Area Forecast Discussion
Issued by NWS Wilmington, NC

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000 FXUS62 KILM 012341 AFDILM AREA FORECAST DISCUSSION NATIONAL WEATHER SERVICE WILMINGTON NC 741 PM EDT FRI AUG 1 2014 .SYNOPSIS... A TROUGH WILL REMAIN STALLED NEAR THE COAST THROUGH THE WEEKEND. THIS WILL BRING A HEIGHTENED RISK FOR FLOODING AS WIDESPREAD SHOWERS AND THUNDERSTORMS PLAGUE THE AREA FOR MUCH OF THE WEEKEND. THE AIRMASS WILL ONLY SLOWLY DRY OUT DURING THE MIDDLE AND LATER PORTIONS OF NEXT WEEK. && .NEAR TERM /THROUGH TONIGHT/... AS OF 730 PM FRIDAY...THE COASTAL TROUGH/WARM FRONT MADE PRETTY GOOD INLAND PROGRESS EARLIER TODAY...REACHING THE INTERSTATE 95 CORRIDOR FROM LUMBERTON DOWN THROUGH FLORENCE. THE BOUNDARY IS STALLING AND IS EXPECTED TO DROP BACK TOWARD THE SOUTH CAROLINA COAST LATE TONIGHT...WITH AT LEAST SOME POTENTIAL IT COULD REACH MYRTLE BEACH BEFORE DAYBREAK. FOCUSED CONVERGENCE ALONG THE FRONT HAS LED TO A LINE OF SHOWERS AND EMBEDDED T-STORMS FROM BLADEN COUNTY THROUGH MARION...FLORENCE TO NEAR ORANGEBURG SC. AN EASTWARD ADVANCING UPPER DISTURBANCE NEAR THE SAVANNAH RIVER SHOULD HELP NUDGE THE FRONT AND A COLLOCATED DEEP MOISTURE CHANNEL EASTWARD TONIGHT...REACHING THE COAST LATE. CHANGES WITH THIS UPDATE WERE FAIRLY MINOR...WITH TWEAKS TO WIND DIRECTIONS AND HOURLY POPS/WX MOST SIGNIFICANT. PREVIOUS DISCUSSION FROM 300 PM FOLLOWS... TROUGH REMAINS STALLED ALONG THE COAST WHILE DEEP GULF MOISTURE CONTINUES TO SPREAD NORTHEAST. ALONG WITH LOW LEVEL CONVERGENCE ASSOCIATED WITH THE BOUNDARY...WEAK DIVERGENCE ALOFT CONTINUES. THIS COUPLED WITH MODERATE INSTABILITY...CAPE IS 1000-1500 J/KG...HAS BEEN PRODUCING SHOWERS AND THUNDERSTORMS ACROSS MUCH OF THE AREA. EXPECT ACTIVITY TO CONTINUE AND INCREASE IN COVERAGE FOR THE REMAINDER OF THE AFTERNOON. LOSS OF DIURNAL HEATING SHOULD BRING ABOUT A DECREASE IN COVERAGE BUT DO NOT THINK ACTIVITY WILL COMPLETELY DISAPPEAR THIS EVENING. TROUGH WILL REMAIN STALLED ALONG OR JUST INLAND OF THE COAST WITH PRECIPITABLE WATER VALUES HANGING AROUND 2 INCHES OVERNIGHT. ADDITIONALLY THERE APPEARS TO BE A WEAK DEFORMATION ZONE EAST OF THE AREA. THIS FEATURE WILL SLOWLY DRIFT WEST THIS EVENING AND OVERNIGHT AS THE MID LEVEL WESTERN ATLANTIC RIDGE EXPANDS. BASED ON THIS HAVE HELD ONTO LIKELY POP ALONG THE COAST ALL NIGHT BUT DROP INLAND AREAS TO HIGH CHANCE AROUND MID NIGHT. MID LEVEL PATTERN AND LACK OF SURFACE LOW IN EASTERN TX SUGGESTS THE TROUGH WILL REMAIN STALLED ALONG THE COAST THROUGH THE END OF THE PERIOD AND THIS IS WHERE THE HIGHEST QPF SHOULD BE FOUND. CLOUD COVER AND MOISTURE ALONG WITH BOUNDARY LAYER WINDS WILL KEEP LOWS NEAR TO ABOVE CLIMO. WEST OF THE BOUNDARY LOWS WILL BE CLOSE TO CLIMO...AROUND 70. ON THE EAST SIDE OF THE BOUNDARY MODEST ONSHORE FLOW WILL KEEP TEMPERATURES IN THE MID 70S. && .SHORT TERM /SATURDAY THROUGH SUNDAY NIGHT/... AS OF 300 PM FRIDAY...A FLOOD WATCH IS IN EFFECT THROUGH SUNDAY. A COASTAL TROUGH WILL REMAIN POSITIONED ALONG THE CAROLINA COAST THIS PERIOD. WHILE SOME OF THE MODELS ARE INDICATING THE TROUGH WILL VERY SLOWLY MOVE INLAND...THE MID-LEVEL FLOW SUGGESTS OTHERWISE. AN EXTREMELY DEEP S/SW FLOW WILL REMAIN LOCKED IN PLACE ALONG WITH A MOIST COLUMN THROUGH A VERY DEEP LAYER. THE PERSISTENT UPPER DIFFLUENCE WITHIN THE ENTRANCE REGION OF JET STREAK ACROSS THE NORTHEAST AND THE LOW LEVEL CONVERGENCE ALONG THE TROUGH WILL PROVIDE THE NECESSARY LIFT FOR A LARGE SCALE...SIGNIFICANT RAINFALL EVENT. WE ARE EXPECTING TOTAL RAINFALL AMOUNTS TO AVERAGE 2 TO 4 INCHES WITH UPWARDS OF 4 AND 5 INCHES ALONG COASTAL CAPE FEAR. HOWEVER...HIGHER AMOUNTS ARE POSSIBLE AND GIVEN THE GROUND IS WET FROM A VERY WET JULY...WE FEEL THE RISK FOR SIGNIFICANT FLOODING IS HIGH ENOUGH TO WARRANT A FLOOD WATCH. THE CLOUDS...RAIN...AND LOWERED THICKNESSES WILL KEEP HIGHS BELOW NORMAL FOR EARLY-AUGUST...BUT AT THE SAME TIME MAINTAIN NORMAL OR SLIGHTLY ABOVE NORMAL LOWS. EXPECT HIGHS IN THE LOWER TO MID 80S BOTH DAYS...AND LOWS IN THE LOWER TO MID 70S. && .LONG TERM /MONDAY THROUGH FRIDAY/... AS OF 300 PM FRIDAY...MID-LEVEL TROUGH AXIS WILL REMAIN WEST OF THE AREA MONDAY AND TUESDAY...RESULTING IN A CONTINUED AMPLE SUPPLY OF MOISTURE TO ENHANCE THE POTENTIAL FOR SHOWERS AND TSTMS. SURFACE CONVERGENCE WILL BE PROVIDED BY THE STALLED FRONTAL BOUNDARY WHICH WILL LINGER ALONG THE COAST AS WELL AS WEAK WAVES OF LOW PRESSURE WHICH MODELS INDICATE MAY DEVELOP ALONG THE BOUNDARY. EXPECT TEMPS WILL BE HELD IN CHECK BY CLOUD COVER MONDAY...BUT LESS SO TUESDAY-WEDNESDAY. THE MID-LEVEL TROUGH AXIS WILL SLOWLY TRANSITION EAST AND ALLOW SOME DRIER AIR TO FILTER IN BY MIDWEEK...SO ALTHOUGH POPS WILL BE INCLUDED EACH DAY...TREND WILL BE DOWNWARD. ANOTHER WEAK FRONTAL BOUNDARY WILL DROP INTO THE AREA THURSDAY AND LINGER INTO FRIDAY...SO SLIGHT/LOW CHANCE POPS WILL BE WARRANTED THOSE DAYS AS WELL. && .AVIATION /00Z SATURDAY THROUGH WEDNESDAY/... AS OF 00Z...A NARROW BAND OF SHRA/ISOLATED TSRA IS OCCURRING ALONG A FRONTAL BOUNDARY FROM NEAR KFLO TO KLBT. CIGS ARE MVFR/TEMPO IFR AT KFLO/KLBT. NO PRECIPITATION IS CURRENTLY OCCURRING AT THE COASTAL TERMINALS. TEMPO MVFR CIGS HAVE BEEN OCCURRING AT KCRE/KMYR. THE CURRENT CONDITIONS SHOULD CONTINUE FOR THE NEXT SEVERAL HOURS. A WEAK UPPER IMPULSE SHOULD MOVE THROUGH THIS EVENING ENDING THE PRECIPITATION AT KFLO/KLBT AND INCREASING THE PRECIPITATION POTENTIAL AT THE COASTAL TERMINALS. MODEL SOLUTIONS VARY WIDELY ON THE EVOLUTION OF THE FRONTAL BOUNDARY NEAR KFLO/KLBT...THUS CONFIDENCE IS LOW. ATTM WILL SWING THE FRONT BACK TOWARDS THE COAST WITH THE PASSAGE OF THE UPPER IMPULSE. THIS SHOULD ALLOW FOR IFR/LIFR TO EVENTUALLY AFFECT ALL TERMINALS EXCEPT ILM BEFORE SUNRISE. HIGHEST CONFIDENCE OF LIFR/IFR CIGS/VSBYS WILL BE AT KFLO/KLBT. LIFR/IFR CIGS IMPROVE TO MVFR BY MID MORNING. SHRA/TSRA RE-DEVELOP BY LATE MORNING...WITH BEST POTENTIAL FOR VCTS ALONG THE BOUNDARY NEAR THE COASTAL TERMINALS. EXTENDED OUTLOOK...SHRA/TSRA LIKELY WITH PERIODS OF MVFR CONDITIONS THROUGH TUESDAY AS A FRONT STALLS AND FINALLY DISSIPATES OVER THE EASTERN CAROLINAS. A CHANCE OF SHOWERS CONTINUES ON WEDNESDAY LATE. && .MARINE... NEAR TERM /THROUGH TONIGHT/... AS OF 730 PM FRIDAY...THE WARM FRONT/COASTAL FRONT HAS MOVED INLAND THROUGH ELIZABETHTOWN AND WHITEVILLE WITH SOUTH WINDS REPORTED AT ALL WEATHER OBS STATIONS ALONG THE COAST. MODELS ARE SHOWING THE BOUNDARY MAY REVERSE COURSE OVERNIGHT AND DROP BACK DOWN TOWARD THE COAST. MY LATEST FORECAST BRINGS IT FAIRLY CLOSE TO MYRTLE BEACH AGAIN LATE TONIGHT. THE PRESSURE GRADIENT IS AWFULLY "BAGGY" IN THE VICINITY OF THE FRONT AND THIS SHOULD RESULT IN WIND SPEEDS DIMINISHING OVERNIGHT...PARTICULARLY ALONG THE SOUTH CAROLINA COAST. WINDS OF 10-15 KNOTS SHOULD CONTINUE ALONG NORTH CAROLINA COAST MUCH OF THE NIGHT. SEAS ARE CURRENTLY 3 FEET AT THE SUNSET BEACH BUOY...AND JUST UNDER 4 FEET AT THE NEARSHORE WRIGHTSVILLE BEACH BUOY AND OFFSHORE LEJEUNE BUOY...NECESSITATING ONLY A SLIGHT INCREASE IN WAVE FORECASTS. PREVIOUS DISCUSSION FROM 300 PM FOLLOWS... COASTAL TROUGH STALLED NEAR THE COAST KEEPS SOUTHEAST FLOW IN PLACE OVER THE WATERS THROUGH THE END OF THE PERIOD. LITTLE CHANGE TO THE GRADIENT IS EXPECTED AND WINDS WILL REMAIN IN THE 10 TO 15 KT RANGE. PROLONGED ONSHORE FLOW WILL KEEP SEAS 3 TO 4 FT. SHORT TERM /SATURDAY THROUGH SUNDAY NIGHT/... AS OF 300 PM FRIDAY...A COASTAL TROUGH WILL LIKELY NOT MOVE MUCH THROUGH THE PERIOD AND WE EXPECT THE TROUGH WILL BE OVER THE AREA OR JUST TO THE WEST THROUGH SUNDAY NIGHT. THE WIND DIRECTION ON THE WEST SIDE OF THE TROUGH WILL BE MORE NORTHERLY WHILE WINDS ON THE EAST SIDE WILL BE MORE SOUTHERLY. AT THIS TIME...EXPECT THE WIND DIRECTION ACROSS THE WATERS WILL BE PREDOMINATELY FROM A S OR SE DIRECTION. THE PROXIMITY OF THE TROUGH SHOULD KEEP WIND SPEEDS FROM EXCEEDING 10 TO 15 KT. SEAS WILL BE 3 TO 4 FT WITH PERHAPS SOME 5 FT SEAS DEVELOPING ACROSS THE OUTERMOST WATERS LATE IN THE WEEKEND. A STILL RATHER WEAK 9 TO 11 SECOND SE SWELL WILL BE PRESENT. LONG TERM /MONDAY THROUGH WEDNESDAY/... AS OF 300 PM FRIDAY...SURFACE FLOW IS EXPECTED TO REMAIN RELATIVELY LIGHT AS THE PRESSURE GRADIENT WILL REMAIN WEAK THROUGH THE PERIOD. HOWEVER THERE IS UNCERTAINTY IN THE WIND DIRECTION DURING THIS TIME AS A STALLED FRONTAL BOUNDARY WILL LINGER ALONG THE COAST. A 3 TO PERHAPS 4 FOOT SWELL WITH 11 SECOND PERIOD WILL BE POSSIBLE TUESDAY-WEDNESDAY FROM BERTHA...WHICH IS CURRENTLY FORECAST TO BE MOVING NORTHWARD WELL OFF THE CAROLINA COAST AT THAT TIME. && .ILM WATCHES/WARNINGS/ADVISORIES... SC...FLOOD WATCH THROUGH SUNDAY EVENING FOR SCZ017-023-024-032-033- 039-053>056. NC...FLOOD WATCH THROUGH SUNDAY EVENING FOR NCZ087-096-099-105>110. MARINE...NONE. && $$ NEAR TERM...III/TRA SHORT TERM...RJD LONG TERM...CRM AVIATION...III/DL

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