Mesoscale Discussion 2200

Issued

Dec 21, 2012, 12:24 AM EST (05:24 UTC)

Expired

Dec 21, 2012, 2:30 AM EST

In force

2 hr

Issued by

the Storm Prediction Center

Chance of a watch

40%

The Norfolk radar (KAKQ), 76 km from the middle of the area, began a volume at 05:24 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.

476 
ACUS11 KWNS 210524
SWOMCD
SPC MCD 210524 
VAZ000-NCZ000-210730-

MESOSCALE DISCUSSION 2200
NWS STORM PREDICTION CENTER NORMAN OK
1124 PM CST THU DEC 20 2012

AREAS AFFECTED...COASTAL NC/SOUTHEAST VA/SOUTHEAST MD

CONCERNING...SEVERE POTENTIAL...WATCH POSSIBLE 

VALID 210524Z - 210730Z

PROBABILITY OF WATCH ISSUANCE...40 PERCENT

SUMMARY...THE POTENTIAL FOR CONVECTIVELY INDUCED DAMAGING
WINDS...AND POSSIBLY EVEN A TORNADO...MAY INCREASE THROUGH 07Z-08Z
ACROSS THE COASTAL PLAIN OF NC AND SOUTHEAST VA. WHILE UNCERTAINTIES
EXIST REGARDING THE LIKELIHOOD/EXTENT OF THE SEVERE
RISK...ORGANIZATIONAL/INTENSITY TRENDS WILL BE CLOSELY MONITORED FOR
A POSSIBLE WATCH.

DISCUSSION...AS AN EXTREMELY STRONG WIND FIELD OVERSPREADS THE
REGION IN ASSOCIATION WITH A MIDWEST-CENTERED UPPER TROUGH...SEVERAL
QUASI-LINEAR/NON-LIGHTNING PRODUCING NARROW CONVECTIVE SEGMENTS HAVE
DEVELOPED ACROSS THE PIEDMONT OF NC SINCE LATE EVENING. THIS IS
OCCURRING NEAR AN EASTWARD-MOVING COLD FRONT AND IN TANDEM WITH THE
DEEPENING PHASE OF A SECONDARY SURFACE LOW. AS OF 05Z...THE SURFACE
LOW IS AROUND 995 MB IN CENTRAL VA...WITH SUBSTANTIAL SURFACE
PRESSURE FALLS NOTED /6-8 MB PER 2HR/ ACROSS EASTERN VA AND ADJACENT
MD/DE. AHEAD OF THE COLD FRONT AND AFOREMENTIONED CONVECTIVE
DEVELOPMENT...A MODESTLY MOIST LOW-LEVEL AIRMASS CONTINUES TO
STEADILY DEVELOP NORTHWARD...WITH AROUND 60F SURFACE DEWPOINTS
BECOMING INCREASINGLY PREVALENT ACROSS SOUTHEAST/EAST-CENTRAL NC AS
OF 05Z.

THE PRIMARY SHORT-TERM UNCERTAINTY RELATES TO MODEST NATURE OF
LOW-LEVEL MOISTURE AND ASSOCIATED MEAGER NEAR-SURFACE BUOYANCY
WITHIN THE WARM SECTOR...ALTHOUGH IT IS PLAUSIBLE THAT A COUPLE
HUNDRED J/KG OF SBCAPE MAY QUICKLY MATERIALIZE EARLY IN THE
OVERNIGHT AS CONSISTENT WITH 00Z NAM/GFS GUIDANCE. EVEN WITH THESE
LIMITATIONS...IF ORGANIZED NEAR-SURFACE BASED STORM STRUCTURES CAN
DEVELOP/MATURE AND REMAIN SUSTAINED...EVEN WITH LITTLE OR NO
CLOUD-GROUND LIGHTNING...AT LEAST CONVECTIVELY ENHANCED WIND GUSTS
WOULD BE POSSIBLE OVERNIGHT AS ACCENTUATED BY ANY SMALL-BOWING
SEGMENTS/SHALLOW SUPERCELL STRUCTURES. LATE EVENING WSR-88D VWP DATA
FROM WAKEFIELD VA/RALEIGH NC ARE INDICATIVE OF 65-70 KT
SOUTHWESTERLY WINDS WITHIN THE LOWEST 0.5-3 KM. 00Z-BASED
CONVECTION-ALLOWING GUIDANCE SUCH AS THE WRF-NMM/WRF-NSSL LEND
CREDITABILITY TO THE IDEA THAT A FORCED CONVECTIVE LINE MAY EVOLVE
AND QUICKLY SPREAD EAST-NORTHEASTWARD THROUGH THE OVERNIGHT.

..GUYER/CARBIN.. 12/21/2012

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

ATTN...WFO...AKQ...MHX...LWX...RAH...ILM...

LAT...LON   36317578 34797660 34257783 34607839 36457802 37917790
            38467750 37627586 36317578

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

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.