000 FXUS62 KCHS 051150 AFDCHS AREA FORECAST DISCUSSION NATIONAL WEATHER SERVICE CHARLESTON SC 650 AM EST FRI DEC 5 2008 .SYNOPSIS... A COLD FRONT WILL STALL SE OF OUR COAST LATER TODAY INTO SAT AS WEAK WAVES OF LOW PRES MOVE NE ALONG IT. HIGH PRES WILL THEN BUILD FROM THE NW ON SUNDAY AND SETTLE OVER THE MID ATLC REGION ON MON. A COASTAL TROUGH WILL DEVELOP LATE MON INTO TUE...THEN A COMPLEX STORM SYSTEM WILL IMPACT THE REGION WED AND THU. && .NEAR TERM /UNTIL 6 PM THIS EVENING/... WHERE SKIES WERE MAINLY CLEAR OVERNIGHT ALONG THE U.S. 17 CORRIDOR AREAS OF SHLW FOG DEVELOPED...ESPECIALLY AROUND WATER SOURCES. WE UPDATED OUR FORECAST PRIOR TO DAWN TO REFLECT SOME REDUCED VSBYS IN PATCHY FOG. A SURFACE COLD FRONT WAS PASSING SE THROUGH SE GEORGIA AND THE COASTAL CAROLINAS AROUND DAYBREAK...JUST AHEAD OF INCREASING LAYERED CLOUDS IN A BROAD BAND OF 55-70 PCNT 1000-500 MB RH. A POSITIVELY TILTED BROAD UPPER TROF AXIS ACROSS THE NORTHERN TIER OF STATES WILL PRESS ESE TODAY WITH A 100-125 KT UPPER JET EASING INTO THE MOUNTAINS BY LATE DAY. SOME UPPER JET FORCING IS EXPECTED TO CAUSE SOME STREAKS OF LIGHT RAIN ANY MAYBE DRIZZLE TO EXPAND A BIT FROM THE EASTERN FLORIDA PANHANDLE INTO THE SOUTHERN SOUTH CAROLINA COAST THIS AFTERNOON. THE PCPN SHOULD BE LIGHT WITH MOST MODELS SUGGESTING QPF AMOUNTS LESS THAN A TENTH INCH. SINCE IT APPEARS MANY AREAS COULD JUST TRACE OR REMAIN DRY...WE HAVE A 20/30 POP SCHEME TODAY TO HANDLE THE LIGHT STRATIFORM PCPN. COOLER AIR WILL FILTER IN THE AREA TODAY BEHIND THE FRONT AND TEMPERATURES ARE A BIT ON THE TRICKY SIDE SINCE CLOUDS ARE NOT WIDESPREAD STARTING THE MORNING. WE HAVE MAINTAINED A SIMILAR FORECAST TO PERSISTENCE WITH HIGHS MAINLY 55 NORTH TO AROUND 60 SOUTH. && .SHORT TERM /6 PM THIS EVENING THROUGH 6 AM SATURDAY/... FRONTAL BOUNDARY OVER THE GULF STREAM SHOULD BE QUASI-STATIONARY TONIGHT WITH WEAK SURFACE RIPPLES FORECAST IN TANDEM WITH SOME SHORT WAVE ENERGY MOVING OVER N FLORIDA IN FAST UPPER SW FLOW. DEEPER MOISTURE IS PROGGED OFF THE COAST BUT WE CANNOT RULE OUT SOME LIGHT RAIN BRUSHING COASTAL COUNTIES OF SE GEORGIA AND SE S CAROLINA OVERNIGHT. MODELS SUGGEST SKIES MAY EVEN BE PARTLY CLOUDY OVERNIGHT WELL INLAND AND MAY EVEN CLEAR ACROSS PARTS OF CENTRAL COASTAL SOUTH CAROLINA LATE. WE LOWERED MINIMUM TEMPERATURES A COUPLE OF DEGREES INLAND W OF LINE FROM REIDSVILLE TO JAMESTOWN GIVEN LATEST GUIDANCE. && .LONG TERM /SATURDAY THROUGH THURSDAY/... MEDIUM RANGE GUIDANCE IS IN GOOD AGREEMENT THROUGH EARLY NEXT WEEK...WITH CONSIDERABLE UNCERTAINTY CONTINUING TO PLAGUE THE LATTER PORTIONS OF THE EXTENDED RANGE FORECAST. A WEAK FRONTAL BOUNDARY WILL REMAIN OFF THE SOUTH CAROLINA AND GEORGIA COAST SATURDAY MORNING...BEFORE GETTING KICKED EASTWARD AND OUT OT SEA SATURDAY AFTERNOON AS A STRONG UPPER LEVEL TROUGH PUSHES THROUGH THE SOUTHEAST UNITED STATES. HIGH PRESSURE WILL THEN BUILD OVER THE AREA SATURDAY NIGHT THROUGH MONDAY. GUIDANCE IS IN GOOD AGREEMENT THAT A COASTAL TROUGH WILL DEVELOP OFF THE SOUTH CAROLINA AND GEORGIA COAST MONDAY NIGHT...THEN LIFT NORTH OF THE AREA TUESDAY. THIS IS WHERE MODEL AGREEMENT COMES TO AN ABRUPT HALT...WITH SOLUTIONS DIVERGING SIGNIFICANTLY THROUGH THE REMAINDER OF THE EXTENDED PERIODS. ALL OPERATIONAL GUIDANCE SUGGESTS THAT A SIGNIFICANT STORM SYSTEM WILL PUSH THROUGH THE SOUTHEAST UNITED STATES SOMETIME WEDNESDAY THROUGH THURSDAY NIGHT...THE GFS AND CANADIAN SOLUTIONS THE FASTEST...WITH THE ECMWF SOLUTION THE SLOWEST. THE VAST MAJORITY OF GFS ENSEMBLE MEMBERS SUGGEST THE STORM SYSTEM WOULD PUSH THROUGH THE AREA TUESDAY NIGHT...FURTHER LOWERING CONFIDENCE IN THE EXTENDED RANGE FORECAST. FOR NOW...WILL FOLLOW A MIDDLE OF THE ROAD SOLUTION TO TRY TO LIMIT THE DEGREE OF FORECAST BUST POTENTIAL WHICH IS QUITE LARGE IN THE TUESDAY NIGHT THROUGH THURSDAY TIME FRAME. THIS RESULTS IN A STRONG COLD FRONT SWEEPING ACROSS THE FORECAST AREA WEDNESDAY NIGHT...WITH HIGH PRESSURE THEN BUILDING BACK INTO THE REGION LATE THURSDAY. AS FOR FORECAST DETAILS...WILL KEEP THE FORECAST RAIN FREE SATURDAY THROUGH MONDAY. CAN/T ENTIRELY RULE OUT A STRAY SHOWER PRIMARILY NEAR THE COAST SATURDAY...BUT CHANCES APPEAR TOO LOW TO INCLUDE IN THE FORECAST AT THIS TIME. AS THE COASTAL TROUGH LIFTS NORTHWARD OFF THE SOUTH CAROLINA AND GEORGIA COAST MONDAY NIGHT AND TUESDAY...WILL CARRY SLIGHT CHANCE/CHANCE POPS PRIMARILY ACROSS SOUTH CARLINA ZONES TO ACCOUNT FOR A FEW SHOWERS DRIFTING IN OFF THE ATLANTIC IN SOUTH-SOUTHEASTERLY LOW LEVEL STEERING FLOW. GIVEN HIGH DEGREE OF TIMING UNCERTAINTY WITH RESPECT TO THE NEXT SYSTEM TO MOVE THROUGH THE REGION...WILL TRY NOT TO GET TO DETAILED WITH POPS AT THIS TIME...AND KEEP CHANCE/SLIGHT CHANCE POPS GOING TUESDAY NIGHT THROUGH THURSDAY. DESPITE TIMING DIFFERENCES...OPERATIONAL GUIDANCE CONTINUES TO AGREE THAT AN UNSEASONABLY STRONG STORM SYSTEM WILL MOVE THROUGH THE REGION ROUGHLY MID WEEK...AND WITH SEVERAL DAYS OF SOUTHERLY FLOW IN ADVANCE OF THE SYSTEM...SEVERE WEATHER MAY BE POSSIBLE. WILL HOLD OFF ON MENTIONING ANY DETAILS IN THE HAZARDOUS WEATHER OUTLOOK UNTIL MODEL SOLUTIONS CONVERGE ON A MORE SPECIFIC TIME FRAME. && .AVIATION /10Z FRIDAY THROUGH TUESDAY/... A COLD FRONT IS CURRENTLY PUSHING THROUGH THE COASTAL CORRIDOR AT DAWN. EVEN THOUGH DEEPER MOISTURE IS IMPINGING ON THE COASTAL CORRIDOR OVERNIGHT...CLOUDS WERE SLOW TO INCREASE THROUGH THE NIGHT AND WE ENDED UP WITH SOME SHLW BUT DENSE GROUND FOG AT TIMES AROUND BOTH AIRPORTS. WE ARE STARTING THE NEW MORNING WITH MVFR VSBYS AND SCT-BKN CLOUDS WITH BASES 5-8 KFT. 050600 WRF SOUNDINGS INDICATE CIGS SHOULD LOWER TO MVFR DURING TODAY WITH OCNL PATCHES OF LIGHT RAIN PASSING THROUGH. MOST OF THE RAIN SHOULD NOT BE SIGNIFICANT ENOUGH TO LOWER VSBYS FOR EXTENDED PERIODS. STILL A LITTLE WORRIED THAT FRONTAL INVERSION MAY TRAP A BIT OF THIS MORNING/S FOG A LITTLE LONGER BUT CONFIDENCE IS LOW. MODELS SUGGEST DRIER AIR ALOFT WILL SPREAD INTO THE REGION TONIGHT EXCEPT RIGHT ALONG THE IMMEDIATE COAST. PROFILES SUGGEST WE WILL HAVE TO WATCH OUT FOR POSSIBLE STRATUS AND/OR FOG ISSUES AFTER MIDNIGHT. THERE IS A POTENTIAL FOR IFR OR LOWER CONDITIONS TO DEVELOP AT EITHER AIRPORT AT SOME JUNCTURE TONIGHT. ONCE AGAIN BOTH TIMING AND CONFIDENCE ARE NOT THERE YET TO ADD ANY DETAIL TO THE TAFS AFTER 060000. EXTENDED AVIATION OUTLOOK...MVFR/IFR CIGS WILL BE POSSIBLE INTO SATURDAY. VFR CONDITIONS ARE EXPECTED TO RETURN SAT NIGHT THROUGH MON. MVFR OR LOWER CIGS MAY IMPACT THE TERMINALS AGAIN MON NIGHT AND TUE. && .MARINE... NO SIGNIFICANT COASTAL ISSUES THROUGH TONIGHT AS THE COLD FRONT STALLS TO THE ESE OF THE WATERS AND NORTHERLY SURGES REMAIN BELOW 15 KT. SEAS NEARLY FLAT EARLY THIS MORNING WILL BUILD TO 2 FT WITHIN 20 NM AND 3 FT WELL OFF THE COAST LATER TONIGHT. HIGH PRESSURE WILL SLOWLY BUILD BACK INTO THE REGION SATURDAY AND SATURDAY NIGHT BEHIND A DEPARTING COLD FRONT...AND WILL REMAIN THE DOMINANT WEATHER FEATURE THROUGH EARLY NEXT WEEK. WINDS AND SEAS ARE EXPECTED TO REMAIN BELOW SMALL CRAFT THRESHOLDS SATURDAY THROUGH MONDAY. PERSISTENT NORTHEAST AND EAST FLOW MAY RESULT IN SEAS MEETING SMALL CRAFT THRESHOLDS MONDAY NIGHT AND TUESDAY ACROSS THE OUTER GEORGIA WATERS...BUT ELSEWHERE CONDITIONS ARE EXPECTED TO REMAIN BELOW SMALL CRAFT ADVISORY LEVELS. && .CHS WATCHES/WARNINGS/ADVISORIES... GA...NONE. SC...NONE. MARINE...NONE. && $$