Alert archive / Virginia / Mesoscale Discussions in 2021
Mesoscale Discussion 533
The Storm Prediction Center issued this mesoscale discussion at May 4, 2021, 3:50 PM EDT for 13 counties in Maryland; 58 counties in Virginia. It was in force for 115 min.
The area
The outline as issued.
The facts
- Issued
- May 4, 2021, 3:50 PM EDT (19:50 UTC)
- Expired
- May 4, 2021, 5:45 PM EDT
- In force
- 115 min
- Issued by
- the Storm Prediction Center
- Concerning
- Severe thunderstorm watch 148
All 71 counties
Anne Arundel County, MD, Baltimore County, MD, Calvert County, MD, Charles County, MD, City of Baltimore, MD, Dorchester 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, Albemarle County, VA, Amelia County, VA, Amherst County, VA, Appomattox County, VA, Arlington County, VA, Buckingham County, VA, Campbell County, VA, Caroline County, VA, Charles City County, VA, Charlotte County, VA, Chesterfield County, VA, City of Alexandria, VA, City of Charlottesville, VA, City of Colonial Heights, VA, City of Fairfax, VA, City of Falls Church, VA, City of Fredericksburg, VA, City of Hopewell, VA, City of Lynchburg, VA, City of Manassas, VA, City of Manassas Park, VA, City of Petersburg, VA, City of Richmond, VA, City of Waynesboro, VA, Clarke County, VA, Culpeper County, VA, Cumberland County, VA, Essex County, VA, Fairfax County, VA, Fauquier County, VA, Fluvanna County, VA, Goochland County, VA, Greene County, VA, Hanover County, VA, Henrico County, VA, King and Queen County, VA, King George County, VA, King William County, VA, Lancaster County, VA, Loudoun County, VA, Louisa County, VA, Madison County, VA, Middlesex County, VA, Nelson County, VA, New Kent County, VA, Northumberland County, VA, Nottoway County, VA, Orange County, VA, Page County, VA, Powhatan County, VA, Prince Edward County, VA, Prince William County, VA, Rappahannock County, VA, Richmond County, VA, Spotsylvania County, VA, Stafford County, VA, Warren County, VA, Westmoreland County, VA
The radar
The Sterling radar (KLWX), 97 km from the middle of the area, began a volume at 19:53 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, 7.8 hours before the alert went out and 96 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
- 82 J/kg
- Mixed-layer CIN
- -253 J/kg
- Mixed-layer LCL
- 1036 m above ground
- 0-6 km bulk shear
- 41 kt
- 0-1 km storm-relative helicity
- 115 m²/s²
- 0-3 km storm-relative helicity
- 97 m²/s²
- Significant tornado parameter
- 0.0
- Supercell composite
- 0.0
The text
As transmitted.
631
ACUS11 KWNS 041950
SWOMCD
SPC MCD 041950
VAZ000-MDZ000-DCZ000-WVZ000-042145-
Mesoscale Discussion 0533
NWS Storm Prediction Center Norman OK
0250 PM CDT Tue May 04 2021
Areas affected...Virginia and Maryland
Concerning...Severe Thunderstorm Watch 148...
Valid 041950Z - 042145Z
The severe weather threat for Severe Thunderstorm Watch 148
continues.
SUMMARY...Damaging winds, and perhaps severe hail, remain likely
across much of Virginia and Maryland as clusters of storms continue
to move east.
DISCUSSION...A few clusters of thunderstorms continue to move east
across central Virginia, and a few reports of wind damage and hail
have been noted within the past hour. Although these storms remain
somewhat unorganized, the environment across central VA into MD
continues to improve. MLCAPE values near 1500 J/kg are noted across
south-central VA, effective bulk shear magnitudes have increased
slightly across the region, and low-level lapse rates have steepened
to around 8 C/km (per recent RAP mesoanalysis). This environment
should remain supportive of a damaging wind/hail threat through the
remainder of the afternoon as boundary-layer heating continues. One
or two bowing segments are possible across north VA/west MD where
low-level shear is slightly stronger (nearly 30 knots 0-3 km bulk
shear noted in KLWX VWP observations), but confidence in this
scenario is low.
..Moore.. 05/04/2021
...Please see www.spc.noaa.gov for graphic product...
ATTN...WFO...PHI...AKQ...LWX...RNK...
LAT...LON 37117963 38097909 39017835 39357760 39537705 39347603
38607579 37917594 37337683 37087781 37007874 37117963SPC that day
Everything else SPC issued on the same UTC day.
| Issued | Product | Office | Counties | Lasted |
|---|---|---|---|---|
| May 4, 1:04 PM EDT | Mesoscale Discussion | SPC | Charles | 56 min |
| May 4, 1:51 PM EDT | Severe Thunderstorm Watch | SPC | Anne Arundel, Baltimore, Calvert, Carroll, Cecil, Charles and 8 more | 6 hr |
| May 4, 5:52 PM EDT | Mesoscale Discussion | SPC | Charles City, Gloucester, Greensville, Isle of Wight, James City, Prince George and 18 more | 53 min |
Nearby
Mesoscale Discussions in Virginia, 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.