Area Forecast Discussion
Issued by NWS Wilmington, NC

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000 FXUS62 KILM 181916 AFDILM AREA FORECAST DISCUSSION NATIONAL WEATHER SERVICE WILMINGTON NC 316 PM EDT SAT APR 18 2015 .SYNOPSIS... AN APPROACHING FRONTAL SYSTEM WILL BRING SHOWERS AND A CHANCE OF THUNDERSTORMS SUNDAY AFTERNOON THROUGH MONDAY. A FEW STORMS COULD BE STRONG TO SEVERE MONDAY. DRY AND SEASONABLE HIGH PRESSURE WILL BUILD INTO THE AREA TUESDAY AND WEDNESDAY. A WEAK COLD FRONT MAY BRING SHOWERS AND ISOLATED THUNDERSTORMS INTO LATE WEEK. && .NEAR TERM /THROUGH TONIGHT/... AS OF 3 PM SATURDAY...A SUBTLE RIDGE WILL DEVELOP ACROSS THE AREA TONIGHT AHEAD OF A POTENT SHORTWAVE THAT IS FINALLY MAKING ITS MOVE TO THE WEST. THIS WILL ALLOW A FRONT NOW LOCATED ACROSS THE OHIO VALLEY TO MAKE A RUN FOR THE AREA LATE TONIGHT. THIS WILL SERVE...ALONG WITH A WEAK SHORTWAVE ALOFT...TO KEEP POPS IN THE FORECAST BASICALLY THE ENTIRE TIME. ON TOP OF THIS THE NAM AND GFS SHOW INDICATIONS OF ATLANTIC STREAMERS THAT TYPICALLY PRECEDE A STRONGLY FORCED EVENT...LIKE ONE WE WILL BE SEEING LATER SUNDAY AND MONDAY...MOVING ONSHORE LATE. I DO HAVE A POP MINIMUM AROUND ZERO UTC...WITH A SLOW INCREASING TREND THEREAFTER. WENT ABOVE GUIDANCE FOR OVERNIGHT LOWS AS DIURNAL RANGES CONTINUE TO BE LIMITED BY THE ABUNDANT MOISTURE. && .SHORT TERM /SUNDAY THROUGH MONDAY NIGHT/... AS OF 3 PM SATURDAY...PRIMARY HEADLINES INCLUDE POTENTIAL FOR A GOOD SOAKING OF RAIN...AND A FEW STRONG THUNDERSTORMS. MONDAY APPEARS THE MORE OPTIMUM SET-UP FOR STRONG/SEVERE STORMS WITH MORE ROBUST KINEMATIC FIELDS AND STRONGER LOW-LEVEL HEATING JUST AHEAD OF A COLD FRONT. EXTENSIVE CLOUD CANOPY SUNDAY MAY IMPEDE CONVECTION INITIATION/GROWTH. SUNDAY MEANWHILE OFFERS THE HIGHER RAIN AMOUNTS AS COLUMN MOISTURE SURGES AS A WARM FRONT LIFTS N OF THE AREA AND PRECIPITABLE WATERS SURGE TO 1.8". SEVERAL MCV PERTURBATIONS ALOFT SWEPT NE IN WAKE OF THE WARM FRONT MAY SUSTAIN SHOWER AND STORM CHANCES INTO SUNDAY NIGHT. CURRENT IR ANIMATIONS SHOW COLD TOPS INDEED FLARING ALONG THE NORTHERN GULF OF MEXICO. WPC QPF DEPICTIONS SHOW .75-1 INCH BASIN AVERAGES SUNDAY...AND WITH CONVECTIVE ELEMENTS...SOME AREAS LIKELY TO RECEIVE GREATER AMOUNTS. MONDAY LESS BASIN QPF BUT MORE POWERFUL STORMS IN THE CARDS WITH MAXIMUMS RISING WELL INTO THE 80S AND PARTIAL SUNSHINE AIDING INSOLATION AND CELL POPS. SPC PAINTS SLIGHT RISK FOR BOTH LATE SUNDAY AND MONDAY. BALMY PERIOD OVERALL AND BEST GUESS ON FRONTAL PASSAGE NOW SLATED AROUND OR AFTER DAYBREAK TUESDAY. && .LONG TERM /TUESDAY THROUGH SATURDAY/... AS OF 3 PM SATURDAY...AN ALMOST WINTERLIKE LOOKING UPPER PATTERN FOR MOST OF THE PERIOD WITH A LARGE VORTEX IN THE VICINITY OF THE GREAT LAKES. WESTERLY FLOW AROUND THIS FEATURE WILL KEEP MUCH OF THE COLUMN DRY AND LEAD TO RAIN-FREE CONDITIONS LOCALLY. LOW LEVELS WILL BE DRY AS WELL THROUGH SOME TIME WEDNESDAY AS HIGH PRESSURE BUILDS IN FROM THE NORTHWEST. SOON THEREAFTER THIS HIGH MOVES OFFSHORE AND SOME MOISTENING RETURN FLOW ENSUES. SOME GUIDANCE SHOWING THIS CALLING FOR RAIN AS SOON AS THURSDAY BUT GIVEN THE AFOREMENTIONED DOWNSLOPE FLOW STILL FEEL THAT THURSDAY NIGHT INTO FRIDAY IS THE BETTER DAY TO INTRODUCE SOME RAIN CHANCES ESPECIALLY GIVEN THE APPROACH OF A COLD FRONT. THOUGH THIS SURFACE BOUNDARY MAY LIE TO OUR SOUTH ON SATURDAY SOME LOW LEVEL BAROCLINICITY PAIRED WITH MID LEVEL VORT APPROACHING TO KEEP RAIN IN THE FORECAST. && .AVIATION /19Z SATURDAY THROUGH THURSDAY/... AS OF 18Z...TRICKY 24 HOUR FORECAST AS ONE SYSTEM IS EXITING AND ANOTHER WILL ENTER THE PICTURE ON SUNDAY. LOOK FOR DIMINISHING RAIN ACTIVITY THIS AFTERNOON WITH STILL SOME ISOLATED STUFF THROUGH 21Z. CEILINGS WILL BE PREDOMINATELY MVFR...BUT WILL BOUNCE AROUND QUITE A BIT. TONIGHT...NO RAIN IS EXPECTED UNTIL MORNING AS THE NEXT SYSTEM APPROACHES. THIS ONE IS RATHER LARGE WITH HIGH PRECIPITABLE WATER FOR THIS TIME OF YEAR. BY DAYBREAK SHOWERS WILL BECOME NUMEROUS...SPREADING NORTHWARD WITH SOUTHEAST FLOW AT THE SURFACE. VISIBILITIES COULD BRIEFLY COME DOWN TO A MILE IN THE HEAVIER ACTIVITY. EXTENDED OUTLOOK...SHOWERS ACCOMPANIED WITH ISOLATED THUNDER TO AFFECT THE FORECAST AREA LATE SUNDAY THROUGH MONDAY MORNING...RESULTING IN OCCASIONAL MVFR AND IFR CONDITIONS. SCATTERED PCPN ASSOCIATED WITH A CFP MONDAY NIGHT FOLLOWED BY MAINLY VFR CONDITIONS TUE. POSSIBLE SHOWERS RETURNING LATE WED INTO THU. && .MARINE... NEAR TERM /THROUGH TONIGHT/... AS OF 3 PM SATURDAY...BENIGN CONDITIONS WILL CONTINUE ACROSS THE COASTAL WATERS THIS AFTERNOON AND THROUGH THE OVERNIGHT HOURS. A VERY WEAK PRESSURE PATTERN WILL SHAPE UP SLOWLY THIS EVENING AS A BROAD SOUTHERLY FLOW AHEAD OF A POWERFUL SYSTEM TO THE WEST DEVELOPS AND NORTHEAST WINDS MOVE IN BRIEFLY VERY LATE AS A BACK DOOR FRONT MAKES A QUICK RUN TO THE SOUTH. OVERALL WILL MAINTAIN AN EASTERLY WIND DIRECTION FOR THE SOUTHERN WATERS AND THE SAME FOR THE NORTH CAROLINA WATERS TURNING NORTHEAST LATE TONIGHT. WIND SPEEDS WILL BE MOSTLY AROUND TEN KNOTS WITH A SLIGHTLY HIGHER RANGE...10 TO 15 KNOTS DEVELOPING NORTHERN LATE. ZONES SEAS WILL REMAIN IN A 2-4 FOOT RANGE. SHORT TERM /SUNDAY THROUGH MONDAY NIGHT/... AS OF 3 PM SATURDAY...EXERCISE CAUTION OR ADVISORY MARINE REGIME ON TAP THIS PERIOD AS A FRONTAL SYSTEM APPROACHES AND WORSENS LOCAL MARINE CONDITIONS. WAVE GROWTH HOWEVER MAY BE LIMITED SINCE SE-S WIND FLOW HAS LIMITED STAYING TIME BEFORE WINDS GO SW EARLY ON MONDAY. HAVE CAPPED SEAS AT 5 FEET SUNDAY FOR NOW WITH GUSTS TO 20 KT AHEAD OF THE COLD FRONT...SET TO CROSS THE WATERS TUESDAY MORNING. SEVERAL STRONG TSTMS ARE POSSIBLE SUNDAY THROUGH THROUGH EARLY TUESDAY AND SPECIAL MARINE WARNINGS MAY BE NEEDED AT TIMES. LONG TERM /TUESDAY THROUGH THURSDAY/... AS OF 3 PM SATURDAY...OFFSHORE/NORTHWESTERLY POST COLD FRONTAL FLOW REGIME ON TUESDAY WILL GROW LIGHTER LATE IN THE DAY AND AT NIGHT AS CENTER OF HIGH PRESSURE APPROACHES. THE CENTER OF HIGH PRESSURE MOVES OFFSHORE BY WEDNESDAY EVENING. THIS WILL BRING A PERIOD OF VERY LIGHT GRADIENT WHEREIN WINDS REMAIN UNDER 10 KNOTS AND VEER IN DIRECTION FOR AN EXTENDED TIME UNTIL FINALLY SETTLING ON SOUTHERLY BY WED EVE. SUCH LIGHT WINDS IN THE ABSENCE OF SWELL ENERGY OUGHT TO BE GOOD FOR MINIMAL SEAS OF 2 FT OR LESS. THE HIGH MOVES FURTHER OFFSHORE ON THURSDAY ALLOWING FOR A ONE CATEGORY RISE IN WINDS AND A WAVES FORECAST RISING TO JUST THE 2 TO 3 FT RANGE. && .ILM WATCHES/WARNINGS/ADVISORIES... SC...NONE. NC...NONE. MARINE...NONE. && $$ SYNOPSIS...MJC NEAR TERM...SHK SHORT TERM...MJC LONG TERM...MBB AVIATION...SHK

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