Quantitative Precipitation Forecast
Issued by NWS

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FOUS30 KWBC 312151
QPFERD

EXCESSIVE RAINFALL DISCUSSION
NWS WEATHER PREDICTION CENTER COLLEGE PARK MD
550 PM EDT MON AUG 31 2015

...VALID 2150Z MON AUG 31 2015 - 12Z TUE SEP 01 2015...
...REFERENCE AWIPS GRAPHIC UNDER...DAY 1 EXCESSIVE RAINFALL...


SLIGHT RISK OF RAINFALL EXCEEDING FFG TO THE RIGHT OF A LINE FROM
30 NW BKV 30 NNE VVG 10 E DAB 15 NE TTS MLB 35 SE BOW 25 E SRQ
20 SW SPG 25 WNW PIE 30 NW BKV.


21Z UPDATE...

BASED ON THE LATEST RADAR AND SATELLITE TRENDS...ALONG WITH THE
LATEST GUIDANCE (INCLUDING THE HIGH-RES/CAM)...HAVE REMOVED THE
SLIGHT RISK AREA THAT WAS ACROSS THE EASTERN CAROLINAS GIVEN THAT
THE DEEPER CONVECTION (BEST INSTABILITY) HAS MOVED OFFSHORE WHILE
THE ACTIVITY LEFT BEHIND ON THE BACKSIDE IS MORE STRATIFORM BASED.
PER THE LATEST SATELLITE IR/WV LOOPS...THE LIMITING STREAMLINE
(BACK EDGE OF THE WARM CONVEYOR BELT/DEEPER MOISTURE) IS NEARING
THE CAROLINA COAST...AS IS THE SHORTWAVE TROUGH. MODEST MID/UPPER
LEVEL RIDGING/SUBSIDENCE/DRYING WILL CONTINUE TO BUILD IN FROM W-E
LATER THIS EVENING BEHIND THE TROUGH.

OVER THE FLORIDA PENINSULA...A FAIRLY WEAK SIGNAL IN THE GUIDANCE
EXISTS FROM THIS POINT (LATE AFTERNOON) INTO THE EVENING
HOURS...CONFINED ACROSS CENTRAL AND NORTH-CENTRAL PORTIONS OF THE
PENINSULA. THIS OUTLOOK AREA IS ESSENTIALLY ALONG AND EAST OF THE
TRACK OF THE MESOSCALE CONVECTIVE VORTICITY (MCV) CENTER...WHICH
WOULD BENEFIT THE MOST FROM ANY SMALL-SCALE UPPER LEVEL DIVERGENCE
WITH AN UPTICK IN LOW-LEVEL MOISTURE FLUX CONVERGENCE. THE LATEST
SATELLITE AND RADAR TRENDS WERE MODEST AT BEST HOWEVER...WITH ONLY
SPOTTY AREAS OF CLOUD TOP COOLING AND ENHANCED (HEAVIER) RAINFALL
RATES. DESPITE MODERATE AVAILABLE DEEP-LAYER INSTABILITY
(SURFACE-BASED CAPES 2000-3000+ J/KG)...THE LACK OF
ORGANIZED/ROBUST LOW-LEVEL INFLOW IS ALLOWING FOR THE CONVECTION
TO REMAIN A BIT UNORGANIZED AND AS SUCH FAIRLY MIGRATORY/OUTFLOW
DOMINANT WITH VERY LITTLE TRAINING OVER THE SAME AREA. THE
LOW-LEVEL INFLOW DOES PICK UP OVERNIGHT...HOWEVER BY THAT TIME THE
DEGREE OF UPPER LEVEL FORCING TO SUPPORT ORGANIZED CONVECTION WILL
BE IN SERIOUS DOUBT (BEHIND THE DEPARTING MCV)...WHILE THE MUCAPES
WILL ALSO BE ON THE DECLINE.

HURLEY


PREVIOUS DISCUSSION BELOW...


15Z UPDATE...

ONLY CHANGE TO PREVIOUS OUTLOOK AREAS WAS A SLIGHT TRIMMING OF WRN
PORTION OF SLIGHT RISK AREA ACRS THE CAROLINAS AS BEST MSTR
CONVERGENCE AXIS REMAINS CLOSER TO THE COAST...WHILE WEAK MID
LEVEL VORT CONTS TO LIFT NEWD INTO SRN VA GIVING A VERY SLIGHT AND
TEMPORARY EWD NUDGE TO N/S UPR SHEAR AXIS.


FAR NORTHEAST SC INTO EASTERN NC

THE CONCERNS FOR VERY HEAVY TO ISOLATED EXCESSIVE RAINFALL AMOUNTS
ARE OVER PORTIONS OF FAR NORTHEAST SC INTO EASTERN NC AHEAD OF THE
WELL DEFINED VORT THAT WILL  CONTINUE TO PRESS EAST NORTHEASTWARD
MONDAY FROM THE SOUTHERN APPALACHIANS THROUGH THE SOUTHERN MID
ATLANTIC.  THIS SYSTEM IS EXPECTED TO BECOME LESS DEFINED WITH
TIME--BUT STILL SUPPORT POTENTIAL FOR HEAVY PRECIPITATION TOTALS
ACROSS NORTHEAST SC INTO EASTERN NC IN A REGION OF FAVORABLE UPPER
DIFFLUENCE AND STRONG MOIST (PW VALUES 2.00-2.25"+) SOUTH
SOUTHWEST WINDS OFF THE ATLANTIC.  THERE ARE SOME TIMING
DIFFERENCES AMONG THE MODELS WITH THE EAST NORTHEAST PUSH OF
PRECIP---WITH THE OVERALL MORE PROGRESSIVE SOLUTIONS OF THE
NAM---ECMWF AND CMC GEM.  WHILE FFG VALUES ARE FAIRLY HIGH ACROSS
THESE AREAS---SLOW MOVING OR TRAINING OF CELLS IN A GENERAL SOUTH
TO NORTH DIRECTION POSSIBLE---ESPECIALLY DURING THE FIRST HALF OF
THE UPCOMING PERIOD---IS POSSIBLE ACROSS THESE AREAS.


WEST CENTRAL COASTAL FL

ISOLATED URBAN RUNOFF ISSUES POSSIBLE OVER THE WEST CENTRAL
COASTAL AREA OF FLORIDA THIS PERIOD.  WHILE PW VALUES ARE EXPECTED
TO FALL OVER SOUTH FLORIDA THIS PERIOD IN THE WAKE OF THE TROPICAL
VORT MOVING NORTHWARD ALONG THE WEST COAST OF FLORIDA---THEY WILL
REMAIN ABOVE AVERAGE IN THE VICINITY OF THIS VORT OVER THE WEST
CENTRAL COASTAL REGIONS.  SLOW MOVING OR TRAINING REGIONS OF HEAVY
RAIN POSSIBLE IN THE MOIST LOW LEVEL SOUTHERLY FLOW ALONG THE WEST
CENTRAL GULF COASTAL AREA AND IN A REGION OF ENHANCED UPPER
DIFFLUENCE IN THE VICINITY OF THE TROPICAL VORT.   THIS WILL
SUPPORT ISOLATED RUNOFF ISSUES---ESPECIALLY IN URBANIZED AREAS.


ORAVEC/SULLIVAN
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