SWODY1
SPC AC 161936
DAY 1 CONVECTIVE OUTLOOK AMEND 1
NWS STORM PREDICTION CENTER NORMAN OK
0236 PM CDT FRI MAY 16 2008
VALID 161933Z - 171200Z
...THERE IS A SLGT RISK OF SVR TSTMS FROM NRN FL ACROSS THE
CENTRAL/ERN CAROLINAS INTO SERN VA...
RETRANSMITTED PER REQUEST
...NRN FL INTO PARTS OF SRN/EAST CENTRAL GA...
CONVECTIVE MESOSYSTEM IS MOVING EWD AT 30-40 KT ACROSS THE NERN GULF
COAST REGION...WITH RADAR INDICATING A BOW ECHO STRUCTURE ADVANCING
ALONG THE NWRN FL COAST. SURFACE WIND GUSTS FROM METAR OBSERVATIONS
ASSOCIATED WITH THE PASSAGE OF THE BOW ECHO DURING THE LAST HOUR
HAVE BEEN LIMITED TO 20-25 KT...SUGGESTING THAT WEAK LOW LEVEL LAPSE
RATES AND NEAR SATURATED LOW LEVEL ENVIRONMENT SHOWN ON TLH SOUNDING
MAY BE CURRENTLY LIMITING DOWNDRAFT ENHANCEMENT.
HOWEVER...INCREASINGLY STRONG WLY FLOW ALOFT/DEEP LAYER SHEAR
SPREADING ACROSS THE REGION MAY SUPPORT CONTINUED EWD MOVEMENT OF
THE CONVECTIVE BAND FROM THE NWRN FL COAST SWD INTO THE ADJACENT
GULF...WITH POTENTIAL TO PRODUCE A FEW DAMAGING WIND GUSTS THROUGH
THE AFTERNOON/EARLY EVENING HOURS.
DOWNSTREAM FROM THE BOW ECHO...AN EXTENSIVE BAND OF SCATTERED
THUNDERSTORMS HAVE DEVELOPED ACROSS PARTS OF NRN FL INTO SRN GA.
DIURNAL HEATING WITHIN THE CONVECTIVE BAND IS LIKELY TO BE
DIMINISHED AND THIS MAY HELP TO ESTABLISH DIFFERENTIAL HEATING
BOUNDARIES ALONG THE NRN AND SRN EDGES OF THE CONVECTIVE BAND.
MESOSCALE CIRCULATIONS ALONG THESE THERMAL BOUNDARIES MAY RESULT IN
NEW CONVECTIVE DEVELOPMENT ACROSS PARTS OF NRN FL AND CENTRAL GA.
DESPITE MODEST DEEP LAYER LAPSE RATES ACROSS THESE REGIONS AND
GENERALLY WESTERLY UNIDIRECTIONAL WINDS IMMEDIATELY ABOVE THE
GROUND...STRONG HEATING AND DEW POINTS NEAR 70F WILL PROMOTE
DEVELOPMENT OF A FEW STRONG THUNDERSTORMS. INCREASING DEEP LAYER
SHEAR WILL ENHANCE STORM ORGANIZATION...AND STEEPENING LOW LEVEL
LAPSE RATES INDICATE POTENTIAL FOR A FEW DOWNBURSTS TO DEVELOP WITH
STRONGEST STORMS.
...CENTRAL/ERN CAROLINAS INTO SERN VA...
WATER VAPOR IMAGERY SHOWS INITIAL SHORT WAVE TROUGH HAS MOVED OFF
THE MID ATLANTIC COAST WITH SUBSIDENCE IN THE WAKE OF THE SYSTEM.
UPSTREAM TROUGH MOVING ACROSS THE MID MS VALLEY IS FORECAST TO
CONTINUE EWD TOWARD THE APPALACHIANS THIS EVENING. CURRENT SURFACE
LOW OVER THE DELMARVA REGION IS EXPECTED TO MOVE EWD OFF THE COAST
THIS EVENING...WITH SWWD TRAILING COLD FRONT PROGRESSING ACROSS VA
AND THE ERN CAROLINAS DURING THE AFTERNOON AND EVENING. LARGE SCALE
DYNAMIC FORCING FOR ASCENT AND COOLING ALOFT ASSOCIATED WITH THE MS
VALLEY TROUGH IS LIKELY TO REMAIN WEST OF THE SURFACE COLD
FRONT...SUGGESTING THAT FRONTAL CONVERGENCE WILL PROVIDE THE PRIMARY
MESOSCALE FOCUS FOR POSSIBLE THUNDERSTORM DEVELOPMENT. THERE IS
SOME QUESTION CONCERNING THE DEPTH OF LOW LEVEL CONVERGENCE LAYER AS
WINDS ALOFT BECOME WLY ABOVE THE SURFACE AND THE EFFECTIVENESS OF
THE FRONT TO INITIATE CONVECTION WITHIN A MARGINALLY UNSTABLE
ENVIRONMENT. HOWEVER...MOST MODELS DEVELOP STORMS ALONG THE FRONT
THIS AFTERNOON...AND GIVEN THE STRONG DEEP LAYER VERTICAL SHEAR
ACROSS THE REGION COUPLED WITH STRONG HEATING/STEEPENING LOW LEVEL
LAPSE RATES EXPECTED...THREAT FOR DAMAGING WIND GUSTS WILL EXIST
FROM EARLY AFTERNOON INTO THE EVENING HOURS.
..SPC.. 05/16/2008
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