Alert archive / Virginia / Mesoscale Discussions in 2021
Mesoscale Discussion 1653
The Storm Prediction Center issued this mesoscale discussion at Aug 30, 2021, 4:51 PM EDT for 4 states. It was in force for 84 min.
The area
The outline as issued.
The facts
- Issued
- Aug 30, 2021, 4:51 PM EDT (20:51 UTC)
- Expired
- Aug 30, 2021, 6:15 PM EDT
- In force
- 84 min
- Issued by
- the Storm Prediction Center
- Concerning
- Severe potential...watch unlikely
- Chance of a watch
- 5%
All 56 counties
Kent County, DE, New Castle County, DE, Anne Arundel County, MD, Calvert County, MD, Caroline County, MD, Cecil County, MD, Charles County, MD, City of Baltimore, MD, Howard County, MD, Kent County, MD, Montgomery County, MD, Prince George's County, MD, Queen Anne's County, MD, Talbot County, MD, Camden County, NJ, Cumberland County, NJ, Gloucester County, NJ, Salem County, NJ, Albemarle County, VA, Amelia County, VA, Amherst County, VA, Appomattox County, VA, Arlington County, VA, Buckingham County, VA, Caroline County, VA, Chesterfield County, VA, City of Alexandria, VA, City of Buena Vista, VA, City of Charlottesville, VA, City of Fairfax, VA, City of Falls Church, VA, City of Fredericksburg, VA, City of Lynchburg, VA, City of Manassas, VA, City of Manassas Park, VA, City of Richmond, VA, City of Waynesboro, VA, Culpeper County, VA, Cumberland County, VA, Fairfax County, VA, Fauquier County, VA, Fluvanna County, VA, Goochland County, VA, Greene County, VA, Hanover County, VA, King George County, VA, Louisa County, VA, Madison County, VA, Nelson County, VA, Orange County, VA, Powhatan County, VA, Prince Edward County, VA, Prince William County, VA, Rappahannock County, VA, Spotsylvania County, VA, Stafford County, VA
The radar
The Sterling radar (KLWX), 84 km from the middle of the area, began a volume at 20:54 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, 8.9 hours before the alert went out and 80 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
- 843 J/kg
- Mixed-layer CIN
- -70 J/kg
- Mixed-layer LCL
- 860 m above ground
- 0-6 km bulk shear
- 20 kt
- 0-1 km storm-relative helicity
- 65 m²/s²
- 0-3 km storm-relative helicity
- 63 m²/s²
- Significant tornado parameter
- 0.0
- Supercell composite
- 0.0
The text
As transmitted.
406
ACUS11 KWNS 302051
SWOMCD
SPC MCD 302051
NJZ000-DEZ000-PAZ000-MDZ000-VAZ000-DCZ000-302215-
Mesoscale Discussion 1653
NWS Storm Prediction Center Norman OK
0351 PM CDT Mon Aug 30 2021
Areas affected...Portions of the Mid-Atlantic into central Virginia
Concerning...Severe potential...Watch unlikely
Valid 302051Z - 302215Z
Probability of Watch Issuance...5 percent
SUMMARY...Scattered thunderstorms ongoing may be capable of a
damaging gust or two into this evening. Given low
coverage/organization a weather watch is not expected.
DISCUSSION...As of 2035 UTC, regional radar showed several clusters
of thunderstorms ongoing across the Mid Atlantic and Virginia. These
storms were located on the periphery of surface high pressure where
SPC mesoanalysis showed warm temperatures and dewpoints in the 60s
and 70s F were contributing to 2000-2500 J/kg of MLCAPE. Vertical
shear remains quite weak with less than 20 kt depicted from regional
VWPs. Thus, many of these storms have exhibited limited organization
with a primarily multicell/pulse storm mode. However,
temperature/dewpoint spreads near 25 degrees F may support a few
stronger downdrafts capable of damaging wind gusts this afternoon
and early evening. As storms continue to move to the south and east,
gradual weakening is expected as diurnal heating diminishes. Given
the limited potential for organized severe weather, a watch is not
expected. However, a few strong wind gusts may occur.
..Lyons/Grams.. 08/30/2021
...Please see www.spc.noaa.gov for graphic product...
ATTN...WFO...PHI...AKQ...LWX...RNK...
LAT...LON 37607951 38597847 39377670 39757567 39957482 39417490
39017537 38687596 38247677 37817719 37557738 37337757
37257805 37217864 37267928 37297948 37607951Nearby
Mesoscale Discussions in Virginia, 2021Mesoscale Discussions in Maryland, 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.