Area Forecast Discussion
Issued by NWS Wilmington, NC

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000
FXUS62 KILM 170220
AFDILM

AREA FORECAST DISCUSSION
NATIONAL WEATHER SERVICE WILMINGTON NC
920 PM EST TUE DEC 16 2014

.SYNOPSIS...
SHOWERS WILL MOVE OFFSHORE TONIGHT AS A COLD FRONT CROSSES THE
COAST. SEASONABLY COOL AND FAIR WEATHER WILL FOLLOW WEDNESDAY
THROUGH FRIDAY. AN APPROACHING STORM SYSTEM COULD BRING WET
WEATHER DURING THE UPCOMING WEEKEND. A DRYING TREND IS EXPECTED
EARLY NEXT WEEK WITH SEASONABLE TEMPERATURES...AS HIGH PRESSURE
FROM THE UPPER MID-WEST DROPS SOUTHEAST INTO THE CAROLINAS.

&&

.NEAR TERM /UNTIL 6 AM WEDNESDAY MORNING/...
AS OF 920 PM TUESDAY...THIS HAS BEEN THE LITTLE LINE OF SHOWERS THAT
COULD!  EVEN THE HRRR HAS NOT SHOWN THE INCREDIBLY SOLID LINE OF
SHALLOW CONVECTION WE HAVE MOVING EAST ACROSS THE AREA. RAINFALL
AMOUNTS HAVE BEEN LIGHT...GENERALLY UNDER A TENTH OF AN INCH. THE
LUMBERTON ASOS REPORTED 0.11 AND THE LUMBERTON MESONET STATION HAD
0.14, THE TWO HIGHEST GAUGE TOTALS AVAILABLE TO US. RADAR ESTIMATES
ARE UPWARDS OF HALF AN INCH ACROSS NORTHERN ROBESON COUNTY NEAR THE
CUMBERLAND COUNTY LINE. CONVECTIVE ACTIVITY SHOULD CONTINUE TO
ADVECT EASTWARD AND OFF THE COAST BY MIDNIGHT. IN ITS WAKE CLEAR
SKIES ARE STILL EXPECTED. PREVIOUS DISCUSSION FROM 645 PM FOLLOWS...

THE FIRST WAVE OF PREFRONTAL SHOWERS AND SPRINKLES HAVE DIMINISHED
AND/OR MOVED EAST OF THE AREA. HOWEVER RADAR COMPOSITES SHOW A
NARROW BAND OF SHOWERS DEVELOPING ALONG THE FRONT ITSELF...CURRENTLY
ACROSS FAYETTEVILLE, LAURINBURG AND BENNETTSVILLE. ENVIRONMENTAL
LAPSE RATES BETWEEN 850 AND 600 MB ARE ACTUALLY QUITE STEEP (NEAR
6.5 DEG/KM OR MOIST-ADIABATIC) AND THIS ACTIVITY IS CONVECTIVE IN
NATURE WITH RADAR REFLECTIVITY IMPLYING THERE MAY BE A FEW MINUTES
OF QUITE HEAVY RAINFALL. SPC AUTOMATED MESOANALYSIS IS SHOWING
ELEVATED CAPE AROUND 100 J/KG AHEAD OF THE FRONT. MOISTURE IS A
LIMITING FACTOR WITH DEWPOINTS GENERALLY IN THE 50S WITH LIMITED
ATLANTIC INFLOW AND VIRTUALLY NO MOISTURE FROM THE GULF OF MEXICO.

LATEST HRRR MODEL RUNS INDICATE SCATTERED SHOWERS MAINLY ACROSS SE
NORTH CAROLINA CONTINUING FOR THE NEXT 2-3 HOURS...THEN SHIFTING
OFFSHORE. ACTIVITY WILL BE MORE SPARSE OR ENTIRELY ABSENT ACROSS NE
SOUTH CAROLINA AS THE BEST SYNOPTIC/UPPER LEVEL FORCING REMAINS
NORTH. NO CHANGES HAVE BEEN MADE TO FORECAST LOW TEMPS...AROUND 40
INLAND WITH MID 40S ON THE NC BEACHES.

&&

.SHORT TERM /6 AM WEDNESDAY MORNING THROUGH THURSDAY NIGHT/...
AS OF 345 PM TUESDAY...FAIR AND DRY WED/THU. SUBSIDENCE
OVERWHELMS THE COLUMN ENSURING A DEEP LAYER OF LOW RH AND WEST
WIND FLOW IN MID/UPPER ALTITUDES. PACIFIC ORIGIN SYSTEM AND
GENERAL WEST TO EAST FLOW RESULTING IN ONLY WEAK COOL AIR
ADVECTION AND MAXIMUMS WED LOOK TO REBOUND A FEW DEGREES ABOVE
NORMAL FOR MID DECEMBER. A SECONDARY BUT WEAK HIGH PRESSURE SURGE
MAY RESULT IN MAXIMUMS A DEGREE OR TWO COOLER THU...WITH
MORE/INCREASING CIRRUS THURSDAY.

&&

.LONG TERM /FRIDAY THROUGH TUESDAY/...
AS OF 345 PM TUESDAY...LOW CONFIDENCE SPLIT FLOW FORECAST EARLY IN
THE  PERIOD. SURFACE HIGH PRESSURE TO BE COVERING A LARGE PAR OF
THE NORTHEAST AND MID ATLANTIC ON FRIDAY. SOUTHERN BRANCH FEATURE
WILL MEANWHILE BE SKIRTING THE GULF COAST. A SURPRISINGLY SLOW
MOVER GIVEN THE FAIRLY ZONAL FLOW, THIS FEATURE WILL AFFECT THE
AREA MOST ON SATURDAY. MODEL AGREEMENT APPEARS TO BE A LITTLE
BETTER IN KEEPING THE SYSTEM TO OUR SOUTH IMPLYING THAT THIS WILL
BE A LIGHT TO PERHAPS MODERATE OVERRUNNING EVENT LOCALLY. RAIN MAY
LAST INTO EARLY SUNDAY BUT AS THE SYSTEM EXITS TO THE NORTHEAST
(WHETHER OR NOT IN A STRENGTHENING STATE) SOME DRY AIR WILL PUSH
INTO THE AREA FROM THE NW. THIS NEW AREA OF HIGH PRESSURE WILL
REMAIN TO OUR NORTHWEST FOR THE REMAINDER OF THE PERIOD WHILE THE
FLOW ALOFT REMAINS WEAKLY SPLIT. EARLY IN THE PERIOD DAYTIME HIGHS
WILL BE A BIT SUPPRESSED BY CLOUDS AND/OR RAIN WHILE NIGHTTIME
LOWS REMAIN SLIGHTLY ELEVATED ABOVE CLIMO FOR THE SAME REASON.
WITH THE ARRIVAL OF THE COOLER DRY AIR DAYTIME HIGHS MAY TAKE A
SMALL HIT WHILE NIGHTTIME LOWS LOSE THE BENEFIT OF CLOUDS AND
RETURN TO NORMAL OR CLOSE TO IT.

&&

.AVIATION /00Z WEDNESDAY THROUGH SUNDAY/...
AS OF 00Z...COLD FRONT APPROACHING KFLO/KLBT. MAINLY MID LEVEL CIGS
THIS EVENING BUT THERE ARE PATCHY 2.5-3.5K CIGS ALONG FRONT. SHOWERS
WELL IN ADVANCE OF THE COLD FRONT ARE EXITING THE COAST NEAREST
KILM...BUT A FEW ISOLATED SHOWERS ARE POPPING UP ALONG THE FRONT NW
OF KLBT.

THE FRONT WILL MOVE THROUGH KFLO/KLBT WITHIN THE NEXT HOUR OR TWO
AND THE COASTAL TERMINALS LATER THIS EVENING. THERE IS SOME CONCERN
FOR SUB-VFR VSBYS/CIGS AS WINDS DECREASE AND COOL AIR MOVES ACROSS
SLIGHTLY MOIST SOILS AT KFLO/KLBT AND KCRE. THIS SHOULD MIX OUT 2-4
HOURS AFTER FROPA.

VFR EXPECTED AFTER SUNRISE WITH NW WINDS 5-9 KT.

EXTENDED OUTLOOK...VFR WED THROUGH FRIDAY. A CHANCE OF RAIN ON
SATURDAY AND SUNDAY WITH POSSIBLE MVFR/IFR CONDITIONS.

&&

.MARINE...
NEAR TERM /THROUGH TONIGHT/...
AS OF 920 PM TUESDAY...WINDS ARE AT THEIR STRONGEST ACROSS THE
COASTAL WATERS CURRENTLY, AROUND 20 KNOTS, AND SHOULD DIMINISH AS
THE FRONT CROSSES OFFSHORE. AT 9 PM THE FRONT EXTENDS FROM WESTERN
PENDER COUNTY ACROSS WHITEVILLE TO WESTERN HORRY COUNTY, MOVING EAST
AT 25 KNOTS. THE BIGGEST CHANGE WITH THIS UPDATE WAS TO INCREASE
SHOWER CHANCES ACROSS THE NC COASTAL WATERS BASED ON UPSTREAM RADAR
IMAGERY AND MESOANALYSIS CONTINUING TO SHOW SMALL BUT POSITIVE
INSTABILITY ALOFT. PREVIOUS DISCUSSION FROM 645 PM FOLLOWS...

WINDS ARE A SOLID 20 KNOTS ACROSS THE COASTAL WATERS AND MAY
ACTUALLY INCREASE TOWARD 25 KNOTS FOR A SHORT PERIOD BETWEEN 7-9 PM
AHEAD OF THE COLD FRONT...NOW MOVING INTO THE WESTERN PORTIONS OF
THE COASTAL PLAIN. THIS FRONT SHOULD PUSH OFF THE COAST LATE THIS
EVENING WITH WINDS VEERING AROUND TO THE NW AND DIMINISHING TO 15
KNOTS OR LESS. SEAS HAVE BUILT TO 6 FEET OUT AT FRYING PAN
SHOALS...WITH BUOYS CLOSER TO SHORE READING ANYWHERE FROM 2-5 FEET
DEPENDING ON HOW OPEN THEY ARE TO FETCH FROM SW WINDS.

THE BIGGEST CHANGE WITH THIS FORECAST UPDATE WAS TO INCREASE
FORECAST WAVES ALONG THE BRUNSWICK COUNTY BEACHES BY ~3 FEET TO 4-5
FEET GIVEN THE LONG ONSHORE FETCH. WHEN WAVE DATA WAS AVAILABLE FROM
THE OCEAN CREST PIER (STILL OUT OF SERVICE AT THIS TIME) IT TAUGHT
US A LOT ABOUT WAVE BEHAVIOR HERE GIVEN VARIOUS WIND DIRECTIONS.
ONCE WINDS VEER NW BEHIND THE FRONT SEAS SHOULD BEGIN TO DIMINISH.

SHORT TERM /WEDNESDAY THROUGH THURSDAY NIGHT/...
AS OF 345 PM TUESDAY...BUMPY SEAS WILL LINGER INTO DAYBREAK
WEDNESDAY AS AN EXERCISE CAUTION STATEMENT RUNS THROUGH 12Z/7AM
WEDNESDAY. SW WAVES 2-4 FT EVERY 4 SECONDS WILL CO-MINGLE WITH
LIGHT NW CHOP AND ESE WAVE 1 FT OR LESS EVERY 10-11 SECONDS FOR A
GOOD PART OF WED BEFORE WIND-WAVES EASE IN THE AFTN. BY THU 2 FT
SEAS ON THE WATERS AND LIGHT N-NNE WIND. NO TSTMS OR RESTRICTIONS
TO VISIBILITY ON THE 0-20NM WATERS WED/THU.

LONG TERM /FRIDAY THROUGH SUNDAY/...
AS OF 345 PM TUESDAY...FLOW REMAINS MOSTLY NORTHERLY ON FRIDAY
WITH HIGH PRESSURE ENTRENCHED ACROSS MOST OF THE NORTHEAST AND
MIDATLANTIC. LOW PRESSURE DEVELOPING ALONG THE GULF STATES TO MOVE
VERY SLOWLY EASTWARD. THIS SYSTEM WILL AFFECT THE AREA ON
SATURDAY...REMAINING TO OUR SOUTH AS IT PASSES BY. THE ENCROACHING
WARM FRONT MAY VEER THE FLOW OVER PART OF THE REGION BUT ITS TOUGH
TO SAY EXACTLY HOW FAR NORTH THIS BOUNDARY TRAVERSES. REGARDLESS
WIND AND SEAS BOTH TO REMAIN BELOW ADVISORY OR SCEC REALM THROUGH
THE PERIOD. NORTHWESTERLY WINDS GET UNDERWAY SUNDAY AS THIS SYSTEM
EXITS...ONCE AGAIN WITH NO REAL STRENGTH TO THE GRADIENT AND THUS
NO CONCERN FOR ANY CAUTIONARY HEADLINES.

&&

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

&&

$$

SYNOPSIS...8
NEAR TERM...TRA
SHORT TERM...MJC
LONG TERM...MBB
AVIATION...MRR




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