National Weather Service Raw Text Product

655 
FXUS62 KILM 120317
AFDILM

AREA FORECAST DISCUSSION
NATIONAL WEATHER SERVICE WILMINGTON NC
1105 PM EDT TUE SEP 11 2012

.SYNOPSIS...
FAIR WEATHER WILL PREVAIL THIS WEEK AS CANADIAN HIGH PRESSURE 
SETTLES INTO THE REGION AS IT SHIFTS SLOWLY EAST. AN APPROACHING
COLD FRONT MAY BRING A FEW SHOWERS OVER THE WEEKEND AND INTO EARLY
NEXT WEEK.

&&

.NEAR TERM /THROUGH TONIGHT/... 
AS OF 11:00 PM TUESDAY...RIDGING SFC AND ALOFT TO DOMINATE THE ILM 
CWA OVERNIGHT. SUBSIDENCE IN THE MID-LAYERS TO PREVENT ANY VERTICAL 
DEVELOPMENT WITH THE CU/SC THAT DEVELOPS OVER THE ADJACENT ATLANTIC 
WATERS AND SPORADICALLY MOVES ONSHORE DURING THIS PERIOD. THE NE-E 
FLOW IN THE LOWER LEVELS WILL FORCE/LIFT WHAT MOISTURE THAT IS 
AVAILABLE UPWARDS...WITH OROGRAPHIC LIFT AIDING ANY CU/SC 
DEVELOPMENT WELL INLAND WITHIN THE ILM CWA. WILL GO WITH MOSTLY 
CLEAR TO PTLY CLOUDY FOR SKY CONDITIONS TONIGHT. HRRR INDICATES 
SPOTTY PCPN OR ISOLATED SHRA TO DEVELOP OVER THE ADJACENT 
WATERS...AND PUSH ONSHORE BEFORE DISSIPATING ALTOGETHER. FOG 
ALGORITHM PORTRAITS PATCHY TO AREAS OF FOG DEVELOPMENT FOR A SHORT 
4-6 HR WINDOW ENDING/DISSIPATING BY 8-9 AM WEDNESDAY.  

DRY AND RELATIVELY COOL WEATHER TO CONTINUE THROUGHOUT THE NEAR TERM 
AS CANADIAN HIGH PRESSURE CENTERED ACROSS THE MID-ATLANTIC STATES TO 
MARTHAS VINEYARD WHICH EVIDENTLY MAINTAINS A STEADY BUT LIGHT NE-E 
FLOW ESPECIALLY FELT ACROSS THE COASTAL CAROLINAS. 

&&

.SHORT TERM /WEDNESDAY THROUGH THURSDAY/... 
AS OF 300 PM TUESDAY...FALL LIKE WEATHER WILL CONTINUE THROUGH MID
WEEK AS CANADIAN HIGH PRESSURE SETTLES DOWN OVER THE SOUTHEAST
WHILE SHIFTING SLOWLY EAST. AS THE CENTER SLIPS OFF THE NEW
ENGLAND COAST...IT WILL CONTINUE TO RIDGE DOWN INTO THE CAROLINAS.
THIS WILL HELP VEER WINDS AROUND THROUGH THE PERIOD TO THE
NORTHEAST WED INTO THURS AND EAST BY END OF THE PERIOD WHICH WILL
PRODUCE A SLIGHT INCREASE IN MOISTURE COMING FROM THE ATLANTIC
WATERS. AN OVERALL RISE IN MOISTURE WILL BRING PCP WATER VALUES
FROM CLOSE TO A HALF INCH WED TO OVER AN INCH BY LATE THURS IN
MOISTURE COMING IN FROM THE E-NE. THEREFORE EXPECT SUNNY WEATHER
ON WED BUT SHOULD SEE MORE IN THE WAY OF CU DEVELOPMENT THURS
AFTERNOON ESPECIALLY ALONG SEA BREEZE BOUNDARY AND MAINLY OVER
NORTH CAROLINA ZONES. MOISTURE PROFILES AND SOUNDING DATA SHOW
MOISTURE LOCKED IN BELOW INVERSION REACHING UP TO 90% IN THE 2-4K
FT LEVEL ON THURS. EASTERLY FETCH OF MOISTURE MAY HELP TO PRODUCE
SOME FOG OR LOW STRATUS ON FRI IN THE EARLY MORNING CLOSER TO THE
COAST.

IN THE MID TO UPPER LEVELS THE RIDGE BECOMES MORE PRONOUNCED OVER 
THE EAST COAST...BUT GETS SQUEEZED OUT BY END OF PERIOD BY BACK 
BUILDING TROUGH OVER THE ATLANTIC AND TROUGH DIGGING DOWN FROM THE 
UPPER GREAT LAKES. OVERALL EXPECT PLENTY OF DRY AIR AND SUBSIDENCE 
THROUGHOUT THE MID LEVELS THROUGHOUT MOST OF WED AND INTO THURS. 

AS FOR TEMPS...HEIGHTS WILL BE RISING THROUGH MID WEEK WITH A RISE 
IN 850 TEMPS FROM 12C ON WED UP CLOSE TO 15C BY THURS. THE VERY DRY 
AIR INITIALLY WILL CONTINUE TO PRODUCE LARGE DIURNAL SWINGS BUT THE 
INCREASED MOISTURE IN THE LOW LEVELS BY THURS WILL BRING DEWPOINT 
TEMPS UP ABOUT 10 DEGREES TO NEAR 65 CLOSER TO THE 
COAST...ESPECIALLY NC COAST. THEREFORE EXPECT DAY TIME HIGHS
RISING A COUPLE OF DEGREES BETWEEN WED AND THURS...BETWEEN 80 AND
85 MOST PLACES. OVERNIGHT LOWS WILL INCREASE ALSO FROM CLOSER TO
60 WED IN MORE IDEAL RADIATIONAL COOLING CONDITIONS TO CLOSER TO
65 BY FRI MORNING.

&&

.LONG TERM /FRIDAY THROUGH TUESDAY/...
AS OF 300 PM TUESDAY...LARGE 5H RIDGE ACROSS THE EAST TRANSITIONS TO 
MID-LEVEL SPLIT FLOW AS A NORTHERN STREAM LOW DRAGS A COLD FRONT 
TOWARDS THE CAROLINAS ON SATURDAY. THIS FRONT TRIES TO PUNCH INTO A 
VERY DRY AIR MASS...AND IS ACCOMPANIED ONLY BY WEAK (AND WEAKENING) 
MID-LEVEL FORCING. WITH PWATS STILL ONLY AROUND ONE-INCH...AND MEX 
P24 VALUES STILL WELL BELOW CLIMO...EXPECT THE WKND TO BE MOSTLY 
DRY. HOWEVER...CANNOT RULE OUT SOME ISOLATED SHOWERS EITHER SAT OR 
SUN AND THUS WILL KEEP INHERITED SCHC POP.

A MORE ROBUST MID-LEVEL SYSTEM ROTATES NORTHEAST FROM THE GULF COAST 
REGION FOR THE BEGINNING OF THE WEEK...AND IS ACCOMPANIED BY AN 
INCREASING SURFACE REFLECTION AND WARM FRONT. ALTHOUGH IT APPEARS 
BEST FORCING REMAINS WEST OF THE IMMEDIATE CWA...LIFT ALONG THE WARM 
FRONT IN A MOISTENING AIR MASS WILL PROVIDE INCREASING SHOWER 
POTENTIAL MONDAY INTO TUESDAY AND WILL CARRY LOW-CHC FOR NOW...BUT 
THIS WILL BE THE BEST CHANCE FOR RAIN THROUGH THE EXTENDED.

MAX TEMPS WILL BE SLIGHTLY ABOVE CLIMO FRI/SAT BEFORE FALLING BACK 
TO NEAR SEASONABLE LEVELS FOR THE BEGINNING OF THE WEEK. MINS EACH 
NIGHT WILL BE AROUND TO JUST ABOVE CLIMATOLOGICAL NORMS.

&&

.AVIATION /00Z WEDNESDAY THROUGH SUNDAY/...
AS OF 00Z...EXPECT VFR TO PREVAIL THROUGH THE PERIOD...WITH
EXCEPTION OF POSSIBLE BRIEF MVFR AT KLBT BEFORE DAYBREAK DUE TO
FOG. OVERNIGHT...GENERALLY LIGHT NORTHEAST WINDS WILL CONTINUE.
MAY SEE A FEW LINGERING MID-LEVEL CLOUDS...BUT OVERALL EXPECT
NEARLY CLEAR SKIES. GIVEN IDEAL RADIATIONAL COOLING
OVERNIGHT...MAY SEE MVFR FOG AT KLBT JUST BEFORE DAYBREAK. THOUGH
CONFIDENCE IS A BIT LOWERED...HAVE OPTED TO INTRODUCE TEMPO GROUP.
AFTER DAYBREAK...VFR WILL PREVAIL WITH NORTHEAST WINDS GRADUALLY
INCREASING TO AOB 10 KTS. GIVEN FCST SOUNDINGS AND
GUIDANCE...CONTINUE TO ANTICIPATE FEW/SCT DIURNAL CU TO DEVELOP
ACROSS THE AREA IN THE AFTERNOON...AROUND 5-6KFT.

THE EXTENDED OUTLOOK THROUGH SUNDAY...POTENTIAL FOR BRIEF REDUCED 
VSBYS AT FOG PRONE TERMINALS KCRE/KLBT IN THE PRE-DAWN HOURS 
THURSDAY THROUGH SUNDAY. OTHERWISE EXPECT VFR.

&&

.MARINE...
NEAR TERM /THROUGH TONIGHT/...
AS OF 11:05 PM TUESDAY...ELONGATED CENTER OF HIGH PRESSURE EXTENDED 
FROM THE MID-ATLANTIC STATES NE TO MARTHAS VINEYARD. THIS PRESSURE 
PATTERN WILL YIELD A NE-E WIND DIRECTION. A SLIGHTLY PINNED SFC PG 
ACROSS THE EASTERN CAROLINAS WILL PRODUCE 10-15 KT WIND SPEEDS. 
DECAYING TROPICAL SWELL AND WIND DRIVEN WAVES TO COMBINE TO PRODUCE 
2 TO 4 FT OVERALL SEAS. 

SHORT TERM /WEDNESDAY THROUGH THURSDAY NIGHT/...
CANADIAN HIGH PRESSURE WILL SETTLE DOWN OVER THE SOUTHEAST WHILE 
SHIFTING SLOWLY EAST. AS THE CENTER SLIPS OFF THE NEW ENGLAND 
COAST...IT WILL CONTINUE TO RIDGE DOWN INTO THE CAROLINAS. THIS WILL 
HELP VEER WINDS AROUND THROUGH THE PERIOD FROM N-NE EARLY WED TO NE 
TO E BY THURS NIGHT. GRADIENT FLOW WILL WEAKEN WITH WINDS NE
AROUND 15 KTS AND UP TO 20 IN OUTER WATERS ON WED. BY LATE THURS
WINDS WILL BE DOWN TO 10 TO 15 KTS. 

OVERALL SEAS WILL DIMINISH A BIT BUT THE ONSHORE PUSH WILL KEEP
SEAS IN THE 2 TO 4 FT RANGE. LONGER PERIOD SWELL WILL DROP OFF BY
WED EVENING. 

LONG TERM /FRIDAY THROUGH SUNDAY/... 
AS OF 300 PM TUESDAY...HIGH PRESSURE RIDGING DOWN THE COAST
THROUGH THE PERIOD CREATES PREDOMINANTLY E/NE WINDS ACROSS THE
WATERS. THE PRESSURE GRADIENT WILL EASE THROUGH THE WKND...SO THE
STRONGEST WINDS...10-15 KTS...WILL OCCUR EARLY FRIDAY...BEFORE
FALLING TO LESS THAN 10 KTS THROUGH THE REST OF THE PERIOD. BY
LATE SUNDAY...RETURN FLOW WILL ONCE AGAIN DEVELOP...TURNING WINDS
TO THE SW BUT REMAINING LESS THAN 10 KTS. SEAS WILL BE PRIMARILY
2-4 FT THANKS TO A NE WIND WAVE..BUT MAY BUILD SUNDAY AS SOME
INCREASING LONG PERIOD SWELL FROM A TROPICAL DISTURBANCE WORKS
INTO THE LOCAL WATERS.

&&

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

&&

$$

NEAR TERM...DCH
SHORT TERM...RGZ
LONG TERM...JDW
AVIATION...SGL