Flash Flood Warning 28, NWS Raleigh, NC

AREA FORECAST DISCUSSION ... UPDATED
NATIONAL WEATHER SERVICE RALEIGH NC
215 PM EDT MON SEP 27 1999

** HAVE DECIDED TO GO FORWARD WITH A FLASH FLOOD WATCH TONIGHT IN
EASTERN SECTIONS OF THE CWA. **

NEAR-TERM: VORT LOBE & ASSOCIATED PVA EXITING TO THE NE OF THE AREA
IS TAKING HEAVY PRECIP BAND WITH IT... LEAVING BEHIND PATCHY LIGHTER
RAIN ACROSS THE CWA. NO ADDITIONAL FLOODING PROBLEMS HAVE BEEN
RECEIVED SO FAR... EVEN FROM THE PREVIOUSLY-FLOODED COASTAL PLAIN
COUNTIES. ISENTROPIC LIFT EXPECTED TO CONTINUE TONIGHT ALONG WITH
THE DEEP SERLY/SRLY WIND FLOW & VERY MOIST AIR THROUGH THE COLUMN...
SO PLAN ON LIKELY TO CATEGORICAL POPS CWA-WIDE TONIGHT.

CONCERN EXISTS THAT NONE OF THE MODELS PICKED UP ON THE 90 KT JETLET
NOTED AT FFC AT 12Z AT 250 MB... AND AS A RESULT THEY MAY BE
UNDERPLAYING THE DEGREE OF UPPER LEVEL DIVERGENCE AND RESULTANT LIFT
OVER THE AREA THIS EVENING & OVERNIGHT. WIDESPREAD SHOWERS OVER SC
HAVE INCREASED IN INTENSITY OVER THE LAST FEW HOURS AS WELL. VERY
HIGH PRECIPITABLE WATERS THIS MORNING BOTH OVER THE AREA AND
UPSTREAM ARE EXPECTED TO INCREASE EVEN FURTHER OVERNIGHT. GIVEN ALL
OF THIS & THE PRE-EXISTING FLOODING IN THE COASTAL PLAIN COUNTIES AS
WELL AS THE HEAVY RAIN OVER THE TRIANGLE THIS MORNING... MAY HAVE A
NEED FOR A FLASH FLOOD WATCH FOR TONIGHT IN THESE AREAS. WILL CHECK
RADAR TRENDS BEFORE MAKING FINAL DECISION ON THIS. THUNDER CHANCE
LOOKS MINISCULE WITH CAPES ONLY 400-800 AT BEST... BUT WILL LEAVE IN
A MINOR MENTION.

LONGER-TERM: AFTER UPPER JET PULLS NORTH OF THE AREA TUESDAY... ANY
FORCING FOR PRECIP LOOKS TO DIMINISH CONSIDERABLY... AS ONLY VERY
WEAK SHORTWAVE RIPPLES ARE FORECAST TO PASS THROUGH THE CWA TUE INTO
WED. WEAK TO MODERATE ISENTROPIC LIFT DOES PERSIST... AND THE
ATMOSPHERE REMAINS QUITE MOIST THROUGH TUE INTO TUE NIGHT... SO
SHOWER ACTIVITY IS NOT OUT OF THE QUESTION BY ANY MEANS...
ESPECIALLY IN THE WEST WHERE THE MODELS CONTINUE TO FOCUS THE
HEAVIEST QPF. MODELS ARE IN FAIR AGREEMENT ON THE OVERALL PATTERN
INTO WED... SHOWING MARKED DIFFERENCES IN THE LATTER PERIODS WITH
RESPECT TO THE INCOMING SFC FRONT AND UPPER TROUGH. ALL AGREE ON THE
LOW-MID LEVEL FLOW TURNING MORE SWRLY BY WED MORNING WHICH SHOULD
AID IN SOME DRYING ABOVE THE BOUNDARY LAYER. PLANS ARE FOR CHANCE
POPS TUE & TUE NIGHT... WITH THE HIGHEST VALUES IN THE WEST... AND
CHANCE POPS ON WED AS UPPER TROUGH APPROACHES.

EXTENDED: PLAN TO KEEP CURRENT TREND OF FRONTAL PASSAGE AND AN
ENDING TO THE SHOWERS THU MORNING. LONG RANGE MODELS ARE IN A BIT
BETTER AGREEMENT ON TIMING... WITH THE NOGAPS COMING MORE IN LINE
WITH THE MRF & THE EUROPEAN STILL SLOWER & DEEPER. DRY AND COOL
WEATHER FOR FRI INTO SAT.

.RAH...FLASH FLOOD WATCH TONIGHT FOR GRANVILLE-VANCE-WARREN-HALIFAX-
DURHAM-WAKE-FRANKLIN-NASH-EDGECOMBE-WILSON-JOHNSTON-WAYNE-SAMPSON.

HARTFIELD