Alert archive / Virginia / Mesoscale Discussions in 2021
Mesoscale Discussion 1899
The Storm Prediction Center issued this mesoscale discussion at Oct 25, 2021, 3:01 PM EDT for 25 counties in North Carolina; 33 counties in Virginia. It was in force for 119 min.
The area
The outline as issued.
The facts
- Issued
- Oct 25, 2021, 3:01 PM EDT (19:01 UTC)
- Expired
- Oct 25, 2021, 5:00 PM EDT
- In force
- 119 min
- Issued by
- the Storm Prediction Center
- Concerning
- Severe potential...watch possible
- Chance of a watch
- 40%
All 58 counties
Alamance County, NC, Alexander County, NC, Caswell County, NC, Chatham County, NC, Davidson County, NC, Davie County, NC, Durham County, NC, Forsyth County, NC, Franklin County, NC, Granville County, NC, Guilford County, NC, Halifax County, NC, Iredell County, NC, Nash County, NC, Northampton County, NC, Orange County, NC, Person County, NC, Randolph County, NC, Rockingham County, NC, Rowan County, NC, Stokes County, NC, Vance County, NC, Wake County, NC, Warren County, NC, Yadkin County, NC, Amelia County, VA, Appomattox County, VA, Brunswick County, VA, Buckingham County, VA, Campbell County, VA, Charles City County, VA, Charlotte County, VA, Chesterfield County, VA, City of Colonial Heights, VA, City of Danville, VA, City of Emporia, VA, City of Hopewell, VA, City of Martinsville, VA, City of Petersburg, VA, City of Richmond, VA, Cumberland County, VA, Dinwiddie County, VA, Fluvanna County, VA, Goochland County, VA, Greensville County, VA, Halifax County, VA, Hanover County, VA, Henrico County, VA, Henry County, VA, Louisa County, VA, Lunenburg County, VA, Mecklenburg County, VA, Nottoway County, VA, Pittsylvania County, VA, Powhatan County, VA, Prince Edward County, VA, Prince George County, VA, Sussex County, VA
The radar
The Raleigh/Durham radar (KRAX), 102 km from the middle of the area, began a volume at 19:04 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 watches that followed
Watches SPC issued over any of the same counties within four hours of this discussion.
The nearest sounding before it
Roanoke, VA (KRNK), launched 12:00Z, 7.0 hours before the alert went out and 91 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
- 1208 m above ground
- 0-6 km bulk shear
- 33 kt
- 0-1 km storm-relative helicity
- 106 m²/s²
- 0-3 km storm-relative helicity
- 41 m²/s²
- Significant tornado parameter
- 0.0
- Supercell composite
- 0.0
The text
As transmitted.
316
ACUS11 KWNS 251902
SWOMCD
SPC MCD 251901
VAZ000-NCZ000-252100-
Mesoscale Discussion 1899
NWS Storm Prediction Center Norman OK
0201 PM CDT Mon Oct 25 2021
Areas affected...parts of central and western North Carolina into
south-central Virginia
Concerning...Severe potential...Watch possible
Valid 251901Z - 252100Z
Probability of Watch Issuance...40 percent
SUMMARY...Severe risk -- largely in the form of locally strong wind
gusts -- will gradually increase this afternoon and into early
evening. A WW may be required.
DISCUSSION...A band of pre-frontal large-scale ascent -- associated
with a mid-/upper-level vort max crossing western Ohio -- continues
to spread across the Appalachians at this time. Ahead of this band
of cloud cover/precipitation, weak heating/destabilization is
ongoing across an area centered from south-central Virginia into
central North Carolina. Here, temperatures warming into the 70s and
dewpoints increasing into the 60s have resulted in 500 J/kg
mixed-layer CAPE development per recent objective analysis. As
large-scale ascent gradually overspreads this slightly more unstable
environment, an increase in coverage/intensity of what thus far has
been weak convection east of the mountains, is expected.
As stronger/southwesterly flow aloft likewise spreads atop the area
of greatest instability, shear will become supportive of organized
storms. While a few rotating cells may evolve initially, which
would include a non-zero tornado risk, upscale growth into
lines/bands is expected -- particularly this evening as the cold
front moves/redevelops east of the mountains. As such, the more
substantial overall risk is likely to be wind.
..Goss/Thompson.. 10/25/2021
...Please see www.spc.noaa.gov for graphic product...
ATTN...WFO...AKQ...LWX...RAH...RNK...GSP...
LAT...LON 35597969 35538083 35958135 36747983 37927859 38047771
37417688 36237739 35847816 35597969SPC that day
Everything else SPC issued on the same UTC day.
| Issued | Product | Office | Counties | Lasted |
|---|---|---|---|---|
| Oct 25, 6:26 PM EDT | Severe Thunderstorm Watch | SPC | Alamance, Caswell, Durham, Forsyth, Granville, Guilford and 6 more | 4 hr |
| Oct 25, 6:41 PM EDT | Mesoscale Discussion | SPC | Loudoun | 2 hr |
Nearby
Mesoscale Discussions in Virginia, 2021Mesoscale Discussions in North Carolina, 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.