Area Forecast Discussion
Issued by NWS Wilmington, NC

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000 FXUS62 KILM 260249 AFDILM AREA FORECAST DISCUSSION NATIONAL WEATHER SERVICE WILMINGTON NC 1049 PM EDT SAT APR 25 2015 .SYNOPSIS... A WARM FRONT WILL APPROACH FROM THE SOUTH AND WILL BE NEAR OR JUST NORTH OF THE AREA SUNDAY MORNING BEFORE GETTING SHOVED SOUTHWARD SUNDAY AFTERNOON AND EVENING. A SMALL RISK FOR STRONG TO SEVERE THUNDERSTORMS WILL REMAIN INTO SUNDAY. DRY HIGH PRESSURE WILL RETURN MONDAY INTO TUESDAY BEFORE A STORM SYSTEM IMPACTS THE AREA DURING THE MIDDLE OF NEXT WEEK. DRY HIGH PRESSURE IS EXPECTED TO RETURN BY FRIDAY. && .NEAR TERM /UNTIL 6 AM SUNDAY MORNING/... AS OF 1000 PM SATURDAY...BASED ON LATEST 88D RADAR MOSAIC TRENDS ...LATEST IR SAT IMAGERY TRENDS...AND LATEST 18Z AND EARLY LOOK AT 00Z VARIOUS MODEL RUNS...HAVE ONCE AGAIN UPDATED LATE EVENING AND OVERNIGHT POPS. BASICALLY KEEPING A SLIGHT TO LOW CHANCE FOR CONVECTION ACROSS ALL LOCATIONS...ALL NIGHT. THIS A RESULT OF AN OSCILLATING SFC BOUNDARY ACROSS THE ILM CWA FOR THE REMAINDER OF THE OVERNIGHT PERIOD. GFS SEEMS A BIT TOO FAR NORTH WITH THE SFC BOUNDARY...OTHERWISE THE FA WOULD HAVE HAD A TASTE OF THAT CLUSTER OF CONVECTION THAT SLID SOUTH OF THE FA AND OFF THE CHS CWA COAST. HAVE STAYED CLOSER TO THE NAM SOLUTION WHICH SLIDES THE SFC FRONT SLIGHTLY SOUTHWARD TO ALONG OR JUST SOUTH OF THE ILM NC- SC BORDER BY DAYBREAK SUNDAY. SHALLOW CONVECTION REMAINS A REMOTE POSSIBILITY WITH SFC BASED CONVERGENCE DURING THE PRE-DAWN SUNDAY HRS. THE DEEPER AND MAIN AREA OF CONVECTION THAT CROSSES THE NC- VA MOUNTAINS...SHOULD REMAIN JUST NORTH OF THE FA AS IT TRACKS TO THE ESE OVERNIGHT. HAVE TWEAKED OVERNIGHT MINS BASED ON WHERE THE SFC FRONT IS EXPECTED TO LIE BY DAYBREAK SUN. HAVE ADDED PATCHY/AREAS OF FOG TO THE OVERNIGHT PERIOD...ESPECIALLY ALONG AND NORTH OF THE SFC FRONTAL BOUNDARY. && .SHORT TERM /6 AM SUNDAY MORNING THROUGH MONDAY NIGHT/... AS OF 300 PM SATURDAY...A WARM FRONT WILL BE SITUATED VERY NEAR OR JUST N OF THE AREA SUNDAY MORNING. MODEL PROFILES SHOW A DEEP WESTERLY FLOW WITH SIGNIFICANT MOISTURE RELEGATED TO THE LOWEST 3 KFT OR SO IN THE WARM SECTOR. A 50 KT JET WILL BE LOCATED 3-5 KFT AGL SUNDAY. THE GFS SHOWS LITTLE IN THE WAY OF INSTABILITY ON SUN WHILE THE NAM PORTRAYS MIXED LAYER CAPE VALUES UP TO AROUND 1500 J/KG AND THIS SEEMS MUCH MORE REASONABLE. THE INSTABILITY WILL BE SHRINKING SOUTHWARD WITH TIME AS THE LAST OF THE WEAK WAVES OF LOW PRESSURE MOVES OFFSHORE TO CONSOLIDATE AND STRENGTHEN WELL OFF THE NC COAST. MODEL SOUNDINGS ACTUALLY SHOW A STRONG FRONTAL INVERSION DEVELOPING FROM N TO S...LASTLY ACROSS THE SOUTHERN GRAND STRAND AND SOUTH SANTEE RIVER AREAS BY MID AFTERNOON SUN. CONFIDENCE IN TIMING IS NOT HIGH...BUT TRENDS LOOK TO BE ON THE RIGHT TRACK. GIVEN MAGNITUDE OF DRY AIR IN STRONG AND DEEPENING WESTERLY FLOW ALOFT...WOULD EXPECT COVERAGE OF CONVECTION TO BE ISOLATED TO SCATTERED. CAN NOT RULE OUT AN ISOLATED STRONG OR SEVERE THUNDERSTORM TO INCLUDE HAIL AND/OR STRONG TO DAMAGING WIND GUSTS. THE SEVERE WEATHER RISK WILL BE PRIMARILY ACROSS THE SOUTHERN REACHES OF OUR FORECAST AREA...WHERE INSTABILITY WILL BE GREATEST...AS WELL AS PERHAPS WHERE SEABREEZE INTERACTS WITH THE FRONT. ANY SEVERE WEATHER WILL INCLUDE STRONG TO DAMAGING WIND GUSTS WILL SHOW POPS TRENDING LOWER FROM N TO S LATE IN THE AFTERNOON AND THROUGH THE EVE HOURS. A SERIES OF SHORTWAVE TROUGHS ROUNDING A RETROGRADING AN UPPER LOW OFF THE NEW ENGLAND COAST WILL HELP TO REINFORCE THE COOLER AND DRIER AIR ADVECTING INTO THE FORECAST AREA MON AND MON NIGHT. A GOOD DEAL OF SUNSHINE MON WILL BE BATTLING THE COOL NW FLOW WITH 850 MB TEMPS DROPPING TO AROUND 3 DEG C. HIGHS SUN WILL LIKELY VARY FROM N TO S AND DEPENDING ON CLOUD COVER...THERE COULD BE A SIGNIFICANT TEMP GRADIENT ACROSS THE AREA. WILL FORECAST LOWER TO MID 80S ACROSS THE SOUTH SANTEE RIVER AREA WITH MID AND UPPER 70S ELSEWHERE. HOWEVER...THE NORTHERN REACHES OF THE AREA COULD BE STYMIED IN THE LOWER 70S GIVEN THEIR PROXIMITY TO THE BOUNDARY AND GREATER CLOUD COVER. HIGHS ON SUN WILL BE IN THE LOWER 70S FOR THE MOST PART...ONE TO TWO CATEGORIES BELOW NORMAL FOR THE WANING DAYS OF APRIL. AFTERNOON RELATIVE HUMIDITY LEVELS WILL BE FALLING THROUGH THE 40S AND 30S ON MON AS DRY AND COOL HIGH PRESSURE TO THE NW BUILDS INTO THE EASTERN CAROLINAS. THE COOLEST NIGHT...MON NIGHT...WILL BE IN THE MID AND UPPER 40S. && .LONG TERM /TUESDAY THROUGH SATURDAY/... AS OF 300 PM SATURDAY....MEDIUM RANGE GUIDANCE CONTINUES TO STRUGGLE WITH THE EVOLUTION OF A MID LEVEL SYSTEM THAT WILL AFFECT THE AREA TO SOME EXTENT FOR MIDWEEK. SEVERAL MODELS KEEP THE TROUGH MORE PROGRESSIVE WHILE OTHERS PHASE THE SYSTEM WITH NORTHERN STREAM ENERGY CREATING A MORE DYNAMIC SYSTEM AND PROLIFIC RAIN MAKER FOR OUR AREA. UNTIL THE MODELS CONVERGE ON A DEPENDABLE SOLUTION...PRUDENCE CALLS FOR KEEPING POPS IN THE FORECAST FROM LATE TUESDAY THROUGH THURSDAY. NO CHANGES TO TEMPERATURE FORECAST WHICH WILL BE A LITTLE BELOW CLIMATOLOGY. && .AVIATION /02Z SUNDAY THROUGH THURSDAY/... AS OF 00Z...THE WARM FRONT HAS MOVED TO NEAR A KLBT TO NORTH OF KILM LINE EARLY THIS EVENING. SOME CLEARING OF LOW CLOUDS FROM THE SW-W SUGGESTS MVFR CIGS MAY DECREASE EARLY THIS EVENING LEAVING VFR CONDITIONS. SHOWERS SHOULD BE AT A MINIMUM THIS EVENING AND OVERNIGHT...BUT WILL NEED TO MONITOR SHOWERS AND THUNDERSTORMS MOVING ENE FROM GEORGIA. THUNDERSTORMS SHOULD STAY SOUTH OF THE TERMINALS BUT SOME LIGHT SHOWERS COULD STILL SPREAD ACROSS THE TERMINALS 04-07Z AS THE ACTIVITY DISSIPATES. SKIES CLEAR AND WINDS BECOME LIGHT SW AFTER MIDNIGHT. VSBYS SHOULD BEGIN TO DECREASE WITH IFR VSBYS AND TEMPO IFR CIGS POSSIBLE. CONFIDENCE OF OCCURRENCE IS MODERATE BUT THERE IS VERY LOW CONFIDENCE IN TIMING AND DURATION. A COLD FRONT WILL MOVE THROUGH THE NORTHERN TERMINALS DURING THE EARLY MORNING AND DURING THE AFTERNOON AT THE SOUTHERN TERMINALS WITH WINDS SHIFTING TO THE NW-N. GOOD CHANCE OF IFR CIGS BECOMING MVFR AT KILM/KLBT DURING THE MORNING...WITH MVFR CIGS AT THE REMAINING TERMINALS. SHOWERS POSSIBLE DURING THE DAY WITH ISOLATED THUNDERSTORMS AT THE SOUTHERNMOST TERMINALS. EXTENDED OUTLOOK...VFR MONDAY AND TUESDAY. SHOWERS POSSIBLE WEDNESDAY AFTERNOON THROUGH THURSDAY MORNING. && .MARINE... NEAR TERM /THROUGH TONIGHT/... AS OF 1015 PM SATURDAY...RAISED A SMALL CRAFT EXERCISE CAUTION FOR ALL WATERS DUE TO COMBINED 15 TO 20 KT WINDS AND SIGNIFICANT SEAS RANGING FROM 2 TO 4 FT...UP TO 5 FT ACROSS THE OUTER WATERS. THE EXCEPTION WILL BE FOR THE WATERS BETWEEN CAPE FEAR SOUTH TO LITTLE RIVER INLET WHERE A SOLID 3 TO 5 FT WILL EXIST THRUOUT. LATEST SFC ANALYSIS HAS THE SFC FRONTAL BOUNDARY JUST NORTH OF CAPE FEAR. PREFER THE LATEST 00Z NAM MODEL RUN...HAVE SLIGHTLY SLOWED THE MOVEMENT OF THE FRONTAL BOUNDARY BACK TO THE SOUTH OVERNIGHT. THIS WILL ALLOW A SW-WSW WIND AT 10 TO 20 KT TO OCCUR FOR A SLIGHTLY LONGER TIME FRAME AND COVERING A BIT MORE ACREAGE THAN EARLIER THOUGHT. THIS INCREASED COVERAGE AND TIME WILL RESULT IN 3 TO 5 FT SIGNIFICANT SEAS...ESPECIALLY FROM CAPE FEAR SOUTHWARD. CURRENT 41013 BUOY WITHIN THE WARM SECTOR INDICATES A SOLID SW 20G25 KT WIND AND SIG. SEAS HAVING BUILT TO 5.9 FT. AS EXPECTED WIND DRIVEN WAVES TO PRIMARILY POPULATE SIGNIFICANT SEAS WITH DOMINANT PERIODS AROUND 6 SECONDS. SHORT TERM /SUNDAY THROUGH MONDAY NIGHT/... AS OF 300 PM SATURDAY...THE WIND DIRECTION WILL BE FROM THE W OR SW SUN MORNING...THEN VEER TO THE NW AND N AS A FRONT SINKS BACK TO THE S THROUGH THE DAY. THE FRONT MAY NOT MOVE S OF THE SOUTHERNMOST WATERS TIL LATE AFTERNOON. THERE WILL BE A MODEST SURGE SUN NIGHT AND THEN A SLIGHTLY STRONGER ONE MON NIGHT AS A SERIES OF SHORTWAVE TROUGHS ROTATE AROUND UPPER LOW RETROGRADING OFF THE NEW ENGLAND COAST. WINDS WILL BE STRONGEST WHEN THE WIND DIRECTION IS FROM THE N OR NNW...UP TO 15 TO 20 KT MON NIGHT. SEAS WILL BE 2 TO 4 FT MOST OF THE TIME. HOWEVER...EXPECT SEAS TO BUILD UP TO 5 FT DURING THE SURGES...WITH THE GREATEST COVERAGE OF 5 FT SEAS MON NIGHT. LONG TERM /TUESDAY THROUGH THURSDAY/... AS OF 300 PM SATURDAY...DESPITE AN INTERESTING AND POSSIBLY DYNAMIC SYNOPTIC WEATHER SCENARIO AT THE MID LEVELS...THE SURFACE FEATURES DRIVING THE WINDS AND SEAS WILL BE RATHER BENIGN IN COMPARISON. HIGH PRESSURE TO THE NORTH WILL MAINTAIN A NORTH TO NORTHEASTERLY FLOW ACROSS THE WATERS THROUGH WEDNESDAY WITH SPEEDS GENERALLY TEN KNOTS OR LESS. FORECAST CHALLENGE THEN ARISES AS MODELS ARE STILL UNSURE HOW TO HANDLE LOW PRESSURE IN THE GULF OR UP THE EAST COAST BOTH IN A PLACEMENT AND STRENGTH PERSPECTIVE. WILL MAINTAIN THE MODEST OFFSHORE FLOW FOR THURSDAY DUE TO UNCERTAINTY. SIGNIFICANT SEAS WILL BE 2-4 FEET. && .ILM WATCHES/WARNINGS/ADVISORIES... SC...NONE. NC...NONE. MARINE...NONE. && $$ SYNOPSIS...JDW NEAR TERM...DCH SHORT TERM...JDW LONG TERM...SHK AVIATION...MRR

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