Area Forecast Discussion
Issued by NWS Charleston, SC

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000
FXUS62 KCHS 300837
AFDCHS

AREA FORECAST DISCUSSION
NATIONAL WEATHER SERVICE CHARLESTON SC
437 AM EDT MON MAR 30 2015

.SYNOPSIS...
A COLD FRONT WILL PUSH INTO THE AREA LATE TODAY WITH WEAK HIGH
PRESSURE TO PREVAIL INTO TUESDAY NIGHT. A COLD FRONT WILL PUSH INTO
THE REGION WEDNESDAY...AND HIGH PRESSURE WILL BUILD FROM THE
NORTHEAST. THE FRONT WILL THEN STALL AND DISSIPATE OVER OR JUST
SOUTH OF THE REGION...AND HIGH PRESSURE WILL SHIFT INTO THE ATLANTIC
THURSDAY THROUGH FRIDAY. A STRONGER COLD FRONT WILL CROSS THE REGION
SATURDAY...FOLLOWED BY HIGH PRESSURE THROUGH EARLY NEXT WEEK.

&&

.NEAR TERM /THROUGH TONIGHT/...
EARLY THIS MORNING...GOOD RADIATIONAL COOLING HAS ALLOWED FOR MANY
INLAND LOCATIONS TO FALL TO THE LOWER AND MIDDLE 30S...WITH EVEN A
FEW POCKETS OF NEAR 32F. THIS IN TURN HAS ALLOWED PATCHY FROST TO
OCCUR OVER MANY INTERIOR SECTIONS OF THE CWFA.

FOR TODAY...THE PESKY TROUGH ALOFT OVER THE EAST THE PAST SEVERAL
DAYS WILL BRIEFLY GIVE WAY TO SHORT WAVE RIDGING AROUND 12Z THIS
MORNING...BUT ANOTHER FAST MOVING SHORT WAVE GENERATING DEEP
CONVECTION IN THE TN VALLEY WILL PROGRESS RAPIDLY EAST/SE THROUGH
THE MORNING...PASSING THROUGH THE CWFA DURING THE EARLY-MID
AFTERNOON. THE FORECAST ZONES WILL LIE BETWEEN 2 SEPARATE
JETS...BUT WE LOOK TO BE CLOSE ENOUGH TO EACH ONE TO AID IN LARGE
SCALE FORCING FOR ASCENT. THE FIRST UPPER JET IS ALONG THE MID-
ATLANTIC COAST THIS MORNING/EARLY AFTERNOON...WHILE THE SECOND IS
STRONGER AND MOVES INTO ALABAMA....WESTERN GEORGIA AND THE
FLORIDA PANHANDLE LATE. WE/LL BE IN CLOSE PROXIMITY TO THE
FAVORABLE RIGHT ENTRANCE REGION OF THE FIRST JET AND NEAR THE LEFT
EXIT REGION OF THE SECOND. CONVERGENCE AND MOISTURE WITH THE
APPROACHING COLD FRONT IS SOMEWHAT RESTRICTED DUE TO DEEP WESTERLY
TRAJECTORIES. BUT THERE IS AN INFLUX OF HIGHER THETA-E AIR AND A
SWATH OF PWATS GREATER THAN 1 INCH THAT IS TRANSPORTED INTO THE
AREA IN ADVANCE OF THE FRONT. THESE CONDITIONS WILL BE ENOUGH TO
GENERATE SCATTERED SHOWERS DURING THE LATE MORNING AND EARLY
AFTERNOON OVER NORTH AND NW SECTIONS...AND DURING THE MID
AFTERNOON INTO THIS EVENING ACROSS SOUTH AND SE AREAS. THE
PROGRESSIVE FLOW AND LARGE DEW POINT DEPRESSIONS WILL KEEP QPF
DOWN UNDER 1/10 TO 1/4 INCH.

THERE REMAINS A RISK OF ISOLATED T-STORMS THIS AFTERNOON...MAINLY
SOUTH OF CHARLESTON AND WALTERBORO IN RESPONSE TO LIFTED INDICES
AS LOW AS -3 TO -5C...DECENT MID LEVEL LAPSE RATES AND MUCAPES OF
500-1000 J/KG. GIVEN COLD MID LEVEL AIR WITH 500 TEMPS DOWN TO
MINUS 18 TO MINUS 20C AND WET BULBS UNDER 8K FT THERE MIGHT
ACTUALLY BE A RISK OF SMALL HAIL IF WE/RE ABLE TO ACHIEVE ANY
DEPTH TO THE CONVECTION. PLUS GIVEN PLENTY OF MID LEVEL DRY AIR WE
MIGHT ALSO BE ABLE TO GENERATE SOME WINDS AS HIGH AS 40 MPH IN A
COUPLE OF SHOWERS AND STORMS.

ALTHOUGH CLOUD COVER WILL INCREASE IN ADVANCE OF THE COLD FRONT
AND CUT DOWN ON THE AMOUNT OF INSOLATION...THERE IS IMPRESSIVE
WARM ADVECTION AS 850 MB TEMPS CLIMB TO 7-8C. THAT ALONG WITH
COMPRESSIONAL HEATING IN ADVANCE OF THE FRONT AND SOME DOWNSLOPE
OFF THE MOUNTAINS WILL ALLOW FOR A HUGE DIURNAL SWING IN TEMPS.
MAXIMUMS WILL HIT UPPER 60S TO NEAR 70 NORTH...LOWER 70S CENTRAL
ZONES AND MAYBE A FEW MID 70S FAR SOUTH WHERE THE GREATEST AMOUNT
OF INSOLATION WILL OCCUR. A RESULTANT SEA BREEZE WILL HOLD SOUTH
CAROLINA SHORELINE COMMUNITIES DOWN IN THE LOWER AND MIDDLE
60S...WHILE THE GEORGIA COAST WILL BE UP CLOSER TO 70 WITH LESS
FETCH OFF THE ATLANTIC.

EFFICIENT MIXING WILL TAP INTO A 35-45 KT LOW LEVEL JET THAT
PASSES THROUGH DURING THE LATE MORNING INTO THIS AFTERNOON IN
ADVANCE OF THE COLD FRONT. THIS WILL ALLOW FOR SW AND WEST WINDS
TO BECOME GUSTY...PEAKING AT 25 OR 30 MPH. WINDS ON LAKE MOULTRIE
WILL ALSO BE GUSTY...ESPECIALLY ALONG THE LAKE SHORE. BUT
CONDITIONS APPEAR TO REMAIN JUST BELOW ANY ADVISORY CRITERIA AS
WEST/SW WINDS PEAK AT 15-20 KT.

TONIGHT...THE COLD FRONT WILL DROP SOUTH/SE OF THE AREA EARLY
ON..AND ANY LINGERING CONVECTION OVER THE FAR SE CORNER OF THE
REGION WILL FADE QUICKLY WITH THE PASSAGE OF THE FRONT AND THE
NOCTURNAL ENVIRONMENT. WEAK HIGH PRESSURE OF PACIFIC ORIGINS WILL
ALLOW FOR CLEARING SKIES...AND ALTHOUGH IT ARRIVE WITH SOME COOLER
AIR IT WON/T BE ANYWHERE NEAR AS COLD AS THE PAST COUPLE OF
NIGHTS. BUT RADIATIONAL COOLING WILL ALLOW FOR LOWS TO FALL TO THE
LOWER AND MIDDLE 40S AWAY FROM THE WARMER BARRIER ISLANDS.

&&

.SHORT TERM /TUESDAY THROUGH THURSDAY/...
TUESDAY...THE REMNANTS OF THE SHALLOW COLD FRONT WILL DISSIPATE AND
WEAK SURFACE HIGH PRESSURE WILL TRAVERSE THE AREA DURING THE
MORNING. THEN...HIGH PRESSURE WILL PUSH OFFSHORE WHILE ANOTHER COLD
FRONT APPROACHES FROM THE NORTH. THUS...THE SURFACE GRADIENT WILL
TIGHTEN AND BECOME MORE ALIGNED WITH WESTERLY 925-850 MB
WINDS...TURNING SURFACE WINDS QUICKLY TO THE WEST/SOUTHWEST AND
PUSHING A LOW-LEVEL THERMAL RIDGE INTO THE REGION. THIS SCENARIO
WILL SUPPORT HIGH TEMPERATURES IN THE MID/UPPER 70S...AND ISOLATED
TEMPS AS HIGH AS 80F CANNOT BE RULED OUT. MEANWHILE...THIS FORECAST
MAINTAINS A RAIN-FREE FORECAST...ALTHOUGH CLOUDS WILL BEGIN TO
INCREASE MID TO LATE AFTERNOON...AND A FEW SHOWERS COULD APPROACH
FAR INLAND/SOUTHERN COUNTIES BY LATE DAY.

TUESDAY NIGHT...A BAND OF ENHANCED MOISTURE FEATURING PWATS AS HIGH
AS 1.25 INCH AND SUPPORTED IN PART BY A WEAK VORT EMBEDDED WITH
WEST/NORTHWEST FLOW ALOFT...SURFACE-700 MB MOISTURE TRANSPORT AND
300-305K ISENTROPIC ASCENT WILL EXPAND INTO THE FORECAST
AREA...ESPECIALLY INTO SOUTHERN COUNTIES. HOWEVER...DESPITE THIS
PLUME OF MOISTURE AND ASSOCIATED MODEL QPF...MODEL SOUNDINGS REMAIN
QUITE DRY IN THE LOW LEVELS. THUS...CAPPED POPS AT SLIGHT CHANCE
ACROSS SOUTHERN COUNTIES TUESDAY NIGHT/WEDNESDAY MORNING...BUT
MOST/ALL AREAS COULD REMAIN RAIN-FREE.

WEDNESDAY...MODELS HAVE TRENDED TOWARD A STRONGER COLD FROPA FROM THE
NORTH/NORTHEAST TO THE SOUTH/SOUTHWEST. AS A RESULT...TEMPERATURES
COULD AVERAGE A FEW DEGREES COOLER AS COMPARED WITH TUESDAY...
ESPECIALLY ALONG THE COAST AND ACROSS INLAND AREAS ALONG/NORTH OF
THE SAVANNAH RIVER....STILL CLOSE TO NORMAL FOR THE END OF MARCH.
ALSO OF NOTE...SUFFICIENT MOISTURE/INSTABILITY COULD POOL AHEAD OF
THE COLD FRONT TO SUPPORT A FEW SHOWERS/THUNDERSTORMS ACROSS FAR
SOUTHERN/INLAND COUNTIES WEDNESDAY AFTERNOON INTO WEDNESDAY EVENING.

WEDNESDAY NIGHT AND THURSDAY...THE PROSPECTS TO A RETURN OF MOISTURE
AND ASSOCIATED PRECIPITATION FROM THE SOUTH/WEST WILL DEPEND ON THE
PROGRESS OF THE WEDNESDAY COLD FRONT AND THE ASSOCIATED STRENGTH OF
THE HIGH PRESSURE WHICH WILL BUILD FROM THE NORTHEAST. A MORE
PROGRESSIVE FRONT FOLLOWED BY STRONGER SUBSIDENCE/DRYING WILL
TRANSLATE TO LITTLE NO MOISTURE RETURN AND NO PRECIPITATION
WEDNESDAY NIGHT AND COULD EVEN WEAKEN THE SHORTWAVE TROUGH PROGGED
TO ADVANCE ACROSS THE REGION THURSDAY...PERHAPS RESULTING IN REDUCED
COVERAGE OF CONVECTION. TRENDED FORECASTS TOWARD A DRIER
SCENARIO...LIMITING SLIGHT CHANCE POPS TO FAR SOUTHERN/INLAND
COUNTIES WEDNESDAY NIGHT AND LIMITING POPS TO SLIGHT CHANCE/CHANCE
THURSDAY. IN TURN...REDUCED PRECIPITATION COVERAGE WILL TRANSLATE TO
HIGH TEMPERATURES 75-80F MOST AREAS THURSDAY.

&&

.LONG TERM /THURSDAY NIGHT THROUGH SUNDAY/...
AHEAD OF A COLD FRONT APPROACHING FROM THE NORTHWEST...EXPECT A WARM
AND RAIN-FREE DAY FRIDAY WITH HIGH TEMPS IN THE LOWER TO MID 80S.
THE COLD FRONT WILL PUSH INTO THE REGION EITHER LATE FRIDAY NIGHT OR
DURING THE DAY SATURDAY. MODELS HAVE TRENDED TOWARD A MORE
PROGRESSIVE COLD FRONT...ALTHOUGH PERSISTENT TIMING DIFFERENCES
OFFERED BY OPERATIONAL MODELS TRANSLATE TO UNCERTAINTY REGARDING
POPS...THE CHANCE FOR THUNDERSTORMS AND HIGH TEMPS SATURDAY. A
FASTER FROPA WILL SUPPORT LOWER POPS...A GREATLY REDUCED CHANCE FOR
THUNDERSTORMS AND A COOLING TREND STARTING SATURDAY. MAINTAINED
CHANCE POPS FOR SHOWERS/THUNDERSTORMS SATURDAY...BUT ADJUSTMENTS
COULD BE NEEDED WITHIN SUBSEQUENT FORECASTS. IN ANY CASE...POST
FROPA HIGH PRESSURE WILL PROVIDE SLIGHTLY COOLER THAN NORMAL
TEMPERATURES BY SUNDAY...PERHAPS EXTENDING INTO EARLY NEXT WEEK.

&&

.AVIATION /09Z MONDAY THROUGH FRIDAY/...
VFR AT BOTH KCHS AND KSAV THROUGH 06Z TUESDAY. HOWEVER...WITH AN
APPROACHING COLD FRONT THERE COULD BE A SHOWER OR TWO AT EITHER
SITE DURING THE EARLY-MID AFTERNOON...WITH A REMOTE POSSIBILITY
OF TSRA NEAR KSAV TO OCCUR. OTHERWISE...A WEST/SW FLOW WILL BE
GUSTY DURING THE LATE MORNING INTO THE AFTERNOON...DURING THE
TIME WHEN THE AXIS OF THE STRONGEST LOW LEVEL JET MOVES THROUGH IN
SYNC WITH PEAK HEATING.

EXTENDED AVIATION OUTLOOK...MAINLY VFR.

&&

.MARINE...
TODAY...A COLD FRONT APPROACHING THE CENTRAL AND SOUTHERN
APPALACHIANS EARLY THIS MORNING WILL NUDGE SUB-TROPICAL ATLANTIC
HIGH PRESSURE TO THE SE...AS THE FRONT REACHES OUR SC WATERS LATE
IN THE DAY. WARM ADVECTION WILL TEMPER THE AMOUNT OF MIXING OF A
35-45 KT LOW LEVEL JET SHIFTING INTO AND THROUGH THE WATERS LATE
THIS MORNING AND AFTERNOON. HOWEVER...THERE IS ENOUGH INTERACTION
OF THE LAND/SEA INTERFACE IN CHARLESTON HARBOR AND A TIGHT ENOUGH
GRADIENT ACROSS THE EASTERN PARTS OF AMZ350 TO ALLOW FOR FREQUENT
GUSTS TO REACH NEAR OR PAST 25 KT...WITH EVEN SOME 6 FOOT SEAS. FOR
THESE REASONS WE HAVE RAISED A SMALL CRAFT ADVISORY FOR THESE 2
BODIES OF WATERS BEGINNING AT 11 AM. THE OTHER WATERS WILL PEAK AT
15 OR 20 KT...SO NO ADVISORIES EXPECTED AT THIS TIME. MARINERS ARE
ADVISED THAT AFTERNOON T-STORMS WILL OCCUR IN ASSOCIATION WITH THE
APPROACHING COLD FRONT...AND A FEW OF THESE COULD BE ON THE STRONG
SIDE WITH GUSTY WINDS AND LIGHTNING STRIKES.

TONIGHT...CONDITIONS WILL STEADILY IMPROVE ACROSS THE WATERS AS
THE COLD FRONT MOVES THROUGH THE GEORGIA WATERS EARLY ON...TAKING
WITH IT LINGERING CONVECTION AND REPLACED BY AN ANEMIC REGION OF
HIGH PRESSURE THAT BUILDS INTO THE SE OVERNIGHT. GIVEN ONLY
MINIMAL COOL ADVECTION AT BEST...WINDS AND SEAS WILL STEADILY
IMPROVE THROUGHOUT THE NIGHT.

TUESDAY THROUGH SATURDAY...A BRIEF SURGE OF SUB-SCA NORTHEAST WINDS
ACROSS SC WATERS TUESDAY MORNING AND LIGHTER NORTH/NORTHWEST WINDS
ELSEWHERE WILL GIVE WAY TO SW WINDS ALL WATERS AS THE GRADIENT
TIGHTENS AHEAD OF ANOTHER APPROACHING COLD FRONT TUESDAY AFTERNOON
INTO TUESDAY NIGHT. MARINE LAYER STABILITY SHOULD HOLD GUSTS AND
ASSOCIATED SEAS BELOW SCA LEVELS THROUGH TUESDAY NIGHT. MODELS HAVE
TRENDED TOWARD A STRONGER COLD FROPA AND ASSOCIATED STRONGER HIGH
PRESSURE BUILDING FROM THE NORTHEAST WEDNESDAY MORNING...AND A SURGE
OF SCA GUSTS AROUND 25 KT/SEAS AS HIGH AS 3-4 FT COULD OCCUR FOR
SEVERAL HOURS ESPECIALLY ACROSS SC WATERS. AS THE HIGH PRESSURE
SHIFTS OFFSHORE...A WEAKER GRADIENT WILL TRANSLATE TO SUB-SCA WINDS
VEERING FROM E/SE TO S/SW WEDNESDAY NIGHT THROUGH THURSDAY NIGHT. A
TIGHTENING GRADIENT AHEAD OF AN APPROACHING COLD FRONT COULD SUPPORT
MARGINAL SCA WINDS FRIDAY AND FRIDAY NIGHT...ALTHOUGH MARINE LAYER
STABILITY COULD AGAIN LIMIT THIS POTENTIAL. AFTER COLD FROPA
SATURDAY...EXPECT A STRONGER SURGE OF NORTHEAST WINDS AS HIGH
PRESSURE BUILDS DOWN THE COAST ESPECIALLY SATURDAY NIGHT AND SUNDAY.
THE PROBABILITY FOR SCA WINDS/SEAS APPEARS RATHER HIGH THIS WEEKEND.

ALSO OF NOTE...HIGHER DEWPOINTS IN THE 60S ADVECTING OVER THE WATERS
COULD SUPPORT SOME SEA FOG ESPECIALLY THURSDAY THROUGH FRIDAY.
WILL CONTINUE TO ASSESS.

&&

.CHS WATCHES/WARNINGS/ADVISORIES...
GA...NONE.
SC...NONE.
MARINE...SMALL CRAFT ADVISORY FROM 11 AM THIS MORNING TO 7 PM EDT THIS
     EVENING FOR AMZ330-350.

&&

$$
SYNOPSIS...
NEAR TERM...
SHORT TERM...SPR
LONG TERM...SPR
AVIATION...
MARINE...


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