AP-SC--ILM-SC E Area Forecast Discussion, SC

000

FXUS62 KILM 151457

AFDILM

AREA FORECAST DISCUSSION

NATIONAL WEATHER SERVICE WILMINGTON NC

1057 AM EDT WED JUL 15 2015

.SYNOPSIS...

A COLD FRONT WILL MOVE SOUTH AND EAST OF THE AREA TONIGHT AND THEN

STALL ON THURSDAY. SCATTERED SHOWERS AND THUNDERSTORMS ARE

EXPECTED TO DEVELOP ALONG THE SEABREEZE THIS AFTERNOON AND PERSIST

INTO THIS EVENING. THE SEABREEZE WILL BE PINNED TO THE COAST...

THUS INLAND CONVECTION WILL BE ISOLATED. WEAK HIGH PRESSURE WILL

PREVAIL THURSDAY AND FRIDAY WITH LITTLE OR NO RISK FOR RAINFALL.

THE HEAT AND HUMIDITY WILL BUILD DURING THE WEEKEND AND INTO NEXT

WEEK AND THIS WILL BE ACCOMPANIED BY AN INCREASING RISK FOR

AFTERNOON THUNDERSTORMS.

&&

.NEAR TERM /THROUGH TONIGHT/...

AS OF 1000 AM WEDNESDAY...A MID-LEVEL SHORTWAVE TROUGH IS

BEGINNING TO PIVOT ACROSS THE FORECAST AREA AND WILL MOVE OFFSHORE

DURING THE AFTERNOON. MUCH DRIER AIR IS IN THE PROCESS OF MAKING

SIGNIFICANT INROADS INTO THE FORECAST AREA THIS MORNING. THIS DRY

AIR COUPLED WITH RATHER WARM AIR AT 500 MB WILL MAKE IT DIFFICULT

FOR ANY CONVECTION TO DEVELOP. HAVE KEPT POPS BELOW THRESHOLD FOR

MUCH OF THE PEE DEE AND ROBESON COUNTY THIS AFTERNOON. AS YOU

PROGRESS TOWARD THE COAST...WILL INCREASE POPS TO JUST ABOVE

THRESHOLD FOR EYF TO CPC TO MAO WITH HIGHEST POPS...UP TO 30 TO 40

PERCENT...ALONG THE MORE IMMEDIATE COAST WHERE THE PINNED

SEABREEZE MAY BE ABLE TO IGNITE WIDELY SCATTERED SHOWERS AND

THUNDERSTORMS. ALONG THE COAST...INSTABILITY WILL BE SIGNIFICANT

WITH MIXED LAYER CAPE VALUES ON THE ORDER OF 3000 J/KG. BULK SHEAR

VALUES WILL BE 25-30 KT. THUS...A STRONG OR SEVERE THUNDERSTORM

CAN NOT BE RULED OUT WITH THE HIGHEST RISK FOR SOUTHERN PORTIONS

OF THE SEABREEZE WHERE THE DEEPER MOISTURE WILL LINGER LONGEST.

IT WILL BE A VERY WARM TO HOT DAY WITH STRONG SUNSHINE BRINGING

TEMPS INLAND TO THE MID 90S. ALONG THE COAST...HIGHS WILL BE IN

THE LOWER 90S. HEAT INDEX VALUES WILL REACH 100 TO 104 DEGREES

WITH A FEW BRIEF 105 DEGREES POSSIBLE ACROSS PORTIONS OF

WILLIAMSBURG AND GEORGETOWN COUNTIES.

A COLD FRONT WILL MOVE ACROSS THE FORECAST AREA FROM NNW TO SSE

TONIGHT. THE PASSAGE OF THIS FRONT WILL ALLOW EVEN DRIER AIR IN

THE LOW LEVELS TO FILTER ACROSS THE EASTERN CAROLINAS. ANY

CONVECTION SHOULD WANE THIS EVE AS THE COLUMN STABILIZES WITH LOSS

OF HEATING. SKIES WILL BE MOSTLY CLEAR TO PARTLY CLOUDY TONIGHT WITH

LOWS BY MORNING IN THE LOWER TO MID 70S.

&&

.SHORT TERM /THURSDAY THROUGH FRIDAY NIGHT/...

AS OF 300 AM WEDNESDAY...COLD FRONT WILL BE OFFSHORE TO START THE

PERIOD...AND WHILE TEMPS THU/FRI WILL REMAIN AROUND SEASONABLE

(LITTLE COLD ADVECTION)...MUCH DRIER AIR IS STILL FORECAST FOR

THURSDAY. MUCH DRIER AIR COMBINED WITH TEMPS AROUND 90 WILL MAKE

THURSDAY A GORGEOUS DAY LOCALLY...AND THE DRY MID-LEVEL AIR WILL

PRECLUDE ANY CONVECTION. HAVE INHERITED SILENT POP ON THURSDAY AND

FEEL THAT IS WARRANTED EVEN IN JULY...AND EVEN ON FRIDAY MOISTURE

RETURN IS SLOW TO DEVELOP SO CONVECTION WILL BE ISOLATED AT BEST ON

FRIDAY WITH SIMILAR TEMPS. ALL IN ALL...A VERY NICE FEW DAYS TO END

THE WEEK WITH HIGHS A DEGREE OR TWO EITHER SIDE OF 90 AND LOWS RIGHT

AROUND 70...LOW 70S AT THE COAST.

&&

.LONG TERM /SATURDAY THROUGH TUESDAY/...

AS OF 300 AM WEDNESDAY...A RETURN TO ABOVE NORMAL HEAT AND HUMIDITY

WILL DEFINE THE EXTENDED AS LARGE RIDGE WILL SPREAD ACROSS MOST OF

THE SOUTHERN TIER OF THE CONUS AND THEN EXPAND NE THROUGH EARLY NEXT

WEEK. RIDGE CENTER WILL PERSIST ACROSS THE MS VLY SATURDAY THROUGH

TUESDAY...BUT ITS EXPANSION TO THE NE WILL BRING WARMER TEMPERATURES

EACH DAY THROUGH THE PERIOD. AT THE SAME TIME...BERMUDA HIGH

PRESSURE AT THE SURFACE WILL ONCE AGAIN EXERT ITS INFLUENCE

LOCALLY...SO MOISTURE ADVECTION WILL INCREASE IN TANDEM WITH THE

RISING TEMPERATURES. ONE THING TO NOTE IS THAT AS THE RIDGE CENTER

PERSISTS TO THE WEST...MID-LEVEL FLOW WILL BE W/NW...SO WEAK

IMPULSES ALOFT WILL HELP FIRE CONVECTION EACH DAY...BUT THIS WILL

OTHERWISE KEEP THE MID-LEVELS RELATIVELY DRY SO DIURNAL CONVECTION

IS EXPECTED TO REMAIN LESS-THAN-SEASONABLE IN COVERAGE. TEMPS WILL

BEGIN RIGHT AROUND NORMAL FOR MID-JULY...AND THEN RISE EACH

DAY...POTENTIALLY BECOMING WELL ABOVE CLIMO EARLY NEXT WEEK...AND

THIS IS ECHOED BY THE CPC 6-10 DAY OUTLOOK.

&&

.AVIATION /12Z WEDNESDAY THROUGH SUNDAY/...

AS OF 12Z...SOME MID AND HIGH CLOUD CONVECTIVE DEBRIS LEFTOVER

FROM A MASSIVE MCS THAT FORMED TO OUR WEST YESTERDAY...WHICH STOLE

ALL THE ENERGY NEEDED FOR CONVECTION HERE. LOOKS LIKE WE COULD

HAVE AN ISOLATED STORM ALONG THE COAST BY MID MORNING...OTHERWISE

WE WILL PROBABLY BE PRECIP FREE THROUGH THE END OF THE FORECAST

PERIOD. ALL THE UPPER LEVEL MOISTURE WILL MOVE OUT OF THE

REGION...WITH PROBABLY ONLY MODERATE CU LEFTOVER THIS AFTERNOON.

STILL EXPECTING A DECENT SOUTHWEST WIND TODAY...GUSTING OVER 20

KT AT TIMES. LIGHT WINDS OVERNIGHT WITH NO FOG EXPECTED.

EXTENDED OUTLOOK...BRIEF MVFR/IFR POSSIBLE OVER THE WEEKEND DUE TO

DIURNALLY DRIVEN CONVECTION. OTHERWISE EXPECT VFR THROUGHOUT THE

EXTENDED.

&&

.MARINE...

NEAR TERM /THROUGH TONIGHT/...

AS OF 1000 AM WEDNESDAY...WILL HANG ONTO A MARGINAL SMALL CRAFT

ADVISORY FOR NOW. PRESSURE GRADIENT REMAINS SUFFICIENTLY TIGHT

FOR SUSTAINED WINDS OF 15 TO 20 KT WITH GUSTS UP TO 25 KT. THE

STRONGEST WINDS ARE EXPECTED THIS AFTERNOON AND EARLY EVE. THE

WIND DIRECTION WILL BE SW TODAY AND THEN SHIFT TO NW AND N WITH

THE PASSAGE OF A LATE NIGHT COLD FRONT. SEAS WILL REMAIN IN THE 4

TO 6 FT RANGE...HIGHEST ACROSS THE OUTER WATERS. SEAS WILL BEGIN

TO SUBSIDE THIS EVE AS THE WIND DIRECTION VEERS AND WIND SPEEDS

DIMINISH.

SHORT TERM /THURSDAY THROUGH FRIDAY NIGHT/...

AS OF 300 AM WEDNESDAY...COLD FRONT WILL BE SOUTH OF THE WATERS

ON THURSDAY...WITH A RELATIVELY WEAK GRADIENT LEFT IN ITS WAKE.

THIS WILL PRODUCE LIGHT N/NE WINDS THURSDAY AND MOST OF FRIDAY

BEFORE DIRECTION VEERS BACK TO THE SOUTH LATE. SPEEDS DURING THE

PERIOD WILL BE AROUND 10 KT OR LESS. EVEN WITH THE LIGHT NORTH

WINDS...SEAS THE FIRST HALF OF THURSDAY WILL BE SURPRISINGLY

AMPLIFIED AS THE RESIDUAL WAVE ENERGY FROM WEDNESDAY SLOWLY

DIMINISHES...AND SEAS OF 3-4 FT EARLY THURSDAY WILL FALL TO 2 FT

THURSDAY NIGHT AND FRIDAY.

LONG TERM /SATURDAY THROUGH SUNDAY/

AS OF 300 AM WEDNESDAY...BERMUDA HIGH PRESSURE WILL REDEVELOP AND

BECOME THE DOMINANT INFLUENCE ACROSS THE WATERS THIS WEEKEND. THE

GRADIENT WILL SLOWLY INCREASE AS WELL...SO WIND SPEEDS WILL RISE

FROM AROUND 10 KT SATURDAY TO 15 KT SUNDAY...WITH A SW WIND

DIRECTION BECOMING PREDOMINANT. SEAS WILL FOLLOW THE INCREASING

WINDS...AIDED AS WELL BY AN AMPLIFYING SWELL ON SUNDAY...RISING

FROM 2 FT SATURDAY TO 3-4 FT SUNDAY.

&&

.ILM WATCHES/WARNINGS/ADVISORIES...

SC...NONE.

NC...NONE.

MARINE...SMALL CRAFT ADVISORY UNTIL MIDNIGHT EDT TONIGHT FOR AMZ250-252-

254-256.

&&

$$

NEAR TERM...RJD

SHORT TERM...JDW

LONG TERM...JDW

AVIATION...DL

Delivered by Weather Underground Inc. Wed Jul 15 2015 10:57AM EDT