Area Forecast Discussion
Issued by NWS Wilmington, NC

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000 FXUS62 KILM 201410 AFDILM AREA FORECAST DISCUSSION NATIONAL WEATHER SERVICE WILMINGTON NC 1009 AM EDT SUN APR 20 2014 .SYNOPSIS...
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SLOW MOVING LOW PRESSURE ABOUT 125 MILES SOUTHEAST OF CAPE FEAR WILL MOVE SLOWLY EASTWARD AND AWAY FROM THE CAROLINAS TONIGHT AND MONDAY. A COLD FRONT MAY BRING ANOTHER ROUND OF SHOWERS LATE TUESDAY... FOLLOWED BY A GRADUAL WARMUP FOR THE REMAINDER OF THE WEEK.
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&& .NEAR TERM /THROUGH TONIGHT/...
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AS OF 1000 AM SUNDAY...VERTICALLY STACKED LOW PRESSURE (1011 MB) IS CENTERED APPROXIMATELY 125 MILES SOUTHEAST OF CAPE FEAR. MODEL ANALYSIS FIELDS STILL INDICATE A COLD CORE ALOFT WITH THIS SYSTEM...BUT DEEP CONVECTION HAS DEVELOPED WITHIN THE CENTER OF THIS LOW WITH NLDN LIGHTNING DISPLAYS SHOWING SEVERAL HUNDRED LIGHTNING STRIKES PER HOUR OFFSHORE. BREEZY NORTH WINDS WILL CONTINUE IN THE BROAD OUTER CIRCULATION AROUND THIS LOW TODAY OVER LAND...WITH GUSTS INLAND AROUND 30 MPH...POSSIBLY APPROACHING 40 MPH AT THE COAST. CURRENT RADAR COMPOSITES SHOW THE BULK OF THE RAIN CONFINED TO COASTAL NORTH CAROLINA FROM WILMINGTON NORTHEASTWARD ACROSS THE SOUTHERN OUTER BANKS. MOVEMENT OF THIS PRECIPITATION IS TOWARD THE SOUTHWEST WHICH PLACES ITS SOURCE REGION RATHER LOW IN THE ATMOSPHERE ON THE 290K ISENTROPIC SURFACE. SATURATION IS INDICATED ON THE NAM AND GFS TO CONTINUE ON THE 290K SURFACE THROUGH THE DAY...WITH LIFT PERHAPS INCREASING EAST OF I-95 THIS AFTERNOON. FOR THIS REASON I AM RELUCTANT TO TRIM BACK POPS BELOW 60-70% (LIKELY) FOR BURGAW...WILMINGTON...SOUTHPORT...AND MYRTLE BEACH. FARTHER INLAND THERE IS A LOT OF VERY DRY AIR (SURFACE DEWPOINTS IN THE 30S) WHICH IS NOT WELL REPRESENTED IN THE MODELS. THIS COULD MAKE IT VERY DIFFICULT FOR RAIN TO OCCUR ALONG AND WEST OF I-95 TODAY...AND I HAVE TRIMMED BACK POPS TO NO HIGHER THAN 20% (SLIGHT CHANCE) HERE. WHERE PRECIPITATION CHANCES ARE HIGHEST NEAR THE COAST I HAVE TRIMMED BACK HIGHS TO BARELY 60 DEGREES...WITH LOWER 60S POSSIBLE FARTHER INLAND. THIS IS A GOOD 15 DEGREES BELOW NORMAL FOR THIS DATE AND WILL HELP TO CANCEL OUT SOME OF THOSE UNUSUALLY WARM DAYS WE HAD THE FIRST HALF OF APRIL. MONTHLY TEMPERATURE DEPARTURES THROUGH YESTERDAY WERE +2.6 DEGREES IN WILMINGTON...+0.7 DEGREES IN FLORENCE...AND +1.1 DEGREES IN MYRTLE BEACH. PREVIOUS DISCUSSION FROM 600 AM FOLLOWS... ANOTHER DREARY AND COOL DAY IS IN STORE FOR THE EASTERN CAROLINAS. THE STIFF NE WINDS WILL ADD INSULT TO INJURY. EXPECT CLOUDS WILL HANG ON THROUGH THE DAY...WITH CLEARER SKIES HOLDING NOT TOO FAR TO OUR W AND SW...BUT UNABLE TO MAKE ANY DECENT EASTWARD PROGRESSION AS ATLANTIC LOW PRESSURE AND ITS ASSOCIATED TROUGH...CUTOFF FROM THE MEAN FLOW...DRIFT EVER SO SLOWLY SEAWARD THROUGH TONIGHT. THE COLUMN DOES SLOWLY DRY OUT ABOVE A PRONOUNCED NEAR SURFACE INVERSION. HOWEVER...THE SATURATED LAYER NEVER SHRINKS TO A DEPTH LESS THAN ABOUT 2 KFT...THUS EXPECT CLOUDS WILL AGAIN HANG ON THROUGH THE PERIOD. ALTHOUGH WE WILL LARGELY BE ON THE BACKSIDE OR SUBSIDENT SIDE OF THE LOW CENTER...PROXIMITY OF SURFACE TROUGH AND WEAK PERTURBATIONS ROTATING AROUND THE UPPER LOW WILL NECESSITATE KEEPING MENTION OF POPS IN THE FORECAST INTO TONIGHT. HIGHEST POPS SEEM WARRANTED THROUGH MIDDAY...UP TO CATEGORICAL WITH POPS TRENDING LOWER THROUGH THE AFTERNOON. TONIGHT...THE CIRCULATION AROUND THE UPPER LOW MOVES PROGRESSIVELY FURTHER AWAY FROM THE AREA WITH SOME RIDGING BUILDING TO THE COAST LATE AT NIGHT AND ON MON. THUS THE DOWNWARD TREND IN POPS WILL CONTINUE WITH ONLY A SLIGHT CHANCE INLAND DURING THE EVE. POPS ALONG THE COAST WILL ALSO TREND TO SLIGHT CHANCE...ALTHOUGH AT A SLIGHTLY SLOWER PACE. THERE WILL BE A TIGHT PRESSURE GRADIENT BETWEEN THE LOW CENTER AND TROUGH OFFSHORE AND THE STRONG HIGH PRESSURE CENTER ACROSS EASTERN NEW ENGLAND...RIDGING INTO THE CAROLINAS. THE RESULT...NE WINDS ON THE ORDER OF 15 TO 25 MPH WITH GUSTS IN EXCESS OF 30 MPH. THE BEACHES MAY EXPERIENCE WIND GUSTS NEAR 40 MPH. THESE WINDS WILL BE TRENDING LOWER THROUGH THE LATE AFTERNOON AND EVE...BUT EVEN TONIGHT...WINDS WILL BE 10 TO 20 MPH MOST OF THE TIME. TEMPS TODAY WILL BE WELL BELOW NORMAL...WILL CAP THEM IN THE LOWER 60S GIVEN THERE WILL BE NO HELP FROM THE SUN TO BOOST THEM ANY HIGHER. TONIGHT...CLOUD COVER AND WINDS...ALLOWING FOR A RATHER WELL MIXED ENVIRONMENT...SHOULD PREVENT TEMPS FROM DROPPING BELOW THE MID AND UPPER 40S.
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&& .SHORT TERM /MONDAY THROUGH TUESDAY NIGHT/... AS OF 300 AM SUNDAY...RAIN-FREE ON MONDAY AS MID LEVEL RIDGING AND WESTERLY DOWNSLOPING KEEP THINGS VERY DRY. AT THE SURFACE HOWEVER THERE WILL STILL BE SOME MOISTURE IN THE NNE FLOW. THUS EXPECT AN EAST-WEST GRADATION IN CLOUD COVER. OVERALL CLOUD COVER WILL DECREASE THROUGH THE DAY THOUGH AS THE PREVIOUSLY CUTOFF ATLANTIC SYSTEM CONTINUES TO OPEN UP AND MOVE EASTWARD. MID LEVEL HEIGHT FALLS SPREAD ACROSS THE REGION ON TUESDAY AS THE RIDGE GIVES WAY TO TROUGHINESS DROPPING OUT OF THE GREAT LAKES AREA. LOW LEVEL MOISTURE ADVECTION THEN FOLLOWS LATE DAY WITH THE APPROACH OF A COLD FRONT. THIS BOUNDARY IS A LITTLE SLOWER THAN PREV PROGGED. SHOWERS WILL BE WIDELY SCATTERED AND INSTABILITY QUITE MEAGER. MONDAY HIGHS HELD BELOW CLIMO BY THE NORTHERLY COMPONENT BUT TEMPS SNAP BACK TO SEASONABLE IF NOT A LITTLE WARMER IN THE PREFRONTAL SRLY FLOW ON TUES. && .LONG TERM /WEDNESDAY THROUGH SATURDAY/... AS OF 300 AM SUNDAY...PRESSURE PATTERN QUITE POORLY DEFINED ON WEDNESDAY AS THE POST FRONTAL HIGH IS QUITE WEAK AND MOSTLY CENTERED WELL TO OUR NORTH. THIS PRECLUDES ANY COOL ADVECTION AND FAIRLY SEASONABLE WEATHER IS EXPECTED. WE MAY SEE A BUMP OF A FEW DEGREES ON THURSDAY AS HIGH MOVES OFF THE COAST. THIS VERY SLIGHT WARMING TREND WILL CONTINUE FOR THE REMAINDER OF THE PERIOD. LOW LEVELS WILL MOISTEN GRADUALLY BASICALLY JUST CHANGING THE MOSTLY SUNNY SKIES OF WED AND THU TO PARTLY SUNNY BY FRIDAY OR THEREABOUTS...AGAIN A GRADUAL PROCESS. THE UPTICK IN MOISTURE PAIRED WITH THE DEVELOPMENT OF A PIEDMONT TROUGH CALLS FOR SOME SLIGHT CHC POPS BY SATURDAY. && .AVIATION /12Z SUNDAY THROUGH THURSDAY/... AS OF 12Z...AT TAF TIME BORDERLINE MVFR/IFR CIGS ARE OCCURRING AT KMYR...WHILE CIGS AT KFLO/KLBT/KCRE ARE VFR. TEMPO MVFR CIGS ARE OCCURRING AT KILM. PATCHY WRAP AROUND RAIN FROM THE OFFSHORE LOW CONTINUES ACROSS THE TERMINALS...BUT IS BECOMING MORE EXPANSIVE IN THE COASTAL WATERS SOUTHEAST OF KILM. THE LOW OFFSHORE WILL MOVE SLOWLY AWAY FROM THE TERMINALS THIS TAF VALID PERIOD...THUS THERE WILL CONTINUE TO BE A GOOD CHANCE CHANCE OF WRAP AROUND BANDS OF GENERALLY LIGHT RAIN THROUGH 00Z. WINDS WILL BE N-NE AND DUE TO A TIGHT GRADIENT GUSTS TO 25-30 KTS ARE POSSIBLE ESPECIALLY AT THE COASTAL TERMINALS. AT KFLO/KLBT VFR EXPECTED...EXCEPT FOR TEMPO MVFR CIGS LATE THIS MORNING INTO EARLY AFTERNOON. AT THE COASTAL TERMINALS THERE IS A GREATER POTENTIAL FOR IFR CIGS AS PROGS INDICATE A BETTER CHANCE OF RAIN MID-LATE MORNING INTO THE EARLY AFTERNOON. AFTER THE PRECIPITATION ENDS AROUND 00Z CONFIDENCE IS HIGHER FOR IFR AT THE COASTAL TERMINALS AS COLD AIR ADVECTION DEVELOPS A LOW LEVEL INVERSION AROUND 1K. EXTENDED OUTLOOK...VFR MONDAY. CHANCE OF SHOWERS/TEMPO MVFR ON TUESDAY WITH A COLD FRONT. VFR WEDNESDAY AND THURSDAY. && .MARINE...
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NEAR TERM /THROUGH TONIGHT/... AS OF 1000 AM SUNDAY...WINDS AT THE FRYING PAN SHOALS BUOY HAVE GUSTED AS HIGH AS 41 KNOTS THIS MORNING...WITH COASTAL OBSERVATIONS SHOWING GUSTS AS HIGH AS 30 KNOTS AT WRIGHTSVILLE BEACH AND BALD HEAD ISLAND. IN THE SEMI-PROTECTED WATERS SOUTHWEST OF CAPE FEAR WINDS ARE RUNNING 5-7 KNOTS LESS NEARSHORE...BUT ARE PROBABLY STILL QUITE STRONG AWAY FROM SHORE. 1011 MB LOW PRESSURE ABOUT 125 MILES SOUTHEAST OF CAPE FEAR HAS BEEN PRODUCING AN IMPRESSIVE AMOUNT OF DEEP CONVECTION WITH NLDN LIGHTNING NETWORK DISPLAYS SHOWING SEVERAL HUNDRED LIGHTNING STRIKES PER HOUR NEAR THE CENTER OF THE CIRCULATION. SINCE THIS LOW IS FORECAST TO ONLY DRIFT EASTWARD THROUGH TODAY LOOK FOR ONLY A SLOW IMPROVING TREND IN WINDS/SEAS TO BEGIN LATE TODAY AND TONIGHT. PREVIOUS DISCUSSION FROM 600 AM FOLLOWS... LOW PRESSURE WAS BROADLY CENTERED OFF THE SOUTHEAST COAST. A TROUGH EXTENDED FROM THE CENTER OF THE LOW AND UP ALONG THE THE CAROLINA COAST. AT THE SAME TIME...STRONG HIGH PRESSURE...CENTERED ACROSS EASTERN NEW ENGLAND...WAS RIDGING DOWN THE COAST AND ACROSS THE CAROLINAS. THIS CONTINUES TO RESULT IN A VERY TIGHT PRESSURE GRADIENT...PRODUCING GALE FORCE WINDS ACROSS THE WATERS...UP TO 25 TO 35 KT WITH GUSTS NEAR 40 KT. WINDS ARE EXPECTED TO SLOWLY DIMINISH TONIGHT. THE DIRECTION WILL REMAIN NE TODAY WITH A SLOW BACKING TO THE N AS THE LOW CENTER AND TROUGH SLOWLY MOVE SEAWARD. SEAS WILL BE HIGHEST INTO THIS AFTERNOON...UP TO 7 TO 12 FT. SEAS WILL SUBSIDE TONIGHT...DOWN TO 6 TO 9 FT BY DAYBREAK MON. WAVE HEIGHTS ACROSS THE NEAR SHORE WATERS OF LONG BAY WILL BE CONSIDERABLY LOWER DUE TO THE VERY LIMITED FETCH ON NE TO N WINDS. SHORT TERM /MONDAY THROUGH TUESDAY NIGHT/... AS OF 300 AM SUNDAY...SHORT TERM WILL START WITH A SMALL CRAFT ADVISORY AS WE CONTINUE TO RAMP DOWN FROM THE GALES OF THE NEAR TERM PERIOD. GRADIENT WILL EASE AS LOW PRESSURE PULLS AWAY SLOWLY TO THE EAST AND A WEAK HIGH TRIES TO GET ESTABLISHED ACROSS THE SOUTHEAST. THE LATTER DOES NOT HAVE MUCH LUCK TO LOCAL WINDS WILL ALMOST EXCLUSIVELY BE A FUNCTION OF THE EXITING LOW. SOUTHERLY FLOW OVERSPREADS THE REGION FROM WEST TO EAST ON TUESDAY AS A COLD FRONT APPROACHES FROM THE NORTHWEST. THIS WILL SLIGHTLY REVERSE THE ABATING TREND IN WAVE HEIGHT BUT NO FLAGS OR CAUTIONARY HEADLINES EXPECTED AS WIND REMAINS QUITE LIGHT BOTH AHEAD OF AND FOLLOWING A TUESDAY NIGHT FROPA. LONG TERM /WEDNESDAY THROUGH THURSDAY/... AS OF 300 AM SUNDAY...FOLLOWING THE PASSAGE OF A COLD FRONT WEDNESDAYS WILL BRING DECREASING AND VEERING WINDS AND ABATING SEAS. HIGH PRESSURE NORMALLY BUILDS IN BEHIND A COLD FRONT BUT THIS TIME THE AIRMASS PRETTY MUCH WASHES OUT AS IT BUILDS SOUTHWARD. A STRONGER HIGH FORMS WEDNESDAY NIGHT UP IN NY/PA AND IT WILL EXTEND A RIDGE AXIS DOWN INTO THE CAROLINAS. THIS WILL INITIALLY YIELD A LIGHT ONSHORE FLOW BUT AS THURSDAY PROGRESSES THE HIGH WILL SPLIT SLIGHTLY WITH ONE CENTER ANCHORING OFF HATTERAS. WIND WILL EVENTUALLY TURN SOUTHERLY OR SOUTHWESTERLY.
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&& .ILM WATCHES/WARNINGS/ADVISORIES... SC...HIGH RIP CURRENT RISK THROUGH THIS EVENING FOR SCZ056. NC...HIGH RIP CURRENT RISK THROUGH THIS EVENING FOR NCZ106-108. MARINE...GALE WARNING UNTIL 11 PM EDT THIS EVENING FOR AMZ250-252-254- 256. && $$ NEAR TERM...RJD/TRA SHORT TERM...MBB LONG TERM...MBB AVIATION...MRR

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