000 FXUS62 KILM 280718 AFDILM AREA FORECAST DISCUSSION NATIONAL WEATHER SERVICE WILMINGTON NC 318 AM EDT SAT JUL 28 2007 .SYNOPSIS... A SERIES OF UPPER LEVEL DISTURBANCES WILL MOVE ACROSS THE AREA THIS WEEKEND. A WEAK SURFACE FRONT WILL STALL ACROSS THE CAROLINAS MONDAY AND SLOWLY DISSIPATE THROUGH WEDNESDAY. HIGH PRESSURE WILL RIDGE IN FROM THE EAST THURSDAY AND FRIDAY. && .NEAR TERM /THROUGH TODAY/... STRONG SHORT WAVE MOVING INTO THE AREA THIS AFTERNOON WILL CAUSE SHRA/TSRA TO DEVELOP ACROSS THE REGION. SOUNDINGS AND CROSS SECTIONS INDICATE THE PRESENCE OF DEEP MOISTURE AND STRONG VERTICAL MOTION AS THE WAVE ARRIVES. LOCAL WRF HINTS AT CONVECTION ALONG THE SEA BREEZE WHICH GETS GOING BEFORE THE SHORT WAVE ARRIVES. SEA BREEZE COULD END UP ENHANCING CONVECTION ASSOCIATED WITH THE WAVE. MARINE LAYER IS NOT AS STABLE THIS TIME OF YEAR AND TENDS TO HELP CONVECTION RATHER THAN HINDER IT. HIGHS THIS AFTERNOON WILL AGAIN RANGE FROM UPPER 80S TO LOW 90S. && .SHORT TERM /TONIGHT THROUGH MONDAY NIGHT/... THE NEXT SEVERAL DAYS WILL FEATURE A VERY UNCLIMATOLOGICAL SUMMER PATTERN HIGHLIGHTED BY A SERIES OF UPPER LEVEL DISTURBANCES PASSING THROUGH A SHARP EASTERN U.S. TROUGH. THIS WILL LEAD TO INCREASING CHANCES OF SHOWERS AND THUNDERSTORMS THROUGH THE PERIOD. THE GFS IS INITIALLY 3-6 HOURS FASTER THAN THE NAM...BUT BOTH MODELS AGREE A STRONG UPPER DISTURBANCE WILL BE MOVING THROUGH EASTERN SOUTH CAROLINA THIS EVENING. HAVE FORECAST HIGHEST POPS THIS EVENING FROM FLORENCE SOUTHEAST TOWARD THE COAST WHERE THE BEST DYNAMICS WILL MOVE. FOR SUNDAY...THE NAM IS FARTHER SOUTH AND EAST DEVELOPING A SURFACE LOW ACROSS CENTRAL SOUTH CAROLINA. THE GFS HOLDS THE LOW LEVEL CIRCULATION WEST OF ATLANTA UNTIL MONDAY MORNING WHEN IT ARRIVES IN THE PALMETTO STATE. THIS DIFFERENCE IS SIGNIFICANT SINCE THE CONVERGENCE PROVIDED BY THE LOW WILL BE INSTRUMENTAL IN DETERMINING HOW MUCH CONVECTION WILL DEVELOP IN THE VERY MOIST AND UNSTABLE AIRMASS SUNDAY AFTERNOON. THE GFS MOS POPS (30-40%) SEEM TOO LOW EVEN GIVEN THE AIRMASS CONVECTIVE PARAMETERS ALONE...SO WILL TREND UP TOWARD THE HIGHER ETA/NGM MOS GUIDANCE POPS IN THE GRIDS. BY MONDAY...BOTH THE GFS AND NAM AGREE THE FINAL PIECE OF THE UPPER LEVEL TROUGH WILL PASS OVER THE CAROLINAS...ALONG WITH THE SURFACE CONVERGENT AXIS LATE IN THE DAY. COVERAGE OF RAIN SHOULD APPROACH 60% DURING THE DAY...WITH A CLEARING TREND DEVELOPING FROM NORTHWEST TO SOUTHEAST MONDAY NIGHT BEHIND THE UPPER TROUGH AXIS. DIURNAL TEMPERATURE RANGES WILL BE HELD TO ONLY 15 DEGREES OR SO THROUGH THE PERIOD GIVEN HIGH DEWPOINTS AND PLENTY OF CLOUD COVER. A COMPROMISE AMONG THE GUIDANCE MEMBERS APPEARS VERY REASONABLE. && .LONG TERM /TUESDAY THROUGH FRIDAY/... MID LEVEL TROUGH DIGGING ACROSS THE EAST COAST IN THE BEGINNING OF THE PERIOD AS COLD FRONT APPROACHES FROM THE WEST NORTHWEST GIVING BEST CHANCE OF PCP FOR MON AFTN. MID LEVEL TROUGH SEEMS TO SHIFT FAR ENOUGH NORTH AND EAST BY TUESDAY INTO WEDNESDAY TO CREATE SOME MID LEVEL DRYING AND SUBSIDENCE...BUT COLD FRONT GETS HUNG UP ALONG THE COAST. THEREFORE WILL KEEP GREATER POPS FOR MON AND KEPT SLIGHT CHC TO CHC POPS FOR MUCH OF THE WEEK ALTHOUGH MID WEEK COULD BE DRIER IF FRONT SHIFTS FAR ENOUGH OFF THE COAST. GFS HAS LOW DEVELOPING ALONG LINGERING FRONTAL BOUNDARY AND LIFTS THE LOW UP THE EAST COAST TUES INTO WED PUTTING OUR LOCAL AREA ON THE BACK SIDE WHICH COULD GIVE US A COUPLE OF DRIER DAYS FOR MID WEEK. AS HIGH PRESSURE RIDGES BACK IN FROM ATLANTIC TOWARD END OF WEEK...MOISTURE GETS PULLED BACK INTO THE SOUTHEAST IN THE RETURN FLOW. FAIRLY PERSISTENT EAST COAST TROUGH WILL HANG ON THROUGH END OF WEEK ALTHOUGH IT DOES DAMPEN OUT A BIT BECOMING MORE ZONAL BY END OF WEEKEND. TEMPS WILL REMAIN WITHIN A FEW DEGREES OF GUIDANCE. MAX TEMPS WILL BE SLIGHTLY LOWER MONDAY DUE TO CLOUD COVER ASSOCIATED WITH COLD FRONT. DEW POINTS WILL BE IN THE 70S THROUGH THE PERIOD WITH A DROP INTO THE 60S BEHIND COLD FRONT. OVERALL TEMPS HOVERING AROUND 70 AT NIGHT AND 90 DURING THE DAY. && .AVIATION /07Z SATURDAY THROUGH WEDNESDAY/... DEBRIS CLOUD AND SOME PATCHY BR REMAIN OVER THE REGION THIS MORNING. FOG IS OCCURRING IN AREAS THAT RECEIVED SIGNIFICANT PRECIP LAST EVENING AND IS NOT LIKELY TO SPREAD OR DROP VIS BELOW 3SM. AFTERNOON AND EVENING SHRA/TSRA WILL DEVELOP AS VIGOROUS SHORT WAVE DROPS IN FROM THE TN VALLEY. BEST CHANCES FOR SIGNIFICANT CONVECTION WILL BE AT ALL SC SITES. GUIDANCE IS POINTING TO A PROLONGED PERIOD OF ACTIVITY...POSSIBLY LASTING THROUGH 12Z SUNDAY. && .MARINE... NEAR TERM /THROUGH TONIGHT/... WATERS REMAIN CAUGHT BETWEEN BERMUDA HIGH AND BROAD SURFACE LOW OVER THE SOUTHEASTERN US. GRADIENT REMAIN WEAK...KEEPING WIND SPEEDS BETWEEN 10 AND 15 KT. SEAS WILL CONTINUE TO RUN 2 TO 3 FT. SHORT TERM /SATURDAY THROUGH SUNDAY NIGHT/... LOW PRESSURE CURRENTLY ACROSS THE OHIO VALLEY WILL GRADUALLY SLIDE SOUTH AND EAST OVER THE NEXT FEW DAYS...EVENTUALLY REACHING THE CAROLINA COASTLINE BY MONDAY AFTERNOON. UNTIL THEN GENERALLY LIGHT SOUTHERLY WINDS ARE EXPECTED WITH SPEEDS LESS THAN 15 KT OUTSIDE OF THUNDERSTORMS. A PERSISTENT SOUTHEASTERLY SWELL (2 FT/8 SECONDS) WILL CONTINUE THROUGH THE PERIOD AS WELL. LONG TERM /MONDAY THROUGH WEDNESDAY/... SOUTHERLY FLOW AHEAD OF STALLED FRONT FOR MONDAY IN THE 10 TO 15 KT RANGE INCREASES AS GRADIENT TIGHTENS. FOR MID WEEK WINDS AND SEAS GET A BIT TRICKIER DEPENDING ON HOW THE SFC LOW AND LINGERING FRONTAL BOUNDARY PANS OUT. WENT MORE IN LINE WITH GFS SHIFTING WINDS AROUND TO THE W-NW FOR MID WEEK ON BACK END OF DEVELOPING LOW AS IT MOVES UP THE COASTAL WATERS FAR ENOUGH EAST. BY END OF WEEK...RETURN FLOW OF SW TO S WINDS SETS UP AGAIN. SEAS REMAIN IN THE 2 TO 4 KT RANGE...WITH SLIGHT INCREASE MID WEEK AS SFC LOW MOVES NORTH JUST EAST OF COASTAL WATERS. && .ILM WATCHES/WARNINGS/ADVISORIES... SC...NONE. NC...NONE. MARINE...NONE. && $$ SYNOPSIS...TRA NEAR TERM...III SHORT TERM...TRA LONG TERM...RGZ AVIATION...III