SWOMCD
SPC MCD 171514
VAZ000-NCZ000-MDZ000-171715-
MESOSCALE DISCUSSION 0796
NWS STORM PREDICTION CENTER NORMAN OK
1014 AM CDT TUE MAY 17 2011
AREAS AFFECTED...PARTS OF CENTRAL/SRN VA...SRN MD AND NRN NC
CONCERNING...SEVERE POTENTIAL...WATCH UNLIKELY
VALID 171514Z - 171715Z
STRONGER AND PERSISTENT UPDRAFTS WILL HAVE THE POTENTIAL TO PRODUCE
AN ISOLATED STRONG WIND GUST OR TWO. GIVEN THE PRESENCE OF AMBIENT
VORTICITY ATTENDANT TO THE CLOSED LOW TRACKING NNWWD FROM CENTRAL NC
AND SURFACE VORTICITY FOCUSED INVOF TWO WARM FRONTS OVER VA...A LOW
PROBABILITY EXISTS FOR AN ISOLATED TORNADO.
LATE MORNING SURFACE ANALYSES SHOWED AN AREA OF LOW PRESSURE
CENTERED OVER WEST CENTRAL NC /40 SSW GSO/ WITH THIS FEATURE MOVING
SLOWLY NWD. ONE WARM FRONT EXTENDED NNEWD FROM THIS LOW INTO WRN VA
/NEAR SHD/ AND THEN THROUGH SERN PA TO ALONG/S OF LONG ISLAND. A
SECOND WARM FRONT/DIFFERENTIAL HEATING BOUNDARY /PER VISIBLE IMAGERY
AND SURFACE OBSERVATIONS/ EXTENDED NEWD INTO CENTRAL VA AND THEN
STRETCHED SEWD TO JUST N OF ORF. SURFACE HEATING ALONG/S OF THE
SECOND WARM FRONT HAS ALLOWED TEMPERATURES TO RISE INTO THE MID 60S
TO AROUND 70...EFFECTIVELY ELIMINATING THE WEAK CAP THAT WAS PRESENT
ON THE 12Z SOUNDINGS AND SUPPORTING CU DEVELOPMENT PER VISIBLE
IMAGERY. DESPITE THE DIABATIC HEATING...MODEST MIDLEVEL LAPSE RATES
/6-6.5 C PER KM/ ARE TENDING TO INHIBIT STRONGER DESTABILIZATION.
ADDITIONAL SURFACE HEATING WILL...HOWEVER...STEEPEN LOW LEVEL LAPSE
RATES AND ENHANCE THE POTENTIAL FOR STRONGER WIND GUSTS WITH MORE
PERSISTENT STORMS TODAY.
AT 15Z...REGIONAL RADAR IMAGERY SHOWED A PERSISTENT AREA OF TSTMS
MOVING NWD ACROSS CENTRAL VA WITH THIS ACTIVITY LOCATED ALONG THE
SECONDARY WARM FRONT/LOW LEVEL CONVERGENCE. TSTMS WERE ALSO
TRACKING NWD THROUGH NERN NC WITH THIS ACTIVITY LIKELY ATTENDANT TO
STRONGER DCVA WITH A MIDLEVEL IMPULSE ROTATING THROUGH THE NERN
PERIPHERY OF THE NC CLOSED LOW. ALTHOUGH DEEP LAYER SHEAR WILL
INCREASE AS STRONGER MIDLEVEL WINDS SPREAD ACROSS VA/NRN NC
SUPPORTING PRIMARILY MULTICELLS...WEAK INSTABILITY IS EXPECTED TO
PRECLUDE GREATER COVERAGE OF STRONGER STORMS. THESE FACTORS SUGGEST
A WW IS NOT WARRANTED AT THIS TIME.
..PETERS.. 05/17/2011
...PLEASE SEE WWW.SPC.NOAA.GOV FOR GRAPHIC PRODUCT...
ATTN...WFO...AKQ...MHX...LWX...RAH...RNK...
LAT...LON 35147612 35957762 36187967 36248036 36738061 38117936
38717844 38917760 38697667 38357631 37607579 36277581
35147612
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