Area Forecast Discussion
Issued by NWS Wilmington, NC

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000
FXUS62 KILM 311029
AFDILM

AREA FORECAST DISCUSSION
NATIONAL WEATHER SERVICE WILMINGTON NC
629 AM EDT THU JUL 31 2014

.SYNOPSIS...
COOL HIGH PRESSURE WILL PERSIST ONE MORE DAY ACROSS THE AREA
TODAY. A COASTAL TROUGH WILL LIFT NORTH ON FRIDAY...AND STALL OVER
THE AREA DURING THE WEEKEND. THIS WILL BRING GOOD RAIN
CHANCES...WITH PERIODS OF HEAVY RAINFALL POSSIBLE...FRIDAY THROUGH
MONDAY. MORE SEASONABLE WEATHER WILL DEVELOP THE MIDDLE OF NEXT
WEEK.

&&

.NEAR TERM /THROUGH TONIGHT/...
AS OF 630 AM THURSDAY...NO CHANGES TO THE FORECAST WITH THE LATEST
UPDATE. PREVIOUS DISCUSSION FOLLOWS:

AN UNSEASONABLY DEEP LONGWAVE TROUGH WILL MAINTAIN ITS POSITION
OVER EASTERN CONUS THROUGH THE NEAR TERM. A SERIES OF WEAK SHORT
WAVE DISTURBANCES WILL ROUND THE BASE OF THE TROUGH THROUGH THE
PERIOD. LOW CONFIDENCE TIMING OF THESE DISTURBANCES DUE TO WIDE
VARIATION IN THE GUIDANCE AND WEAKNESS OF THE FEATURES. CLOSER TO
THE SURFACE A STALLED FRONT WELL OFFSHORE WILL START TO BEND BACK
TOWARDS THE FORECAST AREA...LINING UP AS A NASCENT WARM FRONT
ALONG THE COAST BY DAYBREAK ON FRIDAY. MOISTURE PROFILES CONTINUE
TO SHOW DRY MID LEVELS...HOWEVER...MORE ABUNDANT MOISTURE HIGHER
UP IN THE COLUMN WILL ACT TO KEEP IN A SUBSTANTIAL AMOUNT CIRRUS
TODAY AND TONIGHT.

INCREASINGLY STRONG LIFT OF THE ISENTROPIC VARIETY WILL ALLOW A
GRADUAL RAMPING UP OF POPS THROUGH THE NEAR TERM...ESPECIALLY
OVERNIGHT AS THE WARM FRONT WORKS BACK TOWARDS THE COAST. EVEN
SO...DRY MID LEVELS AND NOT OVERLY GENEROUS LOW LEVEL MOISTURE WILL
LIMIT ANY CONVECTIVE COVERAGE...WHICH I WILL CAP AT SLIGHT CHANCE
FOR THE NEAR TERM.

TEMPERATURES WILL REMAIN ON THE RELATIVELY COOL SIDE...WITH DAYTIME
HIGHS NOT TOO MUCH DIFFERENT THAN THE OCEAN SURFACE...WHICH THE
LOCAL AIRMASS IS CURRENTLY BEING ADVECTED OVER. EXPECT HIGHS IN THE
MID TO UPPER 80S...WITH LOWS OF RIGHT AROUND 70. GUIDANCE IN CLOSE
AGREEMENT ON THESE NUMBERS.

&&

.SHORT TERM /FRIDAY THROUGH SATURDAY NIGHT/...
AS OF 330 AM THURSDAY...THE BEGINNING OF AN UNSETTLED...POSSIBLY
EXCEEDINGLY WET...PERIOD BEGINS FRIDAY. SEVERAL FEATURES WORK
TOGETHER TO MAKE THE SHORT TERM COOL AND WET...AS THE LARGE UPPER
TROUGH WHICH HAS BEEN PLAGUING THE AREA THE LAST WEEK OR SO WILL
BEGIN TO WEAKEN. THIS TROUGH BEGINS TO ERODE THANKS TO THE PARENT
VORTEX FILLING AND LIFTING OFF TO THE NORTHEAST INTO EASTERN
CANADA...AND THE STRONG RIDGE ACROSS THE ATLANTIC BEGINNING TO
EXPAND BACK TO THE WEST. THIS DRIVES THE TROUGH AXIS WEST OF THE
AREA AND CAUSES MID-LEVEL FLOW TO BECOME INCREASINGLY SOUTHERLY...A
DIRECTION WHICH MOISTENS THE ATMOSPHERIC COLUMN. AT THE
SURFACE...THE COLD FRONT WHICH HAS BEEN STALLED OFFSHORE SINCE
TUESDAY...WILL LIFT BACK AS A TROUGH/WARM FRONT FRIDAY BEFORE
STALLING OVER THE AREA ON SATURDAY...FURTHER ENHANCING MOIST
ADVECTION IN THE LOWER LEVELS OF THE COLUMN...AND PWATS CLIMB ABOVE
2 INCHES FRIDAY NIGHT AND REMAIN THERE ON SATURDAY.

ALL OF THIS TOGETHER SUGGESTS INCREASINGLY UNSETTLED WEATHER DURING
THE SHORT TERM...WITH WIDESPREAD SHOWERS AND THUNDERSTORMS LIKELY.
WITH PWATS ABOVE TWO INCHES...SURFACE CONVERGENCE ALONG THE
FRONT...AND 300MB DIFFLUENCE WITHIN A NEARLY STATIONARY JET STREAK
ON DOWNWIND SIDE OF THE UPPER TROUGH...PERIODS OF HEAVY RAIN ARE
LIKELY WITHIN CONVECTION DURING THE PERIOD. WPC IS HIGHLIGHTING THE
AREA FOR 1-3" OF QPF...AND THIS LOOKS MORE THAN REASONABLE FOR THE
TIMEFRAME. WILL BUMP POP TO LIKELY FRI AND SAT...WITH NO TIME PERIOD
FAVORED SPECIFICALLY FOR THE HEAVIEST AND MOST WIDESPREAD RAINFALL.

DUE TO CLOUDS AND THE CONTINUED UPPER TROUGH...TEMPS THROUGH THE
PERIOD WILL REMAIN BELOW NORMAL...TO WELL BELOW NORMAL...FOR HIGHS.
LOW TO MID 80S EXPECTED FRIDAY...WITH HIGHS ONLY SLIGHTLY ABOVE 80
ON SATURDAY. LOWS FRIDAY NIGHT AROUND 70 WILL RISE A FEW DEGREES
INTO THE LOW 70S FOR SATURDAY NIGHT.

&&

.LONG TERM /SUNDAY THROUGH WEDNESDAY/...
AS OF 330 AM THURSDAY...VERY UNSETTLED THE FIRST HALF OF THE
PERIOD...BUT A SLOW RETURN TO MORE TYPICALLY SUMMERTIME CAROLINAS
WEATHER IS EXPECTED BY THE MIDDLE OF NEXT WEEK. LARGE UPPER TROUGH
WILL VERY SLOWLY DAMPEN THROUGH THE EXTENDED WHILE 5H RIDGE
RETROGRADES TO WEST AND BECOMES CENTERED OFF THE SE COAST LATE IN
THE EXTENDED. AT THE SURFACE...A COASTAL TROUGH STALLED IN THE
VICINITY WILL SERVE AS A FOCUS FOR CONVECTION SUN/MON...WHICH
COMBINES WITH PWATS OVER 2 INCHES...AND STRONG DIFFLUENCE ALOFT...TO
PRODUCE AN EXTENDED PERIOD OF WIDESPREAD SHOWERS/STORMS WITH HEAVY
RAINFALL. WPC GRAPHICS SUGGESTS 2-4" OF QPF SUN-TUE...AND WILL CARRY
LIKELY POP SUNDAY...HIGH CHC ON MONDAY. SLOW IMPROVEMENT OCCURS
THEREAFTER AS THE TROUGH MORE QUICKLY ERODES TO THE NORTH AND THE
SURFACE BOUNDARY WASHES OUT...BUT TUESDAY WILL LIKELY FEATURE AGAIN
HIGHER-THAN-CLIMO POP...BEFORE IMPROVEMENT OCCURS WEDNESDAY. A
WARMING TREND WILL OCCUR THROUGH THE EXTENDED...BUT MUCH OF THE
PERIOD WILL REMAIN BELOW NORMAL...WITH SEASONABLE TEMPS DEVELOPING
ONLY BY MID-WEEK.

&&

.AVIATION /12Z THURSDAY THROUGH MONDAY/...
AS OF 06Z...VFR THIS TAF VALID PERIOD...EXCEPT FOR A SHORT PERIOD
OF SUB-VFR VSBYS IN THE PRE-DAWN HOURS AT KFLO/KLBT. ONLY LIMITED
AMOUNTS OF LOW LEVEL MOISTURE ARE AVAILABLE FOR BR FORMATION. THE
BEST MOISTURE IS AT KFLO BUT A BROKEN LAYER OF MID CLOUDS SHOULD
PERSIST THROUGH SUNRISE. THUS BELIEVE THE CHANCE OF IFR IS LOW AT
KFLO AND LOW AT KLBT DUE TO LESS AVAILABLE MOISTURE.

MID LEVEL CLOUDS SCT DURING THE MORNING BUT COULD PERSIST INTO THE
AFTERNOON AT KLBT. SCT LOW/MID CLOUDS WITH THIN BKN HIGH CLOUDS
EXPECTED FOR MOST OF THE DAY AT THE REMAINING TERMINALS. WINDS
WILL BECOME E-ESE WITH STRONGEST SPEEDS AT THE COASTAL TERMINALS.

AFTER SUNSET THERE WILL BE SCT MVFR LEVEL LOW CLOUDS ADVECTING
INTO THE COASTAL TERMINALS...THEN EVENTUALLY THE INLAND TERMINALS
LATE IN THE TAF VALID PERIOD. MVFR CIGS ARE NOT ANTICIPATED AT
THIS TIME.

EXTENDED OUTLOOK...INCREASING CHANCES FOR SHRA/TSRA AND PERIODS OF
MVFR CONDITIONS FRIDAY THROUGH MONDAY AS A FRONT STALLS OVER THE
EASTERN CAROLINAS.

&&

.MARINE...
NEAR TERM /THROUGH TONIGHT/...
AS OF 630 AM THURSDAY...NO CHANGES TO THE FORECAST WITH THE LATEST
UPDATE. PREVIOUS DISCUSSION FOLLOWS:

EXPECT LITTLE CHANGE IN CONDITIONS OVER THE COASTAL WATERS
THROUGH THE NEAR TERM. CURRENTLY...OBS SHOW EASTERLY WINDS IN THE
10 TO 15 KT RANGE...WITH SEAS OF 3 TO 4 FT. THESE CONDITIONS WILL
PERSIST THROUGH TONIGHT.

SHORT TERM /FRIDAY THROUGH SATURDAY NIGHT/...
AS OF 330 AM THURSDAY...COASTAL TROUGH WILL SHARPEN AND MOVE ACROSS
THE WATERS AND THEN ONSHORE DURING FRIDAY...AND THEN PUSH FURTHER
INLAND SATURDAY AS A RIDGE OF HIGH PRESSURE EXPANDS BACK TO THE WEST
FROM THE ATLANTIC. THIS CREATES A TIGHTENING GRADIENT FRIDAY...SO AS
WINDS VEER FROM E TO SE THROUGH THE DAY...THEY WILL INCREASE TO
AROUND 15 KTS FRIDAY NIGHT...BEFORE EASING TO 10-15 KTS DURING
SATURDAY WITH SLIGHTLY MORE DIRECTIONAL CHANGE TO THE SOUTH.
ALTHOUGH A 1 FT SE GROUND SWELL WILL EXIST DURING THE PERIOD...WAVE
HEIGHTS OF 2-3 FT WILL BE FORMED PRIMARILY BY A 5-6 SEC WIND WAVE
VEERING FROM EAST TO SOUTH.

LONG TERM /SUNDAY THROUGH MONDAY/...
AS OF 330 AM THURSDAY...WEAKENING COASTAL TROUGH INLAND WILL WASH
OUT OVER THE LAND THROUGH EARLY IN THE WEEK...LEAVING EXPANDING AREA
OF HIGH PRESSURE AS THE DOMINANT FEATURE. AS THIS HIGH PRESSURE
STRENGTHENS AND PUSHES WEST...S/SW WINDS WILL DEVELOP EARLY IN THE
PERIOD...AND PERSIST INTO THE UPCOMING WEEK...WITH SPEEDS RISING
FROM 10 KTS SUNDAY...TO 15 KTS ON MONDAY WHEN RETURN FLOW BECOMES
MORE SIGNIFICANT. SEAS WILL BE 2-3 FT SUNDAY...RISING TO 3-4 FT
MONDAY ON THE LONGER AND MORE SIGNIFICANT FETCH.

&&

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

&&

$$

SYNOPSIS...JDW
NEAR TERM...REK
SHORT TERM...JDW
LONG TERM...JDW
AVIATION...REK/MRR
MARINE...REK/JDW




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