Area Forecast Discussion
Issued by NWS Wilmington, NC

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000
FXUS62 KILM 182027
AFDILM

AREA FORECAST DISCUSSION
NATIONAL WEATHER SERVICE WILMINGTON NC
327 PM EST THU DEC 18 2014

.SYNOPSIS...
HIGH PRESSURE WILL RIDGE INTO THE CAROLINAS THROUGH FRIDAY. LOW
PRESSURE WILL DEVELOP ALONG THE WESTERN GULF COAST ON FRIDAY AND
TRACK EAST ALONG THE GULF COAST...MOVING OFF THE SOUTHEAST COAST
BY SATURDAY NIGHT. THIS SHOULD BRING A PERIOD OF RAIN AND BELOW
NORMAL TEMPERATURES. A WEDGE OF HIGH PRESSURE WILL MAINTAIN COOL
AND CLOUDY CONDITIONS INTO EARLY NEXT WEEK. AN OFFSHORE STORM
SYSTEM MAY BRING RAIN ON MONDAY. A COLD FRONT WILL MOVE ACROSS THE
AREA TUESDAY NIGHT INTO WEDNESDAY. COLD AND DRY WEATHER IS
EXPECTED ON CHRISTMAS.

&&

.NEAR TERM /THROUGH TONIGHT/...
AS OF 300 PM THURSDAY...A WEAK PRESSURE GRADIENT WILL PREVAIL AT
THE SURFACE UNDER A FLAT MID LEVEL PATTERN ALOFT. MID AND HIGH
LEVEL MOISTURE WILL CONTINUE TO STREAM BY IN INTERVALS FROM THE
SOUTHWEST. THE ONLY FORECAST CHALLENGE IS TEMPERATURES. THE NAM
AND GFS ARE IN REALLY GOOD AGREEMENT WITH WIDESPREAD LOWER 30S. I
HAVE ADDED A MARGINAL RADIATIONAL COMPONENT WHICH LOWERS READINGS
SLIGHTLY IN THE FAVORED AREAS. POSSIBILITY FOR FOG LOOKS MINIMAL
AS THE VERY DRY BOUNDARY LAYER AND MID LEVEL CLOUDS SHOULD
PRECLUDE THREAT.

&&

.SHORT TERM /FRIDAY THROUGH SATURDAY NIGHT/...
AS OF 300 PM THURSDAY...STILL LOOKS LIKE IT WILL RAIN SAT...BUT
THE MODELS HAVE NOT ONLY BEEN GUIDING US TO A SLOWER PROGRESSION...
BUT NOW A DRIER AND MORE SUPPRESSED SOLUTION FOR OUR FORECAST
AREA. GIVEN THAT...HAVE DECIDED TO DIAL BACK SOME ON BOTH POPS AND
QPF. NEVERTHELESS...A SOUTHERN STREAM SHORTWAVE WILL MOVE OUT OF
THE SOUTHWESTERN U.S. FRI AND THEN ACROSS THE MID SOUTH AND
SOUTHEAST FRI NIGHT AND SAT. HIGH PRESSURE IS EXPECTED TO BEGIN
WEDGING INTO THE CAROLINAS ON SAT WHICH WILL ALLOW A SHALLOW N TO NE
FLOW THROUGH 3 KFT TO BE TOPPED BY A DEEP W OR WSW FLOW. THE FLOW
ALOFT IS MARGINALLY MOIST AND THIS ALLOWS PRECIPITABLE WATER
VALUES TO CLIMB TO AROUND THREE-QUARTERS OF AN INCH. THE SYNOPTIC
SETUP DOES ALLOW ISENTROPIC UPGLIDE TO INCREASE AND THE
COMBINATION DOES SUPPORT HIGH POPS. HOWEVER...THE LOWEST 3-5 KFT
DO SHOW INDICATIONS OF HANGING ONTO THE DRY AIR IN THIS RATHER
QUICK HITTING SYSTEM. THEREFORE...WILL FORECAST LIKELY TO
CATEGORICAL POPS AT THIS TIME WITH QPF AMOUNTS ON THE ORDER OF ONE
TENTH TO A QUARTER OF AN INCH. OTHERWISE...FRIDAY WILL SHOW
INCREASING CLOUDS...ESPECIALLY OF THE HIGH VARIETY WITH CLOUDS
LOWERING THROUGH THE AFTERNOON AND EVE. IT WILL BE SOLIDLY CLOUDY
LATER FRI NIGHT AND SAT. CLOUDS MAY BEGIN TO PARTIALLY ERODE FROM
INLAND TO THE COAST SAT NIGHT AS DRIER AIR TRIES TO WORK
IN...ALTHOUGH WE MAY BE LEFT WITH CONSIDERABLE STRATUS FOR MUCH OF
THE NIGHT.

TEMPS ON FRI WILL BE NEAR NORMAL...MID AND UPPER 50S. HOWEVER...
SAT IS SHAPING UP TO BE A CHILLY DAY WITH TEMPS ONLY REACHING THE
UPPER 40S TO LOWER 50S. AN ALL LIQUID EVENT WITH LOWS FRI NIGHT
MAINLY IN THE 40S AND UPPER 30S TO LOWER 40S SAT NIGHT.

&&

.LONG TERM /SUNDAY THROUGH THURSDAY/...
AS OF 300 PM THURSDAY...SUNDAY APPEARS TO BE RAIN-FREE BUT STILL
RATHER CLOUDY WITH NO REAL IMPETUS FOR LOW LEVEL MOISTURE TO BE
ROUTED OUT FOLLOWING THE SATURDAY SYSTEM. THIS MAY CHANGE AS SOON AS
SUNDAY NIGHT HOWEVER AS A VERY WEAK UPPER IMPULSE LEADS TO A LITTLE
CYCLOGENESIS ALONG THE FRONT SITTING OFF THE COAST. FOR A FEW RUNS
NOW THE GFS HAS BEEN QUITE WET LOCALLY WITH THIS SYSTEM AND NOW THE
CMC IS ON BOARD. WILL RAISE POPS BUT NOT GO WITH QUITE THE BULLISH
RAINFALL AMOUNTS SHOWN GIVEN THE WEAK FORCING OVERALL AND TO A
LESSER EXTENT THE BACKING OFF TREND SEEN IN MODELS WITH THE SATURDAY
SYSTEM. ATTENTION THEN TURNS WESTWARD ON TUESDAY AS A DEEP TROUGH
DIGS INTO THE MIDDLE OF THE NATION. THE SURFACE BOUNDARY MAY REACH
THE MOUNTAINS BY EVE BUT LOCALLY THIS SHOULD MEAN ONE DRY DAY.
STRONG DYNAMICS START TO IMPINGE UPON OUR AREA TUESDAY NIGHT AND MAX
OUT WEDNESDAY ALTHOUGH THE FRONT AND DEEP MOISTURE LONG GONE/WELL
OFFSHORE BY MORNING. WEDNESDAY`S COLD AIR ADVECTION MAY BE STRONG
ENOUGH FOR NON-DIURNAL TEMP CURVES AND WED NIGHT THROUGH THURSDAY
NIGHT SHOULD BE RATHER CHILLY.

&&

.AVIATION /18Z THURSDAY THROUGH TUESDAY/...
AS OF 18Z...LOOK FOR MAINLY A CIRRUS CEILING OVER THE NEXT 24
HOURS...AFTER WHICH CEILINGS WILL LOWER IN ADVANCE OF THE NEXT
SYSTEM. NORTHERLY FLOW THIS AFTERNOON...GENERALLY LESS THAN 10
KTS. NO WEATHER TO SPEAK ABOUT WITH NO FOG EXPECTED TONIGHT AS
MOISTURE PROFILES ARE UNFAVORABLE. FRIDAY...THICKENING HIGH CLOUDS
IN ADVANCE OF A WEAK SYSTEM THAT WILL DEVELOP OVER THE
SOUTHEASTERN US.

EXTENDED OUTLOOK...VFR THROUGH FRIDAY. GOOD CHANCE OF RAIN ON
SATURDAY WITH POSSIBLE MVFR/IFR CONDITIONS. A SLIGHT CHANCE OF
PRECIP ON SUN...WITH A BETTER CHANCE MON AND TUE.

&&

.MARINE...
NEAR TERM /THROUGH TONIGHT/...
AS OF 300 PM THURSDAY...THE WEAK PRESSURE GRADIENT THAT RESIDES
OVER THE COASTAL WATERS WILL WEAKEN FURTHER THROUGH THE AFTERNOON
AND OVERNIGHT HOURS. NORTH TO NORTHEAST WINDS CURRENTLY RUNNING
NEAR TEN KNOTS WILL DROP TO THE SINGLE DIGITS AND PERSIST THROUGH
1200 UTC FRIDAY. SEAS...COMPRISED OF A VERY SUBTLE 10 SECOND SWELL
COMPONENT AND FOUR SECOND WIND WAVE WILL CONTINUE TO BE 1-2 FEET.

SHORT TERM /FRIDAY THROUGH SATURDAY NIGHT/...
AS OF 300 PM THURSDAY...N WINDS FRI WILL VEER TO NNE AND NE FRI
NIGHT WITH NE WINDS PERSISTING THROUGH SAT NIGHT. WIND SPEEDS WILL
BE UP TO 10 TO 15 KT...ESPECIALLY IN THE WAKE OF A SOUTHERN STREAM
SYSTEM SAT NIGHT. SEAS WILL BE 2 FT OR SO INTO FRI NIGHT WITH 3 TO
4 FT SEAS BECOMING MORE COMMON DURING SAT AND ESPECIALLY SAT NIGHT.

LONG TERM /SUNDAY THROUGH TUESDAY/...
AS OF 300 PM THURSDAY...SUNDAY SHOULD BRING A FAIRLY LIGHT GRADIENT
WITH HIGH PRESSURE HOLDING ON TO OUR NORTH AND A WEAK TROUGH OFF THE
COAST. THE OFFSHORE TROUGH WILL CREEP CLOSER TO THE COAST SUNDAY
NIGHT. AS THIS IMPULSE PASSES TO OUR NORTH AN AREA OF EXITING LOW
PRESSURE WILL BE DEVELOPING. NORMALLY THIS WOULD OFFER AN
OPPORTUNITY FOR A BIT OF A SURGE IN WINDS AND SEAS BUT THIS DOES NOT
PAN OUT THIS TIME. FLOW WILL TURN SLIGHTLY OFFSHORE BUT NOT PICK UP
IN SPEED. BACKING WINDS EXPECTED MOST OF TUESDAY AS A FAIRLY STRONG
COLD FRONT APPROACHES FROM THE WEST.

&&

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

&&

$$

NEAR TERM...RJD
SHORT TERM...SHK
LONG TERM...MBB
AVIATION...DL



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