Alert archive / Virginia / Mesoscale Discussions in 2021
Mesoscale Discussion 1928
The Storm Prediction Center issued this mesoscale discussion at Oct 29, 2021, 3:36 PM EDT for Sussex County, Delaware; 10 counties in Maryland; 20 counties in Virginia. It was in force for 2 hr.
The area
The outline as issued.
The facts
- Issued
- Oct 29, 2021, 3:36 PM EDT (19:36 UTC)
- Expired
- Oct 29, 2021, 6:00 PM EDT
- In force
- 2 hr
- Issued by
- the Storm Prediction Center
- Concerning
- Severe potential...watch unlikely
- Chance of a watch
- 20%
All 31 counties
Sussex County, DE, Anne Arundel County, MD, Calvert County, MD, Caroline County, MD, Dorchester County, MD, Queen Anne's County, MD, Saint Mary's County, MD, Somerset County, MD, Talbot County, MD, Wicomico County, MD, Worcester County, MD, Accomack County, VA, City of Chesapeake, VA, City of Hampton, VA, City of Newport News, VA, City of Norfolk, VA, City of Poquoson, VA, City of Portsmouth, VA, City of Suffolk, VA, City of Virginia Beach, VA, City of Williamsburg, VA, Gloucester County, VA, Isle of Wight County, VA, James City County, VA, Lancaster County, VA, Mathews County, VA, Middlesex County, VA, Northampton County, VA, Northumberland County, VA, Richmond County, VA, York County, VA
The radar
The Norfolk radar (KAKQ), 122 km from the middle of the area, began a volume at 19:38 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, 7.6 hours before the alert went out and 65 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
- 0 J/kg
- Mixed-layer CIN
- No buoyant parcel
- Mixed-layer LCL
- 516 m above ground
- 0-6 km bulk shear
- 67 kt
- 0-1 km storm-relative helicity
- 462 m²/s²
- 0-3 km storm-relative helicity
- 744 m²/s²
- Significant tornado parameter
- 0.0
- Supercell composite
- 0.0
The text
As transmitted.
076
ACUS11 KWNS 291936
SWOMCD
SPC MCD 291936
MDZ000-DEZ000-VAZ000-292200-
Mesoscale Discussion 1928
NWS Storm Prediction Center Norman OK
0236 PM CDT Fri Oct 29 2021
Areas affected...Portions of eastern Virginia...southern/central
Maryland...and Delaware
Concerning...Severe potential...Watch unlikely
Valid 291936Z - 292200Z
Probability of Watch Issuance...20 percent
SUMMARY...Isolated strong to locally damaging wind gusts are
possible, though a Watch is unlikely this afternoon.
DISCUSSION...Broken bands of convection will continue to spread
northward within a broad area of warm air advection located south of
a lifting warm front across portions of the coastal Mid-Atlantic
states. Lower/middle 60s dewpoints located south of the warm front
combined with pockets of diurnal heating are contributing to
generally weak instability amid a favorable vertically veering wind
profile (bulk wind differences of 45 to 55 kts) sampled by the DOX
VAD wind profile. While this environment would generally support the
maintenance and perhaps strengthening of ongoing convection
(especially along immediate coastal areas), poor mid-level lapse
rates along with current inflow layers rooted just above the surface
are limiting the overall intensity of convection and related hazards
thus far. Any convection that can become surface-based could pose a
localized damaging wind gust risk, and a brief tornado cannot be
entirely ruled out owing to favorable effective SRH values of 100 to
200 m2/s2 across the warm sector. Regardless, the overall severe
threat appears too marginal to support Watch issuance.
..Weinman/Gleason/Hart.. 10/29/2021
...Please see www.spc.noaa.gov for graphic product...
ATTN...WFO...PHI...AKQ...LWX...
LAT...LON 36657597 36587639 36677674 37407679 37937675 38657690
39127670 39107625 38977561 38657493 38247496 37217570
36657597SPC that day
Everything else SPC issued on the same UTC day.
| Issued | Product | Office | Counties | Lasted |
|---|---|---|---|---|
| Oct 29, 11:44 AM EDT | Mesoscale Discussion | SPC | Gloucester, King and Queen, King William, Lancaster, Mathews, Middlesex and 9 more | 61 min |
Nearby
Mesoscale Discussions in Virginia, 2021Mesoscale Discussions in Maryland, 2021Mesoscale Discussions in Delaware, 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.