Area Forecast Discussion
Issued by NWS Wilmington, NC

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000
FXUS62 KILM 260252
AFDILM

AREA FORECAST DISCUSSION
NATIONAL WEATHER SERVICE WILMINGTON NC
952 PM EST TUE NOV 25 2014

.SYNOPSIS...
RAIN WILL CONTINUE TONIGHT INTO WEDNESDAY MORNING AS LOW PRESSURE
MOVES UP THE SOUTHEAST COAST. SKIES WILL CLEAR OUT BY THANKSGIVING
DAY...WITH TEMPERATURES RUNNING SEVERAL DEGREES BELOW NORMAL INTO
THE WEEKEND BEFORE WARMER TEMPERATURES RETURN EARLY NEXT WEEK.

&&

.NEAR TERM /UNTIL 6 AM WEDNESDAY MORNING/...
AS OF 1000 PM TUESDAY...SO FAR SO GOOD WITH THE EARLIER CHANGES TO
QPF AMOUNTS. WITH THE EXCEPTION OF A NARROW BAND OVER WILMINGTON
WHICH IS DROPPING FAIRLY HEAVY RAIN NOW...RATES ARE 0.05 INCHES PER
HOUR OR LESS ACROSS THE BULK OF THE FORECAST AREA. RADAR COMPOSITES
SOUTH TO THE FLORIDA GEORGIA LINE SHOW A SIZABLE GAP IN RAINFALL...
PERHAPS KEEPING THOSE RED CLAY ROADS A LITTLE LESS MUDDY THAN THEY
OTHERWISE MIGHT BE. DEEP CONVECTION CONTINUES ACROSS CENTRAL FLORIDA
AND OFF THE FLORIDA EAST COAST AND THIS SHOULD CONTINUE TO
NEGATIVELY IMPACT OUR PRECIPITATION INTENSITY FOR THE NEXT 3-5 HOURS.

LATEST HRRR MODEL RUNS SHOW THE SYNOPTIC LOW MAY ACTUALLY MOVE
INLAND BRIEFLY ACROSS SE NORTH CAROLINA AROUND 11-12Z WED. A TRACK
THIS FAR WEST WOULD KEEP LOW TEMPERATURES IN WILMINGTON IN THE 60S
DUE TO ONSHORE EASTERLY FLOW. I HAVE TWEAKED THE IMPLIED SYNOPTIC
LOW TRACK A LITTLE CLOSER TO THE COAST...JUST NICKING BALD HEAD
ISLAND BEFORE DAYBREAK. PREVIOUS DISCUSSION FROM 700 PM FOLLOWS...

WE ARE ENTERING THE PERIOD OF WHAT SHOULD BE THE STRONGEST UPPER
LEVEL DIVERGENCE AND LOW-TO-MID LEVEL ISENTROPIC LIFT NOW. 305K-310K
ISENTROPIC LIFT FORECASTS FROM THE 18Z NAM OR GFS SUGGEST IT SHOULD
BE POURING EVERYWHERE! HOWEVER THE BROAD-SCALE RADAR COMPOSITE SHOWS
THE FORECAST PROBLEM FOR TONIGHT: WIDESPREAD DEEP CONVECTION ACROSS
THE FLORIDA PENINSULA AND OFFSHORE EAST OF JAX IS PRODUCING
DOWNSTREAM MID-LEVEL WARMING AND DRYING THAT IS NEGATIVELY IMPACTING
PRECIPITATION COVERAGE ACROSS SOUTH GEORGIA AND THE CAROLINAS. THIS
IS A CLASSIC PROBLEM WE SEE LOCALLY DURING THE COOL SEASON THAT HAS
FRANKLY NEVER BEEN HANDLED WELL BY THE SYNOPTIC MODELS.

BOTH THE HRRR AND HRRRX (AN EXPERIMENTAL VERSION AVAILABLE ON THE
RAPIDREFRESH.NOAA.GOV SERVER) ARE INITIALIZING WITH THE CORRECT
"HOLE" IN THE PRECIPITATION SHIELD AND SHOW THIS ANOMALY MAY
CONTINUE TO PLAGUE THE REGION`S RAINFALL FORECAST THROUGH THE NIGHT.
THE 18Z SYNOPTIC RAINFALL GUIDANCE FROM WPC ALSO SEEMS TO AGREE WITH
THIS IDEA OF LESSER RAINFALL TOTALS THAN ORIGINALLY THOUGHT. WITH
THIS IN MIND I HAVE KEPT FORECAST POPS AT 100% (EVERYONE WILL GET AT
LEAST 0.01 INCHES OF RAIN) BUT I HAVE TRIMMED BACK FORECAST RAINFALL
AMOUNTS SUBSTANTIALLY. FROM RIGHT NOW THROUGH THE END OF THE EVENT
LATE WEDNESDAY MORNING IT APPEARS TOTALS SHOULD AVERAGE HALF OF AN
INCH...PERHAPS APPROACHING AN INCH ALONG THE COAST IF RAINFALL RATES
CAN INCREASE TOWARD THE END OF THE EVENT WEDNESDAY MORNING.

OVER THE PAST FEW DAYS SYNOPTIC GUIDANCE HAS TRENDED FARTHER WEST
WITH THE FORECAST PATH OF THE LOW MOVING NORTH FROM FLORIDA. 18Z
MODELS CONTINUED THIS TREND AND I HAVE SHIFTED THE IMPLIED TRACK OF
THE LOW IN THE FORECAST WIND GRIDS TO ONLY ABOUT 10 MILES EAST OF
CAPE FEAR LATE TONIGHT. THIS WILL HAVE THE ADDED IMPACT OF
MAINTAINING A WARMER AIRMASS NEAR THE COAST...PARTICULARLY SE NORTH
CAROLINA...AND I HAVE RAISED FORECAST LOWS BY SEVERAL DEGREES HERE.
FARTHER INLAND THE COLD AIR SHOULD BEGIN TO BLEED IN FROM THE NW
SHORTLY AND VERY FEW CHANGES WERE NEEDED TO THE OVERALL TEMP/WIND
FORECAST.

&&

.SHORT TERM /6 AM WEDNESDAY MORNING THROUGH THURSDAY NIGHT/...
AS OF 300 PM TUESDAY...LOW PRESSURE HUGGING THE COAST WILL BE MOVING
N OF THE WATERS WEDNESDAY MORNING. AS THE LOW MOVES UP THE NORTH
CAROLINA AND MID ATLANTIC COAST WED...THE RAIN WILL SHUT OFF FROM
SSW TO NNE. PERIODS OF HEAVY RAIN ARE STILL POSSIBLE WED
MORNING...BUT EXPECT BY AFTERNOON...THE RISK FOR RAINFALL WILL HAVE
ENDED ACROSS ALL BUT THE CAPE FEAR AREA WHERE A SLIGHT RISK OF
AFTERNOON RAIN WILL STILL BE POSSIBLE. WILL INCLUDE CATEGORICAL POPS
WED MORNING THROUGHOUT. CONVECTION IS EXPECTED TO STAY OFFSHORE...
EAST OF THE LOW CENTER WHERE THERE WILL BE AN INFLUX OF WARMER AND
MORE UNSTABLE AIR.

ONE VERY POTENT MID-LEVEL SHORTWAVE TROUGH WILL PIVOT ACROSS THE
FORECAST AREA WED AFTERNOON WHILE ANOTHER SKIRTS OUR FORECAST AREA
TO THE N LATE WED NIGHT AND THU MORNING BEFORE LIFTING OUT. THE
INFLUX OF COLDER AND DRIER AIR WORKING INTO THE EASTERN CAROLINAS ON
THE BACKSIDE OF FIRST SHORTWAVE WILL HELP TO SIGNIFICANTLY DRY THE
COLUMN WITH PRECIPITABLE WATER VALUES DROPPING TO LESS THAN HALF AN
INCH. THIS WILL HELP TO PROMOTE DECREASING AFTERNOON CLOUDINESS...
ESPECIALLY ACROSS SOUTHERN AND WESTERN ZONES. THE SECOND SHORTWAVE
MAY ACTUALLY BRING A BRIEF INCREASE IN CLOUD COVER...BUT
PRECIPITATION IS EXPECTED TO REMAIN TO OUR N.

TEMPS ON WED WILL NOT MOVE MUCH AS COLD AIR ADVECTION GETS UNDERWAY.
IN FACT HIGHS WILL BE ACHIEVED IN MANY CASES PRIOR TO OR AROUND
SUNRISE. WE EXPECT HIGHS TO BE IN THE LOWER TO MID 50S ON THE COAST
WITH UPPER 40S TO AROUND 50 FROM EYF TO HYW AND POINTS W. DAYTIME
TEMPS WILL HOLD STEADY OF NOT DROP A DEGREE OR TWO. TEMPS WED NIGHT
WILL DROP INTO THE 30S TO AROUND 40. EVEN THE COLDEST SPOTS SHOULD
NOT REACH THE FREEZING MARK GIVEN THE LACK OF RADIATIONAL COOLING.
CHILLY HIGH PRESSURE WORKING TO THE COAST FROM THE W WILL ALLOW THE
PRESSURE GRADIENT TO LOOSEN THU NIGHT. THE COOLEST TEMPS AT 850 MB
THU WILL BE OFFSET BY SUNSHINE AND WE DO EXPECT HIGHS TO STILL REACH
THE MID 50S. RADIATIONAL COOLING WILL DEVELOP THU NIGHT WHICH SHOULD
ALLOW LOWS TO DROP INTO THE UPPER 20S TO LOWER 30S OVERNIGHT.

&&

.LONG TERM /FRIDAY THROUGH TUESDAY/...
AS OF 300 PM TUESDAY...LONG TERM PERIOD WILL REMAIN DRY WITH MID
LEVEL FLOW BECOMING PROGRESSIVE. COLD ADVECTION WILL BE WINDING DOWN
FRI...BUT TEMPS STILL END UP WELL BELOW CLIMO. DEEP WESTERLY FLOW
WILL BE QUICK TO SHIFT THE CENTER OF THE MODIFYING HIGH OFF THE
COAST WITH RETURN FLOW DEVELOPING SAT. TEMPS REMAIN BELOW CLIMO SAT
BUT WILL BE WARMER THAN FRI. EARLY NEXT WEEK 5H RIDGE TRIES TO BUILD
NORTH FROM THE EASTERN GOMEX AND FL. BUILDING HEIGHTS AND INCREASING
SOUTHWEST FLOW EARLY NEXT WEEK WILL PUSH TEMPS ABOVE CLIMO. BACKDOOR
COLD FRONT DEPICTED IN MEDIUM RANGE GUIDANCE YESTERDAY NOW LOOKS
TIMED TO CROSS THE AREA TUE MORNING...WITH BOTH GFS/ECMWF IN DECENT
AGREEMENT. FRONT WILL PASS DRY FOLLOWED BY WEAK COLD ADVECTION WITH
TEMPS DROPPING BACK NEAR CLIMO.

&&

.AVIATION /00Z WEDNESDAY THROUGH SUNDAY/...
AS OF 00Z...EXPECT VFR/MVFR CONDITIONS EARLY THIS EVENING TO
DETERIORATE TO IFR AS RAIN CONTINUES THROUGH THE OVERNIGHT HOURS. A
SHALLOW LAYER OF LIGHT NORTHEAST WINDS BEHIND THE FRONT WILL HELP TO
PROMOTE IFR STRATUS AS MOISTURE IS TRAPPED BENEATH A LOW-LEVEL
INVERSION. MEANWHILE...A DEVELOPING AREA OF LOW PRESSURE ALONG THE
FRONT WILL MOVE UP THE SOUTHEAST COAST OVERNIGHT... BRINGING MORE
PERSISTENT RAIN THAT MAY LOWER VSBYS TO MVFR/IFR LEVELS AT TIMES.
LIGHT NORTHEAST WINDS WILL BECOME MORE NORTHERLY AFTER MIDNIGHT...
AND THEN NORTHWEST BY 12Z ON THE BACK SIDE OF THE LOW AS IT MOVES UP
THE MID-ATLANTIC COAST. THE ENHANCED GRADIENT WILL RESULT IN GUSTY
NORTHWEST WINDS 15-20 KT DURING THE MORNING/EARLY AFTN HOURS.
CONDITIONS WILL IMPROVE FROM SW TO NE ACROSS OUR AREA DURING THE
AFTN AS THE LOW RACES AWAY AND DRIER AIR IS PULLED INTO THE
CAROLINAS. RAIN SHOULD END BY 18Z AS MVFR CIGS GRADUALLY IMPROVE TO
VFR BY THE END OF THE PERIOD.

EXTENDED OUTLOOK...VFR CONDITIONS EXPECTED THURSDAY THROUGH SUNDAY.

&&

.MARINE...
NEAR TERM /THROUGH TONIGHT/...
AS OF 1000 PM TUESDAY...LATEST HRRR MODEL RUNS SHOW THE LOW TRACKING
A BIT FARTHER WEST THAN THE AFTERNOON MODELS INDICATED. I HAVE
TWEAKED THE IMPLIED TRACK OF THE LOW ANOTHER 5 MILES WEST IN THE
LATEST GRIDDED WIND FORECAST...JUST NICKING BALD HEAD ISLAND BEFORE
DAYBREAK. THIS WOULD BRING SOUTHERLY WINDS ACROSS MOST OF THE
COASTAL WATERS NORTH OF CAPE FEAR LATE TONIGHT. OTHERWISE FEW
CHANGES WERE NEEDED TO THE FORECAST THIS EVENING. PREVIOUS
DISCUSSION FROM 700 PM FOLLOWS...

THE CAROLINA COASTAL WATERS ARE IN A LULL CURRENTLY AS LOW PRESSURE
DEVELOPS ALONG A FRONT STALLED ACROSS THE FLORIDA PENINSULA. THIS
FRONT EXTENDS NORTHEASTWARD TO VERY NEAR CAPE FEAR WHICH EXPLAINS
THE WEAK PRESSURE GRADIENT WE SEE ON SURFACE CHARTS. AS THE NIGHT
PROGRESSES THE LOW SHOULD FOLLOW THE FRONT
NORTH-NORTHEASTWARD...GRADUALLY DEEPENING AND PASSING JUST EAST OF
CAPE FEAR BEFORE DAYBREAK WEDNESDAY MORNING. WITH THE FRONT
REMAINING JUST OFF THE COAST WE SHOULD NOT SEE VERY STRONG WINDS
ACROSS THE COASTAL WATERS TONIGHT...15 KNOTS OR LESS THROUGH EARLY
WEDNESDAY MORNING. THE EXCEPTION TO THIS MAY BE ACROSS THE WATERS
10-20 MILES EAST OF CAPE FEAR WHERE STRONG SOUTH WINDS DEVELOPING
AROUND MIDNIGHT AHEAD OF THE INTENSIFYING LOW COULD REACH 25 KNOTS.
CERTAINLY OFFSHORE BEYOND 20 MILES WINDS ARE GOING TO INTENSIFY
QUITE A BIT OVER THE NEXT 6 HOURS AHEAD OF THE LOW. THIS WILL BE
IMPORTANT SINCE SEAS WILL BUILD QUITE SUBSTANTIALLY OFFSHORE...AND A
GOOD DEAL OF SOUTHERLY SWELL ENERGY SHOULD PROPAGATE INTO THE
COASTAL WATERS BEGINNING LATE THIS EVENING. FOR THIS REASON THE
SMALL CRAFT ADVISORY WILL REMAIN IN EFFECT FOR THESE 4-6 FOOT SEAS
DEVELOPING AFTER MIDNIGHT.

SHORT TERM /WEDNESDAY THROUGH THURSDAY NIGHT/...
AS OF 300 PM TUESDAY...SMALL CRAFT ADVISORY CONDITIONS WILL CONTINUE
THROUGH THE DAY WED. WE DO THINK THESE CONDITIONS MAY WANE WED EVE.
HOWEVER...IT IS POSSIBLE THAT SMALL CRAFT ADVISORY CONDITIONS
REDEVELOP FOR A TIME LATE WED NIGHT AND THU AS BACKSWELL FROM
COASTAL LOW PRESSURE WELL NORTH OF THE AREA WORKS DOWN THE COAST.
ALSO...THE PRESSURE GRADIENT BETWEEN HIGH PRESSURE TO OUR W AND
COASTAL LOW WILL HELP TO INCREASE LOW-LEVEL WIND SPEEDS AS SURGE OF
COLDEST AIR ARRIVES ACROSS THE WATERS. THE WIND DIRECTION WILL BE NW
OR TRANSITIONING TO NW WED MORNING AS THE LOW MOVES FURTHER UP THE
COAST. THE DIRECTION WILL THEN BACK TO A MORE WESTERLY DIRECTION WED
NIGHT AND THU. AS HIGH PRESSURE TO THE W BEGINS TO ASSERT ITSELF
LATE THU AND THU NIGHT...THE WIND DIRECTION WILL VEER TO NW AND THEN
N. HIGHEST WIND SPEEDS THIS PERIOD WILL BE UP TO 20 TO 25 KT AND
SEAS UP TO 5 TO 8 FT.

LONG TERM /FRIDAY THROUGH SUNDAY/...
AS OF 300 PM TUESDAY...DECREASING NORTHWEST FLOW ON FRI WILL BECOME
LIGHT AND VARIABLE FRI NIGHT INTO SAT AS SURFACE RIDGE AXIS MOVES
OVERHEAD. LIGHT SOUTHERLY FLOW DEVELOPS SAT AFTERNOON AS THE
CENTER OF THE HIGH PUSHES EAST OF THE WATERS. GRADIENT BECOMES A
LITTLE MORE DEFINED LATER SAT WITH SOUTHWEST FLOW INCREASING TO 10
TO 15 KT SAT NIGHT AND SUN. SEAS 2 TO 4 FT FRI MORNING DROP TO 2
TO 3 FT FRI NIGHT AND 2 FT OR LESS SAT AND SUN.

&&

.ILM WATCHES/WARNINGS/ADVISORIES...
SC...NONE.
NC...NONE.
MARINE...SMALL CRAFT ADVISORY FROM MIDNIGHT TONIGHT TO 7 PM EST
     WEDNESDAY FOR AMZ250-252-254-256.

&&

$$

NEAR TERM...TRA
SHORT TERM...RJD
LONG TERM...III
AVIATION...BJR





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