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-- Discussion containing changed information from previous version are highlighted. --
000
FXUS62 KILM 090244
AFDILM

AREA FORECAST DISCUSSION
NATIONAL WEATHER SERVICE WILMINGTON NC
944 PM EST SUN DEC 8 2013

.SYNOPSIS...
A WARM FRONT ACROSS NORTHERN FLORIDA WILL MOVE NORTHWARD...BRINGING
A SHORT-LIVED RETURN TO UNSEASONABLE WARMTH ALONG THE COAST MONDAY
AND TUESDAY. CHILLY AIR MAY HANG ON MONDAY ACROSS THE INTERIOR
CAROLINAS. COOLER WEATHER WILL RETURN WITH A COLD FRONT EXPECTED TO
MOVE THROUGH FROM THE WEST TUESDAY AFTERNOON...WITH COOL CONDITIONS
PERSISTING INTO NEXT WEEKEND.

&&

.NEAR TERM /UNTIL 6 AM MONDAY MORNING/...
-- Changed Discussion --
AS OF 930 PM SUNDAY...THE FRONT IS STILL HUNG UP ACROSS EXTREME
NORTHERN FLORIDA INTO SOUTHERN ALABAMA THIS EVENING...WITH A
WELL-DEFINED AIRMASS DIFFERENCE NOTED ALONG THE EDGE OF THE LOW
STRATUS CLOUDS. OFFSHORE THE FRONT IS DISCERNIBLE IN INFRARED
SATELLITE IMAGERY 80-100 MILES SOUTHEAST OF CAPE FEAR. THE DEPTH OF
THIS MODIFIED ARCTIC AIR IS BECOMING SHALLOWER WITH TIME AND THIS
EVENING`S 00Z SOUNDINGS AT MHX AND CHS SHOWED ONLY 1500-1800 FEET OF
COLD AIR REMAINING...WITH A WARM SUBTROPICAL AIRMASS ALOFT.

THERE ARE SEVERAL FORECAST CHALLENGES TO DEAL WITH TONIGHT. THE
FIRST IS TEMPERATURES. PRESSURES ARE BEGINNING TO FALL WITHIN THE
COLD DOME ACROSS THE INTERIOR CAROLINAS AND UPSTREAM TEMPERATURES
ACROSS CENTRAL NORTH CAROLINA ARE NOT APPRECIABLY DIFFERENT THAT
WHAT WE ARE OBSERVING LOCALLY. THESE ARE BOTH SIGNS THAT COLD
ADVECTION HAS ENDED. OUR CURRENT TEMPERATURES ARE LIKELY GOING TO BE
OUR NIGHTTIME LOWS (UPPER 30S INLAND WITH LOWER 40S AT THE COAST)
AND STEADY OR EVEN SLOWLY RISING TEMPERATURES ARE ANTICIPATED
OVERNIGHT. INCREASINGLY WARM SOUTHWEST FLOW ACROSS THE TOP OF THE
SHALLOW COLD DOME PLUS EROSION FROM THE SOUTHEAST AS THE FRONT
APPROACHES LATE TONIGHT SHOULD SPELL THE END OF THE COLD AIR ALONG
THE COAST SOMETIME MONDAY MORNING.

ANOTHER CHALLENGE IS HOW MUCH (IF ANY) MEASURABLE RAIN WILL OCCUR
OVERNIGHT. OBSERVED AND FORECAST SOUNDINGS IMPLY A MUCH MORE SHALLOW
CLOUD DEPTH NOW THAN WE SAW LAST NIGHT. THIS PLUS MUCH LESS
IMPRESSIVE ISENTROPIC LIFT (LIMITED TO A THIN LAYER ALONG THE 295K
THETA SURFACE) SHOULD BE INSUFFICIENT FOR MUCH MORE THAN DRIZZLE. MY
HIGHEST POPS (30 PERCENT) ARE ALONG THE COAST THIS EVENING...THEN
SHIFTING WEST TO THE DARLINGTON-BENNETTSVILLE AREA LATE TONIGHT.

AND THE LAST FORECAST CHALLENGE IS THE POTENTIAL FOR DENSE FOG. THE
BASE OF THE LOW STRATUS CLOUDS IS CURRENTLY 300-400 FEET ABOVE
GROUND LEVEL WITH SURFACE VISIBILITIES GENERALLY GREATER THAN 2
MILES IN DRIZZLE. GFS FORECAST SOUNDINGS PLUS GFS LAMP GUIDANCE
INDICATE CLOUD BASES DESCENDING PRACTICALLY TO GROUND LEVEL LATE
TONIGHT...WITH DENSE FOG THE POSSIBLE RESULT. THE NEW 00Z NAM
MAINTAINS CLOUD BASES AT LEAST A FEW HUNDRED FEET UP. THE MORE
PESSIMISTIC GFS IS PROBABLY THE WAY TO GO...AND AREAS OF DENSE FOG
WILL REMAIN IN THE FORECAST (AND HAZARDOUS WX OUTLOOK) FOR EARLY
MONDAY MORNING.
-- End Changed Discussion --

&&

.SHORT TERM /MONDAY THROUGH TUESDAY NIGHT/...
AS OF 3 PM SUNDAY...A BIT OF A TRICKY FORECAST FOR MUCH OF THE
PERIOD. PROBABLY THE BIGGEST BUST POTENTIAL IS WITH RESPECT TO
MONDAY HIGH TEMPS. COOL AIR WEDGE INITIALLY TO BE FIRMLY IN PLACE
ALBEIT TO A DEPTH OF JUST 600FT...WITH A VERY SHARP INVERSION
THROUGH ABOUT 1200 FT. IN FACT THE WEDGE MAY HOLD THROUGH MUCH OF
THE MORNING HOURS KEEPING TEMPERATURES RISING ONLY VERY SLOWLY. THIS
WILL BE MOST PRONOUNCED FURTHER INLAND. THE WRF HANGS ON TO THE
WEDGE LONGER THAN THE GFS...AND THE SLOWER MODEL ENDS UP BEING MORE
CORRECT A VAST MAJORITY OF THE TIME. EVEN SO...THE LATER DAY
BREAKING OF THE WEDGE OVER FAR NWRN ZONES WILL KEEP HIGHS CLOSER TO
CLIMO WHILE AREAS ALONG THE MORE IMMEDIATE COAST WARMS UP INTO THE
LOW 70S. WHEN AND WHERE THE WEDGE BREAKS HOWEVER WILL LEAD TO LARGE
JUMPS IN TEMPS DUE TO THE SHALLOWNESS AND STRENGTH OF THE INVERSION.
POPS ARE ALSO RATHER PERPLEXING ON MONDAY...DESPITE THE FACT THAT A
WARM FRONT WILL BE LIFTING THROUGH MODELS ARE SHOWING LITTLE TO NO
ASCENT THROUGH THE COLUMN. ADDITIONALLY...THE MID LEVELS WILL HAVE
DRIED OUT QUITE A BIT WHILE THE LOW LEVELS REMAIN DAMP. DRIZZLE
SEEMS A BIT MORE LIKELY THAN MEASURABLE RAINFALL. NOT SO ON MONDAY
NIGHT HOWEVER AS THE MOISTURE DEEPENS AND A COLD FRONT APPROACHES
FROM THE NW. MODEL TIMING DIFFERENCES WITH THIS FRONT CONTINUE
ALTHOUGH THEY ARE SOMEWHAT DIMINISHED. PREFER THE SLIGHTLY SLOW GFS
AS THE BOUNDARY IS WELL ALIGNED WITH THE DEEP LAYER FLOW AND THUS
WILL HAVE NO LARGE SOUTHWARD PUSH. A FLAT WAVE DEVELOPING IN THE LEE
OF THE MOUNTAINS WILL ALSO SLOW THE PROGRESS SOMEWHAT. ASSUMING THIS
IS CORRECT THE FRONT WILL ENTER NWRN ZONES BY 18Z AND PROBABLY CLEAR
THE AREA 3 TO 4 HOURS LATER. THIS WILL MEAN THAT TUESDAY AFTERNOON
HIGHS WILL SHOW A CONSIDERABLE GRADIENT FROM NRN TO SRN ZONES JUST
AS THEY SHOULD ON MONDAY. STRONG COOL AND DRY AIR ADVECTION UNDERWAY
BY TUESDAY EVENING BRINGING CLEARING SKIES AND NIGHTTIME LOWS BACK
IN THE 30S.

&&

.LONG TERM /WEDNESDAY THROUGH SUNDAY/...
AS OF 3 PM SUNDAY...CONFIDENCE REMAINS ON THE LOW SIDE FOR THE
PERIOD WITH MEDIUM RANGE GUIDANCE SHOWING LITTLE RUN TO RUN
CONSISTENCY. BROAD MID LEVEL TROUGHING OVER THE CONUS WILL PERSIST
THROUGH NEXT WEEK BUT WILL BECOME FLATTER LATER IN THE WEEK. EARLY
IN THE PERIOD FRONT STALLED OFF THE COAST MAY MOVE CLOSER TO THE
AREA AS A WEAK SURFACE WAVE MOVES NORTHEAST ALONG THE BOUNDARY. HAVE
LOW CONFIDENCE IN THIS BUT WILL CARRY SLIGHT CHC POP FOR EASTERN
HALF OF FORECAST AREA WED NIGHT INTO THU AS THERE COULD BE A BRIEF
PERIOD OF ISENTROPIC LIFT COMBINED WITH AN INCREASE IN MOISTURE.

HIGH PRESSURE BUILDS IN BEHIND THE EXITING WAVE WITH THE AREA DRYING
OUT THU AND FRI AS MUCH DRIER AIR MASS MOVES IN. ALTHOUGH PLENTY OF
SUNSHINE IS EXPECTED THU AND FRI NORTHERLY FLOW WILL KEEP
TEMPERATURES BELOW CLIMO.

THE WEEKEND BRINGS ANOTHER LOW CONFIDENCE EVENT WITH THE GUIDANCE
SHOWING A WEAK COASTAL TROUGH SAT. THE TROUGH MAY OR MAY NOT MOVE
ONSHORE SAT NIGHT AHEAD OF A SOUTHERN STREAM SYSTEM ARRIVING LATE
SAT NIGHT OR SUN. HAVE HIGHER CONFIDENCE IN THE COASTAL TROUGH
DEVELOPING GIVEN THE SURFACE HIGH SHIFTING OFF THE COAST FRI INTO
SAT BUT LESS CONFIDENCE IN IT MOVING ONSHORE. THE WEAK SOUTHERN
STREAM SYSTEM REMAINS AN ENIGMA AT THIS POINT WITH VERY LITTLE
AGREEMENT BETWEEN THE GFS...ITS ENSEMBLE MEMBERS...AND THE ECMWF.
THINK SOMETHING WILL BE THERE BUT HAVE LITTLE CONFIDENCE ON THE
PARTICULARS. HIGH TEMP FORECAST FOR SUN QUITE NICELY SUMS UP THE
RANGE OF SOLUTIONS LATE IN THE PERIOD. GFS SOLUTION WOULD PRODUCE
HIGHS IN THE LOW TO MID 70S WITH ECMWF SOLUTION PRODUCING HIGHS IN
THE LOW TO MID 40S. UNTIL THE PICTURE BECOMES CLEARER SEE NO REASON
TO MAKE CHANGES LATE IN THE PERIOD.

&&

.AVIATION /00Z MONDAY THROUGH FRIDAY/...
AS OF 00Z...IFR/LIFR CIGS BLANKET OUR CWA THIS EVENING WITH THE COLD
AIR WEDGE FIRMLY IN PLACE OVER THE REGION. CIGS WILL GRADUALLY LOWER
TONIGHT...BECOMING LIFR AT ALL SITES AFTER MIDNIGHT. INCREASING LOW
LEVEL SOUTHWEST FLOW OVERNIGHT ALSO ENHANCES OUR FOG THREAT...AS
DEWPOINTS INCREASE WITH WARMER AIR ADVECTING INTO THE AREA. SOME
PATCHY AREAS OF FOG ARE EXPECTED AFTER MIDNIGHT WITH VSBYS DROPPING
TO IFR/LIFR LEVELS. IFR CIGS WILL LIKELY PERSIST THROUGH THE MORNING
HOURS UNTIL THE SFC WINDS BECOME SOUTHWESTERLY AND THE WEDGE BEGINS
TO ERODE. THE GFS SOUNDINGS ARE MORE OPTIMISTIC THAN THE NAM IN
TERMS OF THE TIMING OF THE COLD WEDGE ERODING. IT APPEARS THAT
CONDITIONS COULD IMPROVE TO MVFR ALONG THE COAST BY MIDDAY. IFR WILL
PERSIST LONGER AT KFLO/KLBT AND COULD LAST THROUGH THE AFTN HOURS.

EXTENDED OUTLOOK...EXPECT MVFR/IFR CONDITIONS AND RAIN ON TUESDAY
AHEAD OF ANOTHER COLD FRONT. MODERATE CONFIDENCE FOR VFR WEDNESDAY
AND THURSDAY...EXCEPT FOR POTENTIAL IFR STRATUS ALONG THE COAST ON
THURSDAY MORNING.

&&

.MARINE...
-- Changed Discussion --
NEAR TERM /UNTIL 6 AM MONDAY MORNING/...
AS OF 930 PM SUNDAY...A WARM FRONT EXTENDING ABOUT 80-100 MILES OFF
THE CAPE FEAR COAST WILL SLOWLY MOVE NORTHWESTWARD TOWARD THE COAST
TONIGHT...JUMPING ONSHORE MONDAY MORNING. SURFACE PRESSURES ARE
BEGINNING TO RISE IN THE MIDDLE OF THE COLD AIR ACROSS THE INTERIOR
CAROLINAS WHICH WILL HELP THE WARM FRONT TO MAKE PROGRESS ONSHORE.
NORTH TO NORTHEAST WINDS WERE EARLIER BLOWING 15-20 KNOTS BUT ARE
BEGINNING TO DIMINISH AS THE FRONT APPROACHES. A FEW HOURS BEFORE
THE FRONT ARRIVES EXPECT NORTH WINDS TO SUBSIDE TO 10 KNOTS OR
LESS...THEN ABRUPTLY SHIFT 180 DEGREES MONDAY MORNING.

SEAS HAVE DIMINISHED TO ONLY 3 FEET AT THE CAPE FEAR RIVER HARBOR
BUOY AND TO 5 FEET OUT AT FRYING PAN SHOALS BUOY. WITH DIMINISHING
WINDS EXPECT SEA HEIGHTS TO DIMINISH BY ABOUT ANOTHER FOOT BY
DAYBREAK.

SHORT TERM /MONDAY THROUGH TUESDAY NIGHT/...
AS OF 3 PM SUNDAY...THE COLD AIR WEDGE THAT HAD BRINGING THE
NORTHERLY FLOW WILL ERODE FROM SE TO NW ON MONDAY. THIS SHOULD
HAPPEN QUITE READILY OVER THE WATERS BUT MAY BE MORE SLUGGISH AND
PROBLEMATIC TO FORECAST OVER LAND. AS SUCH A LIGHT SOUTHERLY FLOW
WILL JUST BE GETTING ESTABLISHED OVER THE WATERS EARLY IN THE
PERIOD. THE REST OF THE DAY WILL BRING A SLIGHT VEER AND INCREASE
IN THE SPEEDS AS THE BOUNDARY MOVES FURTHER INLAND...POSSIBLY
ENOUGH FOR A 15 TO 20KT FCST BY LATER IN THE DAY. A COLD FRONT AND
FLAT WAVE OF LOW PRESSURE APPROACHING FROM THE NW WILL INCREASE
THE GRADIENT ACROSS THE WEST ATLANTIC BUT GENERALLY EAST OF THE 20
NM FORECAST ZONES. EVEN SO...EVEN BY LATER MONDAY SEAS MAY MANAGE
TO BUILD TO 3 TO 5 FT RANGE WITH THE HIGHER VALUES FOUND WELL
OFFSHORE DUE TO THE LARGELY COAST-PARALLEL WIND DIRECTION. COLD
FRONT BRINGS A SHARP VEER TO NRLY WINDS TUESDAY EVENING ALTHOUGH
THE SPEED OF THE BOUNDARY IS A LITTLE BIT UNCERTAIN...WITH SOME
GUIDANCE BEING FASTER THAN CURRENT FCST.

LONG TERM /WEDNESDAY THROUGH FRIDAY/...
AS OF 3 PM SUNDAY...NORTH TO NORTHEAST FLOW WILL PERSIST FOR MUCH OF
THE PERIOD THOUGH SPEEDS REMAIN A QUESTION. PERIOD BEGINS WITH
SPEEDS 15 TO 20 KT BUT DROPPING TO 10 TO 15 KT BY MIDDAY AS GRADIENT
RELAXES. SPEEDS START TO INCREASE WED NIGHT INTO THU AS SURFACE WAVE
MOVES NORTHEAST ALONG A STALLED FRONT. GRADIENT TIGHTENS UP AS THE
WAVE PASSES WITH SPEEDS INCREASING TO CLOSE TO 20 KT AND BECOMING
MORE NORTHERLY. GRADIENT RELAXES AND SPEEDS DROP TO 10 TO 15 KT THU
NIGHT AND FRI AS WAVE EXITS AND CENTER OF HIGH MOVES TO THE NC
COAST. SEAS 3 TO 5 FT FOR MUCH OF THE PERIOD WILL DROP TO 2 TO 4 FT
ON FRI.
-- End Changed Discussion --

&&

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

&&

$$

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