Flash Flood Warning 3, NWS Greenville-Spartanburg, SC

AREA FORECAST DISCUSSION
NATIONAL WEATHER SERVICE GREENVILLE-SPARTANBURG SC
150 PM EDT TUE MAY 2 2000

LOCATION OF SFC FRONT AGREES WELL WITH THE 12Z ETA. FRONT IS PROGGED
TO DEVELOP ALONG BARRIER COMPONENT AND SLIDE JUST S AND W OF THE
CWA BY WED MORNING. HIGH CONTINUES TO BUILD INTO THE REGION...
PUSHING SFC CONVERGENCE WELL W OF THE AREA WED AFTN THROUGH THU.
THIS RAISES SOME INTERESTING QUESTIONS AS THERE ARE RATHER LARGE
MODEL DIFFERENCES IN THE QPF FIELDS.

THE FIRST PERIOD LOOKS REASONABLE AS THE ETA GENERATES CONVECTIVE
PCPN ALONG ZONE OF STRONG SFC CONVERGENCE AS THE BACK DOOR FRONT
DROPS INTO THE NC PIEDMONT. THIS CONVECTION MOVES SE...ALONG THE
SFC BNDRY...OVERNIGHT. WEAK H5 MINOR WAVE AND RETREATING H3 JET
LEND SUPPORT FROM SOME KIND OF RELATIVELY WEAK MCS. LAPSE RATES ARE
NOT VERY STEEP...THOUGH LVLV MOISTURE IS INCREASING. CAPES AVERAGING
AROUND 1000 OVER MOST OF THE CWA ATTM. THUS...SOME CONVECTION IS
POSSIBLE ALMOST ANYWHERE THIS EVENING. WL KEEP AN EYE ON TRENDS...BUT
PLAN TO HAVE HIGHEST POPS ERN ZONES...AND LOWER POPS W.

BY WED MOST OF THE BNDRY LAYER FLOW OVER THE CWA IS E TO ENE...AND
RATHER BRISK IF THE ETA IS CORRECT. HARD TO IMAGINE MUCH CONVECTION
WL DEVELOP WHERE THERE IS NO SFC CONVERGENCE AND PRACTICALLY NO
FORCING ALOFT AS UPPER RIDGE ROLLS OVER THE AREA. THINK MOST
CONVECTION WOULD DEVELOP ON SFC CONVERGENCE WELL W OF THE CWA. THE
MTNS...HOWEVER...SHOULD SEE SOME TSRA DEVELOP W/DIFFERENTIAL HEATING
AND AS THEY WL BE ABOVE THS COLD POOL. ETA HAS LLVL DWPTS POOL
ALONG AND N OF THE BNDRY W/M60 DWPTS FEEDING ANYTHING THAT DOES GO
IN THE HIGHER ELEVATIONS. WL UNDERCUT TEMPS AS WE WL HAVE NE FLOW
AND A CLOUD DECK OVER THE COLD POOL. 12Z SFC TRAJECTORIES HAVE THE
SOURCE REGION FOR THE AIRMASS NOT TOO FAR TO THE N...SO WL ONLY
UNDERCUT RAFS BY 5 OR 6 DEG UNLESS OTHER OFFICES OBJECT.

ETA DEVELOPS A HUGE AREA OF RAIN OVER THE SW CWA WED NGHT AND KEEPS
IT THERE THROUGH THU. WE/D BE LOOKING AT 2 INCHES OF RAIN IF IT WAS
RIGHT. THE AVN IS FURTHER SW AND THE UKMET SIMPLY HAS A LOT LESS
PCPN. AGAIN...THINK MOST CONVECTION WL FORM ALONG SFC CONVERGENCE W
OF CWA...WITH ONLY THE MTN ELEVATIONS REALLY SEEING ANY SIG PCPN.
HARD TO COMPLETELY ARGUE AGAINST THE ETA HOWEVER...AND WL BUMP POPS
UP TO GOOD CHANCE SW HALF OF CWA WED NGHT AND THU.

STILL LOOKS WARM WITH AFTN AND EVENING TSRA IN THE EXTENDED.

PRELIMINARY NUMBERS:

AVL 53/72/54/73/56 3355
CLT 57/73/59/76/59 5333
GSP 58/74/60/77/60 3344

.GSP...NONE.

MCAVOY