Area Forecast Discussion
Issued by NWS Wilmington, NC

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000
FXUS62 KILM 261755
AFDILM

AREA FORECAST DISCUSSION
NATIONAL WEATHER SERVICE WILMINGTON NC
155 PM EDT SAT JUL 26 2014

.SYNOPSIS...
HIGH PRESSURE OVER THE WATERS WILL CIRCULATE HOT AND HUMID AIR
ACROSS THE CAROLINAS THROUGH MONDAY. AN UNUSUALLY STRONG COLD
FRONT MAY BRING SEVERE THUNDERSTORMS LATE ON MONDAY. COOLER AND
DRIER WEATHER WILL RETURN ON TUESDAY...LASTING THROUGH MUCH OF
NEXT WEEK.

&&

.NEAR TERM /THROUGH TONIGHT/...
AS OF 10 AM SATURDAY...WARM AND HUMID LATE JULY SATURDAY UNDERWAY
AND NOTHING UNCOMMON IN THAT. CONVECTIVE FORECASTS TODAY HOWEVER
ARE MURKY...AS OPPOSING ATMOSPHERIC ELEMENTS INTERACT INTO THE
AFTERNOON. ALOFT WE ARE SEEING BUILDING HEIGHT RISES AS AN UPPER
TROUGH AXIS LIFTS NE OFF OUR COAST. THIS WILL SOON IMPART SLIGHT
SINKING OF AIR INTO PRIME SURFACE HEATING. VWP PRESENTLY SHOWS NW
DOWNSLOPE TRAJECTORY AIR PARCELS. THIS CAN BE A PROBLEM AT TIMES
WHEN CELLS MOVE INTO THE SEA BREEZE FRONT NEARLY DIRECTLY CAUSING
SPIKED CONVECTION. RIGHT NOW BASED ON CLOUD COVER WE CAN INFER
DIFFERENTIAL HEATING VERTICAL CIRCULATIONS ARE MOVING AND A ROBUST
CUMULUS FIELD SHOULD SUSTAIN THE LOW AND MID LEVEL TURBULENCE. 18Z
ONWARD DRY AIR INTRUSION ALOFT FROM THE NW DIVES DOWNWARD TO 8
KFT. ESSENTIALLY CONVECTION LOOKS TO BECOME INCREASINGLY THWARTED
INTO THE MAXIMUM OF INSOLATION. TO REFLECT THIS IN THE FORECAST
WE WILL MAINTAIN ISOLATED TSTMS IN THE FORECAST BUT SHOW A QUICK
TREND OF DISSIPATION IN THE LATER AFTERNOON TO VERY EARLY EVENING.
EVEN IN DRYING ALOFT PWATS REMAIN AT OR JUST ABOVE 1.5 INCHES THIS
AFTERNOON. ZONE OF ENHANCED LOW-LEVEL CONVERGENCE FROM THE SEA
BREEZE FRONT WILL DICTATE WHERE INITIAL POPS ARE PLANNED EARLY
AFTERNOON THEN EXPANDING THESE MENTIONABLE POPS WEST ACROSS THE
EASTERN 1/2 TO 2/3 OF OUR ZONES THROUGH AFTERNOON PRIOR TO
DIMINISHING.

JULY HEATING AND DEWPOINTS IN THE MIDDLE 70S HAS ALREADY BROUGHT
HEAT INDICES TO 90 DEGREES AND WE ARE LOOKING TO TOP OUT AT AN
APPARENT MAXIMUM TEMPERATURE OF AROUND 100 DEGREES...WITH MAXIMUM
AIR TEMPS OF UPPER 80S NEAR THE OCEAN TO LOWER 90S INLAND.

&&

.SHORT TERM /SUNDAY THROUGH MONDAY NIGHT/...
AS OF 3 AM SATURDAY...START OF NEXT WEEK WILL BE QUITE WARM WITH
HIGHS ON BOTH SUN AND MON RUNNING WELL INTO THE 90S. MID LEVEL RIDGE
WILL EXTEND EAST FROM THE SOUTHWESTERN CONUS SUN. FORECAST SOUNDINGS
SHOW CAPPING AROUND 800 MB...A RESULT OF SUBSIDENCE ON THE PERIPHERY
OF THE 5H RIDGE. CAPPING ALONG WITH DEEP WESTERLY FLOW WILL MAKE
EVEN ISOLATED CONVECTION HARD TO COME BY. CANNOT RULE OUT AN
ISOLATED SHORT LIVED SHOWER ALONG OR JUST BEHIND THE SEA BREEZE BUT
NOTHING WORTH CARRYING A POP ABOVE 10%. 850 TEMPS IN THE 20C TO 22C
RANGE AND LACK OF MUCH CLOUD COVER/CONVECTION WILL PUSH HIGHS INTO
THE MID TO UPPER 90S AREA WIDE. DESPITE LIMITED CLOUD COVER SUN
NIGHT LOWS WILL BE KEPT IN THE UPPER 70S TO AROUND 80 BY
STRENGTHENING LOW LEVEL JET.

STRONG COLD FRONT WILL CROSS THE AREA ON MON WITH IMPRESSIVE 5H
TROUGH THE DRIVING FACTOR. BEST PRECIP CHANCES DURING THE PERIOD
WILL BE ON MON...AHEAD OF THE COLD FRONT WHEN PRECIPITABLE WATER
VALUES WILL BE AROUND 2 INCHES. MON IS ALSO SHAPING UP TO BE A HOT
DAY WITH 850 TEMPS ONCE AGAIN IN THE LOWER 20C RANGE. HIGHS IN THE
MID 90S COMBINED WITH DEWPOINTS IN THE LOW 70S WILL NOT ONLY PRODUCE
HEAT INDEX VALUES AT OR ABOVE 105F...LIKELY WARRANTING A HEAT
ADVISORY...BUT WILL SET THE STAGE FOR AFTERNOON CONVECTION. MID
LEVEL COOLING COMBINED WITH STRONG LOW LEVEL CONVERGENCE ALONG THE
FRONT AND VERY WARM LOW LEVELS IS LIKELY TO PRODUCE WIDESPREAD
SHOWERS AND THUNDERSTORMS. WHILE IT APPEARS THE CORE OF THE UPPER
LEVEL JET WILL REMAIN NORTH OF THE AREA STRONG TO SEVERE CONVECTION
REMAINS A POSSIBILITY BASED ON THERMODYNAMIC PROFILES MON
AFTERNOON/EVENING AND SPC HAS  PLACED MUCH OF THE FORECAST AREA
WITHIN A SLIGHT RISK AREA FOR DAY 3.

&&

.LONG TERM /TUESDAY THROUGH FRIDAY/...
AS OF 3 AM SATURDAY...NOTICEABLE AIR MASS CHANGE FROM MON AFTERNOON
TO TUE AFTERNOON AS BOTH HEAT AND HUMIDITY WILL BE LACKING.
PRECIPITABLE WATER VALUES DROP DOWN TO AROUND AN INCH TUE WHILE
NORTHERLY FLOW USHERS COOLER AIR INTO THE REGION. TROUGH AXIS
REMAINS JUST WEST OF THE AREA FOR THE PERIOD WITH GENERALLY DEEP
WESTERLY FLOW KEEPING MID LEVELS DRY. GFS/ECMWF BOTH SHOW A
SHORTWAVE CROSSING THE AREA TUE NIGHT INTO WED BUT DIFFER ON ITS
STRENGTH AND IMPACT. WILL NOT BE ADDING ANY PRECIP CHANCES GIVEN THE
UNFAVORABLE ENVIRONMENT AND DIFFICULTY IN ACCURATELY DEPICTING SUCH
FEATURES IN THE EXTENDED PERIOD.

FORECAST SOUNDINGS DO NOT SHOW MUCH OF AN INCREASE IN DEEP MOISTURE
THROUGH THE PERIOD...PWATS BARELY EXCEED 1.25 INCHES DURING THE
PERIOD...SO DIURNAL CONVECTION WILL BE SCARCE. CANNOT RULE OUT SOME
ISOLATED STORMS ANY GIVEN AFTERNOON BUT DO NOT THINK A MENTIONABLE
POP IS WARRANTED. BEST CHANCES WOULD BE NEAR THE COAST...ALONG OR
JUST BEHIND THE SEA BREEZE BUT EVEN HERE COVERAGE ABOVE 20% IS
UNLIKELY. TEMPERATURES WILL REMAIN BELOW CLIMO THROUGH THE PERIOD
WITH POTENTIAL FOR SOME RADIATIONAL COOLING OVERNIGHT DURING THE
MIDDLE OF THE WEEK.

&&

.AVIATION /18Z SATURDAY THROUGH THURSDAY/...
AS OF 18Z...VFR THIS AFTERNOON. WINDS WILL BE SW WITH STRONGEST
AVERAGE WINDS OF 8-15 KTS AT THE COASTAL TERMINALS. THROUGH EARLY
EVENING TWO SFC BASED FEATURES...THE SEA BREEZE AND THE PIEDMONT
TROF...WILL BE THE DRIVING FORCE FOR POSSIBLE CONVECTION. HOWEVER
THE ENVIRONMENT WILL BECOME MORE HOSTILE AS THE EVENING APPROACHES.
ANY ACTIVITY WILL BE ISOLATED...AND AS SUCH WILL NOT MENTION ANY
CONVECTION IN TAFS EXCEPT FOR VCSH AT KILM EARLY THIS AFTERNOON.

WINDS DECREASE THIS EVENING AS ANY CONVECTION DISSIPATES. ALTHOUGH
WINDS DECREASE THEY SHOULD REMAIN SOMEWHAT ELEVATED OVERNIGHT. THIS
SHOULD PREVENT ANY DENSE FOG FROM DEVELOPING...BUT SCT IFR STRATUS
AND MVFR VSBYS IN BR ARE POSSIBLE IN THE PRE-DAWN HOURS MAINLY AT
THE INLAND TERMINALS. OTHERWISE VFR THROUGH THE END OF THE TAF VALID
PERIOD. BY 14-16Z WINDS WILL BECOME SSW 10-15 KTS.

EXTENDED OUTLOOK...SHOWERS/TSTMS/TEMPO MVFR POSSIBLE SUNDAY AND
MONDAY. OTHERWISE EXPECT VFR.

&&

.MARINE...
NEAR TERM /THROUGH TONIGHT/...
AS OF 1030 AM SATURDAY...THE PIEDMONT TROF ACROSS THE CENTRAL
CAROLINAS IS PROGGED TO BECOME STRONGER THRU TONIGHT. RIDGING FROM
THE OFFSHORE ATLANTIC HIGH WILL EXTEND WESTWARD JUST SOUTH OF THE
AREA WATERS. THE SFC PRESSURE PATTERN AND GRADIENT BETWEEN THESE 2
FEATURES WILL PRODUCE A TIGHTENING GRADIENT THAT YIELDS AT LEAST
15 KT FOR SPEEDS LATER TODAY AND TONIGHT. THE SFC PRESSURE PATTERN
WILL TRANSITION INTO A SW FLOW DIRECTION TODAY THRU TONIGHT.

SIGNIFICANT SEAS INITIALLY WILL BE DOMINATED BY A 2 FOOT ESE
GROUND SWELL. LATER THIS AFTERNOON AND TONIGHT...LOCALLY PRODUCED
WIND WAVES WILL INCREASE IN SIZE AND COVERAGE AND LIKELY BECOME
THE MORE DOMINATE OF THE 2. SEVEN SECOND DOMINATE PERIODS WILL
OCCUR.

SHORT TERM /SUNDAY THROUGH MONDAY NIGHT/...
AS OF 3 AM SATURDAY...INCREASING SOUTHERLY FLOW AHEAD OF STRONG COLD
FRONT WILL LIKELY RESULT IN HEADLINES FOR ALL ZONES LATER SUN NIGHT
AND MON. NATURE OF THE HEADLINES IS AS OF YET UNDETERMINED. IT MAY
END UP THAT SCEC IS NEEDED SUN NIGHT AND THEN SCA MON AND PART OF
MON NIGHT. SOUTHWEST FLOW 15 TO 20 KT SUN WILL INCREASE TO A SOLID
20 KT SUN NIGHT AND MON. COMBINATION OF PROLONGED SOUTHWEST FLOW AND
INCREASE IN SPEEDS BUILDS SEAS FROM 3 TO 4 FT AT THE START OF THE
PERIOD TO 4 TO 6 FT ON MON. OFFSHORE FLOW DEVELOPS IN THE WAKE OF
THE FRONT LATER MON NIGHT WITH SPEEDS DROPPING TO 10 KT OR LESS BY
TUE MORNING. OFFSHORE COMPONENT AND DECREASE IN SPEEDS LATE MON
NIGHT WILL RESULT IN SEAS FALLING TO 3 TO 4 FT BY THE END OF THE
PERIOD.

LONG TERM /TUESDAY THROUGH WEDNESDAY/...
AS OF 3 AM SATURDAY...HIGH PRESSURE WILL BE SLOW TO BUILD IN BEHIND
THE DEPARTING COLD FRONT TUE INTO WED...LEAVING A WEAK AND ILL
DEFINED GRADIENT OVER THE WATERS DURING THE FIRST HALF OF THE
PERIOD. WINDS WILL BE VARIABLE WITH SPEEDS UNDER 10 KT TUE INTO WED.
INFLUENCE OF SURFACE HIGH OVER THE MIDWEST BECOMES MORE PRONOUNCED
ON WED WITH 10 TO 15 KT NORTHEAST FLOW DEVELOPING BY AFTERNOON. SEAS
WILL TREND DOWN TUE AND TUE NIGHT BEFORE INCREASING SLIGHTLY ON WED
INTO WED NIGHT AS WIND FIELD BECOMES MORE DEFINED.

&&

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

&&

$$

NEAR TERM...MJC
SHORT TERM...III
LONG TERM...3
AVIATION...MRR/8




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