Area Forecast Discussion
Issued by NWS Charleston, SC

Current Version | Previous Version | Text Only | Print | Product List | Glossary Off
Versions: 1 2 3 4 5 6 7 8 9 10 11 12 13 14 15 16 17 18 19 20 21 22 23 24 25 26 27 28 29 30 31 32 33 34 35 36 37 38 39 40 41 42 43 44 45 46 47 48 49 50
-- Highlight Changed Discussion --
-- Discussion containing changed information from previous version are highlighted. --
000 FXUS62 KCHS 040834 AFDCHS AREA FORECAST DISCUSSION NATIONAL WEATHER SERVICE CHARLESTON SC 434 AM EDT SAT JUL 4 2015 .SYNOPSIS... ATLANTIC HIGH PRESSURE WILL PREVAIL AS A TROUGH OF LOW PRESSURE LINGERS INLAND THROUGH THE MIDDLE OF NEXT WEEK. && .NEAR TERM /THROUGH TONIGHT/... THE PERSISTENT LONG WAVE TROUGH WILL REMAIN OVER THE EASTERN UNITED STATES TODAY...AS A SERIES OF UPPER LEVEL DISTURBANCES ROUND THE BASE OF THE TROUGH. HOWEVER...IT DOES APPEAR THAT ATLANTIC RIDGING MAY BE ABLE TO EXPAND A BIT WESTWARD INTO THE REGION AS THE TROUGH AMPLIFIES/DEEPENS TO THE WEST. THIS MAY BE SUFFICIENT TO KEEP THE GREATEST FORCING JUST NORTHWEST OF THE AREA WITH EACH PASSING SHORT WAVE. MEANWHILE AT THE SURFACE...THE REGION WILL REMAIN ALONG THE WESTERN FRINGES OF ATLANTIC HIGH PRESSURE CENTERED WELL OFFSHORE WHILE A PIEDMONT TROUGH PERSISTS NORTHWEST OF THE AREA. OVERALL...THE INDEPENDENCE DAY FORECAST IS NOT VERY CLEAR CUT IN TERMS OF PRECIPITATION POTENTIAL. RADAR MOSAICS INDICATE A SERIES OF CONVECTIVE COMPLEXES LINED UP ACROSS NORTHERN MISSISSIPPI...ALABAMA AND GEORGIA IN ASSOCIATION WITH EACH SHORT WAVE DISTURBANCE. WHILE THE BUILDING RIDGE SHOULD GENERALLY STEER THESE COMPLEXES JUST NORTHWEST OF THE AREA...HIGH RESOLUTION MESOSCALE MODELS SHOW A GOOD POTENTIAL FOR ADDITIONAL CONVECTION TO DEVELOP ALONG OUTFLOW BOUNDARIES PROPAGATING SOUTHEAST DUE TO COLD POOLING. THIS CONVECTION COULD ORGANIZE INTO MULTI-CELLULAR CLUSTERS AS IT ADVANCES SOUTHEAST ACROSS THE AREA THIS AFTERNOON INTO THIS EVENING. IN ADDITION...CONVECTION APPEARS TO DEVELOP ALONG THE NORTHEAST FLORIDA/SOUTHERN GEORGIA COAST EARLY THIS AFTERNOON IN AN AREA OF ENHANCED LOW LEVEL CONVERGENCE...THEN LIFT NORTHWARD INTO THE AREA LATE IN THE DAY AND THIS EVENING. ALL OF THIS SEEMS TO SUPPORT INCREASED SHOWER/THUNDERSTORM POTENTIAL ACROSS THE AREA AND HAVE RAISED POPS ACCORDINGLY. THE FORECAST GENERALLY SHOWS RAIN CHANCES AROUND 40 PERCENT...BUT THIS WILL LIKELY NEED TO BE RAISED AS TRENDS BECOME BETTER ESTABLISHED. THERE IS THE POTENTIAL FOR SOME OF THE THUNDERSTORMS TO BECOME SEVERE...WITH SURFACE BASED CAPE VALUES RISING TO 2500-3000 J/KG ACROSS MUCH OF THE AREA. IN ADDITION...DOWNDRAFT CAPE VALUES OF 750-1000 J/KG AND INVERTED-V SOUNDINGS SUPPORT A DAMAGING WIND THREAT. GIVEN THESE FACTORS...WILL ADD MENTION TO THE HAZARDOUS WEATHER OUTLOOK. AS FOR TEMPERATURES...HAVE LOWERED HIGHS FROM PREVIOUS FORECASTS TO ACCOUNT FOR THE GREATER POTENTIAL FOR CONVECTION AND ASSOCIATED CLOUD COVER. THE FORECAST NOW INDICATES HIGHS OF 92-94 ACROSS MUCH OF THE AREA...EXCEPT IN THE UPPER 80S TOWARD THE IMMEDIATE COAST. LATE THIS EVENING AND OVERNIGHT...THE UPPER RIDGE MAY BEGIN TO BREAK DOWN A BIT...WITH THE LOWERING HEIGHTS AND SOME PASSING UPPER LEVEL SHORT WAVE DISTURBANCES SUPPORTING LOW CHANCES OF SHOWERS AND THUNDERSTORMS...WITH THE GREATEST COVERAGE NEAR THE COAST. LOWS SHOULD BE IN THE LOWER TO MID 70S ACROSS THE AREA. && .SHORT TERM /SUNDAY THROUGH TUESDAY/... GENERALLY A CONTINUATION OF THE SAME PATTERN WITH HIGH PRESSURE OVER THE ATLANTIC AND LOW PRESSURE INLAND. THE MAIN CHALLENGE IS TIMING OF SHORTWAVE TROUGHS ALOFT WHICH WILL BE THE MAIN FORCING FOR CONVECTION. SUNDAY...CLOSE PROXIMITY TO THE UPPER TROUGH ALONG WITH DEEP MOISTURE WILL MEAN ABOVE NORMAL RAIN CHANCES...HIGHEST INLAND CLOSER TO POSSIBLE ORGANIZED CONVECTION UPSTREAM. HIGH TEMPERATURES IN THE LOWER 90S...MAINLY NEAR AND WEST OF I-95. SOME SHOWERS AND STORMS WILL LINGER INTO SUNDAY NIGHT WITH LOWS MAINLY IN THE LOWER TO MID 70S. MONDAY...SCATTERED TO POSSIBLY NUMEROUS SHOWERS AND THUNDERSTORMS EXPECTED AGAIN WITH ABUNDANT CLOUDS LIKELY HELPING KEEP TEMPERATURES SLIGHTLY BELOW NORMAL CLOSER TO 90. SEVERE RISK APPEARS LOW GIVEN REDUCED INSTABILITY/SHEAR. TUESDAY...SCATTERED CONVECTION AGAIN ALTHOUGH PROBABLY NOT QUITE AS MUCH AS THE UPPER TROUGH WEAKENS AND HIGH PRESSURE EXERTS MORE INFLUENCE. HIGHS A BIT WARMER CLOSER TO NORMAL IN THE LOWER 90S AWAY FROM THE LOCALLY COOLER COASTAL AREAS. && .LONG TERM /TUESDAY NIGHT THROUGH FRIDAY/... MEDIUM RANGE GUIDANCE IS IN FAIRLY GOOD AGREEMENT THROUGH MID WEEK INDICATING MORE HIGH PRESSURE RIDGING. ANOTHER TROUGH COULD RETURN LATE IN THE WEEK. SHOULD SEE LOW RAIN CHANCES THROUGH AT LEAST THURSDAY...MAINLY EACH AFTERNOON/EVENING. TEMPERATURES WILL GENERALLY BE NEAR NORMAL...WITH HIGHS IN THE LOWER TO MID 90S AND LOWS IN THE LOWER TO MID 70S. && .AVIATION /08Z SATURDAY THROUGH WEDNESDAY/... VFR CONDITIONS ARE THEN GENERALLY EXPECTED TO PREVAIL THROUGH 06Z SUNDAY. SCATTERED SHOWERS AND THUNDERSTORMS ARE POSSIBLE THIS AFTERNOON AND EVENING...AND COULD RESULT IN TEMPORARY FLIGHT RESTRICTIONS AND GUSTY/ERRATIC WINDS. HOWEVER...CONFIDENCE IN TIMING/COVERAGE TOO LOW TO INCLUDE MENTION IN THE FORECAST AT THIS TIME. EXTENDED AVIATION OUTLOOK...BRIEF FLIGHT RESTRICTIONS ARE POSSIBLE IN MAINLY AFTERNOON/EARLY EVENING SHOWERS AND THUNDERSTORMS...WITH THE BEST CHANCES LIKELY THROUGH TUESDAY. && .MARINE... TODAY AND TONIGHT...THE TIGHT SURFACE PRESSURE FOUND BETWEEN ATLANTIC HIGH PRESSURE CENTERED WELL OFFSHORE AND A TROUGH OF LOW PRESSURE NORTHWEST OF THE AREA WILL BEGIN TO RELAX SOME THIS MORNING...RESULTING IN DIMINISHING WINDS OVER THE WATERS. SMALL CRAFT ADVISORIES REMAIN IN EFFECT FOR THE CHARLESTON COUNTY NEAR SHORE WATERS AND THE OUTER GEORGIA WATERS...BUT ARE SET TO EXPIRE AT 7 AM AS CONDITIONS IMPROVE. LOOK FOR SOUTH TO SOUTHWEST WINDS TO THEN PREVAIL WITH SPEEDS UPWARDS OF AROUND 15 KT THROUGH TONIGHT. SEAS WILL MAY SUBSIDE A BIT AS WINDS DIMINISH...BUT OVERALL SHOULD RANGE FROM 2-4 FT...HIGHEST IN THE OUTER GEORGIA WATERS. SUNDAY THROUGH THURDSAY...EXPECT A PERSISTENT PATTERN FEATURING ATLANTIC HIGH PRESSURE AND AN INLAND TROUGH OF LOW PRESSURE. A TIGHTENED PRESSURE GRADIENT BETWEEN THESE FEATURES WILL MAINTAIN ELEVATED WINDS/SEAS THROUGH THE PERIOD BUT CONDITIONS SHOULD LARGELY REMAIN BELOW ADVISORY LEVELS. SEAS WILL BE 2-4 FEET ON AVERAGE...BUT COULD REACH 5 FT AT TIMES MOSTLY BEYOND 20 NM. RIP CURRENTS...THE COMBINATION OF LINGERING LUNAR INFLUENCES...AN EASTERLY SWELL OF 2 FT EVERY 9 SECONDS AND GUSTY WINDS WILL SUPPORT A MODERATE RISK FOR RIP CURRENTS FOR THE LOWER SOUTH CAROLINA BEACHES TODAY. IT APPEARS SLIGHTLY LOWER WINDS FROM SOUTH ALONG GEORGIA COAST WILL LIMIT THE RIP CURRENT RISK TO A HIGH-END LOW CATEGORY. && .CHS WATCHES/WARNINGS/ADVISORIES... GA...NONE. SC...NONE. MARINE...SMALL CRAFT ADVISORY UNTIL 7 AM EDT THIS MORNING FOR AMZ350- 374. && $$ NEAR TERM...JAQ SHORT TERM...RJB LONG TERM...RJB AVIATION...JAQ/RJB MARINE...JAQ/RJB

USA.gov is the U.S. government's official web portal to all federal, state and local government web resources and services.