Severe potential...watch possible
- Chance of a watch
- 40%
All 32 counties
New Castle County, DE, Cecil County, MD, Harford County, MD, Bergen County, NJ, Burlington County, NJ, Camden County, NJ, Essex County, NJ, Gloucester County, NJ, Hudson County, NJ, Hunterdon County, NJ, Mercer County, NJ, Middlesex County, NJ, Morris County, NJ, Passaic County, NJ, Salem County, NJ, Somerset County, NJ, Sussex County, NJ, Union County, NJ, Warren County, NJ, Richmond County, NY, Rockland County, NY, Berks County, PA, Bucks County, PA, Chester County, PA, Delaware County, PA, Lancaster County, PA, Lehigh County, PA, Monroe County, PA, Montgomery County, PA, Northampton County, PA, Philadelphia County, PA, York County, PA
The radar
The Philadelphia radar (KDIX), 103 km from the middle of the area, began a volume at 18:27 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 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, 6.4 hours before the alert went out and 215 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
- 381 J/kg
- Mixed-layer CIN
- -55 J/kg
- Mixed-layer LCL
- 947 m above ground
- 0-6 km bulk shear
- 42 kt
- 0-1 km storm-relative helicity
- -8 m²/s²
- 0-3 km storm-relative helicity
- 73 m²/s²
- Significant tornado parameter
- -0.0
- Supercell composite
- -0.1
The text
As transmitted.
433
ACUS11 KWNS 041827
SWOMCD
SPC MCD 041826
NYZ000-NJZ000-PAZ000-DEZ000-MDZ000-042000-
Mesoscale Discussion 0848
NWS Storm Prediction Center Norman OK
0126 PM CDT Fri Jun 04 2021
Areas affected...eastern Pennsylvania into New Jersey and vicinity
Concerning...Severe potential...Watch possible
Valid 041826Z - 042000Z
Probability of Watch Issuance...40 percent
SUMMARY...A few stronger storms will continue shifting eastward
across the Delaware Valley and southeastern Pennsylvania into New
Jerse and the New York City area this afternoon. Locally
strong/gusty winds are expected. A WW may be considered.
DISCUSSION...Latest radar Loop shows a area of thunderstorms moving
slowly eastward across eastern Pennsylvania and into northwestern
New Jersey at this time. A few stronger storms have evolved --
aided by 1000 to 1500 J/kg mixed-layer CAPE as boundary-layer
heating occurs beneath cool air aloft/steep lapse rates in
conjunction with the vort max/short-wave trough crossing the central
Appalachians. While lower tropospheric flow remains rather weak,
moderate westerly mid-level flow is sufficient to support
multicell-type organization, and thus potential for gusty winds
capable of minor damage -- primarily limited to tree damage.
As storms continue shifting eastward, they will begin affecting
western fringes of the New York City metro area in the next 1 to 2
hours.
..Goss/Guyer.. 06/04/2021
...Please see www.spc.noaa.gov for graphic product...
ATTN...WFO...OKX...PHI...BGM...CTP...LWX...
LAT...LON 39797722 40997549 41397470 41267391 39927428 39517543
39467619 39797722SPC that day
Everything else SPC issued on the same UTC day.
| Issued | Product | Office | Counties | Lasted |
|---|---|---|---|---|
| Jun 4, 3:09 PM EDT | Severe Thunderstorm Watch | SPC | New Castle | 5 hr |
| Jun 4, 4:12 PM EDT | Mesoscale Discussion | SPC | Kent, New Castle, Sussex | 93 min |
| Jun 4, 12:46 PM EDT | Mesoscale Discussion | SPC | Anne Arundel, Calvert, Charles, Prince George's, Queen Anne's, Saint Mary's and 2 more | 59 min |
| Jun 4, 12:59 PM EDT | Severe Thunderstorm Watch | SPC | Calvert, Charles, Dorchester, Saint Mary's, Somerset, Wicomico | 7 hr |
Nearby
Mesoscale Discussions in New Jersey, 2021Mesoscale Discussions in Pennsylvania, 2021Mesoscale Discussions in Maryland, 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.