Alert archive / Maryland / Mesoscale Discussions in 2021
Mesoscale Discussion 1140
The Storm Prediction Center issued this mesoscale discussion at Jul 1, 2021, 2:36 PM EDT for 5 states. It was in force for 84 min.
The area
The outline as issued.
The facts
- Issued
- Jul 1, 2021, 2:36 PM EDT (18:36 UTC)
- Expired
- Jul 1, 2021, 4:00 PM EDT
- In force
- 84 min
- Issued by
- the Storm Prediction Center
- Concerning
- Severe thunderstorm watch 331
All 45 counties
Kent County, DE, New Castle County, DE, Anne Arundel County, MD, Baltimore County, MD, Calvert County, MD, Caroline County, MD, Cecil County, MD, Charles County, MD, City of Baltimore, MD, Dorchester County, MD, Harford County, MD, Howard County, MD, Kent County, MD, Montgomery County, MD, Prince George's County, MD, Queen Anne's County, MD, Saint Mary's County, MD, Talbot County, MD, Burlington County, NJ, Camden County, NJ, Cumberland County, NJ, Gloucester County, NJ, Mercer County, NJ, Salem County, NJ, Bucks County, PA, Chester County, PA, Delaware County, PA, Montgomery County, PA, Philadelphia County, PA, Arlington County, VA, Caroline 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, Essex County, VA, Fairfax County, VA, King George County, VA, Prince William County, VA, Richmond County, VA, Spotsylvania County, VA, Stafford County, VA, Westmoreland County, VA
The radar
The Dover AFB radar (KDOX), 78 km from the middle of the area, began a volume at 18:35 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, 6.6 hours before the alert went out and 98 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
- 604 J/kg
- Mixed-layer CIN
- -48 J/kg
- Mixed-layer LCL
- 928 m above ground
- 0-6 km bulk shear
- 32 kt
- 0-1 km storm-relative helicity
- 61 m²/s²
- 0-3 km storm-relative helicity
- 108 m²/s²
- Significant tornado parameter
- 0.2
- Supercell composite
- 1.2
The text
As transmitted.
255
ACUS11 KWNS 011836
SWOMCD
SPC MCD 011836
NJZ000-PAZ000-DEZ000-MDZ000-VAZ000-DCZ000-012000-
Mesoscale Discussion 1140
NWS Storm Prediction Center Norman OK
0136 PM CDT Thu Jul 01 2021
Areas affected...Portions of northern VA into MD...DC...DE...far
southeastern PA...and southern NJ
Concerning...Severe Thunderstorm Watch 331...
Valid 011836Z - 012000Z
The severe weather threat for Severe Thunderstorm Watch 331
continues.
SUMMARY...The greatest threat for scattered damaging wind gusts in
the short term should exist from parts of northern Virginia to the
Delmarva Peninsula and southern New Jersey.
DISCUSSION...Storms have begun to congeal into clusters across
northern VA and MD, with a leading supercell approaching the
Chesapeake Bay. Deep-layer shear of 30-40 kt will continue to
support storm organization, with a mix of multicell clusters and
leading supercells possible. Even though lapse rates aloft remain
modest, hail up to 1.75 inches in diameter has been reported with
the leading supercell in MD. Occasional severe hail may remain
possible in the short term with any storm that can remain at least
semi-discrete. Otherwise, scattered damaging wind gusts will likely
be the primary severe threat as storms continue spreading eastward
this afternoon. The greatest threat for damaging wind gusts should
exist across parts of northern VA into central/eastern MD and DE
where robust heating is supporting MLCAPE of 1000-2000 J/kg and
steep low-level lapse rates. At least an isolated damaging wind
threat may also exist with a small cluster of storms moving eastward
across far southeastern PA into southern NJ, but instability is
comparatively weaker with northward extent across this region owing
to earlier precipitation/storms.
..Gleason.. 07/01/2021
...Please see www.spc.noaa.gov for graphic product...
ATTN...WFO...PHI...AKQ...LWX...
LAT...LON 37997770 38577786 39317722 39727608 40317553 40437531
40337461 39857451 38867546 37907633 37887704 37997770SPC that day
Everything else SPC issued on the same UTC day.
| Issued | Product | Office | Counties | Lasted |
|---|---|---|---|---|
| Jul 1, 11:45 AM EDT | Mesoscale Discussion | SPC | Kent, New Castle, Sussex | 2 hr |
| Jul 1, 12:46 PM EDT | Severe Thunderstorm Watch | SPC | Kent, New Castle, Sussex | 7 hr |
| Jul 1, 4:16 PM EDT | Mesoscale Discussion | SPC | Kent, New Castle, Sussex | 89 min |
Nearby
Mesoscale Discussions in Maryland, 2021Mesoscale Discussions in Virginia, 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; radar from the NEXRAD Level II archive.