MESOSCALE PRECIPITATION DISCUSSION 0348...CORRECTED
NWS WEATHER PREDICTION CENTER COLLEGE PARK MD
1009 AM EDT SUN SEP 07 2014
 
CORRECTED FOR TYPOS

AREAS AFFECTED...EASTERN CAROLINAS 
 
CONCERNING...HEAVY RAINFALL...FLASH FLOODING POSSIBLE 
 
VALID 071404Z - 071904Z
 
SUMMARY...THUNDERSTORMS ARE FORMING WITHIN A WARM AND INCREASINGLY
UNSTABLE AIR MASS NEAR AND AHEAD OF A COLD FRONT.  HOURLY RAIN
RATES UP TO 2.5" COULD LEAD TO FLASH FLOODING.

DISCUSSION...A THIN BAND OF THUNDERSTORMS HAS FORMED NEAR A SLOWLY
PROGRESSIVE COLD FRONT OVER THE PAST HOUR, WHICH SEEMS TO
CORRELATE BEST TO THE 00Z NAM CONEST AND 00Z NMM MESOSCALE
GUIDANCE PLACEMENT FOR CONVECTION LATE THIS MORNING INTO THIS
AFTERNOON; RECENT RAP AND HRRR RUNS APPEAR TO BE HANDLING THIS
ACTIVITY THE WORST.  SOUNDINGS SHOW LOW THRESHOLDS FOR CONVECTION
ACROSS THE REGION WITH CONVECTIVE TEMPERATURES IN THE LOW 80S. 
PRECIPITABLE WATER VALUES ARE 2-2.25" ACROSS THE REGION, ABOVE THE
90TH PERCENTILE FOR EARLY SEPTEMBER.  LOW-LEVEL INFLOW IS WEAK,
WHICH WOULD NORMALLY IMPLY SINGLE CELL/PULSE CONVECTION.  HOWEVER,
THE 0-6 KM BULK SHEAR IS NEAR 25 KTS, WHICH SEEMS TO BE ORGANIZING
THE CONVECTION.  MOST UNSTABLE CAPE ACROSS THE REGION REMAINS
>1000 J/KG, WHILE MIXED LAYER CAPES RECENTLY ROSE >500 J/KG. 

DEEP UNIDIRECTIONAL WEST-SOUTHWESTERLY FLOW IS SEEN IN AREA
SOUNDINGS, UPPING THE ANTE FOR FLASH FLOODING AND CELL TRAINING. 
DAYTIME HEATING IS EXPECTED TO INCREASE INSTABILITY ACROSS THE
REGION, WHICH SHOULD FUEL LATER CONVECTION.  THE NEARBY FRONTAL
ZONE, 850 HPA TROUGH AXIS, AND ANTICIPATED SEA BREEZES SHOULD ACT
AS FOCI FOR CONVECTION.  WHILE SUBSTANDARD LOW-LEVEL INFLOW
EXISTS, CELL MERGERS AND/OR TRAINING COULD LEAD TO LOCALLY HEAVY
RAINFALL.  CONVECTION COULD BE OUTFLOW DOMINANT DUE TO THE MINIMAL
LOW-LEVEL INFLOW PRESENT AND EXPECTED.  SYNOPTICALLY, THIS
SITUATION IS REMINISCENT OF JULY 21ST AND AUGUST 10TH, WHEN LOCAL
AMOUNTS OF 5-8" OCCURRED IN THIS REGION.  THE 00Z AND 06Z SSEO
NEIGHBORHOOD PROBABILITIES ARE MOST EMPHATIC ACROSS NORTHEAST NC,
WHERE THERE IS A 70% OF EXCEEDING FLASH FLOOD GUIDANCE STARTING AT
16Z.  HOURLY RAIN RATES UP TO 2.5", WITH MESOSCALE GUIDANCE
GENERALLY INDICATING LOCAL AMOUNTS OF 4", COULD LEAD TO FLASH
FLOODING. 

ROTH

ATTN...WFO...AKQ...CAE...CHS...ILM...MHX...RAH...

ATTN...RFC...SERFC...

LAT...LON   36537633 36517603 36497577 36157565 35717542 
            35387539 35147550 35027601 34687637 34577654 
            34577711 34207771 33897801 33627895 32997928 
            32568035 33798018 34648010 34938000 34977996 
            35377896 36017759 36187728 36527637 36527635