Alert archive / Virginia / Mesoscale Discussions in 2012

Mesoscale Discussion 135

February 19, 20124 states

The Storm Prediction Center issued this mesoscale discussion at Feb 19, 2012, 12:47 PM EST for 4 states. It was in force for 4 hr.

The area

The outline as issued.

The facts

Issued: Feb 19, 2012, 12:47 PM EST (17:47 UTC)
Expired: Feb 19, 2012, 4:45 PM EST
In force: 4 hr
Issued by: the Storm Prediction Center

All 49 counties

Alleghany County, NC, Ashe County, NC, Caswell County, NC, Person County, NC, Rockingham County, NC, Stokes County, NC, Surry County, NC, Watauga County, NC, Wilkes County, NC, Johnson County, TN, Appomattox County, VA, Bedford County, VA, Bland County, VA, Botetourt County, VA, Buchanan County, VA, Campbell County, VA, Carroll County, VA, Charlotte County, VA, City of Danville, VA, City of Galax, VA, City of Lynchburg, VA, City of Martinsville, VA, City of Radford, VA, City of Roanoke, VA, City of Salem, VA, Craig County, VA, Dickenson County, VA, Floyd County, VA, Franklin County, VA, Giles County, VA, Grayson County, VA, Halifax County, VA, Henry County, VA, Lunenburg County, VA, Mecklenburg County, VA, Montgomery County, VA, Patrick County, VA, Pittsylvania County, VA, Prince Edward County, VA, Pulaski County, VA, Roanoke County, VA, Russell County, VA, Smyth County, VA, Tazewell County, VA, Washington County, VA, Wythe County, VA, McDowell County, WV, Mercer County, WV, Monroe County, WV

The radar

The Roanoke radar (KFCX), 14 km from the middle of the area, began a volume at 17:49 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 12:00Z, 5.8 hours before the alert went out and 85 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: 1367 m above ground
0-6 km bulk shear: 95 kt
0-1 km storm-relative helicity: 105 m²/s²
0-3 km storm-relative helicity: 364 m²/s²
Significant tornado parameter: 0.0
Supercell composite: 0.0

Open this sounding in Storm Lab

The text

As transmitted, in the capitals the NWS used until 2016.

968 
ACUS11 KWNS 191748
SWOMCD
SPC MCD 191747
VAZ000-NCZ000-WVZ000-TNZ000-KYZ000-192145-

MESOSCALE DISCUSSION 0135
NWS STORM PREDICTION CENTER NORMAN OK
1147 AM CST SUN FEB 19 2012

AREAS AFFECTED...FAR ERN KY AND SRN WV...WRN/S CNTRL VA...NWRN AND N
CNTRL NC

CONCERNING...HEAVY SNOW

VALID 191747Z - 192145Z

HEAVY SNOW IS BEGINNING TO DEVELOP ACROSS PORTIONS OF THE CNTRL
APPALACHIANS...LIKELY CONTINUING THROUGH THE AFTERNOON WHILE ALSO
SPREADING EWD WITH TIME. INCH AN HOUR RATES WILL OCCUR...ESPECIALLY
LATER THIS AFTERNOON. ISOLATED INSTANCES OF THUNDERSNOW MAY BE
POSSIBLE LATE THIS AFTERNOON INTO THE EARLY EVENING.

17Z SURFACE ANALYSIS SHOWS MOST MODEL SOLUTIONS ARE GENERALLY ON
TRACK WITH THE PROGRESSION OF A SURFACE LOW / ANALYZED NEAR THE SERN
GA/SWRN SC BORDER /...EXPECTED TO GRADUALLY SHIFT OFFSHORE. GREATEST
SURFACE PRESSURE FALLS OVER ERN NC AND ADJACENT WATERS CONFIRM THIS
PROGRESSION...WHICH WILL ALLOW SURFACE WINDS TO THE NORTH TO BACK TO
A MORE NLY DIRECTION...DRAWING COLDER TEMPERATURES INTO THE MID
ATLANTIC REGION. SOME COOLING HAS ALREADY BEEN NOTED...WITH 5 DEGREE
SURFACE TEMPERATURE FALLS OVER THE PAST 3 HRS ACROSS INTERIOR
PORTIONS OF SRN VA...NC...AND NWRN SC. COOLING HAS ALSO BEEN
PARTICULARLY NOTED NEAR ROANOKE WHERE DYNAMIC PROCESSES MAY BE
CONTRIBUTING TO AN OVERALL DROP IN TEMPERATURES THROUGHOUT THE
COLUMN. IN THIS AREA...THE APPROACHING UPPER WAVE NOTED ON WV
IMAGERY ACROSS THE TN VALLEY AS WELL AS FAVORABLE UPPER LEVEL JET
DYNAMICS SHOULD SUPPORT A CONTINUATION OF VERTICAL MOTION...WITH
MOISTENING FROM THE SOUTHWEST FURTHER ENHANCING HEAVY SNOWFALL
POTENTIAL THIS AFTERNOON.

IN THE ADJACENT AREAS TO THE EAST...FURTHER COOLING AND MOISTENING
WILL BE NECESSARY FOR THE ONSET OF SNOW/HEAVY SNOW...WHICH SHOULD
OCCUR LATER TODAY AS GREATER MOISTURE NOTED IN SC ADVECTS NWD AND
COLD AIR DAMMING CONTINUES. ADDITIONAL FORCING FOR ASCENT WILL
ARRIVE THIS EVENING AS ANOTHER SHORT WAVE /CURRENTLY OVER ERN MO/
PROGRESSES SEWD. TO THE WEST...A TRANSITORY THREAT OF HEAVY SNOW MAY
BE POSSIBLE AS COLD AIR ADVECTION OCCURS ON THE HEELS OF GREATER
MOISTURE.

..HURLBUT.. 02/19/2012

...PLEASE SEE WWW.SPC.NOAA.GOV FOR GRAPHIC PRODUCT...

ATTN...WFO...AKQ...LWX...RAH...RNK...RLX...MRX...JKL...

LAT...LON   37608031 37627898 37217814 36547818 36287934 36318054
            36128165 36948243 37208271 37468206 37608031

SPC that day

Everything else SPC issued on the same UTC day.

Issued	Product	Office	Counties	Lasted
Feb 19, 6:02 PM EST	Mesoscale Discussion	SPC	Gates, Halifax, Hertford, Northampton	3 hr

Nearby

Mesoscale Discussions in Virginia, 2012 Mesoscale Discussions in North Carolina, 2012 Mesoscale Discussions in West Virginia, 2012 Every mesoscale discussion in 2012

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.