Alert archive / Virginia / Mesoscale Discussions in 2021
Mesoscale Discussion 124
The Storm Prediction Center issued this mesoscale discussion at Feb 19, 2021, 4:56 AM EST for 5 states. It was in force for 3 hr.
The area
The outline as issued.
The facts
- Issued
- Feb 19, 2021, 4:56 AM EST (09:56 UTC)
- Expired
- Feb 19, 2021, 8:00 AM EST
- In force
- 3 hr
- Issued by
- the Storm Prediction Center
- Concerning
- Freezing rain
All 42 counties
Kent County, DE, Calvert County, MD, Caroline County, MD, Dorchester County, MD, Saint Mary's County, MD, Talbot County, MD, Durham County, NC, Franklin County, NC, Granville County, NC, Vance County, NC, Warren County, NC, Atlantic County, NJ, Cumberland County, NJ, Brunswick County, VA, Charles City County, VA, Chesterfield County, VA, City of Colonial Heights, VA, City of Emporia, VA, City of Hopewell, VA, City of Petersburg, VA, City of Richmond, VA, City of Williamsburg, VA, Dinwiddie County, VA, Essex County, VA, Greensville County, VA, Henrico County, VA, James City County, VA, King and Queen County, VA, King William County, VA, Lancaster County, VA, Lunenburg County, VA, Mecklenburg County, VA, Middlesex County, VA, New Kent County, VA, Northumberland County, VA, Nottoway County, VA, Prince George County, VA, Richmond County, VA, Southampton County, VA, Surry County, VA, Sussex County, VA, Westmoreland County, VA
The radar
The Norfolk radar (KAKQ), 90 km from the middle of the area, began a volume at 10:00 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 00:00Z, 9.9 hours before the alert went out and 116 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
- 482 m above ground
- 0-6 km bulk shear
- 79 kt
- 0-1 km storm-relative helicity
- 419 m²/s²
- 0-3 km storm-relative helicity
- 615 m²/s²
- Significant tornado parameter
- 0.0
- Supercell composite
- 0.0
The text
As transmitted.
492
ACUS11 KWNS 190956
SWOMCD
SPC MCD 190956
NJZ000-DEZ000-MDZ000-VAZ000-NCZ000-191300-
Mesoscale Discussion 0124
NWS Storm Prediction Center Norman OK
0356 AM CST Fri Feb 19 2021
Areas affected...northern NC...southeast and eastern VA...eastern
shore of MD...DE...far southern NJ
Concerning...Freezing rain
Valid 190956Z - 191300Z
SUMMARY...Freezing rain rates around 0.05 inch per 3 hours are
forecast from eastern VA into southern NJ through 8am EST.
DISCUSSION...Radar mosaic shows a shield of light precipitation from
the Carolinas northward into the Delmarva as of 445am EST. The
precipitation is occurring on the northwestern periphery of a deep
tropospheric moisture plume (according to water-vapor imagery) with
origins emanating from the Gulf of Mexico/northwest Caribbean.
Model guidance indicates the spatial expansion and increase in
precipitation rate over VA is primarily a result of strengthening
frontogenesis in the 700-600 mb layer. This band of frontogenetic
ascent is co-located with surface temperatures in the 30-32 degree F
range on the northwestern edge of the precipitation shield.
Forecast soundings show a warm layer near 850 mb atop a shallow
sub-freezing layer near near the surface---supporting freezing rain
as the precipitation type. Precipitation rates will probably
approach and perhaps locally exceed 0.05 inch per 3 hours through
8am EST.
..Smith.. 02/19/2021
...Please see www.spc.noaa.gov for graphic product...
ATTN...WFO...PHI...AKQ...LWX...RAH...RNK...
LAT...LON 38757546 38127610 36517725 35997822 36027907 37197805
38927629 39577446 38757546Nearby
Mesoscale Discussions in Virginia, 2021Mesoscale Discussions in Maryland, 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.