041 
FXUS62 KILM 061046
AFDILM

AREA FORECAST DISCUSSION
NATIONAL WEATHER SERVICE WILMINGTON NC
644 AM EDT SAT SEP 6 2014

.SYNOPSIS...
SHOWERS AND THUNDERSTORMS WILL CONTINUE TO INCREASE IN COVERAGE 
TODAY AS A COLD FRONT APPROACHES. LOW PRESSURE MAY ENHANCE THE 
RAINFALL SUNDAY AND MONDAY. A GRADUAL DRYING TREND WILL GET UNDERWAY 
ON TUESDAY AND PERSIST INTO LATE NEXT WEEK WHILE AFTERNOON HIGHS 
CLIMB.

&&

.NEAR TERM /THROUGH TONIGHT/...
AS OF 600 AM SATURDAY...COLD CLOUD TOPS WERE ORGANIZING OFF THE 
CAROLINA COAST NEAR DAYBREAK. WATER VAPOR IMAGERY SHOWS A GOOD SLUG 
OF DEEP MOISTURE ALONG AND JUST OFF THE SOUTH CAROLINA COAST... 
MOVING NORTH. SHOWERS AND SOME THUNDERSTORMS WERE INCREASING IN 
NUMBER IN THIS AREA AND MOVING NORTH AT ABOUT 18 MPH. THUS...EXPECT 
SHOWERS/THUNDERSTORMS TO INCREASE THROUGH THE MORNING AND INTO THE
AFTERNOON... ESPECIALLY ALONG THE COAST...BUT EVEN INLAND AS HEATING 
GETS UNDERWAY.

THE COLUMN WILL BE SLIGHTLY MORE MOIST THAN ON FRI WHILE THE 
INSTABILITY SHOULD BE SLIGHTLY LESS. THERE ARE NO SIGNIFICANT UPPER 
LEVEL FEATURES TO ENHANCE CONVECTION.  HOWEVER... THE RIDGE IS 
EXPECTED TO GRADUALLY BREAK DOWN WITH MODEST HEIGHT FALLS DEVELOPING 
ACROSS THE CAROLINAS. THIS SHOULD ALLOW A COLD FRONT TO MAKE SOME 
DECENT PROGRESS TO THE SOUTHEAST WITH THE FRONT DROPPING INTO THE 
LEE SIDE TROUGH POSITION TONIGHT.

WE EXPECT CONVECTION TO BE LARGELY DRIVEN BY AN ACTIVE SEABREEZE 
BOUNDARY WITH LITTLE TO NO CONVECTIVE INHIBITION. THE ACTIVITY 
SHOULD START EARLY ALONG THE COAST AND THEN REDEVELOP ALONG OUTFLOW 
BOUNDARIES WITH SHOWERS AND THUNDERSTORMS EXPANDING INLAND THROUGH 
THE DAY. IN FACT OFFSHORE SHOWERS ARE EXPECTED TO MOVE ONTO THE 
COAST PRIOR TO SUNRISE.

THE COVERAGE OF SHOWERS AND THUNDERSTORMS WILL BE GREATER THAN ON 
FRI...PERHAPS APPROACHING NUMEROUS IN SOME LOCATIONS. THE SOUTHERLY 
FLOW WILL BE UP THROUGH ABOUT 20 KFT TODAY...SO THE MOISTURE WILL BE 
A LITTLE DEEPER THAN PREVIOUS DAYS. STORM MOTIONS SHOULD BE PICKING 
UP THE PACE...ESPECIALLY LATER TODAY AND TONIGHT AS LOW LEVEL WINDS 
INCREASE AHEAD OF THE APPROACHING FRONT. WILL CONTINUE TO ADVERTISE 
THE RISK FOR HEAVY RAIN. WILL CONTINUE TO MENTION SHOWERS AND SOME 
THUNDERSTORMS THROUGH THE EVE AND OVERNIGHT GIVEN A FRONT WILL BE 
NEARING THE EASTERN CAROLINAS AND WEAK UPSTREAM DISTURBANCES 
EMBEDDED IN THE FLOW MAY BEGIN TO IMPINGE ON THE AREA. IF NOTHING 
ELSE TONIGHT...EXPECT SHOWERS TO INCREASE ACROSS THE ATLANTIC WITH
SOME OF THIS ACTIVITY MOVING ONTO THE COAST.

HIGH TEMPS WILL BE IN THE UPPER 80S TO LOWER 90S...WARMEST ALONG THE 
INTERSTATE 95 CORRIDOR. TEMPS AT THE BEACHES SHOULD NOT RISE 
SIGNIFICANTLY TODAY...MAINLY MID 80S THIS AFTERNOON. TEMPS WILL OF 
COURSE FLUCTUATE WHERE HEAVY RAIN KNOCKS TEMPS DOWN SIGNIFICANTLY 
FOLLOWED BY A RECOVERY ONCE THE CONVECTION MOVES AWAY. SOUTH WINDS 
WILL GUST TO 15 TO 20 MPH... HIGHEST AT THE COAST THIS AFTERNOON. 
LOWS TONIGHT WILL BE SIMILAR TO THE LAST SEVERAL NIGHTS...LOWER TO 
MID 70S...BUT NEAR 80 ALONG THE OCEAN FRONT WHERE NOCTURNAL MIXING 
WILL BE LEAST INHIBITED.

&&

.SHORT TERM /SUNDAY THROUGH MONDAY NIGHT/...
AS OF 300 AM SATURDAY...VERY ACTIVE WEATHER IS EXPECTED THROUGH THE 
SHORT TERM PERIOD WITH POTENTIAL FOR SOME HEAVY RAINFALL. THERE IS 
JUST ENOUGH VARIATION IN MODEL SOLUTIONS TO SAY FOR SURE WHEN THE 
BEST WINDOW OF OPPORTUNITY FOR THAT WILL BE. PIEDMONT TROUGH NEARLY 
LINKED WITH NORTHWARD EXTENSION OF CARIBBEAN TROPICAL WAVE EXTENDED 
JUST WEST OF FL RIGHT NOW. THROUGH SUNDAY THIS MOISTURE IS PROGGED 
TO ADVECT NORTH AND EASTWARD...SURGING INTO THE COASTAL CAROLINAS. 
MULTIPLE SOURCES OF LIFT INCLUDE BUT ARE NOT LIMITED TO THE SEA 
BREEZE, THE PIEDMONT TROUGH, AND PVA ASSOC WITH THE MID LEVEL SYSTEM 
MOVING NE UP THE COAST. A COLD FRONT WILL ALSO BE APPROACHING FROM 
THE NORTH TO PROVIDE A SQUEEZE PLAY FOR THIS MOISTURE TRYING TO MOVE 
NORTHWARD. WHERE THIS ZONE OF SURFACE-BASED OVERRUNNING SETS UP 
LIKELY STANDS TO SEE THE HEAVIEST RAINFALL ON SUNDAY. WRF IS A BIT 
NORTH OF THE REGION WHEREAS THE GFS TAKES AIM AT MOST OF THE COASTAL 
CAROLINAS. THE LATTER HALF OF THE PERIOD GETS TRICKY. THE GFS WOULD 
IMPLY THAT COPIOUS RAINS CONTINUE THROUGH ABOUT MONDAY MORNING. 
THEREAFTER THE SURFACE REFLECTION OF THE FL UPPER LOW MOVES NE ALONG 
THE FRONT AS A FAIRLY FLAT WAVE. THE WRF WHICH WAS INITIALLY A 
STRONG OUTLIER CONTINUES TO SHOW A SIMILAR SCENARIO. ITS MORE CLOSED 
OFF LOW IS SLOWER TO ZIPPER ITS WAY UP THE FRONT...BUT IT JUST SEEMS 
TO BE IMPLYING TOO MUCH BAROTROPIC/LATENT HEATING DRIVEN 
STRENGTHENING PROCESSES TAKING PLACE...ALL WHILE THE LOW REMAINS 
OVER LAND. ANY OF THOSE PROCESSES MAY VERY WELL TAKE PLACE BUT 
PROBABLY WELL AFTER IT HAS PASSED NORTH OF HATTERAS A LA THE 
CANADIAN GEM MODEL. THE ECMWF IS A RATHER NICE COMPROMISE SHOWING 
THAT MUCH OF MONDAY IS JUST AS WET FOR MOST AREAS AS SUNDAY...WHICH 
PERHAPS A MORE DEFINED COASTAL VS INLAND GRADIENT IN QPF...BOTH DAYS 
WETTEST ALONG THE COAST. 

&&

.LONG TERM /TUESDAY THROUGH FRIDAY/...
AS OF 300 AM SATURDAY...LOW LEVEL MOISTURE ASSOCIATED WITH 
DISSIPATING FRONT SHOULD LINGER FOR LOW END CHANCE POPS ESPECIALLY 
ALONG THE COAST. MID LEVEL ZONAL FLOW WILL BE DRYING OUT MUCH OF THE 
COLUMN ABOVE THE BOUNDARY LAYER THOUGH. WEDNESDAY LOOKS LIKE A 
TRANSITION BACK TO A WARM SEASON PATTERN WITH FLAT WEAK RIDGING 
ACROSS NRN GOMEX AND SRN U.S. WHILE BERMUDA HIGH STRUGGLES TO 
REASSERT ITSELF. THE LATTER FACT NOT THAT GREAT FOR DIURNAL 
CONVECTION-INDUCING LOW LEVEL MOISTURE ADVECTION BUT SOME FRONTAL 
MOISTURE MAY STILL LINGER. ISO POPS AND CLIMO TEMPS APPEAR A GOOD 
BET. THE MID LEVEL RIDGE INCREASES IN AMPLITUDE ON THURSDAY BRINGING 
A WARMER AFTERNOON WHILE INCREASING TROUGINESS OVER THE NRN PLAINS 
DRIVES A STRONG FRONT INTO THE GREAT LAKES. PREFRONTAL TROUGH 
DEVELOPS ACRS THE PIEDMONT ON FRIDAY WITH A LITTLE EXTRA MOISTURE 
FLUX INTO THE COASTAL PLAIN AS A RESULT. 

&&

.AVIATION /12Z SATURDAY THROUGH WEDNESDAY/...
AS OF 12Z...TROPICAL MOISTURE CONTINUES WITH PRECIPITABLE WATER 
HOVERING AROUND TWO INCHES AND THE LEVEL OF FREE CONVECTION ONLY 800 
METERS. WITH LITTLE CONVECTIVE INHIBITION...EXPECT NUMEROUS SHOWERS 
AND STORMS ALONG THE COAST WITH SCATTERED CONVECTION INLAND. 
VISIBILITIES COULD DROP AS LOW AS A MILE...BUT ONLY BRIEFLY. 
SOUTHERLY FLOW WILL CONTINUE...WITH POSSIBLE GUSTS TO 20 KTS OR SO 
IN THE CONVECTION. MOST OF THE CONVECTION WILL WANE THIS 
EVENING...HOWEVER DEEP MOISTURE WILL MOVE IN TOWARDS DAYBREAK WITH 
NUMEROUS SHOWERS AND STORMS EXPECTED TO RETURN.

EXTENDED OUTLOOK...A COLD FRONT WILL DROP INTO THE REGION SUNDAY AND 
MONDAY... WITH A HIGHER RISK FOR SHOWERS AND STORMS BOTH DAYS. THE 
FRONT STALLS WITH A CONTINUED CHANCE FOR SHOWERS TUESDAY.

&&

.MARINE...
NEAR TERM /THROUGH TONIGHT/...
AS OF 600 AM SATURDAY...THE PRESSURE GRADIENT WILL TIGHTEN SLIGHTLY 
THIS PERIOD AS A TROUGH APPROACHES THE WATERS FROM THE NW. WINDS 
WILL REMAIN ELEVATED TONIGHT AS LOW LEVEL WINDS INCREASE AHEAD OF 
THE TROUGH AND MIX MORE EFFICIENTLY DOWN TO THE SURFACE. SUSTAINED 
WIND SPEEDS WILL INCREASE TO AROUND 15 KT WITH GUSTS TO AROUND 20 
KT. THE DIRECTION WILL BE SOUTH. SEAS WILL BUILD SLIGHTLY...WITH 
MORE 4 FT SEAS EXPECTED TO BE OBSERVED LATER TODAY AND TONIGHT. 
HEAVY DOWNPOURS ARE EXPECTED IN SHOWERS AND THUNDERSTORMS WHICH WILL 
CREATE SIGNIFICANT VISIBILITY RESTRICTIONS. CONDITIONS ARE SOMEWHAT 
FAVORABLE FOR WATERSPOUTS AS WELL.

SHORT TERM /SUNDAY THROUGH MONDAY NIGHT/...
AS OF 300 AM SATURDAY...SWRLY GRADIENT WINDS WILL STILL BE QUITE 
'SEASONABLE' DESPITE COLD FRONT PUSHING INTO THE CAROLINAS. THE 
TEMPORAL PERSISTENCE OF THE FETCH HOWEVER MAY CAUSE THE OCCASIONAL 5 
FT WAVE TO APPEAR ALONG OUTER EDGES OF NRN LEGS. HOW THE REMAINDER 
OF THE PERIOD UNFOLDS IS RATHER UNCERTAIN AS IT WILL INVOLVE LOW 
PRESSURE TRAVELING NORTH AND EAST ALONG THE STALLED FRONTAL 
BOUNDARY. SOME GUIDANCE IS PROBLEMATICALLY DEVELOPING A STRONG LOW 
THAT LOOKS LIKE IT IS BORNE OF TROPICAL STRENGTHENING DESPITE THE 
LOW REMAINING OVER LAND. THE SLOWER AND WEAKER MODELS ARE THUS 
PREFERRED AND EVEN THIS MAY PUSH WIND OR SEAS CLOSE TO BUT GENERALLY 
SHY OF SCEC CRITERIA. FUTURE MODEL RUNS SHOULD CLARIFY THESE 
UNCERTAINTIES. 

LONG TERM /TUESDAY THROUGH WEDNESDAY/...
AS OF 300 AM SATURDAY...THE DEPARTURE OF THE SURFACE LOW OF THE 
SHORT TERM AND THE APPARENT RAPID WEAKENING OF ITS ASSOCIATED 
FRONTAL BOUNDARY AND TUESDAY WINDS AND SEAS MAY FALL TO QUITE 
MINIMAL LEVELS WITH A GENERALLY OFFSHORE FLOW DIRECTION. A CONTINUED 
WEAKENING OF THE BOUNDARY ON WEDNESDAY SHOULD ALLOW FOR A GRADUAL 
TURN TO THE SOUTH WHILE WIND AND SEAS REMAIN MINIMAL. 

&&

.ILM WATCHES/WARNINGS/ADVISORIES...
SC...NONE.
NC...NONE.
MARINE...NONE.

&&

$$

NEAR TERM...RJD
SHORT TERM...MBB
LONG TERM...MBB
AVIATION...43