HAMweather.com Area Forecast Discussion for County Warning Area ILM

Thu, 16 Feb 2012 05:15:15 GMT
AREA FORECAST DISCUSSION
NATIONAL WEATHER SERVICE WILMINGTON NC
922 PM EST WED FEB 15 2012

.SYNOPSIS...
HIGH PRESSURE WILL MOVE EAST OFF THE VIRGINIA AND NORTH CAROLINA 
COASTS OVERNIGHT...FOLLOWED BY THE PASSAGE OF A WEAK COLD FRONT LATE 
THURSDAY. HIGH PRESSURE WILL BUILD BACK ACROSS THE AREA FRIDAY THEN 
SLIDE OFF THE CAROLINA COASTS SATURDAY. A POTENTIALLY POTENT STORM 
SYSTEM WILL TRACK FROM THE GULF COAST STATES SATURDAY...ACROSS THE 
FORECAST AREA LATE SATURDAY INTO SUNDAY. HIGH PRESSURE WILL FOLLOW 
AND BUILD BACK ACROSS THE REGION THROUGH EARLY NEXT WEEK. 

.NEAR TERM /THROUGH TONIGHT/...
AS OF 915 PM WEDNESDAY...UPPER FOLLOWED BY MID LEVEL CLOUD DECK TO 
OVERSPREAD THE ILM CWA FROM BASICALLY WEST TO EAST DURING THE 
OVERNIGHT. ACROSS THE SOUTHERNMOST PORTIONS OF THE ILM CWA...WHERE 
LOW LEVELS ARE MUCH MORE MOIST DUE TO THE ONSHORE FLOW...SUB 1K FT 
STRATUS AND/OR PATCHY/AREAS OF FOG COULD AFFECT THIS AREA OVERNIGHT. 
WEAK MID LEVEL IMPULSE(S) TO APPROACH FROM THE WSW LATE TONIGHT... 
RESULTING IN POPS INCREASING TO JUST SLIGHT CHANCE FOR RW- ACROSS 
THE WESTERNMOST PORTION OF THE ILM CWA BY DAYBREAK THU. LOOKING AT 
MODEL PARTIAL THICKNESS AND 8H AND 9H PROGGED TEMPS...NEUTRAL TO 
SLIGHT WAA ADVECTION TO OCCUR OVERNIGHT...WITH THE MAJORITY OF THE 
WAA RESERVED FOR DAYLIGHT THURSDAY. WILL GO WITH THE LOWER SIDE OF 
MODEL MOS GUIDANCE FOR TONIGHTS LOWS...ESPECIALLY THE NORTHERN 
PORTIONS OF THE ILM CWA. SFC BASED INVERSION WILL KEEP SFC WINDS 
CALM OR E-SE WINDS 5 MPH OR LESS. 

.SHORT TERM /THURSDAY THROUGH FRIDAY NIGHT/...
AS OF 300 PM WEDNESDAY...A COLD FRONT WILL MOVE THROUGH THE AREA 
THURSDAY AFTERNOON AND NIGHT...PRECEDED BY SHOWERS.  IT LOOKS LIKE 
THE MOST PROBABLE TIME FOR PRECIP IS IN THE 18Z TO 03Z WINDOW AS THE 
SYSTEM MOVES THROUGH THE AREA.  POPS WILL BE IN THE LIKELY TO 
CATEGORICAL RANGE FOR THE EVENT BUT RAINFALL AMOUNTS ARE EXPECTED TO 
BE LESS THAN ONE-QUARTER OF AN INCH.  CLEARING SKIES ARE ON TAP FOR 
THE REMAINDER OF THURSDAY NIGHT SUCH THAT MOSTLY CLEAR SKIES ARE 
EXPECTED FRIDAY.  CLOUD COVER WILL INCREASE FRIDAY NIGHT IN 
ADVANCE OF THE NEXT SYSTEM.  MAX TEMPS EACH DAY SHOULD REACH THE 
LOWER TO MIDDLE 60S WITH LOWS OF 45 TO 50 THURSDAY NIGHT AND 
GENERALLY 40 TO 45 FRIDAY NIGHT.

.LONG TERM /SATURDAY THROUGH WEDNESDAY/...
AS OF 300 PM WEDNESDAY...THE 00Z/12Z ECMWF AND THE 06Z GFS RUNS WERE 
ALL IN FAIRLY GOOD AGREEMENT WITH THE EVOLUTION OF OUR WEEKEND 
RAIN-MAKER. THE 12Z GFS APPEARS TO BE AN OUTLIER WITH ITS 
FAR-NORTHERN POSITION OF THE SURFACE FRONT AND WAS NOT USED. 

A WARM FRONT ACROSS THE GULF COAST AND SOUTH GEORGIA SATURDAY 
MORNING WILL MOVE NORTH INTO CENTRAL SOUTH CAROLINA SATURDAY 
AFTERNOON AS SURFACE LOW PRESSURE DEVELOPS ALONG THE LOUISIANA 
COAST. MOIST SOUTHERLY WINDS OVERRIDING THE FRONT SHOULD CREATE 
SHOWERS WHICH WILL GRADUALLY INCREASE IN COVERAGE SATURDAY INTO 
SATURDAY NIGHT. WE HAVE INCREASED POPS INTO THE 60-70 PERCENT RANGE 
EXPRESSING THE HIGH CONFIDENCE WE HAVE IN THIS EVENT EVEN 4-5 DAYS 
OUT. THE SURFACE LOW WILL MOVE INTO SOUTH GEORGIA SUNDAY NIGHT WITH 
THE FRONT STALLING OUT IN THE GEORGETOWN VICINITY. THIS MEANS A 
SHALLOW COLD AIRMASS SHOULD REMAIN ENTRENCHED ACROSS MOST OF OUR 
FORECAST AREA. BEFORE THE SURFACE LOW EXITS THE COAST SUNDAY 
AFTERNOON AND RAIN TAPERS OFF SUNDAY EVENING WE'RE LOOKING FOR THE 
POTENTIAL OF A WIDESPREAD ONE INCH RAIN EVENT ACROSS OUR AREA... 
PERHAPS THE FIRST WIDESPREAD ONE-INCH EVENT SINCE NOVEMBER 4 OF LAST 
YEAR.

DRIER AND COOLER AIR WILL BUILD IN SUNDAY NIGHT INTO MONDAY WITH 
HIGH PRESSURE MOVING FROM THE GREAT LAKES TO THE MID-ATLANTIC COAST. 
THE HIGH WILL PUSH OFFSHORE TUESDAY WITH MOIST RETURN FLOW 
DEVELOPING LATE IN THE DAY AND CONTINUING INTO WEDNESDAY AHEAD OF 
THE NEXT SYNOPTIC LOW PRESSURE AREA. THIS COULD BRING CLOUDS AND 
SHOWERS BACK TO THE CAROLINAS...BUT CONFIDENCE IS FAIRLY LOW AT THIS 
TIME.

.AVIATION /00Z THURSDAY THROUGH MONDAY/...
AS OF 00Z...VFR CONDITIONS ARE EXPECTED THROUGH THE OVERNIGHT HOURS  
AS HIGH PRESSURE SLOWLY RETREATS...REPLACED BY THICKENING HIGH 
CLOUDS. BY DAYBREAK...WINDS WILL SHIFT TO THE SOUTHEAST AS A FRONTAL 
SYSTEM APPROACHES FROM THE WEST. MODERATE OMEGA FROM ISENTROPIC LIFT 
WILL PRODUCED PRECIPITATION MOVING FROM WEST TO EAST ACROSS THE CWA 
FROM MID MORNING...THROUGH THE AFTERNOON HOURS. CONDITIONS WILL 
DETERIORATE AT FLO AND LBT BY 16Z...WITH THE COASTAL TERMINALS 
GETTING INTO THE ACT BY 18-19Z. ATMOSPHERE WILL BE FAIRLY SATURATED 
TO 500 MB WITH MODERATE CONFIDENCE FOR PRECIPITATION INDUCED 
CEILINGS LOWERING TO IFR AS THE AFTERNOON HOURS WEAR ON.

EXTENDED OUTLOOK...BECOMING VFR FRIDAY MORNING THROUGH SATURDAY 
MORNING. MODERATE CONFIDENCE IN RAIN DEVELOPING SATURDAY 
AFTERNOON...POSSIBLY HEAVY WITH LIFR CONDITIONS SATURDAY EVENING. 
IMPROVING CONDITIONS SUNDAY WITH VFR MONDAY. 

.MARINE...
NEAR TERM /THROUGH TONIGHT/...
AS OF 915 PM WEDNESDAY...BROAD CENTER OF SFC HIGH PRESSURE TO REACH 
COASTAL VA AND NC BY DAYBREAK THURSDAY. THIS WILL PRODUCE A VEERING 
WIND PROFILE AT THE SFC...WITH WINDS BECOMING E OVERNIGHT...POSSIBLY 
REACHING SE DIRECTION BY DAYBREAK THU. LACK OF A SFC PG WILL RESULT 
IN WIND SPEEDS AROUND 10 KT. COULD SEE OCCASIONALLY 15 KT ACROSS THE 
OUTER WATERS OFF CAPE FEAR LATE TONIGHT WHERE THE 60S SSTS LIE. THIS 
WILL ALLOW THE HIER WINDS JUST OFF THE DECK TO MIX DOWN DURING THIS 
VERY WEAK WEAK WAA REGIME. SIG SEAS AROUND 2 FT...EXCEPT UP TO 3 FT 
LATE ACROSS THE OUTER WATERS OFF CAPE FEAR. SIG. SEAS PRIMARILY 
RESULTING FROM A 6-8 SECOND PERIOD BORDERLINE SE-S 1-2 FT 
SWELL...WHICH WILL MIX WITH LOCALLY PRODUCED 4-5 SECOND PERIOD WIND 
WAVES. 

SHORT TERM /THURSDAY THROUGH FRIDAY NIGHT/...
AS OF 300 PM WEDNESDAY...VARYING WINDS AND SEAS EXPECTED THROUGH THE 
SHORT TERM. COLD FRONT APPROACHING FROM THE WEST AT THE START OF THE 
PERIOD BRINGS INCREASING SOUTHERLY WINDS AND BUILDING SEAS THROUGH 
THURSDAY. WINDS OF 10-15 KTS BUILD AS HIGH AS 20 KTS AND VEER TO THE 
SW THROUGH THE EVE...BUILDING SOUTHERLY WIND WAVES UP TO 3-4 
FT...WITH 5 FOOTERS POSSIBLE NEAR FRYING PAN SHOALS. AS COLD FRONT 
CROSSES THE WATERS THURSDAY NIGHT...WINDS QUICKLY EASE AND VEER TO 
THE NORTH AS HIGH PRESSURE BUILDS DOWN FROM THE MID-ATLANTIC REGION. 
SEAS FALL IN RESPONSE TO DECREASING WINDS...SUBSIDING TO 2-3 FT. BY 
LATE FRIDAY NIGHT...GRADIENT TIGHTENS BETWEEN MID-ATLANTIC HIGH 
PRESSURE AND A STORM SYSTEM DEVELOPING ACROSS THE GULF OF MEXICO. 
THIS CREATES NORTHEASTERLY WINDS WHICH INCREASE TO 15 KTS...AND SEAS 
BUILD TO 3 FT...PERHAPS 4 FT BY THE END OF THE PERIOD.

NEAR TERM /SATURDAY THROUGH MONDAY/...
AS OF 300 PM WEDNESDAY...A WARM FRONT LYING ACROSS SOUTHERN GEORGIA 
WEST ALONG THE GULF COAST SATURDAY MORNING WILL LIFT NORTH DURING 
THE DAY...PERHAPS REACHING THE GEORGETOWN VICINITY BY AFTERNOON. LOW 
PRESSURE WILL DEVELOP ALONG THE FRONT ON THE LOUISIANA COASTLINE AND 
SHOULD MOVE INTO SOUTH GEORGIA SATURDAY NIGHT. NORTHEAST WINDS 
SHOULD INCREASE SATURDAY AND ESPECIALLY SATURDAY NIGHT IN THE 
TIGHTENING GRADIENT AHEAD OF THE LOW...REACHING A SOLID 20 KNOTS OR 
MORE. THE LOW WILL MOVE OFF THE SOUTH CAROLINA COAST AND INTO THE 
ATLANTIC SATURDAY AFTERNOON...WITH WINDS BACKING TO THE NORTH AND 
NORTHWEST SUNDAY NIGHT INTO MONDAY.

OUR CURRENT FORECAST IS BASED PRIMARILY ON THE 00Z/12Z ECMWF MODELS 
WHICH WERE HEAVILY ENDORSED BY THE NWS HYDROMETEOROLOGICAL 
PREDICTION CENTER. THE 12Z GFS WAS MUCH FARTHER NORTH WITH THE FRONT 
AND DID NOT APPEAR REASONABLE. THIS WILL LEAD TO A PERIOD OF LARGE 
SEAS AND MODERATE TO STRONG WINDS SATURDAY NIGHT INTO SUNDAY WITH 
SMALL CRAFT ADVISORIES ALMOST CERTAIN.

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