Alert archive / New Jersey / Mesoscale Discussions in 2021
Mesoscale Discussion 1307
The Storm Prediction Center issued this mesoscale discussion at Jul 17, 2021, 3:02 PM EDT for 6 states. It was in force for 88 min.
The area
The outline as issued.
The facts
- Issued
- Jul 17, 2021, 3:02 PM EDT (19:02 UTC)
- Expired
- Jul 17, 2021, 4:30 PM EDT
- In force
- 88 min
- Issued by
- the Storm Prediction Center
- Concerning
- Severe thunderstorm watch 382
All 58 counties
Kent County, DE, New Castle County, DE, Anne Arundel County, MD, Baltimore County, MD, Caroline County, MD, Cecil County, MD, Charles County, MD, City of Baltimore, MD, Harford County, MD, Howard County, MD, Kent County, MD, Montgomery County, MD, Prince George's County, MD, Queen Anne's County, MD, Talbot County, MD, Atlantic County, NJ, Bergen County, NJ, Burlington County, NJ, Camden County, NJ, Cumberland County, NJ, Essex County, NJ, Gloucester County, NJ, Hudson 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, Union County, NJ, Warren County, NJ, Bronx County, NY, Kings County, NY, New York County, NY, Queens County, NY, Richmond County, NY, Berks County, PA, Bucks County, PA, Chester County, PA, Delaware County, PA, Lancaster County, PA, Lehigh County, PA, Montgomery County, PA, Northampton County, PA, Philadelphia County, PA, Arlington County, VA, City of Alexandria, VA, City of Fairfax, VA, City of Falls Church, VA, City of Fredericksburg, VA, City of Manassas, VA, City of Manassas Park, VA, Fairfax County, VA, Prince William County, VA, Stafford County, VA
The radar
The Dover AFB radar (KDOX), 86 km from the middle of the area, began a volume at 19:04 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
Washington/Dulle, VA (KIAD), launched 12:00Z, 7.0 hours before the alert went out and 147 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
- 538 J/kg
- Mixed-layer CIN
- -141 J/kg
- Mixed-layer LCL
- 1337 m above ground
- 0-6 km bulk shear
- 21 kt
- 0-1 km storm-relative helicity
- 37 m²/s²
- 0-3 km storm-relative helicity
- 43 m²/s²
- Significant tornado parameter
- 0.0
- Supercell composite
- 0.0
The text
As transmitted.
367
ACUS11 KWNS 171903
SWOMCD
SPC MCD 171902
NYZ000-NJZ000-PAZ000-DEZ000-MDZ000-DCZ000-VAZ000-172030-
Mesoscale Discussion 1307
NWS Storm Prediction Center Norman OK
0202 PM CDT Sat Jul 17 2021
Areas affected...Portions of northern VA...DC...central/eastern
MD...eastern PA...DE...NJ...and southern NY
Concerning...Severe Thunderstorm Watch 382...
Valid 171902Z - 172030Z
The severe weather threat for Severe Thunderstorm Watch 382
continues.
SUMMARY...The best chance for scattered damaging wind gusts in the
next couple of hours should focus across parts of northern Virginia
into central/eastern Maryland, eastern Pennsylvania, Delaware, New
Jersey, and far southern New York.
DISCUSSION...Storms have started to form into small clusters along
and ahead of a pre-frontal trough across the Mid-Atlantic. The
airmass downstream of these storms is moderately to strongly
unstable, with MLCAPE of 2000-3000 J/kg present. Steep low-level
lapse rates owing to strong diurnal heating of a very well mixed
boundary layer are promoting efficient downdraft accelerations. KEWR
(Newark NJ) measured a peak severe wind gust to 50 kt when a storm
moved through at 1849Z, while KOMH (Orange County Airport in
northern VA) similarly recorded a wind gust to 46 kt at 1815Z.
Modest but sufficient effective bulk shear around 20-30 kt will
likely continue fostering modest storm organization, with multicell
clusters the primary storm mode. Current expectations are for these
clusters to pose a scattered damaging wind threat for the next
couple of hours as they move eastward across northern VA, DC,
central/eastern MD, eastern PA, DE, NJ, and far southern NY,
including the NYC metro area.
..Gleason.. 07/17/2021
...Please see www.spc.noaa.gov for graphic product...
ATTN...WFO...OKX...PHI...CTP...LWX...
LAT...LON 38167794 38717781 39317724 39647653 40637612 41107490
41147392 40917359 39927403 39507426 39127481 38797570
38307739 38167794SPC that day
Everything else SPC issued on the same UTC day.
| Issued | Product | Office | Counties | Lasted |
|---|---|---|---|---|
| Jul 17, 12:00 PM EDT | Mesoscale Discussion | SPC | Kent, New Castle | 3 hr |
| Jul 17, 1:13 PM EDT | Severe Thunderstorm Watch | SPC | Kent, New Castle, Sussex | 10 hr |
| Jul 17, 4:38 PM EDT | Mesoscale Discussion | SPC | New Castle | 97 min |
| Jul 17, 6:54 PM EDT | Mesoscale Discussion | SPC | Kent, New Castle | 2 hr |
| Jul 17, 1:15 PM EDT | Mesoscale Discussion | SPC | Amelia, Appomattox, Brunswick, Buckingham, Campbell, Charlotte and 18 more | 3 hr |
Nearby
Mesoscale Discussions in New Jersey, 2021Mesoscale Discussions in Maryland, 2021Mesoscale Discussions in Virginia, 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.