000
FXUS62 KILM 210321
AFDILM

AREA FORECAST DISCUSSION
NATIONAL WEATHER SERVICE WILMINGTON NC
944 PM EST FRI NOV 20 2009

.SYNOPSIS...
HIGH PRESSURE WILL BUILD INTO THE AREA FROM THE NORTHWEST TODAY
AND SATURDAY. LOW PRESSURE EMERGING FROM THE GULF OF MEXICO WILL
BRING RAIN TO THE EASTERN CAROLINAS SUNDAY THROUGH EARLY
MONDAY...PULLING AWAY TO THE NORTHEAST BY MONDAY AFTERNOON. MILD
WEATHER CONDITIONS CAN BE EXPECTED MUCH OF NEXT WEEK.

.NEAR TERM /UNTIL 6 AM SATURDAY MORNING/...
AS OF 9 PM FRIDAY...LOW STRATUS DECK OF CLOUDS AND ITS PROGRESSION
ACROSS THE ILM CWA WILL BE THE FOCUS FOR THE OVERNIGHT. HAVE USED
RUC/NAM 1000-900MB RH LAYER TO IDENTIFY ITS PROGRESSION
SOUTHWARD/INLAND AND ITS AREAL COVERAGE ACROSS THE ILM CWA FOR THE
REMAINDER OF THE OVERNIGHT. ITS COVERAGE TO BASICALLY INCLUDE THE
IMMEDIATE COASTAL COUNTIES AND INLAND BY 1 COUNTY. COULD OBSERVE
PATCHY FOG BUT ITS OCCURRENCE TOO ISOLATED TO INCLUDE. HAVE TWEAKED
UP OVERNITE MINS MAINLY UNDER THE CANOPY OF LOW CLOUDS. NE WINDS TO
STAY MORE ACTIVE CLOSER TO THE COAST AND UNDERNEATH THE STRATUS DECK
AS IT ADVECTS IT SOUTHWARD. QUITE DRY ABOVE THE STRATUS...850MB AND
HIER VIA LATEST NAM MODEL TIME HEIGHT SECTIONS AND THEREFORE DO NOT
EXPECT ANY PCPN OUT OF THESE CLOUDS. UPSTREAM INLAND CI WILL LIKELY
STREAM OVERHEAD FROM THE SW BY DAYLIGHT SATURDAY.

.SHORT TERM /6 AM SATURDAY MORNING THROUGH SUNDAY NIGHT/...
AS OF 3 PM FRIDAY...HIGH PRESSURE BUILDING IN FROM THE NORTH WILL
KEEP THE FORECAST AREA DRY ON SAT. UPPER LEVEL MOISTURE ADVECTION
AHEAD OF DEVELOPING GULF COAST STORM WILL RESULT IN A LOT OF MID AND
UPPER LEVEL CLOUDS. ALONG THE COAST COOLER LOW LEVEL FLOW WILL
RESULT IN SOME LOW CU DEVELOPING...BUT WEAK SUBSIDENCE INVERSION
BETWEEN 850 AND 750 MB WILL PREVENT ANY PRECIP FROM FALLING. CLOUD
COVER AND NORTHERLY FLOW WILL KEEP TEMPERATURES A LITTLE COOLER THAN
FRI...RIGHT AROUND CLIMO.

CLOUD BASES LOWER SAT NIGHT INTO SUN WITH CROSS SECTIONS SHOWING THE
ATMOSPHERE BECOMING NEARLY SATURATED FROM THE SURFACE THROUGH 200 MB
AROUND MIDNIGHT WITH LIGHT RAIN DEVELOPING. BEST ISENTROPIC LIFT
ARRIVES SUN MORNING ACROSS SW PORTIONS...SPREADING OVER NE PARTS OF
THE FORECAST AREA BY NOON. CANNOT FIND ANY REASON TO NOT GO WITH
CATEGORICAL POPS ON SUN. BIG QUESTION IS HOW WILL THE SYSTEM EVOLVE
ONCE IT REACHES THE AREA. DO NOT LIKE THE LATEST NAM SOLUTION WHICH
TRACKS MAIN LOW WEST OF THE MOUNTAINS. THE FAVORED SOLUTION...AND
ONE SUPPORTED BY THE LATEST GFS/ECMWF/CANADIAN...TAKES THE LOW INTO
THE SOUTHEAST US AND DEVELOPS A SECONDARY LOW ALONG OR JUST OFF THE
COAST. STILL UNSURE EXACTLY WHERE THIS LOW WILL TRACK...BUT LIKE THE
ECMWF AND CANADIAN SOLUTION WITH THE LOW MOVE NORTHEAST JUST OFF THE
COAST. THIS WOULD KEEP THE ENTIRE AREA IN STRATIFORM PRECIP AND
COOLER NORTHERLY FLOW. HAVE TRENDED HIGHS DOWN TO ACCOUNT FOR
THIS...BUT THERE STILL REMAINS PLENTY OF POTENTIAL FOR THE FORECAST
TO GO AWRY. LOW PASSING OVER OR WEST OF THE AREA WOULD LEAD TO HIGH
TEMPS WHILE A LOW FARTHER OFFSHORE WILL RESULT IN MUCH COOLER TEMPS.

CLOUDS LINGER SUN NIGHT BUT PRECIP WILL BE ENDING AS THE SYSTEM
MOVES OFF TO THE NORTHEAST AND STARTS TO DEEPEN. NORTHERLY FLOW WILL
INCREASE WITH CLOUDS AND MIXING KEEPING LOWS WELL ABOVE CLIMO.

.LONG TERM /MONDAY THROUGH FRIDAY/...
AS OF 3 PM SATURDAY...WEAK HIGH PRESSURE WILL BUILD IN BEHIND COLD
FRONT MON THROUGH TUES...BUT GFS SHOWS WEAK SHORT WAVE CROSSING THE
AREA MON NIGHT. PCP WATER CLOSE TO AN INCH MON MORNING WILL DECREASE
THROUGH THE DAY REACHING DOWN TO AROUND A HALF INCH BY TUES. ANY
LINGERING PRECIP SHOULD EXIT THE AREA THROUGH MON MORNING. OVERALL
EXPECT VERY DRY MID LEVELS BUT MAY SEE SOME LOW CLOUDS AND DRIZZLE
HANGING AROUND THROUGH TUES MORNING. DRIER WESTERLY FLOW TAKES OVER
THROUGH MID WEEK. TUES NIGHT A COLD FRONT REACHES THE WRN
CAROLINAS...BUT BECOMES VERY DIFFUSE AFTER CROSSING THE MOUNTAINS
INTO THE COASTAL CAROLINAS. MAY NOT SEE MUCH IN THE WAY OF PCP AS
THE FRONT MOVES INTO LOCAL AREA...BUT BOUNDARY WILL REACH THE COAST
WHILE A COASTAL TROUGH BECOMES MORE PRONOUNCED HEADING INTO THURS.
PCP WATER INCREASES BUT MAY BE MORE IN THE WAY OF UPPER LEVEL
MOISTURE IN HIGH CLOUDS IN W-SW JET. GFS KEEPS THIS PCP OFF
SHORE...BUT TOO CLOSE FOR COMFORT AND MAY SEE A WETTER FORECAST FOR
THANKSGIVING DAY...ESPECIALLY ALONG THE COAST. WITH BOUNDARY SO
CLOSE AND FORECAST SO OUT IN TIME...WILL KEEP SOME LOW END POPS IN
FORECAST FOR NOW ESPECIALLY CLOSE TO THE COAST. BY FRI HIGH
AMPLITUDE MID TO UPPER TROUGH SWINGS ACROSS THE EAST COAST SCOURING
OUT ALL THE WEATHER AND BRINGING DRY AND COOL HIGH PRESSURE FOR THE
WEEKEND. DEEP LAYER NW FLOW ADVECTS PLENTY OF DRY AIR IN FOR FRI
WITH PCP WATER DOWN TO A QUARTER INCH OR LESS.

TEMPS WILL HOLD AROUND NORMAL OR ABOVE THROUGH MUCH OF THE WEEK
UNTIL FRI WHEN COLD AND DRY HIGH PRESSURE BUILDS IN.

.AVIATION /00Z SATURDAY THROUGH WEDNESDAY/...
BIT OF A STRANGE SYNOPTIC SITUATION. HIGH PRESSURE BUILDING IN...BUT
SOME MVFR STRATA CU HAS MANAGED TO WORK ITS WAY UNDERNEATH THE HIGH
PRESSURE AND DOWN THE COAST...AFFECTING JUST ILM AT PRESENT. THINK
THIS DECK COULD WORK ITS WAY WEST AND SOUTH ENOUGH TO AFFECT LBT
AND CRE RESPECTIVELY...BUT IT SHOULD BE JUST A TRANSITORY FEATURE.
SOME LIGHT FOG INLAND POSSIBLE...BUT WINDS ALOFT TOO STRONG TO
SUPPORT ANY HEAVY FOG. SATURDAY...CONTINUED NORTHEAST FLOW WITH A
VFR STRATA CU CEILING EXPECTED. THERE IS AN OUTSIDE CHANCE OF SOME
LIGHT PATCHY RAIN...BUT NOT ENOUGH TO PUT IN THE TAFS. CONTINUED
NORTHEAST FLOW WITH THICKENING AND LOWERING MID AND HIGH CLOUDS IN
ADVANCE OF THE NEXT SYSTEM TOWARD THE END OF THE FORECAST PERIOD.

EXTENDED OUTLOOK...VFR SATURDAY. SHOWERS AND LOW CEILINGS MOVE BACK
IN SATURDAY NIGHT THROUGH MONDAY.

.MARINE...
NEAR TERM /THROUGH TONIGHT/...
AS OF 9 PM FRIDAY...SCEC CONDITIONS TO CONTINUE ACROSS THE ILM NC
WATERS WHICH MAY NEED TO BE EXTENDED AND EXPANDED TO INCLUDE THE
REMAINDER OF THE ILM WATERS THRU SATURDAY. A TIGHTENED SFC PRESSURE
GRADIENT TO REMAIN ACROSS THE ILM WATERS WHICH WILL EXTEND ACROSS
THE ILM SC WATERS OVERNIGHT INTO SATURDAY. THIS WILL RESULT IN NE
WINDS INCREASING AND BECOMING 15-20 KT THRUOUGHT BY SATURDAY
DAYLIGHT. SEAS 3 TO 5 FT WILL BE ONGOING ACROSS THE ILM NC WATERS
AND WILL EXPAND INTO THE SOUTHERNMOST ILM SC WATERS DURING DAYLIGHT
SATURDAY. THE PRESSURE GRADIENT BETWEEN THE STATIONARY FRONTAL
BOUNDARY PARALLEL TO THE CAROLINAS OFFSHORE AND A SLITELY STRONGER
HIGH THAN ANTICIPATED...CENTERED JUST SE OF THE GREAT LAKES AT THE
MOMENT...HAVE RESULTED WITH THE CONTINUED AND EXPANDING NE 15-20 KT
WIND FLOW ACROSS THE ILM WATERS. THE WINDS HAVE LOCALLY PRODUCED THE
3 TO 5 FT MAINLY WIND DRIVEN SEAS WITH SHORT PERIODS RUNNING 5-7
SECONDS...WHICH WILL BE THE MAINSTAY FOR THE OVERNIGHT PERIOD. AN
UNDERLYING 2-3 FT EASTERLY SWELL RUNNING AT 8-9 SECONDS WILL LIKELY
CONTINUE DISSIPATE UNDER THE LOCALLY PRODUCED WIND WAVES AS TIME
GOES BY.

SHORT TERM /SATURDAY THROUGH SUNDAY NIGHT/...
AS OF 3 PM FRIDAY...NORTHEAST FLOW SAT WILL INCREASE LATER IN THE
DAY AS GRADIENT BEGINS TO TIGHTEN BETWEEN HIGH PRESSURE TO THE NORTH
AND DEVELOPING GULF COAST LOW. CURRENT FORECAST DOES NOT CALL FOR
WINDS TO EXCEED SCA CRITERIA DURING THE PERIOD...BUT THERE REMAINS A
FAIR AMOUNT OF UNCERTAINTY. GULF COAST LOW WILL MOVE NORTHEAST SAT
NIGHT INTO SUN BUT TRACK OF LOW IS THE BIGGEST QUESTION. FAVORED
SCENARIO WOULD BE A SECONDARY LOW TO DEVELOP OFF THE SOUTHEAST
COAST. THIS LOW WOULD THEN MOVE NORTHEAST PASSING EAST OF THE WATERS
SUN INTO SUN NIGHT. ONCE THE LOW PASSES...NORTH TO NORTHEAST WINDS
BECOME OFFSHORE WITH A BRIEF DECREASE IN SPEEDS DURING THE SHIFT.
THINK SCA WILL BE NEEDED AT SOME POINT...LATER SAT OR SAT NIGHT BUT
NOT CONFIDENT ENOUGH TO RAISE IT JUST YET.

LONG TERM /MONDAY THROUGH WEDNESDAY/...
AS OF 3 PM SATURDAY...WEAK HIGH PRESSURE WILL BUILD IN BEHIND
DEPARTING STORM SYSTEM THROUGH TUES. OFF SHORE FLOW BECOMES
NORTHERLY BUT REMAINS VERY LIGHT LIGHT...10 KTS OR LESS THROUGH MUCH
OF PERIOD. SEAS ON A DECREASING TREND THROUGH MON STARTING AROUND
2-4 FT IN THE MORNING AND ENDING AROUND 3 FT BY MON NIGHT. SEAS WILL
REMAIN LOW IN A LIGHT NORTHERLY FLOW THROUGH WED. WITH DEVELOPMENT
OF COASTAL TROUGH HEADING INTO WED NIGHT...SHOULD SEE GRADIENT
TIGHTEN WITH WINDS BECOMING MORE ON SHORE AND SEAS INCREASING BY END
OF PERIOD.

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

SYNOPSIS...III
NEAR TERM...DCH
SHORT TERM...III
LONG TERM...RGZ
AVIATION...HDL