Alert archive / Virginia / Mesoscale Discussions in 2014

Mesoscale Discussion 71

February 4, 20144 states

The Storm Prediction Center issued this mesoscale discussion at Feb 4, 2014, 9:45 PM EST for 4 states. It was in force for 6 hr.

The area

The outline as issued.

The facts

Issued: Feb 4, 2014, 9:45 PM EST (02:45 UTC)
Expired: Feb 5, 2014, 3:45 AM EST
In force: 6 hr
Issued by: the Storm Prediction Center

All 65 counties

Allegany County, MD, Baltimore County, MD, Carroll County, MD, Cecil County, MD, City of Baltimore, MD, Frederick County, MD, Garrett County, MD, Harford County, MD, Howard County, MD, Montgomery County, MD, Washington County, MD, Adams County, PA, Bedford County, PA, Chester County, PA, Cumberland County, PA, Fayette County, PA, Franklin County, PA, Fulton County, PA, Greene County, PA, Lancaster County, PA, Somerset County, PA, York County, PA, Alleghany County, VA, Augusta County, VA, Bath County, VA, Botetourt County, VA, City of Buena Vista, VA, City of Covington, VA, City of Harrisonburg, VA, City of Lexington, VA, City of Roanoke, VA, City of Salem, VA, City of Staunton, VA, City of Waynesboro, VA, City of Winchester, VA, Clarke County, VA, Craig County, VA, Fauquier County, VA, Frederick County, VA, Giles County, VA, Highland County, VA, Loudoun County, VA, Montgomery County, VA, Page County, VA, Rappahannock County, VA, Roanoke County, VA, Rockbridge County, VA, Rockingham County, VA, Shenandoah County, VA, Warren County, VA, Berkeley County, WV, Grant County, WV, Hampshire County, WV, Hardy County, WV, Jefferson County, WV, Marion County, WV, Mineral County, WV, Monongalia County, WV, Monroe County, WV, Morgan County, WV, Pendleton County, WV, Pocahontas County, WV, Preston County, WV, Taylor County, WV, Tucker County, WV

The radar

The Sterling radar (KLWX), 126 km from the middle of the area, began a volume at 02:43 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

Washington/Dulle, VA (KIAD), launched 00:00Z, 2.8 hours before the alert went out and 134 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: 970 m above ground
0-6 km bulk shear: 86 kt
0-1 km storm-relative helicity: 259 m²/s²
0-3 km storm-relative helicity: 357 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.

680 
ACUS11 KWNS 050245
SWOMCD
SPC MCD 050245 
PAZ000-DEZ000-MDZ000-DCZ000-VAZ000-WVZ000-050845-

MESOSCALE DISCUSSION 0071
NWS STORM PREDICTION CENTER NORMAN OK
0845 PM CST TUE FEB 04 2014

AREAS AFFECTED...SRN PA...ERN WV...WRN VA...NRN MD...NRN DE

CONCERNING...FREEZING RAIN 

VALID 050245Z - 050845Z

SUMMARY...FREEZING RAIN WILL DEVELOP EAST OF THE APPALACHIANS INTO
THE NRN DELMARVA OVER THE NEXT FEW HOURS.  RAIN RATES WILL LIKELY
EXCEED 0.05 IN/HR.  SLEET WILL BE COMMON ACROSS SOUTHERN PORTIONS OF
PA THROUGH MIDNIGHT.

DISCUSSION...MATURING WARM CONVEYOR WITH AN EXPANSIVE ZONE OF
PRECIPITATION IS SPREADING ACROSS THE OH/TN VALLEY AND WILL SOON
SPREAD ACROSS HIGHER TERRAIN OF WRN PA/WV INTO WRN VA/MD AREA. 
ADDITIONALLY...WARM ADVECTION ACROSS THE DELMARVA APPEARS TO BE
PRIMARILY RESPONSIBLE FOR RECENT RASH OF SHOWERS THAT HAVE DEVELOPED
ACROSS THIS REGION.  WEDGE OF COOL AIR WEST OF THE BLUE RIDGE IS
SEVERAL DEGREES BELOW FREEZING AT 02Z AND IS LIKELY ON THE ORDER OF
1KM DEEP.  THIS WILL GRADUALLY SHALLOW WITH TIME BUT SHOULD NOT WARM
ABOVE FREEZING IN MANY PLACES PRIOR TO 06Z.

FARTHER NORTH...INITIAL PRECIPITATION WILL FALL IN THE FORM OF
SLEET...OR PERHAPS EVEN SOME SNOW...ACROSS SRN PA.  WITH TIME MUCH
WARMER TEMPERATURES AROUND 2KM WILL SPREAD ATOP COOL BOUNDARY LAYER
RESULTING IN SUFFICIENT MELTING FOR A SWITCH TO FREEZING RAIN AFTER
06Z.  PRECIPITATION RATES WILL INCREASE TO NEAR 0.10 INCH PER HOUR
IN PLACES AS WARM ADVECTION CREATES A FAVORABLE PROFILE FOR
SIGNIFICANT ICING.  WBZ LEVELS REMAIN BELOW FREEZING ALONG THE I-95
CORRIDOR FROM DC THROUGH BWI TO PHL.  WHILE WARMING WILL EVENTUALLY
DRIVE SFC TEMPERATURES ABOVE FREEZING...THIS MAY NOT OCCUR UNTIL
AFTER 10Z.

..DARROW.. 02/05/2014

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

ATTN...WFO...PHI...CTP...LWX...RNK...PBZ...RLX...

LAT...LON   39568052 40108003 40447777 40237585 39787545 39337608
            38457841 37477946 37048026 37328077 37928041 38857973
            39328004 39568052

SPC that day

Everything else SPC issued on the same UTC day.

Issued	Product	Office	Counties	Lasted
Feb 4, 8:12 PM EST	Mesoscale Discussion	SPC	Armstrong, Beaver, Butler, Cameron, Clarion, Crawford and 10 more	6 hr
Feb 5, 12:44 AM EST	Mesoscale Discussion	SPC	Bucks, Delaware, Montgomery, Philadelphia	5 hr
Feb 5, 12:57 AM EST	Mesoscale Discussion	SPC	Bradford, Cameron, Carbon, Centre, Clearfield, Clinton and 20 more	5 hr

Nearby

Mesoscale Discussions in Virginia, 2014 Mesoscale Discussions in West Virginia, 2014 Mesoscale Discussions in Maryland, 2014 Every mesoscale discussion in 2014

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.