Area Forecast Discussion
Issued by NWS Wilmington, NC

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000
FXUS62 KILM 190217
AFDILM

AREA FORECAST DISCUSSION
NATIONAL WEATHER SERVICE WILMINGTON NC
1017 PM EDT THU SEP 18 2014

.SYNOPSIS...
HIGH PRESSURE WILL BUILD INTO THE CAROLINAS FROM THE NORTH AS LOW
PRESSURE DEVELOPS OFF THE SOUTHEAST COAST AND MOVES NORTHWARD INTO
THE WEEKEND. A COLD FRONT WILL MOVE ACROSS THE AREA MONDAY NIGHT
FOLLOWED BY COOL AND DRY HIGH PRESSURE DURING THE MIDDLE OF NEXT
WEEK.

&&

.NEAR TERM /THROUGH FRIDAY/...
AS OF 1017 PM THURSDAY...LOWER DEWPOINTS ARE PRESSING SOUTHWARD
INTO OUR NE ZONES THIS EVENING AS SURFACE HIGH PRESSURE RIDGES
SOUTHWARD. THIS FEATURE WILL TIGHTEN THE LOCAL PRESSURE GRADIENT
WHICH WILL INCREASE ONSHORE WINDS OVERNIGHT...HIGHEST ALONG THE
COAST WHERE MIXING WILL BE MUCH MORE VIGOROUS. EVEN AT 2Z/10P ENE
GUSTS TO 20 MPH WERE COMMON ALONG BOTH THE SC AND NC COASTS. THE
SLIGHT DRY AIR INTRUSION WILL HINDER SHOWER DEVELOPMENT OVER MUCH
OF NC BUT FURTHER SOUTH OVERNIGHT MENTIONABLE POP VALUES WILL BE
RETAINED DUE TO STRONGER LOW-LEVEL CONVERGENCE...DEEPER MOISTURE
AND MORE PARCEL BUOYANCY IN THE LOWER TROPOSPHERE. MINIMUM TEMPS
MAY REQUIRE ADJUSTMENTS NEAR THE IMMEDIATE COAST WHERE MOUNTING
WINDS WILL LIKELY KEEP TEMPS LEVELED-OFF AND ELEVATED COMPARED TO
INTERIOR LOCATIONS MORE DECOUPLED FROM THE BOUNDARY LAYER FLOW.
1500 FOOT PATCHY STRATUS MAY FORM LATE BUT WINDS SHOULD KEEP FOG
AND MIST FROM GAINING A SUBSTANTIAL AND MENACING FOOTHOLD TONIGHT.

&&

.SHORT TERM /FRIDAY NIGHT THROUGH SATURDAY NIGHT/...
AS OF 300 PM THURSDAY...HIGH PRESSURE WILL RIDGE DOWN THROUGH THE
INLAND CAROLINAS IN A TYPICAL WEDGE-LIKE FASHION WHILE LOW
PRESSURE OFF THE SOUTHEAST COAST STRENGTHENS AS IT TRACKS
NORTHWARD FRI THROUGH SATURDAY. THE MID TO UPPER TROUGH PULLS OFF
TO THE NORTHEAST LEAVING A WEAKNESS IN THE MID TO UPPER LEVELS
OVER GA/SC COAST. THE SFC LOW WILL TRACK NORTH REACHING EAST OF
THE CAPE FEAR COAST BY SAT NIGHT. THE INCREASING E-NE FETCH AHEAD
OF THE SYSTEM SHOULD AFFECT MAINLY COASTAL SECTIONS WITH CLOUDS
AND POSSIBLE SHOWERS. THE NAM CONTINUES TO BE MUCH SLOWER WITH THE
EVOLUTION OF THIS LOW...NOT REACHING THE CAPE FEAR COAST UNTIL
LATE SUNDAY. THEREFORE KEEPING A MORE EASTERLY FETCH...BEING MORE
AGGRESSIVE WITH ITS ONSHORE PUSH OF MOISTURE WITH PCP WATER VALUES
UP TO 1.8 INCHES OVER PORTIONS OF LOCAL FORECAST AREA FRI INTO
SAT. THE GFS HOLDS THE MOISTURE CLOSER TO THE COAST IN A TIGHTER
MORE NE FLOW AROUND THE LOW WITH MOIST AIR IN A TIGHTER GRADIENT
BETWEEN THE COAST AND INLAND. WILL NEED TO WATCH HOW THIS LOW
EVOLVES AS IT MAY EVEN TAKE ON SOME TROPICAL CHARACTERISTICS OVER
THE NEXT COUPLE OF DAYS. FOR NOW WILL MAINTAIN MAINLY SHALLOW
MOISTURE WITH CLOUDS AND PCP CONFINED CLOSER TO THE COAST AND
SPREADING NORTHWARD AS LOW APPROACHES. AS WINDS STRENGTHEN THERE
MAY BE INCREASED CONVERGENCE AND MORE WIDESPREAD SHWR CHANCES BUT
UNCERTAINTY EXISTS AS TO HOW FAST AND HOW CLOSE TO COAST THE LOW
WILL MOVE AND THEREFORE WILL KEEP BRUNT OF ACTIVITY ALONG AND OFF
SHORE.

CLOUD COVER MAINLY ALONG THE COAST AND EAST-NORTHEAST FLOW WILL
KEEP HIGH TEMPERATURES NEAR TO SLIGHTLY BELOW CLIMO THROUGH THE
PERIOD. LOWS WILL END UP NEAR TO SLIGHTLY ABOVE CLIMO...A
COMBINATION OF CLOUD COVER AND LINGERING LOW LEVEL MOISTURE.

&&

.LONG TERM /SUNDAY THROUGH THURSDAY/...
AS OF 300 PM THURSDAY...BIGGEST QUESTION MARK DURING THE EXTENDED
INVOLVES A LOW PRESSURE MOVING ALONG THE COAST SUNDAY. GFS/CMC/NAM
SUGGEST THAT A HYBRID/WARM-CORE LOW PRESSURE SYSTEM WILL BE JUST OFF
THE NC COAST SUNDAY MORNING...WHILE THE ECMWF SHOWS BARELY A TROUGH
MOVING TO THE NORTHEAST. TIMING DIFFERENCES EXIST...AS THE NAM IS
QUITE SLOW COMPARED TO THE OTHER GUIDANCE...AND IS LIKELY TOO SLOW
SINCE ANY LOW PRESSURE SHOULD BE PICKED UP AND SLUNG TO THE NE BY A
SECONDARY TROUGH DROPPING INTO THE GREAT LAKES. THE GFS SEEMS TO BE
A CONSISTENT COMPROMISE...AND IS FAVORED FOR THE EXTENDED. THIS
SUGGESTS THAT WHILE RAPID DRYING WILL OCCUR DURING SUNDAY...THE
FIRST PART OF THE DAY WILL BE CLOUDY AND POSSIBLY UNSETTLED WITH
SHOWERS...ESPECIALLY ALONG THE COAST. AS THIS SYSTEM PULLS
AWAY...RAPID DRYING WILL OCCUR AND THE SECOND HALF OF SUNDAY WILL BE
SUNNY WITH SEASONABLE TEMPERATURES.

A VERY BRIEF PERIOD OF WAA DEVELOPS LATE SUNDAY INTO MONDAY BEFORE A
STRONGER COLD FRONT CROSSES THE CAROLINAS LATE MONDAY. THIS FRONT
NOW LOOKS TO BE MOISTURE STARVED DUE TO SUCH A BRIEF PERIOD OF MOIST
ADVECTION AHEAD OF IT...AND THUS ONLY A SCHC OF SHOWERS IS EXPECTED
WITH SOME ENHANCED CLOUD COVER. THIS WILL RAPIDLY CLEAR AND DRY BY
TUESDAY...AND SOME BEAUTIFUL FALL WEATHER WILL OVERSPREAD THE REGION
WITHIN CANADIAN HIGH PRESSURE FROM LATE TUESDAY THROUGH THE REST OF
THE PERIOD. HIGHS AND LOWS ARE EXPECTED TO BE A FEW DEGREES BELOW
CLIMO...BUT LOW HUMIDITY AND LOTS OF SUNSHINE WILL PRODUCE GREAT
WEATHER AS THE CALENDAR TICKS OFFICIALLY INTO ASTRONOMICAL FALL.

&&

.AVIATION /02Z FRIDAY THROUGH TUESDAY/...
AS OF 02Z...THE RADAR IS QUIET TONIGHT AS ISOLATED SHOWER
ACTIVITY HAS FADED WITH THE LOSS OF DAYTIME HEATING. EAST-
NORTHEAST FLOW AROUND 4-8 KT WILL PERSIST OVERNIGHT...WHICH MEANS
THE BOUNDARY LAYER SHOULD REMAIN DISTURBED ENOUGH TO KEEP VSBYS
FROM DROPPING. ONLY POSSIBLE RESTRICTIONS WOULD BE MVFR CIGS
DEVELOPING AFTER 09Z. THE BEST CHANCE FOR MVFR WOULD BE ALONG THE
COAST WHERE SCT/BKN 2-3KFT MARINE STRATOCU MAY BRUSH
KILM/KCRE/KMYR EARLY FRI MORNING. WILL STILL INCLUDE MVFR CIGS FOR
THE INLAND TERMS AS WELL. EASTERLY FLOW WILL STRENGTHEN ON FRI AS
CANADIAN HIGH PRESSURE CONTINUES BUILDING SOUTHWARD INTO THE
CAROLINAS. EXPECT EAST WINDS 10-12 KT DURING THE DAY WITH GUSTS UP
20 KT...ESPECIALLY ALONG THE COAST. AN UPPER DISTURBANCE MOVING
OVER THE SOUTHEAST COULD PRODUCE SOME AFTERNOON SHOWERS. BEST PCPN
CHANCES WILL BE OVER SOUTH CAROLINA... WARRANTING A MENTION OF
VCSH FOR OUR SOUTHERN TERMINALS.

EXTENDED OUTLOOK...CHANCE OF SHOWERS ALONG THE COAST SAT. GUSTY
NORTHEAST WINDS SAT WILL BECOME NORTHWEST ON SUN AS LOW PRESSURE
WELL OFFSHORE MOVES UP THE EAST COAST. VFR ON MON/TUE.

&&

.MARINE...
NEAR TERM /THROUGH TONIGHT/...
AS OF 10 PM THURSDAY...WILL NEED TO TAKE A CLOSER LOOK AT
POTENTIAL OF AN EXERCISE CAUTION STATEMENT AS WINDS HOLD NEAR 20
KT INTO EARLY FRIDAY. SEAS HOLDING AT 4 FEET BUT NOT GOING TO TAKE
TOO MUCH MORE WIND TO REACH 5 FT. STRONG HIGH PRESSURE WILL BUILD
SOUTHWARD AND INCREASE NE-ENE WINDS INTO EARLY FRIDAY. SEAS OF 3
TO 4 FT MAY SEE A 4-5 FT RANGE EARLY FRIDAY...HIGHEST OFFSHORE
AND NORTH OF CAPE FEAR. SEAS SHOWING WANING SWELL FROM EDOUARD OF
1-2 FEET EVERY 10-11 SECONDS BUT BUILDING E WAVES 3-4 FT EVERY
5-6 SECONDS. A FEW SHOWERS OR AN ISOLATED TSTMS IS POSSIBLE ON THE
0-20 NM WATERS OVERNIGHT AS NIGHT-TIME INSTABILITY RISES.

SHORT TERM /FRIDAY THROUGH SATURDAY NIGHT/...
AS OF 300 PM THURSDAY...WINDS WILL WILL INCREASE THROUGH FRI IN
PINCHED GRADIENT FLOW BETWEEN WEDGE OF HIGH PRESSURE INLAND AND
LOW PRESSURE DEVELOPING OFF THE SOUTHEAST COAST. NE WINDS WILL
INCREASE UP TO 20 KT WITH HIGHER GUSTS THROUGH FRI INTO FRI NIGHT.
AS NE WINDS INCREASE THROUGH FRI...SEAS WILL REACH SCA THRESHOLDS
INTO FRI EVE...ESPECIALLY NORTH OF CAPE FEAR...BUILDING TO 4 TO 6
FT. SEAS WILL REMAIN LOWER CLOSE TO THE COAST SOUTH OF CAPE FEAR
WHERE NE FLOW IS BLOCKED. HIGH PRESSURE WILL WEAKEN INLAND AS HIGH
SHIFTS FARTHER OFF THE NEW ENGLAND COAST LOSING ITS GRIP. THIS
SHOULD HELP GRADIENT WINDS TO DIMINISH AND SEAS TO LOWER THROUGH
SATURDAY...BUT AS LOW MOVES NORTHWARD CLOSER TO THE LOCAL
WATERS...NE WINDS SHOULD INCREASE ONCE AGAIN...POSSIBLY REACHING
SCA THRESHOLDS ONCE AGAIN.

LONG TERM /SUNDAY THROUGH TUESDAY/...
AS OF 300 PM THURSDAY...LOW PRESSURE WILL BE MOVING UP THE COAST ON
SUNDAY...AND WILL BE JUST OFFSHORE...EAST OR NORTHEAST...OF THE
WATERS TO START THE PERIOD. THIS LOW WILL MOVE AWAY DURING
SUNDAY...WITH WINDS BACKING FROM NE TO NW...AND THEN WEST BY MONDAY
MORNING. STILL SOME UNCERTAINTY INTO THE STRENGTH AND TRACK OF THIS
LOW PRESSURE...BUT ATTM IT LOOKS LIKE IT WILL BE WEAK ENOUGH AND FAR
ENOUGH OFFSHORE TO KEEP WINDS TO 15 KTS OR LESS REGARDLESS OF
DIRECTION ON SUNDAY. SEAS WILL FEATURE HIGHLY VARIABLE DIRECTIONS ON
SUNDAY WHICH WILL MAKE A CONFUSED SPECTRUM...BUT WAVE HEIGHTS WILL
FALL FROM 3-5 FT EARLY TO 2-3 FT BY MONDAY MORNING. OF COURSE...IF
THIS LOW PRESSURE BECOMES STRONGER OR MOVES CLOSER...CONDITIONS
COULD END UP BEING WORSE THAN CURRENTLY FORECAST.

A BRIEF PERIOD OF W/SW WINDS MONDAY WILL QUICKLY BECOME NW BEHIND A
COLD FRONT WHICH WILL CROSS THE WATERS LATE IN THE DAY...FOLLOWED BY
A NE SURGE ON TUESDAY WITH WINDS AGAIN RISING TO 15 KTS.
LOW-AMPLITUDE SEAS OF 1-2 FT MONDAY WILL RISE SLOWLY DURING TUESDAY
AS THE NE WINDS INCREASE...BECOMING 3-5 FT LATE IN THE PERIOD.

&&

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

&&

$$

NEAR TERM...MJC
SHORT TERM...RGZ
LONG TERM...JDW
AVIATION...BJR/8






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