Alert archive / Virginia / Mesoscale Discussions in 2021

Mesoscale Discussion 791

May 28, 20216 counties in Maryland; 7 counties in Virginia

The Storm Prediction Center issued this mesoscale discussion at May 28, 2021, 7:18 PM EDT for 6 counties in Maryland; 7 counties in Virginia. It was in force for 87 min.

The area

The outline as issued.

The facts

Issued: May 28, 2021, 7:18 PM EDT (23:18 UTC)
Expired: May 28, 2021, 8:45 PM EDT
In force: 87 min
Issued by: the Storm Prediction Center
Concerning: Severe potential...watch unlikely
Chance of a watch: 5%

Counties Calvert County, MD, Charles County, MD, Dorchester County, MD, Saint Mary's County, MD, Somerset County, MD, Wicomico County, MD, Accomack County, VA, Essex County, VA, Lancaster County, VA, Middlesex County, VA, Northumberland County, VA, Richmond County, VA, Westmoreland County, VA

The radar

The Dover AFB radar (KDOX), 114 km from the middle of the area, began a volume at 23:18 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

Wallops Is Stn, VA (KWAL), launched 12:00Z, 11.3 hours before the alert went out and 79 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.

Skew-T log-p

Temperature in red, dew point in green, the mixed-layer parcel dashed.

Hodograph

The wind turning with height, colored by layer: ground to 1 km, 1 to 3 km, 3 to 6 km, 6 to 10 km.

Mixed-layer CAPE: 0 J/kg
Mixed-layer CIN: No buoyant parcel
Mixed-layer LCL: 1176 m above ground
0-6 km bulk shear: 42 kt
0-1 km storm-relative helicity: 71 m²/s²
0-3 km storm-relative helicity: 226 m²/s²
Significant tornado parameter: 0.0
Supercell composite: 0.0

Open this sounding in Storm Lab

The text

As transmitted.

152 
ACUS11 KWNS 282319
SWOMCD
SPC MCD 282318 
MDZ000-VAZ000-290045-

Mesoscale Discussion 0791
NWS Storm Prediction Center Norman OK
0618 PM CDT Fri May 28 2021

Areas affected...far eastern Virginia into southern Maryland

Concerning...Severe potential...Watch unlikely 

Valid 282318Z - 290045Z

Probability of Watch Issuance...5 percent

SUMMARY...Strong storms are expected to continue for a couple more
hours. A damaging gust or a brief tornado cannot be ruled out. A WW
issuance is not expected.

DISCUSSION...An uptick in convective intensity has been noted with
discrete storms traversing a warm front across far eastern Virginia,
with MRMS mosaic radar data showing 50 dBZ extending up to 25 kft
with some of the stronger cells. KDOX has also shown some transient
rotation associated with these storms as well. MLCAPE is roughly 500
J/kg on the warm side of the front. However, recent KDOX VWPs show
around 250 m2/s2 0-1 km SRH present, with RAP forecast soundings
suggesting that much of the SRH is within the effective inflow
layer. As such, a damaging gust or a brief tornado may occur before
boundary layer stabilization reduces the severe threat. Nonetheless,
the severe threat is expected to remain sparse enough to preclude a
WW issuance.

..Squitieri/Edwards.. 05/28/2021

...Please see www.spc.noaa.gov for graphic product...

ATTN...WFO...AKQ...LWX...

LAT...LON   37687685 38267712 38537700 38577629 38407545 38097527
            37667538 37557639 37687685

SPC that day

Everything else SPC issued on the same UTC day.

Issued	Product	Office	Counties	Lasted
May 28, 3:56 PM EDT	Mesoscale Discussion	SPC	Charles, Saint Mary's	2 hr

Nearby

Mesoscale Discussions in Virginia, 2021 Mesoscale Discussions in Maryland, 2021 Every 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.