Area Forecast Discussion
Issued by NWS Wilmington, NC

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000 FXUS62 KILM 241934 AFDILM AREA FORECAST DISCUSSION NATIONAL WEATHER SERVICE WILMINGTON NC 334 PM EDT SUN AUG 24 2014 .SYNOPSIS... HIGH PRESSURE WILL EXPAND SOUTH ACROSS THE AREA THROUGH WEDNESDAY...BRINGING A PERIOD OF COOL AND DRY WEATHER. TROPICAL STORM CRISTOBAL MAY BECOME A HURRICANE IN THE NEXT FEW DAYS AS IT PASSES A FEW HUNDRED MILES EAST OF THE CAROLINAS. A WARMING TREND WILL DEVELOP LATE IN THE WEEK. A BACKDOOR FRONT MAY APPROACH BY NEXT WEEKEND...BRINGING A RISK FOR SHOWERS AND THUNDERSTORMS. && .NEAR TERM /THROUGH TONIGHT/... AS OF 300 PM SUNDAY...COOL BUT BEAUTIFUL LATE SUMMER AFTERNOON COMING TO AN END...LEAVING WHAT WILL BE ONE OF THE COOLER NIGHTS THIS AREA HAS SEEN IN QUITE SOME TIME. COLD FRONT CONTINUES TO SAG WELL SOUTH OF THE AREA...AND HAS PUSHED TO NEARLY THE FLORIDA STATE LINE TODAY. DRIVING THIS BOUNDARY IS A STRONG RIDGE OF HIGH PRESSURE OF CANADIAN ORIGIN...WITH THE CENTER OF THIS HIGH ACTUALLY WELL NORTH OF WINNIPEG, CANADA IN THE NORTH CENTRAL PART OF THE COUNTRY. THIS HIGH IS RIDGING INTO NEW ENGLAND AND THEN DOWN THE EASTERN SEABOARD...WITH ABNORMALLY COOL AND DRY AIR FOR LATE AUGUST FILTERING INTO THE REGION. THIS AIR MASS IS VERY FALL-LIKE...AND DEWPOINTS HAVE FALLEN INTO THE LOW AND MID 60S AREA-WIDE TODAY. THIS DRY AIR HAS LIMITED TOTAL INSTABILITY...AND ALTHOUGH HIGH-RES GUIDANCE CONTINUES TO SUGGEST THE POTENTIAL FOR ISOLATED SEA-BREEZE SHOWERS THROUGH THIS EVE...THE CHANCE FOR THAT IS WANING...AND EVEN DIURNAL CU IS HAVING TROUBLE GAINING MUCH AGITATION. STILL CONTINUED JUST VERY SCHC ALONG THE SC PORTION OF THE SEA BREEZE FOR THE NEXT FEW HOURS. IF A SHOWER DOES DEVELOP IT WILL ERODE QUICKLY AFTER DARK...AS WILL THE MAJORITY OF THE CLOUD COVER. NE WINDS WILL REMAIN ELEVATED TONIGHT...LIKELY STAYING 5-10 MPH INTO MONDAY MORNING. THESE WINDS WILL CONTINUE TO ADVECT COOL/DRY AIR...THUS DRIVING MINS WELL BELOW 70...WITH LOWER 60S ENCOMPASSING THE NORTHERN HALF OR 2/3 OF THE CWA. WHILE ELEVATED WINDS TEND TO LIMIT OVERALL COOLING...NE WINDS HAVE A TENDENCY TO COOL THE AREA MORE THAN WOULD TYPICALLY BE EXPECTED...ESPECIALLY ACROSS THE CAPE FEAR REGION. FOR THIS REASON HAVE FORECAST THE LOWEST TEMPS IN THE NE ZONES TONIGHT...AND WILMINGTON MAY SEE ITS COOLEST NIGHT SINCE EARLY JUNE. && .SHORT TERM /MONDAY THROUGH TUESDAY NIGHT/... AS OF 300 PM SUNDAY...THE FORECAST AREA WILL REMAIN IN THE GRIP OF AN UNSEASONABLE NE FLOW AS HIGH PRESSURE CENTERED ACROSS THE NORTHEAST U.S. RIDGES SOUTH...WITH ITS AXIS REMAINING TO THE WEST OF OUR FORECAST AREA. AT THE SAME TIME...SLOW STRENGTHENING OF THE VERY SLOW MOVING TROPICAL STORM ACROSS THE BAHAMAS IS EXPECTED. THIS WILL SERVE TO PROLONG THE RATHER TIGHT PRESSURE GRADIENT BETWEEN THESE TWO SYSTEMS. AS THESE NE WINDS PERSIST...THEY WILL SERVE TO PILE UP WATER ON THE IMMEDIATE COAST. THIS IN COMBINATION WITH THE NEW MOON WILL INCREASE THE RISK FOR MINOR BEACH EROSION FOR THOSE BEACHES EXPOSED TO A NE FETCH AND MINOR COASTAL FLOODING DURING THE NIGHTTIME HIGH TIDE... BOTH AT THE BEACHES AND ALONG THE LOWER CAPE FEAR RIVER. OTHER HAZARDS WILL INCLUDE A STRONG LONG SHORE CURRENT...MODERATE TO PERHAPS STRONG RIP CURRENTS AND HIGHER THAN NORMAL...ROUGH SURF. TEMPS WILL BE COOL IN THIS BREEZY NE FLOW REGIME. HIGHS WILL BE IN THE LOWER TO MID 80S...WITH TUE PERHAPS SLIGHTLY COOLER THAN MON. LOWS WILL BE IN THE LOWER TO MID 60S WITH PERHAPS UPPER 60S AT THE BEACHES. WIND SPEEDS ON MON WILL BE UP TO 10 TO 20 MPH WITH HIGHER GUSTS...ESPECIALLY AT THE BEACHES. OFFSHORE SHOWERS ARE EXPECTED TO REMAIN THERE FOR MUCH OF THE PERIOD. TRAJECTORIES WILL AT TIMES BRING THE SHOWERS VERY NEAR THE BEACHES...BUT GIVEN THE DRYNESS OF THE COLUMN...EXPECT THESE SHOWERS TO LARGELY ERODE BEFORE MOVING ONSHORE. && .LONG TERM /WEDNESDAY THROUGH SUNDAY/... AS OF 300 PM SUNDAY...THE MID LEVEL PATTERN WILL SHOW TYPICAL LATE SUMMER LETHARGY THROUGH THE PERIOD AS RIDGING WILL BE THE CENTRAL THEME. THE AXIS OF THE RIDGE MOVES FROM THE MISSISSIPPI VALLEY TO OFF THE PENINSULA OF FLORIDA BY THE END OF THE PERIOD. AT THE SURFACE...WEAK HIGH PRESSURE WILL PREVAIL AS WELL AND AS THE MID LEVEL RIDGE REPOSITIONS...A RELATIVELY WEAK BACKDOOR FRONT WILL MOVE ACROSS FRIDAY. THIS WILL SERVE TO ENHANCE THE POPS BOTH FRIDAY AND SATURDAY. HOWEVER MOISTURE AND FORCING REMAIN RELATIVELY WEAK AND SLIGHT CHANCE FRIDAY TO LOW CHANCE SATURDAY WILL SUFFICE FOR NOW. THERE IS ALSO SLIGHT CHANCE POPS FOR WEDNESDAY AND THURSDAY ALONG THE COASTAL AREAS. THE COOL REFRESHING AIRMASS WILL BE A THING OF THE PAST AS TEMPERATURES WEDNESDAY THROUGH FRIDAY WILL BE AT OR JUST ABOVE CLIMATOLOGY. FOR NEXT WEEKEND...A SLIGHT DROP IN TEMPERATURES IS SEEN AS THE BACKDOOR FRONT MOVES ACROSS BUT JUST A COUPLE OF DEGREES. && .AVIATION /18Z SUNDAY THROUGH FRIDAY/... AS OF 18Z...CIGS 3-5K EXPECTED AT THE TERMINALS THIS AFTN. MID/LOW LEVEL MOISTURE COMBINED WITH SURFACE HEATING...WEAK LIFT AND A WEAK UPPER IMPULSE COULD PRODUCE ISOLATED SHRA NEAR SOUTHERN COASTAL TERMINALS THIS AFTERNOON...BUT HAVE OPTED TO LEAVE ANY MENTION OUT OF TAFS DUE TO ISOLATED NATURE. WINDS WILL BE NE 10-15 KT WITH GUSTS TO 20 KT...OCCASIONALLY HIGHER. CIGS WILL SCATTER OUT AT THE COASTAL TERMINALS TONIGHT. WIND GUSTS DECREASE AROUND 00Z AS DOES SHRA POTENTIAL. VFR CONTINUES THE REMAINDER OF THE TAF VALID PERIOD WITH SCT MVFR LEVEL CLOUDS AND NE WINDS 5-10 KT. EXTENDED OUTLOOK...VFR THROUGH THE PERIOD. A SLIGHT CHANCE COASTAL SHOWERS THROUGH THURS. ISOLATED TSRA FRIDAY. && .MARINE... NEAR TERM /THROUGH TONIGHT/... AS OF 300 PM SUNDAY...PINCHING NE GRADIENT EAST OF A RIDGE OF HIGH PRESSURE EXPANDING DOWN THE COAST IS CAUSING DETERIORATING MARINE CONDITIONS TODAY. WINDS ARE SLOWLY BUT STEADILY RISING OUT OF THE NE...WITH SPEEDS OF 15-20 KTS COMMON ACROSS THE WATERS...WITH SOME GUSTS APPROACHING 30 KTS DEVELOPING OVER THE NORTHERN WATERS AND OUTSIDE OF 20 NM. AS THE HIGH PRESSURE STRENGTHENS TONIGHT...THE GRADIENT WILL TIGHTEN FURTHER...AIDED BY THE DISTANT BUT STRENGTHENING TROPICAL STORM CRISTOBAL NEAR THE BAHAMAS. THIS WILL CAUSE WIDESPREAD 15-25 KT NE WINDS THROUGH THE PERIOD...WITH SEAS BUILDING TO 5-8 FT. WAVE HEIGHTS WILL BE DRIVEN ALMOST ENTIRELY BY A NE WIND CHOP TONIGHT. HOWEVER...LONGER PERIOD SWELL ASSOCIATED WITH TROPICAL STORM CRISTOBAL IS FORECAST TO BEGIN TO ENTER THE SPECTRUM TONIGHT. ONLY NOTICEABLE LONG-SWELL PRESENTLY EXISTS AT 41004 /EDISTO BUOY/ WHICH IS OBSERVING A LOW-AMPLITUDE 13 SEC SWELL. EXPECT THIS TO GRADUALLY LIFT NE INTO THE LOCAL WATERS...BUT HAVE ONLY MINIMAL CONTRIBUTION TO THE SIGNIFICANT SEAS UNTIL MONDAY. SHORT TERM /MONDAY THROUGH TUESDAY NIGHT/... AS OF 300 PM SUNDAY...THE PRESSURE DIFFERENCE BETWEEN HIGH PRESSURE TO THE NORTH AND A SLOWLY DEVELOPING TROPICAL STORM ACROSS THE BAHAMAS WILL KEEP A TIGHT PRESSURE GRADIENT ACROSS THE WATERS. A SMALL CRAFT ADVISORY REMAINS IN EFFECT. WINDS WILL COMMONLY BE SUSTAINED AT 20 TO 25 KT. THE LONG NE FETCH WILL KEEP SEAS IN THE 4 TO 7 FT RANGE WITH AT LEAST 8 FT SEAS BEYOND 20 NM. A 10 TO 12 SECOND SE SWELL IS EXPECTED TO SLOWLY BUILD THROUGH THE PERIOD. LONG TERM /WEDNESDAY THROUGH FRIDAY/... AS OF 300 PM SUNDAY...CONFIDENCE CONTINUES TO BUILD THAT THE ONLY IMPACTS FROM CRISTOBAL WILL BE THE SWELL COMPONENT ADDED TO THE WAVE SPECTRUM. THE LATEST WAVEWATCH HURRICANE BULLETIN FOR FRYING PAN SHOALS SHOWS 7-8 FEET DEVELOPING OR PERSISTING WEDNESDAY THROUGH EARLY THURSDAY WITH A GOOD PORTION OF THIS BEING THE WIND WAVE COMPONENT. THIS MAKES SENSE AS THE GFS IS NOT DEVELOPING THE SYSTEM APPRECIABLY. FOR THE 0-20 MILE COASTAL WATERS 4-6 FEET WEDNESDAY AND EARLY THURSDAY SHOULD SUFFICE. BY FRIDAY A WEAK PRESSURE PATTERN YIELDS LIGHT WINDS AND SEAS. FOR THE WINDS WEDNESDAY AND THURSDAY...A NORTHEASTERLY FLOW OF 10-15 KNOTS WEDNESDAY DROPS TO SINGLE DIGITS THURSDAY. && .TIDES/COASTAL FLOODING... AS OF 300 PM SUNDAY...RIDGE OF HIGH PRESSURE EXPANDING DOWN THE COAST IS DRIVING A PINCHED GRADIENT...AND FORCING A LONG PERIOD OF GUSTY NE WINDS LOCALLY. THESE WINDS ARE FORCING WATER TO "PILE UP" NEAR THE COASTLINE...AS NOTED BY TIDAL ANOMALIES OF 1 TO 2 FEET AT THE LOCAL BEACHES. THIS FORCING COMBINED WITH ASTRONOMICAL HIGH TIDES DUE TO THE APPROACH OF THE NEW MOON (NEW MOON IS MONDAY)...WILL CAUSE HIGH TIDE LEVELS THIS EVENING TO APPROACH OR SLIGHTLY EXCEED MINOR FLOOD THRESHOLDS ON THE EAST FACING BEACHES NORTH OF CAPE FEAR. HIGH TIDE IS AROUND 730 PM AT WRIGHTSVILLE BEACH...AND A COASTAL FLOOD ADVISORY HAS BEEN ISSUED...VALID FROM 6PM TO 9PM. THE EAST FACING BEACHES OF SC WILL FARE SLIGHTLY BETTER DUE TO THE COASTLINE ORIENTATION WITH RESPECT TO WIND DIRECTION...AND THUS SHOULD STAY BELOW MINOR FLOOD THRESHOLDS TONIGHT. && .ILM WATCHES/WARNINGS/ADVISORIES... SC...NONE. NC...COASTAL FLOOD ADVISORY FROM 6 PM TO 9 PM EDT THIS EVENING FOR NCZ106-108. MARINE...SMALL CRAFT ADVISORY UNTIL 8 PM EDT TUESDAY FOR AMZ250-252-254- 256. && $$ NEAR TERM...JDW SHORT TERM...RJD LONG TERM...SHK AVIATION...JDW/MRR TIDES/COASTAL FLOODING...JDW

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