Area Forecast Discussion
Issued by NWS Wilmington, NC

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000
FXUS62 KILM 202331
AFDILM

AREA FORECAST DISCUSSION
NATIONAL WEATHER SERVICE WILMINGTON NC
631 PM EST SAT DEC 20 2014

.SYNOPSIS...
WEAK HIGH PRESSURE ALONG WITH A FRONT JUST OFFSHORE WILL KEEP CLOUDY
AND COOL CONDITIONS IN PLACE THROUGH SUNDAY. ANOTHER ROUND OF RAIN
IS EXPECTED EARLY MONDAY WHEN A STORM MOVES UP THE COAST. SHOWERS
AND THUNDERSTORMS RETURN TUESDAY NIGHT INTO WEDNESDAY WITH A COLD
FRONT. CLEAR WEATHER IS EXPECTED FOR CHRISTMAS DAY INTO NEXT
WEEKEND.

&&

.NEAR TERM /UNTIL 6 AM SUNDAY MORNING/...
AS OF 615 PM SATURDAY...THE FIRST BATCH OF LIGHT RAIN HAS EXITED THE
COAST AS DRY MID-LEVEL AIR HAS SPREAD ACROSS MUCH OF THE CAROLINAS.
MAY NEED TO BUMP POPS UPWARD...ESPECIALLY ACROSS SC ZONES...AS NEXT
ROUND OF ISENTROPIC LIFT COMES INTO PLAY DURING THE EARLY MORNING
HOURS. THE REMAINDER OF THE FORECAST IS ON TRACK...WITH NO MAJOR
CHANGES.

PREVIOUS DISCUSSION...
AS OF 330 PM SATURDAY...REGIONAL RADAR AND SATELLITE SHOW BACK EDGE
OF PRECIP SHIELD ENTERING THE WESTERN EDGES OF THE FORECAST AREA.
DURING THE NEXT SEVERAL HOURS THIS DRYING WILL CONTINUE FROM WEST
TO EAST...REACHING THE COAST DURING THE LATE AFTERNOON/EARLY
EVENING TIME FRAME. THIS IS DOWN TO A SUBTLE BUT SIGNIFICANT SHIFT
IN THE WINDS IN THE 2-4K FT AS THE WEAK SURFACE LOW SLOWLY MOVES
AWAY FROM THE COAST. ALTHOUGH LOW LEVEL MOISTURE WILL LINGER
OVERNIGHT THE LAYER ABOVE 800 MB DRIES OUT IN PART DUE TO DEEP
WESTERLY FLOW. AT THE SURFACE THE WEDGE HOLDS ON WITH LOW LEVEL
NORTHEAST FLOW MAINTAINING A STRATUS DECK THROUGH THE END OF THE
PERIOD. ALTHOUGH MOISTURE BELOW 800 MB REMAINS ELEVATED FORECAST
SOUNDINGS DO NOT SHOW ANY LAYER AS BEING SATURATED. WILL NOT CARRY
ANY MENTION OF DRIZZLE BUT MAY MENTION FOG EARLY SUN MORNING.
BOUNDARY LAYER WINDS DO NOT GO CALM BUT THEY WILL BE LIGHT.
COMBINED WITH RECENT PRECIP THESE CONDITIONS COULD LEAD TO SOME
PATCHY FOG DEVELOPMENT THOUGH LOWEST VIS WOULD BE ON THE ORDER OF
3 OR 4 MILES...SO DO NOT ANTICIPATE ISSUANCE OF DFA. LOWS END UP A
LITTLE BELOW CLIMO...A COMBINATION OF HIGHS 10 DEGREES TODAY BELOW
CLIMO...LIGHT NORTHEAST FLOW AND SUBTLE COLD ADVECTION BEHIND THE
EXITING 5H SHORTWAVE.

&&

.SHORT TERM /6 AM SUNDAY MORNING THROUGH MONDAY NIGHT/...AS OF 330
PM SATURDAY...DREARY CONDITIONS WILL CONTINUE FOR THE SHORT TERM
PERIOD. A BROAD SOUTHWEST FLOW ALOFT WILL INTERACT WITH A PERSISTENT
BAROCLINIC ZONE JUST OFFSHORE AND A WEDGE OF HIGH PRESSURE INLAND.
THE MODELS ARE IN GENERAL AGREEMENT ON SUNDAY REMAINING DRY FOR THE
MOST PART. THERE COULD BE THE ISOLATED SPRINKLE OR MORE LIKELY PATCH
OF DRIZZLE BUT OVERCAST SKIES AND COOL CONDITIONS SHOULD DO IT.

A 300MB JET STREAK BRINGS ANOTHER ROUND OF RAIN FOR LATE SUNDAY INTO
MONDAY MORNING. THE NAM AND GFS PAINT MOST OF THE HEAVIER QPF
OFFSHORE WHERE THE BEST DIVERGENCE ALOFT RESIDES. THE BEST
ISENTROPIC LIFT ON THE 300K SURFACE RESIDES WEST OF I-95 AND THE
COAST IS LEFT IN BETWEEN WITH WEAK FORCING. HOWEVER THE QPF AMOUNTS
WEST OF THE INTERSTATE ARE CERTAINLY NOT IMPRESSIVE MAKING THE
OVERALL QPF AMOUNTS FAIRLY PALTRY. BEYOND MONDAY MORNING THE BEST
FORCING MOVES OFF QUICKLY LEAVING OVERCAST/DRIZZLY SKIES.

TEMPERATURE GUIDANCE IS IN GENERAL AGREEMENT OTHER THAN MONDAYS
HIGHS WHEN THE GFS/MAV NUMBERS ARE MUCH WARMER. HARD TO TRUST THESE
HOWEVER AS SURFACE PRESSURE PLOTS SHOW THE WEDGE...ALTHOUGH
WEAKENING REMAINING IN PLACE. I DID USE A BLEND BUT WOULD NOT BE
SURPRISED TO SEE SUBSEQUENT BULLETINS FROM THE GFS COOL.

&&

.LONG TERM /TUESDAY THROUGH SATURDAY/...
AS OF 330 PM SATURDAY...WEDGE WILL BE ERODED ON TUES AS A WAVE OF
LOW PRESSURE MOVES NORTH ALONG THE CAROLINA COAST. AT THE SAME TIME
A HIGH AMPLITUDE MID TO UPPER TROUGH WILL DIG DOWN FROM THE UPPER
GREAT LAKES INTO TEXAS PUSHING A COLD FRONT EAST. A DEEP S-SW FLOW
WILL BRING PLENTY OF WARM AIR AND MOISTURE INTO THE SOUTHEAST AHEAD
OF THE FRONT. INITIALLY ON TUES SHALLOW COOLER AIR WILL BE IN PLACE
AS THE WARMER AIR OVERRIDES IT PRODUCING INCREASED ISENTROPIC LIFT
AND INCREASED RAIN CHANCES. AS THE DAY WEARS ON...THE WINDS WILL
COME AROUND WITH WARMER AND MOISTER AIR FLOWING IN. ALWAYS TOUGH TO
TIME THIS AS COLD DENSE AIR HOLDS ON LONGER THAN MODELS USUALLY
PREDICT. FOR NOW WILL KEEP WITH TEMPS WARMING THROUGH LATE DAY WITH
WARMER AND MORE HUMID AIR MASS IN PLACE TUES NIGHT INTO WED.

UNSETTLED WEATHER WILL REMAIN AHEAD THE COLD FRONT THROUGH TUES
NIGHT INTO WED BEFORE COLD FRONT MOVES THROUGH LATE WED. INCREASING
LOW LEVEL JET UP TO 40 KTS WILL COMBINE WITH BETTER UPPER LEVEL
FORCING TO PRODUCE MORE WIDESPREAD SHOWERS THROUGH TUES NIGHT INTO
WED. KEPT ISOLATED THUNDERSTORMS IN FORECAST TUES NIGHT INTO WED AS
WARM FRONT LIFTS NORTH AND LOCAL AREA GETS INTO BEST MOISTURE AND
LIFT. PCP WATER VALUES REACH UP TO 2 INCHES ALONG THE COAST WED AFTN

THE DIGGING MID TO UPPER TROUGH WILL PUSH THE COLD FRONT THROUGH WED
NIGHT BEFORE FINALLY MOVE OFF SHORE BY THURS MORNING LEAVING DRIER
AND COOLER WEATHER FOR CHRISTMAS DAY. OVERALL EXPECT CLOUDY AND DAMP
TO WET WEATHER THROUGH THE FIRST HALF OF THE PERIOD WITH COOLER MORE
SEASONABLE WEATHER THURS INTO FRI AS HIGH PRESSURE BUILDS ACROSS THE
SOUTH. THE HIGH WILL SHIFT OFF SHORE THROUGH FRI LEAVING A LIGHT
RETURN FLOW AND WARMER TEMPS FRI INTO SATURDAY WITH A GOOD DEAL OF
SUNSHINE. NEXT COLD FRONT SHOULD MOVE THROUGH SAT NIGHT BUT LOOKS
LIKE IT MAY BE LACKING ANY DEEP MOISTURE.


&&

.AVIATION /00Z SUNDAY THROUGH THURSDAY/...
AS OF 00Z...CIGS WILL LIKELY BOUNCE AROUND BETWEEN MVFR/VFR LEVELS
OVERNIGHT AND INTO SUNDAY AS WE ENTER A PERIOD OF UNSETTLED WEATHER.
FCST SOUNDINGS REMAIN SATURATED IN THE 3-10KFT LAYER THROUGH MUCH OF
THE PERIOD. WILL MAINTAIN MVFR CIGS THROUGH TONIGHT...LOWEST AT THE
COASTAL TERMINALS. THERE HAVE BEEN PATCHES OF STRATUS AROUND 1KFT
REPORTED ALONG THE COAST THIS EVENING...BUT DO NOT ANTICIPATE ANY
PERSISTENT IFR CIGS TONIGHT AS FCST SOUNDINGS NEVER COMPLETELY LOCK
IN THIS LOW LEVEL MOISTURE. THE LATEST HRRR AND SREF CIG PROBS ALSO
SUPPORT KEEPING IFR OUT OF THE TAFS ATTM. IN FACT...CIGS SHOULD
GRADUALLY LIFT TOWARD DAYBREAK IF THE CURRENT GUIDANCE TRENDS ARE
CORRECT. NORTHEAST WINDS AOB 10 KT WILL PERSIST THROUGH THE DAY
SUNDAY. ANOTHER ROUND OF MOIST ISENTROPIC LIFT WILL BRING MORE
-RA/DZ TO THE AREA DURING THE DAY...SPREADING FROM SOUTH TO NORTH
BEGINNING AROUND 15Z AT THE SOUTHERN TERMINALS AND AFTER 18Z AT
KILM/KLBT. THIS SHOULD AGAIN HELP LOWER CIGS TO MVFR LEVELS THROUGH
THE AFTERNOON.

EXTENDED OUTLOOK...RAIN LIKELY MON WITH MVFR/IFR CIGS AS A COASTAL
TROUGH DEVELOPS OFFSHORE. SHOWERS/TEMPO MVFR EXPECTED TUE/WED AHEAD
OF A STRONG COLD FRONT. GUSTY WINDS WED/THU BEFORE AND AFTER FROPA.
THU WILL BE VFR AT ALL TERMINALS.

&&

.MARINE...
NEAR TERM /THROUGH TONIGHT/...
AS OF 615 PM SATURDAY...THE CURRENT FORECAST IS ON TRACK. NO MAJOR
CHANGES WERE MADE WITH THE LATEST CWF ISSUANCE.

PREVIOUS DISCUSSION...
AS OF 330 PM SATURDAY...NORTHEAST FLOW OF 10 TO 15 KT THIS AFTERNOON
AND OVERNIGHT MAY BRIEFLY JUMP INTO THE 15 TO 20 KT RANGE AS
GRADIENT TIGHTENS A BIT. EXIT OF SURFACE LOW TO THE EAST WILL BE
FOLLOWED BY HIGH REASSERTING ITSELF SO GRADIENT DOES NOT CHANGE A
LOT. 12 TO 18 HOUR PERIOD OF ENHANCED NORTHEAST FLOW WILL PUSH
SEAS...CURRENTLY RUNNING 2 TO 3 FT...TO 3 TO 5 FT THIS EVENING AND
OVERNIGHT. EXCEPTION WILL BE ALONG THE BRUNSWICK COAST WHERE
OFFSHORE FLOW WILL KEEP SEAS 1 TO 2 FT CLOSER TO SHORE.

ALTHOUGH CONDITIONS ARE LIKELY TO BE CLOSE TO SCEC ADVISORY DO NOT
PLAN TO RAISE ONE AT THIS TIME. MAINLY BECAUSE THE INCREASE IN
WIND SPEEDS SO FAR TODAY HAVE BEEN A LITTLE UNDER WHAT WAS
EXPECTED. GIVEN THE ALREADY MARGINAL NATURE OF THE EVENT WILL HOLD
OFF FOR NOW...THOUGH THE EVENING SHIFT MAY DECIDE TO RAISE ONE.

SHORT TERM /SUNDAY THROUGH MONDAY NIGHT/...
AS OF 330 PM SATURDAY...A FAIRLY BRISK NORTHEAST FLOW WILL PERSIST
ACROSS THE COASTAL WATERS SUNDAY IN BETWEEN A BAROCLINIC ZONE TO THE
EAST AND HIGH PRESSURE INLAND. AS LOW PRESSURE DEVELOPS AND MOVES UP
ALONG THIS FRONT SUNDAY NIGHT...THE FLOW WILL TURN MORE EASTERLY.
SPEEDS THROUGHOUT WILL BE 15-20 KNOTS. SOME HIGHER SEAS CAN BE
EXPECTED WITH THE SOMEWHAT PROLONGED NATURE OF THE WINDS...3-5 FEET.
CANT RULE OUT A FEW SIX FOOTERS BUT THINK A SMALL CRAFT HEADLINE CAN
BE AVOIDED. LIGHTER WINDS AND SEAS CAN BE EXPECTED MONDAY ALTHOUGH
THE FLOW WILL GENERALLY BE THE SAME.

LONG TERM /TUESDAY THROUGH THURSDAY/...
AS OF 330 PM SATURDAY...WAVE OF LOW PRESSURE WILL MOVE UP THE
CAROLINA COAST ON TUES WITH WINDS COMING AROUND THROUGH THE DAY.
LIGHT NORTHERLY WINDS WILL SHIFT AROUND BECOMING MORE ON SHORE
THROUGH THE DAY AND EVENTUALLY SOUTHERLY BY TUES EVENING.

A LARGE AND POTENT STORM SYSTEM WILL PUSH A COLD FRONT EAST WITH
INCREASING SOUTHERLY WINDS IN A TIGHTENING GRADIENT FLOW TUES NIGHT
INTO WED. WINDS WILL INCREASE UP TO 15 TO 25 KTS TUES NIGHT INTO WED
AHEAD OF THE COLD FRONT. THIS WILL PUSH SEAS UP FROM 2 TO 4 FT EARLY
TUES TO 3 TO 5 FT BY LATE TUES. WNA SHOWS SEAS RAMPING UP ABOVE 6 FT
BY WED MORNING AND POSSIBLE UP TO 7 TO 9 FT IN OUTER WATERS IN
STRONGER SW TO W FLOW AS FRONT MOVES THROUGH THE WATERS LATE WED
INTO WED NIGHT. EXPECT SMALL CRAFT CONDITIONS WED AND LASTING INTO
THURS WITH HIGHEST SEAS GETTING PUSHED FARTHER OFF SHORE IN STRONGER
W-NW FLOW BEHIND FRONT.

&&

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

&&

$$

SYNOPSIS...SHK
NEAR TERM...SRP
SHORT TERM...SHK
LONG TERM...RGZ
AVIATION...BJR








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