Alert archive / New Jersey / Severe Thunderstorm Watches in 2021
Severe Thunderstorm Watch 304
The Storm Prediction Center issued this severe thunderstorm watch at Jun 21, 2021, 4:33 PM EDT for 5 states. It was in force for 6 hr.
The area
The outline as issued.
The facts
- Issued
- Jun 21, 2021, 4:33 PM EDT (20:33 UTC)
- Expired
- Jun 21, 2021, 10:41 PM EDT
- In force
- 6 hr
- Issued by
- the Storm Prediction Center
- Largest hail expected
- 1.5 in
- Strongest gust expected
- 60 kt
All 37 counties
Kent County, DE, New Castle County, DE, Sussex County, DE, Caroline County, MD, Kent County, MD, Queen Anne's County, MD, Talbot County, MD, Atlantic County, NJ, Burlington County, NJ, Camden County, NJ, Cape May County, NJ, Cumberland County, NJ, Essex County, NJ, Gloucester County, NJ, Hunterdon County, NJ, Mercer County, NJ, Middlesex County, NJ, Monmouth County, NJ, Morris County, NJ, Ocean County, NJ, Passaic County, NJ, Salem County, NJ, Somerset County, NJ, Sussex County, NJ, Union County, NJ, Warren County, NJ, Orange County, NY, Berks County, PA, Bucks County, PA, Carbon County, PA, Chester County, PA, Delaware County, PA, Lehigh County, PA, Monroe County, PA, Montgomery County, PA, Northampton County, PA, Philadelphia County, PA
The radar
The Philadelphia radar (KDIX), 63 km from the middle of the area, began a volume at 20:36 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.
What SPC expected
The probabilities SPC published with the watch, for the watch area over its life.
- Two or more tornadoes
- 10%
- One or more EF2 to EF5 tornadoes
- 2%
- Ten or more severe wind reports
- 40%
- One or more gusts of 65 knots or more
- 20%
- Ten or more severe hail reports
- 20%
- One or more hailstones of 2 inches or more
- 10%
- Six or more combined severe hail and wind reports
- 60%
Warnings issued inside it
10 tornado, severe thunderstorm and flash flood warnings for its counties while it was in force.
| Issued | Product | Office | Counties | Lasted |
|---|---|---|---|---|
| Jun 21, 6:08 PM EDT | Severe Thunderstorm Warning | PHI | Berks, Lehigh | 52 min |
| Jun 21, 6:21 PM EDT | Severe Thunderstorm Warning | PHI | New Castle | 54 min |
| Jun 21, 6:47 PM EDT | Severe Thunderstorm Warning | PHI | Kent, New Castle | 58 min |
| Jun 21, 7:02 PM EDT | Severe Thunderstorm Warning | PHI | Berks, Carbon, Lehigh, Northampton | 43 min |
| Jun 21, 7:12 PM EDT | Severe Thunderstorm Warning | PHI | New Castle | 48 min |
| Jun 21, 7:38 PM EDT | Severe Thunderstorm Warning | PHI | Warren | 52 min |
| Jun 21, 7:43 PM EDT | Severe Thunderstorm Warning | PHI | Kent, New Castle, Sussex | 47 min |
| Jun 21, 8:13 PM EDT | Severe Thunderstorm Warning | PHI | Morris, Sussex, Warren | 62 min |
| Jun 21, 8:47 PM EDT | Severe Thunderstorm Warning | OKX | Orange | 43 min |
| Jun 21, 9:26 PM EDT | Severe Thunderstorm Warning | OKX | Bergen, Passaic | 49 min |
Discussions around it
SPC mesoscale discussions over the same counties from four hours before the watch to its end.
The nearest sounding before it
Brookhaven, NY (KOKX), launched 12:00Z, 8.6 hours before the alert went out and 205 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
- 171 J/kg
- Mixed-layer CIN
- -149 J/kg
- Mixed-layer LCL
- 802 m above ground
- 0-6 km bulk shear
- 25 kt
- 0-1 km storm-relative helicity
- 66 m²/s²
- 0-3 km storm-relative helicity
- 77 m²/s²
- Significant tornado parameter
- 0.0
- Supercell composite
- 0.0
The text
As transmitted.
331 WWUS20 KWNS 212028 SEL4 SPC WW 212028 DEZ000-MDZ000-NJZ000-NYZ000-PAZ000-CWZ000-220400- URGENT - IMMEDIATE BROADCAST REQUESTED Severe Thunderstorm Watch Number 304 NWS Storm Prediction Center Norman OK 430 PM EDT Mon Jun 21 2021 The NWS Storm Prediction Center has issued a * Severe Thunderstorm Watch for portions of Delaware Eastern Maryland New Jersey Southeast New York Eastern Pennsylvania Coastal Waters * Effective this Monday afternoon from 430 PM until Midnight EDT. * Primary threats include... Scattered damaging wind gusts to 70 mph possible Isolated large hail events to 1.5 inches in diameter possible SUMMARY...Thunderstorms over central NY/PA will track eastward through this evening, affecting the watch area. Locally damaging wind gusts and hail are the main threats. The severe thunderstorm watch area is approximately along and 50 statute miles east and west of a line from 45 miles northwest of Newark NJ to 45 miles southwest of Dover DE. For a complete depiction of the watch see the associated watch outline update (WOUS64 KWNS WOU4). PRECAUTIONARY/PREPAREDNESS ACTIONS... REMEMBER...A Severe Thunderstorm Watch means conditions are favorable for severe thunderstorms in and close to the watch area. Persons in these areas should be on the lookout for threatening weather conditions and listen for later statements and possible warnings. Severe thunderstorms can and occasionally do produce tornadoes. && OTHER WATCH INFORMATION...CONTINUE...WW 299...WW 300...WW 301...WW 302...WW 303... AVIATION...A few severe thunderstorms with hail surface and aloft to 1.5 inches. Extreme turbulence and surface wind gusts to 60 knots. A few cumulonimbi with maximum tops to 500. Mean storm motion vector 27030. ...Hart
SPC that day
Everything else SPC issued on the same UTC day.
| Issued | Product | Office | Counties | Lasted |
|---|---|---|---|---|
| Jun 21, 1:51 PM EDT | Mesoscale Discussion | SPC | New Castle | 114 min |
| Jun 21, 6:15 PM EDT | Mesoscale Discussion | SPC | Kent, New Castle, Sussex | 60 min |
| Jun 21, 2:20 PM EDT | Severe Thunderstorm Watch | SPC | Allegany, Anne Arundel, Baltimore, Calvert, Carroll, Cecil and 9 more | 6 hr |
| Jun 21, 6:50 PM EDT | Mesoscale Discussion | SPC | Passaic, Sussex, Warren | 55 min |
| Jun 21, 11:59 AM EDT | Mesoscale Discussion | SPC | Cattaraugus, Chautauqua | 91 min |
| Jun 21, 12:31 PM EDT | Mesoscale Discussion | SPC | Clinton, Essex, Franklin, Fulton, Hamilton, Herkimer and 12 more | 89 min |
| Jun 21, 12:31 PM EDT | Severe Thunderstorm Watch | SPC | Allegany, Cattaraugus, Cayuga, Chautauqua, Erie, Genesee and 14 more | 7 hr |
| Jun 21, 1:11 PM EDT | Severe Thunderstorm Watch | SPC | Broome, Chemung, Chenango, Clinton, Cortland, Essex and 14 more | 10 hr |
| Jun 21, 3:35 PM EDT | Mesoscale Discussion | SPC | Clinton, Essex, Franklin, Fulton, Hamilton, Herkimer and 7 more | 85 min |
| Jun 21, 3:45 PM EDT | Severe Thunderstorm Watch | SPC | Albany, Columbia, Delaware, Dutchess, Greene, Otsego and 5 more | 7 hr |
| Jun 21, 3:47 PM EDT | Mesoscale Discussion | SPC | Allegany, Livingston, Ontario, Steuben, Wayne, Yates | 58 min |
Nearby
Severe Thunderstorm Watches in New Jersey, 2021Severe Thunderstorm Watches in Pennsylvania, 2021Severe Thunderstorm Watches in Maryland, 2021Every severe thunderstorm watch 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.