089 
FXUS62 KILM 061433
AFDILM

AREA FORECAST DISCUSSION
NATIONAL WEATHER SERVICE WILMINGTON NC
1033 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 10 AM SATURDAY...ALTHOUGH CONVECTION CONTINUES TO MOVE
ONSHORE COVERAGE HAS BEEN DECREASING AND CLOUD TOPS WARMING. AT
THIS POINT THE ONLY NOTEWORTHY CONVECTION IS MOVING NORTH FROM
CAPE FEAR AND APPEARS TO BE ASSOCIATED WITH OUTFLOW FROM EARLY
MORNING MARINE CONVECTION. MOISTURE CONTINUES TO STREAM NORTH FROM
WEAK DISTURBANCE ALONG THE GA COAST...BUT THIS MORNINGS CONVECTION
HAS LIKELY WORKED TO TEMPORARILY STABILIZE THE ATMOSPHERE. SHOWERS
AND THUNDERSTORMS ALONG THE COAST MAY BE DONE FOR MOST OR ALL OF
THE DAY...ONCE THE DIMINISHING CONVECTION MOVING NORTH ACROSS
PENDER COUNTY ENDS.

MEANWHILE FARTHER WEST ONGOING HEATING WILL RESULT IN AFTERNOON
SHOWERS AND THUNDERSTORMS DEVELOPING ACROSS THESE AREAS. GIVEN THE
EXPANSIVE MORNING CLOUDS ALONG THE COAST A DIFFERENTIAL HEATING
BOUNDARY MAY ALSO SET UP. THIS COULD INITIATE ADDITIONAL
AFTERNOON CONVECTION AS WELL AS ENHANCING ANY ONGOING STORMS. HIGH
RESOLUTION SHORT RANGE GUIDANCE DOES DEPICT CONVECTION SHIFTING
FROM THE COAST THIS MORNING TO INLAND AREAS THIS AFTERNOON...AS
HAS BEEN THE CASE THE LAST FEW DAYS. CANNOT RULE OUT ADDITIONAL
CONVECTION ALONG THE COAST THIS EVENING ONCE THE ATMOSPHERE
RELOADS BUT THE DIURNAL HEATING WINDOW WILL BE LIMITED.

BIGGEST CHANGES FOR THE UPDATE WERE TO POP DISTRIBUTION DURING THE
DAY BUT OVERALL NUMBERS HAVE NOT CHANGED MUCH. HAVE ONLY MADE
SLIGHT CHANGES TO TEMPERATURES FOR TODAY WITH INLAND AREAS STILL
EXPECTED TO REACH LOWER 90S. COASTAL AREAS WILL BE A LITTLE MORE
DIFFICULT GIVEN LINGERING CLOUD COVER AND SLIGHTLY COOLER ONSHORE
FLOW.

&&

.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 /14Z 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 10 AM SATURDAY...BERMUDA HIGH WILL MAINTAIN SOUTHERLY FLOW
TODAY ALTHOUGH WEAK COASTAL TROUGH EXTENDING NORTH INTO SC MAY
INDUCE SOUTHEAST OR EVEN EAST WINDS ALONG THE COAST. GRADIENT
REMAINS WEAK AND SPEEDS WILL NOT CLIMB MUCH ABOVE 10 KT TODAY.
GRADIENT MAY BECOME SLIGHTLY BETTER DEFINED TONIGHT AS COLD FRONT
TO THE NORTHWEST CREEPS CLOSER. SPEEDS MAY CLIMB INTO THE 10 TO 15
KT RANGE BUT WILL REMAIN WELL BELOW HEADLINE CRITERIA. SEAS 2 TO 3
FT TODAY WITH POTENTIAL FOR ISOLATED 4 FT SEAS OVERNIGHT.

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...III
SHORT TERM...MBB
LONG TERM...MBB
AVIATION...43