Area Forecast Discussion
Issued by NWS Charleston, SC

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000 FXUS62 KCHS 241159 AFDCHS AREA FORECAST DISCUSSION NATIONAL WEATHER SERVICE CHARLESTON SC 659 AM EST MON NOV 24 2014 ...ISOLATED STRONG TO SEVERE THUNDERSTORMS POSSIBLE TODAY... ...DENSE SEA FOG TO LINGER OFF THE COAST... .SYNOPSIS... A SLOW MOVING COLD FRONT WILL SHIFT TOWARD THE COAST AND OFFSHORE TODAY AND TONIGHT. THE FRONT WILL THEN MEANDER OFF THE SOUTHEAST COAST TUESDAY...BEFORE AN OFFSHORE LOW SYSTEM DEVELOPS ON THE FRONT AND PULLS THE FEATURE FURTHER INTO THE ATLANTIC ON WEDNESDAY. HIGH PRESSURE WILL THEN PREVAIL FOR THE HOLIDAY WEEKEND. && .NEAR TERM /UNTIL 6 PM THIS EVENING/... A PLUME OF TROPICAL MOISTURE FEATURING PWATS OF 1.5-2.0 INCHES WILL REMAIN IN PLACE ACROSS THE SOUTHEAST U.S. TODAY AS A LARGE UPPER TROUGH REMAINS POSITIONED WELL TO THE WEST. AN ANOMALOUSLY MOIST AND WARM LOW-LEVEL FLOW FROM OFF THE GULF OF MEXICO WILL RESULT IN THE CONTINUATION OF WARM AND HUMID CONDITIONS TODAY WITH THE 70 DEGREE ISODROSOTHERM FORECAST TO PUSH INTO PARTS OF THE FORECAST AREA THIS AFTERNOON--HIGHLY UNUSUAL FOR LATE NOVEMBER. DESPITE THE EXPECTED CLOUD COVER...TEMPERATURES ARE FORECAST TO SOAR WELL INTO THE UPPER 70S TO NEAR 80 DEGREES...WHICH WILL BE APPROACHING RECORD TERRITORY FOR BOTH THE SAVANNAH AND CHARLESTON AIRPORTS. INSTABILITY IS FORECAST TO INCREASE AS TEMPERATURES AND DEWPOINTS INCREASE WITH SBCAPES APPROACHING 1500 J/KG BY EARLY AFTERNOON. THIS COUPLED WITH SOME UVM ASSOCIATED WITH WEAK PERTURBATIONS MOVING RAPIDLY NORTHEAST IN THE FAST UPPER FLOW ALOFT WILL SUPPORT A REDEVELOPMENT OF SCATTERED SHOWERS AND TSTMS LATER TODAY. THE BEST COVERAGE IS EXPECTED TO OCCUR ACROSS THE WESTERN ZONES EARLY THIS AFTERNOON...WITH ACTIVITY FORECAST TO SPREAD SLOWLY EAST INTO THE EARLY EVENING HOURS. MOST OF THE MESOSCALE MODELS APPEAR TO CAPTURE THIS TREND WELL...SO POPS WILL BE INCREASED TO 40-50 PERCENT ACROSS THE WESTERN HALF OF THE FORECAST AREA WITH POPS 30 PERCENT AT THE COAST. THERE WILL BE A RISK FOR ISOLATED STRONG TO SEVERE TSTMS THIS AFTERNOON WITH MODELS SHOWING THE AREA REMAINING EMBEDDED IN A LARGE RIBBON OF 50-55 KT OF 0-6 KM BULK SHEAR. THE 850 HPA LOW- LEVEL JET IS FORECAST TO WEAKEN EVER SO SLIGHTLY BY LATE MORNING...BUT SPEEDS ARE STILL PROGGED TO BE 40-50 KT DURING PEAK HEATING AS MID-LEVEL DRY AIR PROMOTES DCAPE VALUES OVER 1200 J/KG. A FEW OF THE TSTMS THEREFORE WILL HAVE THE POTENTIAL TO PRODUCE DAMAGING WIND GUSTS...POSSIBLY EXHIBITING OCCASIONAL SUPERCELLUAR CHARACTERISTICS AT TIMES GIVEN THE STRENGTH OF THE SHEAR. THERE IS A POTENTIAL FOR A QLCS TYPE FEATURE TO DEVELOP BY MID-AFTERNOON... WHICH THE LATEST H3R HAS BEEN SHOWING A SQUALL LINE SIGNAL FOR THE PAST SEVERAL RUNS...BUT CONFIDENCE IN THIS SCENARIO REMAINS LOW ATTM. THIS WILL HAVE TO BE MONITORED THROUGHOUT THE DAY...HOWEVER. SEA FOG REMAINS A CONCERN AT THE COAST TODAY AS HIGH THETA AIR ADVECTS OVER THE COLD ATLANTIC SHELF WATERS. WITH SOUTHERLY TRAJECTORIES IN PLACE...ANY SEA FOG THAT FORMS OVER THE ATLANTIC WILL BE DRAWN TO THE BEACHES AND INTRACOASTAL WATERS. && .SHORT TERM /6 PM THIS EVENING THROUGH THURSDAY/... TONIGHT...A WEAK COLD FRONT WILL APPROACH FROM THE WEST THIS EVENING AND BE POSITIONED ROUGHLY ALONG THE I-95 CORRIDOR BY SUNRISE TUESDAY. A RISK FOR SHOWERS/TSTMS WILL LINGER THROUGH THE NIGHT WITH THE RIBBON OF TROPICAL MOISTURE HOLDING IN PLACE... ALTHOUGH ACTIVITY WILL TEND TO DIMINISH BY MID-EVENING WITH THE LOSS OF INSOLATION. FOG/STRATUS WILL BE POSSIBLE THROUGH THE NIGHT WITH STRATUS BUILDING A POSSIBILITY. LOWS WILL RANGE FROM THE LOWER 50S ACROSS FAR INTERIOR SOUTHEAST GEORGIA BEHIND THE FRONT TO THE UPPER 50S/LOWER 60S EAST OF THE I-95 CORRIDOR. TUESDAY AND TUESDAY NIGHT...STRONG SHORTWAVE ENERGY WILL SWEEP FROM THE SOUTHERN PLAINS STATES ACROSS THE LOWER MISSISSIPPI VALLEY...DRIVEN EAST BY A NOTABLE 150 KT UPPER LEVEL JET. THIS SIGNIFICANT LARGE SCALE SUPPORT WILL ASSIST IN CYCLOGENESIS ALONG THE STALLED COLD FRONT LINGERING OFF THE SOUTHEAST COAST. A DEEPENING WAVE OF LOW PRESSURE WILL THUS LIFT FROM THE GULF OF MEXICO UP TOWARD THE CAROLINA COAST LATE TUESDAY NIGHT/EARLY WEDNESDAY. MUCH OF THE SENSIBLE WEATHER ON TUESDAY WILL BE HIGHLY DEPENDENT ON THE TRACK OF THE COASTAL LOW AND THE LOCATION OF THE WAVERING AXIS OF DEEP MOISTURE. IN GENERAL...EXPECT RAIN COVERAGE TO INCREASE FROM EAST TO WEST AS THE DAY PROGRESSES...PEAKING DURING THE LATE NIGHT TIME FRAME WHEN BOTH THE CORE OF THE SHORTWAVE AND THE COASTAL LOW MAKE THEIR CLOSEST APPROACH TO THE FORECAST AREA. NUMEROUS TO WIDESPREAD RAIN...THICK CLOUD COVER...AND WINDS STEADILY VEERING NORTH ON THE BACK SIDE OF THE SYSTEM SUGGEST THAT HIGH AND LOW TEMPERATURES WILL BE SIGNIFICANTLY COOLER THAN THE PREVIOUS DAY. EXPECT HIGHS TO PEAK IN THE LOW TO MID 60S AND OVERNIGHT LOWS TO FALL INTO THE MID TO UPPER 40S. WEDNESDAY AND WEDNESDAY NIGHT...THE COASTAL LOW WILL RAPIDLY LIFT NORTH AWAY FROM THE REGION...AS DAMPENING SHORTWAVE ENERGY MOVES TOWARD AND ACROSS THE EAST COAST. RAIN COVERAGE WILL GRADUALLY DECREASE FROM SOUTHWEST TO NORTHEAST DURING THE DAYTIME HOURS BEHIND THE DEPARTING SYSTEM...WITH PRECIPITATION CHANCES FALLING BELOW 15 PERCENT BY THE EVENING PERIOD. DRY HIGH PRESSURE WILL BUILD FROM THE SOUTHWEST IN THE WAKE OF THE COASTAL LOW...WHILE COLD ADVECTION SUPPORTS EVEN COOLER CONDITIONS. HIGH TEMPERATURES WILL BE SUPPRESSED IN THE LOW TO MID 50S...MORE THAN 10 DEGREES BELOW SEASONAL AVERAGES. CLEARING SKIES AND LIGHT WINDS OVERNIGHT WILL ALLOW TEMPERATURES TO FALL INTO THE MID TO UPPER 30S. THURSDAY...A STRONGER AREA OF SURFACE HIGH PRESSURE WILL BUILD SOUTH/SOUTHEAST FROM THE NORTHERN PLAINS/UPPER MISSISSIPPI VALLEY. EXPECT TEMPERATURES TO MODERATE SLIGHTLY ON THE PERIPHERY OF THE SURFACE HIGH...REACHING THE UPPER 50S TO LOWER 60S UNDER CLEAR SKIES. && .LONG TERM /THURSDAY NIGHT THROUGH SUNDAY/... HIGH PRESSURE WILL CONTINUE TO BUILD INTO THE REGION FROM THE NORTH LATE THURSDAY...DESCENDING INTO THE SOUTHEAST STATES BY FRIDAY...BEFORE GRADUALLY SHIFTING TOWARD THE COASTLINE AND NEARBY ATLANTIC WATERS OVER THE WEEKEND. EXPECT TEMPERATURES TO SLOWLY MODERATE AS A RESULT OF THE TRACK OF THE HIGH PRESSURE CENTER. HIGH TEMPERATURES WILL ONLY REACH THE UPPER 50S FRIDAY...WHILE PEAKING IN THE MID TO UPPER 60S BY EARLY NEXT WEEK. LOW TEMPERATURES WILL ALSO REFLECT THIS WARMING TREND...RANGING FROM THE LOW TO MID 30S THURSDAY AND FRIDAY NIGHTS...TO THE LOW TO MID 40S BY SUNDAY NIGHT. CONDITIONS APPEAR DRY THROUGH THE EXTENDED PERIOD...AND WILL KEEP RAIN OUT OF THE FORECAST. && .AVIATION /12Z MONDAY THROUGH FRIDAY/... FOG HAS SO FAR BEEN HELD AT BAY WITH 300 FT WINDS HOLDING 20-25 KT. CIGS NEAR ALTERNATE MINIMUMS WILL LINGER THROUGH ABOUT 14Z WITH LEVELS RISING TO HIGH-END IFR OR LOW-END MVFR. VFR SHOULD RETURN BY EARLY AFTERNOON AS MIXING HEIGHTS INCREASE IN RESPONSE TO TEMPS RISING WELL INTO THE 70S. SCATTERED SHOWERS AND TSTMS WILL LIKELY APPROACH THE TERMINALS FROM THE WEST AFTER 20Z...BUT IT IS UNCLEAR THIS FAR OUT WHETHER THIS ACTIVITY WILL SURVIVE BEFORE REACHING THE TERMINALS. WILL LEAVE MENTION OF SHRA/TSRA OUT FOR NOW. ANOTHER ROUND OF LOW CIGS ARE LIKELY AGAIN TONIGHT. LIMITED CONDITIONS TO LOW-END MVFR FOR NOW...ALTHOUGH IFR OR LOWER IS CERTAINLY A REASONABLE POSSIBILITY. EXTENDED AVIATION OUTLOOK...A BETTER CHANCE FOR MVFR OR LOWER CONDITIONS IN RAIN LATE TUESDAY OR TUESDAY NIGHT INTO EARLY WEDNESDAY...AS AN AREA OF LOW PRESSURE DEVELOPS ON A COLD FRONT STALLED OFF THE SOUTHEAST COAST. SOLID VFR CONDITIONS WILL RETURN FOR THE REMAINDER OF THE PERIOD. BREEZY WEST/NORTHWEST WINDS EXPECTED WEDNESDAY. && .MARINE...
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WEBCAMS AT TYBEE ISLAND INDICATE WIDESPREAD SEA FOG HAS PUSHED SOUTH INTO THE GEORGIA NEARSHORE WATERS. ITS UNCLEAR HOW FAR SOUTH THE FOG EXTENDS...BUT HAVE GONE AHEAD AND EXPANDED THE MARINE DENSE FOG ADVISORY TO INCLUDE THE GEORGIA NEARSHORE WATERS THROUGH 11 AM. TODAY...ELEVATED WINDS AND SEAS WILL REMAIN IN PLACE ACROSS THE WATERS TODAY WITH CONDITIONS REMAINING WELL INTO SMALL CRAFT ADVISORY THRESHOLDS. FLAGS WILL THEREFORE BE MAINTAINED WITH SEAS DIMINISHING TO 4-7 FT NEARSHORE WATERS AND 6-8 FT OFFSHORE WATERS THIS AFTERNOON. THERE REMAINS A RISK FOR SEA FOG DEVELOPMENT TODAY AS HIGH DEWPOINT AIR FLOWS OVER THE RELATIVELY COOL ATLANTIC SHELF WATERS. IT IS UNCLEAR EXACTLY HOW WIDESPREAD ANY FOG WILL BECOME... BUT THE CHARLESTON HARBOR PILOT BOAT RECENTLY REPORTED WIDESPREAD DENSE SEA FOG JUST OFFSHORE OF THE CHARLESTON HARBOR WITH VSBYS MEASURED IN TERMS OF FEET. HILTON HEAD ALSO DROPPED TO 1 MILE IN FOG WITH A CEILING OF 100 FT...SO SUSPECT THE FOG EXTENDS DOWN TO NEAR THE SAVANNAH RIVER ENTRANCE. A MARINE DENSE FOG ADVISORY IS IN EFFECT FOR ALL NEARSHORE ZONES THROUGH 11 AM. TONIGHT...WINDS WILL VEER TO THE SOUTHWEST AHEAD OF AN APPROACHING COLD FRONT. SEAS ARE EXPECTED TO DROP ENOUGH THAT SMALL CRAFT ADVISORIES WILL LIKELY BE DISCONTINUED. THE RISK FOR AT LEAST PATCHY SEA FOG WILL LINGER THROUGH THE NIGHT. TUESDAY THROUGH SATURDAY...THE COLD FRONT WILL STALL NEAR THE GULF STREAM TUESDAY...BEFORE LOW PRESSURE DEVELOPS ALONG THE LINGERING BOUNDARY AND RAPIDLY LIFTS NORTH WEDNESDAY. SMALL CRAFT ADVISORIES...AS WELL AS A SMALL CHANCE FOR GALES IN THE OUTER GEORGIA ZONES...ARE POSSIBLE TUESDAY NIGHT INTO WEDNESDAY. THE TIMING AND DURATION OF SURGING WEST FLOW ALONG AND WEST OF THE TIGHTENED PRESSURE GRADIENT WILL BE HIGHLY DEPENDENT ON THE EXACT TRACK AND LOCATION OF THE DEEPENING LOW SYSTEM. WINDS AND SEAS WILL FALL BELOW ADVISORY THRESHOLDS BY THURSDAY...YET COULD REMAIN SOMEWHAT ELEVATED AS THE GRADIENT REMAINS TIGHT ON THE PERIPHERY OF BUILDING HIGH PRESSURE INLAND. CONDITIONS WILL IMPROVE BY LATE WEEK INTO THE WEEKEND...AS THE SURFACE HIGH SHIFTS TOWARD THE WATERS AND THE GRADIENT RELAXES.
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&& .CLIMATE... RECORD HIGHS FOR 24 NOVEMBER... KCHS...82 SET IN 1986 AND PREVIOUS. KCXM...81 SET IN 1998. KSAV...83 SET IN 1967. RECORD HIGH MINIMUMS FOR 24 NOVEMBER... KCHS...63 SET IN 2001 AND PREVIOUS. KCXM...66 SET IN 2001. KSAV...65 SET IN 1979. && .CHS WATCHES/WARNINGS/ADVISORIES...
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GA...NONE. SC...NONE. MARINE...DENSE FOG ADVISORY UNTIL 11 AM EST THIS MORNING FOR AMZ350-352- 354. SMALL CRAFT ADVISORY UNTIL 11 PM EST THIS EVENING FOR AMZ352. SMALL CRAFT ADVISORY UNTIL 5 AM EST TUESDAY FOR AMZ350-374. SMALL CRAFT ADVISORY UNTIL 5 PM EST THIS AFTERNOON FOR AMZ354.
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&& $$ ST/WMS

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