FXUS62 KILM 112334
AFDILM
AREA FORECAST DISCUSSION
NATIONAL WEATHER SERVICE WILMINGTON NC
634 PM EST FRI DEC 11 2009
.SYNOPSIS...
COLD AND DRY HIGH PRESSURE WILL RIDGE INTO THE CAROLINAS FROM THE
NORTH THROUGH SATURDAY. LOW PRESSURE DEVELOPING OFF THE COAST WILL
BRING RAIN SATURDAY NIGHT AND SUNDAY. MILDER TEMPERATURES WILL
RETURN MONDAY AND TUESDAY...FOLLOWED BY A STRONG COLD FRONT
LATE TUESDAY. COLD HIGH PRESSURE WILL BUILD IN WEDNESDAY THROUGH
FRIDAY.
&&
.NEAR TERM /UNTIL 6 AM SATURDAY MORNING/...
AS OF 3 PM FRIDAY...NO CHANGE TO THE OVERALL PICTURE WITH THE LATEST
GUIDANCE. COLD DRY HIGH PRESSURE BUILDS IN FROM THE WEST WITH THE
CENTER OF THE HIGH PASSING TO OUR NORTH IN THE EARLY MORNING HOURS.
MEANWHILE...A COASTAL TROUGH BEGINS TO FORM OFFSHORE BY DAYBREAK
SATURDAY MORNING....TURNING FLOW MORE NORTHEASTERLY AND TIGHTENING
THE GRADIENT A BIT. SATELLITE LOOPS AND MODEL SOUNDINGS INDICATE AN
EXTENSIVE LAYER OF MOSTLY UPPER LAYER CLOUDS OF VARIOUS EXTENT AND
THICKNESS WILL CONTINUE TO STREAM ACROSS THE CWA. THIS HAS ACTED TO
SUPPRESS MAX TEMPS TODAY BELOW WHAT WAS EXPECTED BUT IT MAY HAVE THE
OPPOSITE EFFECT OVERNIGHT...ESPECIALLY WHEN COMBINED WITH INCREASED
NELY FLOW. DUE TO THIS HAVE STAYED ON THE HIGH SIDE OF TEMPERATURE
GUIDANCE...AND EVEN A BIT HIGHER THAN THAT OVER OUR SC COASTLINE
WHERE NELY ONSHORE FLOW WILL BE STRONGEST. THIS WILL STILL GIVE US
AN EXTENSIVE AREA OF SUB FREEZING TEMPERATURES. EXPECT EVERYPLACE
WILL SEE FREEZING OR BELOW WITH THE LIKELY EXCEPTION OF THE
IMMEDIATE COAST SOUTH OF CAPE FEAR. WITH A VERY STABLE ATMOSPHERE
AND BONE DRY MID AND LOWER LEVELS SEE ZERO CHANCE OF PRECIP.
&&
.SHORT TERM /6 AM SATURDAY MORNING THROUGH SUNDAY NIGHT/...
AS OF 3 PM FRIDAY...MAIN PLAYER WILL BE A WET LOW PRESSURE SYSTEM
THAT WILL RIDE ALONG THE COASTAL TROF SATURDAY NIGHT AND
SUNDAY. TIMING IS THE TRICKY PART IN TERMS OF PRECIP ONSET...BOTH
FOR EVAPORATIONAL QPF LOSSES AND EXPECTED NON-DIURNAL TEMP TRENDS.
THINK THERE WILL BE ENOUGH DRY AIR IN PLACE ON SATURDAY THAT MOST
OF THE PRECIP WILL HOLD OFF UNTIL AFTER 00Z SUN...BUT HAVE
INCLUDED A LOW CHANCE POP IN THE SOUTHERN ZONES. TEMPS ON THE LOW
END OF GUIDANCE OUT OF RESPECT FOR CLOUD COVER AND COLD ADVECTION.
SAT NIGHT WILL CARRY CATEGORICAL POPS AS THE SOUTHEASTERLY
MOISTURE FEED IS MAXIMIZED. WARM ADVECTION SHOULD SUPPORT RISING
TEMPS AFTER A SLIGHT...AND BRIEF DROP IN TEMPS SAT EVENING.
CONTINUED THE CATEGORICAL POPS THRU AT LEAST SUNDAY MORNING...BUT
SHOULD TAPER OFF QUICKLY IN THE AFTERNOON ONCE THE MOISTURE AXIS
SHIFTS NE OF OUR AREA. DUE TO THE EXPECTED TRACK OF THE LOW VERY
CLOSE TO THE COAST...WENT FOR A BIT TIGHTER GRADIENT IN TEMPS THAN
MOS GUIDANCE WOULD SUGGEST...FOLLOWING THE COOLER GFS MOS INLAND AND
THE WARMER NAM MOS ALONG THE COAST.
DRYING CONDITIONS SUNDAY NIGHT...WITH TEMPS STILL ABOVE NORMAL AS
THE AIR MASS BEHIND THIS SYSTEM IS OF A MILDER PACIFIC ORIGIN.
&&
.LONG TERM /MONDAY THROUGH FRIDAY/...
AS OF 3 PM FRIDAY...SOUTHERN STREAM REMAINS BUSY AT LEAST DURING
THE FIRST PART OF THE EXTENDED AS A SHORT WAVE MOVES ACROSS TEXAS
AND PHASES WITH A NORTHERN STREAM SYSTEM. CONTINUED TO ADVERTISE
CHANCE POPS FOR LATE MONDAY INTO THE DAY TUESDAY WITH THIS SYSTEM.
AIR MASS IN THE WAKE OF THIS SYSTEM IS VERY SIMILAR TO THE CURRENT
ONE WITH 850MB TEMPERATURES DROPPING JUST BELOW FREEZING. 850MB
TEMPERATURES IN THE 50S WILL ALLOW SPRING LIKE READINGS MONDAY AND
TUESDAY. WITH THESE TEMPERATURES...THERE COULD BE A SEVERE THREAT
WITH A TYPICAL LOW CAPE/HIGH SHEAR SCENARIO BUT A BIT FAR OUT IN
TIME TO NAIL DOWN TIMING OR MAGNITUDE.
&&
.AVIATION /00Z SATURDAY THROUGH WEDNESDAY/...
AS OF 00Z...ALL TERMINALS ARE VFR AND ARE EXPECTED TO REMAIN VFR
THROUGHOUT THIS TAF PERIOD. COLD HIGH PRESSURE OVER THE VIRGINIAS IS
IN CONTROL FOR THE TIME BEING AS IT SLIDES EAST AND OFF THE ATLANTIC
SEABOARD BY THE END OF THE PERIOD. LOW PRESSURE IS EXPECTED TO FORM
OVER THE EASTERN GULF OF MEXICO LATE IN THE PERIOD.
CIRRUS STRATUS CEILINGS AND SCATTERED ALTOCUMULUS FOR VFR TO START
OUT AT ALL TERMINALS. WIND TO DIE DOWN TO LIGHT AND VARIABLE OVER
NIGHT. AFTER SUNRISE SCATTERED STRATOCUMULUS TO GO ALONG WITH THE
MID AND HIGH CLOUDS. MID CLOUDS THICKEN AS DAY PROGRESSES AND BECOME
A CEILING BY 18Z AT THE SC TERMINALS...AND SOON AFTER AT LBT/ILM. AS
THE LOW PRESSURE IN THE GULF OF MEXICO BECOMES MORE ORGANIZED...LOW
CLOUD CEILINGS AROUND 3500 FEET FORM AFTER 21Z. WIND AFTER SUNRISE
MORE EASTERLY AT 6 TO 14 KNOTS.
EXTENDED OUTLOOK... CEILINGS BEGIN TO LOWER FOR A CHANCE OF VFR LATE
SATURDAY NIGHT AND LOWERING EVEN FURTHER INTO IFR FOR SUNDAY.
&&
.MARINE...
NEAR TERM /THROUGH TONIGHT/...
AS OF 3 PM FRIDAY...COLD DRY HIGH PRESSURE BUILDS IN FROM THE WEST
WITH THE CENTER OF THE HIGH PASSING TO OUR NORTH IN THE EARLY
MORNING HOURS. MEANWHILE...A COASTAL TROUGH BEGINS TO FORM OFFSHORE
BY DAYBREAK SATURDAY MORNING....TURNING FLOW MORE NORTHEASTERLY AND
TIGHTENING THE GRADIENT A BIT. THIS WILL CAUSE WINDS TO GRADUALLY
INCREASE OVERNIGHT WITH WINDS INCREASING FROM NORTH TO
SOUTH...RANGING FROM 10 TO 15 KTS NORTH OF CAPE FEAR TO 15 TO 20 KTS
OVER OUR WATERS OFF OF GEORGETOWN COUNTY. SEAS WILL PICK UP A COUPLE
OF FEET AS A RESULT...FROM 2 TO 4 FT UP NORTH TO 3 TO 5 FT DOWN
SOUTH.
SHORT TERM /SATURDAY THROUGH SUNDAY NIGHT/...
AS OF 3 PM FRIDAY...WILL BEGIN SATURDAY WITH A RESPECTABLE ENE
GRADIENT BETWEEN HIGH PRESSURE ALONG THE VA/NC BORDER AND A
DEVELOPING COASTAL TROF OFF THE SC COAST. EXPECT WINDS TO STAY
JUST SHY OF ADVISORY THRESHOLDS...BUT GRADUALLY VEER TO SE THRU
THE DAY AS THE HIGH MOVES EAST OFF THE VIRGINIA CAPES. LONG
DURATION OF 20 KT WINDS AND WIDE OPEN FETCH WILL ALLOW SEAS TO
BUILD TO SCA THRESHOLDS AS THE DAY PROGRESSES. WILL RAISE THE
ADVISORY AT 15Z SAT FOR THE SC WATERS AND CLOSER TO 20Z FOR THE
NC WATERS.
ONSHORE WINDS AND ROUGH SEAS WILL PERSIST INTO SUNDAY...UNTIL THE
LOW PRESSURE CENTER PASSES OVER THE WATERS. SWAN WAVES LOOKED
OVERDONE FOR THE EXPECTED WINDS LATE SAT NIGHT INTO SUN MORNING...SO
WENT CLOSER TO WNA NUMBERS AND CAPPED SEAS AT 8-10 FT WITHIN 20NM.
WINDS WILL COME AROUND TO THE WEST AND DIMINISH TO AROUND 15 KT
FOR SUN AFTERNOON...AND THE OFFSHORE TRAJECTORY WILL START TO
KNOCK SEAS DOWN. EXPECT TO FALL BELOW ADVISORY THRESHOLDS LATE SUN
AFTERNOON IN THE SOUTH...AND SUN NIGHT IN THE NORTH WHERE THE
LONGER FETCH WILL KEEP SEAS UP SLIGHTLY ALONG FRYING PAN SHOALS.
LONG TERM /MONDAY THROUGH WEDNESDAY/...
AS OF 3 PM FRIDAY...BENIGN WINDS INITIALLY INCREASE QUICKLY FROM THE
SOUTHWEST EARLY TUESDAY PRECEDING THE COLD FRONT MOVING ACROSS THE
SOUTHEAST. WILL MOST LIKELY SEE AT LEAST SMALL CRAFT WINDS AND SEAS
FOR TUESDAY. WITH STRONG COLD AIR ADVECTION IN THE WAKE OF THE FRONT
LATE TUESDAY AND WEDNESDAY...EXPECT SMALL CRAFT WINDS TO PERSIST
ALTHOUGH SEAS WILL BE WORKED OVER NEAR SHORE WITH THE OFFSHORE FETCH.
&&
.ILM WATCHES/WARNINGS/ADVISORIES...
SC...NONE.
NC...NONE.
MARINE...SMALL CRAFT ADVISORY FROM 10 AM SATURDAY TO 6 PM EST SUNDAY
FOR AMZ254-256.
SMALL CRAFT ADVISORY FROM 3 PM SATURDAY TO MIDNIGHT EST SUNDAY
NIGHT FOR AMZ250-252.
&&
$$
NEAR TERM...REK
SHORT TERM...RAS
LONG TERM...SHK
AVIATION...MDC
