Alert archive / Virginia / Mesoscale Discussions in 2021

Mesoscale Discussion 63

February 7, 202162 counties in Virginia; 4 counties in West Virginia

The Storm Prediction Center issued this mesoscale discussion at Feb 7, 2021, 4:24 AM EST for 62 counties in Virginia; 4 counties in West Virginia. It was in force for 6 hr.

The area

The outline as issued.

The facts

Issued: Feb 7, 2021, 4:24 AM EST (09:24 UTC)
Expired: Feb 7, 2021, 10:30 AM EST
In force: 6 hr
Issued by: the Storm Prediction Center
Concerning: Heavy snow

All 66 counties

Albemarle County, VA, Alleghany County, VA, Amherst County, VA, Appomattox County, VA, Augusta County, VA, Bath County, VA, Bedford County, VA, Bland County, VA, Botetourt County, VA, Buckingham County, VA, Campbell County, VA, Caroline County, VA, Carroll County, VA, City of Buena Vista, VA, City of Charlottesville, VA, City of Covington, VA, City of Fredericksburg, VA, City of Galax, VA, City of Harrisonburg, VA, City of Lexington, VA, City of Lynchburg, VA, City of Manassas, VA, City of Manassas Park, VA, City of Martinsville, VA, City of Radford, VA, City of Roanoke, VA, City of Salem, VA, City of Staunton, VA, City of Waynesboro, VA, Craig County, VA, Culpeper County, VA, Cumberland County, VA, Fauquier County, VA, Floyd County, VA, Fluvanna County, VA, Franklin County, VA, Giles County, VA, Goochland County, VA, Greene County, VA, Henry County, VA, Highland County, VA, King George County, VA, Louisa County, VA, Madison County, VA, Montgomery County, VA, Nelson County, VA, Orange County, VA, Page County, VA, Patrick County, VA, Pittsylvania County, VA, Powhatan County, VA, Prince William County, VA, Pulaski County, VA, Rappahannock County, VA, Roanoke County, VA, Rockbridge County, VA, Rockingham County, VA, Shenandoah County, VA, Spotsylvania County, VA, Stafford County, VA, Warren County, VA, Wythe County, VA, Greenbrier County, WV, Mercer County, WV, Monroe County, WV, Summers County, WV

The radar

The Roanoke radar (KFCX), 114 km from the middle of the area, began a volume at 09:26 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

Roanoke, VA (KRNK), launched 00:00Z, 9.4 hours before the alert went out and 63 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: 2168 m above ground
0-6 km bulk shear: 96 kt
0-1 km storm-relative helicity: 191 m²/s²
0-3 km storm-relative helicity: 80 m²/s²
Significant tornado parameter: 0.0
Supercell composite: 0.0

Open this sounding in Storm Lab

The text

As transmitted.

368 
ACUS11 KWNS 070925
SWOMCD
SPC MCD 070924 
MDZ000-VAZ000-WVZ000-071530-

Mesoscale Discussion 0063
NWS Storm Prediction Center Norman OK
0324 AM CST Sun Feb 07 2021

Areas affected...Virginia...Southeast West Virginia

Concerning...Heavy snow 

Valid 070924Z - 071530Z

SUMMARY...Moderate to heavy snow is expected to develop from
southeast West Virginia into western, central and northern Virginia
early this morning. Snowfall rates of 1 inch per hour will be
possible.

DISCUSSION...The latest mosaic radar imagery shows a large area of
precipitation from the central Appalachians eastward to the
Mid-Atlantic. At this time, temperatures are below freezing at the
higher elevations across the central Appalachian Mountains, where
heavy snow was reported last hour in southeastern West Virginia.
This band of snow is forming ahead of a shortwave trough evident on
water vapor imagery. As the shortwave trough moves northeastward
across the central Appalachians early this morning, isentropic
ascent will increase markedly across much of western and central
Virginia. In response, moderate to heavy snow is forecast to develop
with the band across western and central Virginia. The band will
develop northeastward with time, reaching northern Virginia toward
daybreak. Snowfall rates are expected to peak near 1 inch per hour
in the heaviest part of the band. Snow accumulation rates will not
be maximized in areas where surface temperatures remain slightly
above freezing. The potential for this limitation appears greatest
across parts of east-central and northeast Virginia.

..Broyles.. 02/07/2021

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

ATTN...WFO...AKQ...LWX...RNK...RLX...

LAT...LON   36758145 37198147 37738115 38238006 38697904 38977836
            39017761 38717711 38307704 37847737 37217850 36627966
            36568085 36758145

Nearby

Mesoscale Discussions in Virginia, 2021 Mesoscale Discussions in West Virginia, 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.