Area Forecast Discussion
Issued by NWS Charleston, SC

Home | Current Version | Previous Version | Text Only | Print | Product List | Glossary On
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
000
FXUS62 KCHS 270529
AFDCHS

AREA FORECAST DISCUSSION
NATIONAL WEATHER SERVICE CHARLESTON SC
129 AM EDT FRI MAR 27 2015

.SYNOPSIS...
ATLANTIC HIGH PRESSURE WILL WEAKEN AHEAD OF A STRONG COLD FRONT
APPROACHING TONIGHT AND SWEEPING THROUGH THE REGION FRIDAY.
COLDER HIGH PRESSURE WILL THEN BUILD FOR THE WEEKEND SUPPORTING A
POSSIBLE FREEZE FOR SOME INLAND AREAS EARLY SUNDAY. HIGH PRESSURE
THEN SHIFTS SOUTH OF THE REGION MONDAY...BEFORE ANOTHER COLD FRONT
MOVES THROUGH LATE MONDAY OR EARLY TUESDAY. HIGH PRESSURE WILL
THEN PREVAIL INTO THE MIDDLE OF NEXT WEEK.

&&

.NEAR TERM /UNTIL 6 AM THIS MORNING/...
WE ADJUSTED POPS SLIGHTLY TO ACCOUNT FOR THE SHORT WAVE PUSHING
THROUGH THE NEARBY ATLANTIC FROM SW TO NE OVERNIGHT. THE BULK OF
THE ACTIVITY WILL STAY OFFSHORE...BUT WE HAVE SLIGHT CHANCE AND
CHANCES POPS AS A RESULT...HIGHEST ON THE SC COAST.

TEMPS SHOULD BE LINGERING IN THE 60S OVERNIGHT WITH DEW POINTS
REMAINING ELEVATED IN THE LOWER 60S MOST AREAS. LOW LEVEL WIND
FIELDS SHOULD INCREASE OVERNIGHT WHICH DO NOT FAVOR FOG HOWEVER
THE RICH LOW LEVEL MOISTURE CONTENT MAY RESULT IN SOME FORM OF
ADVECTION STRATUS FROM THE GULF OR ATLC OVERNIGHT...PLUS NEARBY
SEA FOG OVER THE ATLANTIC WILL SKIRT COASTAL SECTIONS.

&&

.SHORT TERM /6 AM THIS MORNING THROUGH SUNDAY/...
FRIDAY...A SURFACE TROUGH WILL BE LOCATED ALONG THE MID ATLANTIC
AND SOUTHEAST COASTLINE BY DAYBREAK...WITH A STRONG COLD FRONT
STEADILY DESCENDING FROM THE UPSTATE REGION. THERE IS EVIDENCE OF
A DRY SLOT DEVELOPING ACROSS PORTIONS OF THE FORECAST AREA AHEAD
OF THE APPROACHING COLD FRONT DURING THE MORNING HOURS...LENDING
SOME UNCERTAINTY TO TIMING AND COVERAGE OF RAIN ASSOCIATED WITH
THE FRONTAL PASSAGE. CONSIDERING DEEP MOISTURE ACROSS THE
REGION...A STRONG MID/UPPER LEVEL JET INTENSIFYING OVER THE
AREA...AND DECENT CONVERGENCE ALONG THE FRONTAL ZONE...PREFER TO
INDICATE RAIN CHANCES INCREASING THROUGH THE MORNING HOURS INTO
THE LIKELY RANGE FOR MOST LOCATIONS. WILL ADVERTISE HIGHEST
POTENTIAL DURING THE LATE MORNING AND EARLY AFTERNOON...WITH
FAVORED LOCATIONS TO THE NORTH AND EAST...INCLUDING THE CHARLESTON
TRI COUNTY AND ALONG THE COASTLINE. RAIN CHANCES WILL THEN
DECREASE FROM WEST TO EAST LATER IN THE AFTERNOON...AS THE COLD
FRONT CROSSES THE FORECAST AREA AHEAD OF STRONG SHORTWAVE ENERGY
APPROACHING FROM THE WEST. HIGH TEMPERATURES ON FRIDAY WILL LIKELY
BE REACHED BY EARLY AFTERNOON...WITH A COOLING TREND INTO LATE
AFTERNOON. TEMPERATURES WILL PEAK IN THE MID 60S NORTH TO THE LOW
70S SOUTH.

FRIDAY NIGHT...THE COLD FRONT WILL RAPIDLY EXIT THE COASTLINE AND
PROCEED INTO THE ATLANTIC DURING THE EVENING HOURS...WITH STRONG
SURFACE HIGH PRESSURE BUILDING IN ITS WAKE. NORTHERN AND SOUTHERN
STREAM ENERGY WILL MERGE INTO AN AMPLIFYING UPPER TROUGH THAT
SHIFTS DIRECTLY OVER THE COAST AFTER MIDNIGHT. RATHER SIGNIFICANT
UPPER LEVEL FORCING COULD THUS SUPPORT A FEW ISOLATED SHOWERS
ACROSS NORTHERN BERKELEY AND CHARLESTON COUNTIES BETWEEN MIDNIGHT
AND DAWN SATURDAY MORNING. THERE REMAINS A SMALL POTENTIAL FOR
ISOLATED GRAUPEL OR SOFT HAIL CONSIDERING SUCH COLD AIR ALOFT AND
DECENT LARGE SCALE FORCING. HOWEVER...TEMPERATURES AT THE SURFACE
WILL REMAIN ABOVE FREEZING...WITH LOWS IN THE UPPER 30S TO LOW
40S. WIND SPEEDS APPEAR TO HIGH OVERNIGHT...AND GROUNDS WILL
LIKELY BE TOO WET...TO SUPPORT FROST DEVELOPMENT.

SATURDAY...THE DEEP UPPER LEVEL TROUGH WILL LINGER ALONG THE
EASTERN THIRD OF THE UNITED STATES...WHILE COLD CANADIAN HIGH
PRESSURE SHIFTS TOWARD THE EAST COAST. DESPITE DRY CONDITIONS AND
MOSTLY SUNNY SKIES...TEMPERATURES WILL REMAIN SUPPRESSED IN THE
UPPER 50S TO AROUND 60 DEGREES WITHIN BREEZY WEST/NORTHWEST
WINDS...10 TO 15 DEGREES BELOW SEASONAL NORMALS. ADDITIONAL
SHORTWAVE ENERGY SWEEPING SOUTHEAST FROM THE GREAT LAKES REGION
WILL HELP REINFORCE THE STALLED UPPER TROUGH OVERNIGHT...WITH THE
CENTER OF THE SURFACE HIGH SETTLING DIRECTLY OVER THE REGION. LOW
TEMPERATURES SATURDAY NIGHT WILL REACH THE LOW 30S INLAND TO THE
MID/UPPER 30S CLOSER TO THE COAST. A LIGHT FREEZE REMAINS POSSIBLE
FOR FAR INLAND COUNTIES...WHERE TEMPERATURES COULD REACH 32
DEGREES FOR AN HOUR OR TWO. IT SHOULD BE NOTED THAT IF
NIGHTTIME/EARLY MORNING WIND SPEEDS CAN DIMINISH MORE THAN
CURRENTLY FORECAST...THEN TEMPERATURES COULD BE EVEN COLDER AND
FROST WOULD ALSO BE A CONCERN.

SUNDAY...THE SURFACE HIGH WILL STEADILY DESCEND TOWARD THE
SOUTHEAST COAST...AS THE UPPER TROUGH MOVES INTO THE ATLANTIC.
TEMPERATURES WILL MODERATE JUST A DEGREE OR TWO...AND THUS DESPITE
ANOTHER SUNNY AND DRY DAY...EXPECT HIGHS TO ONLY REACH THE UPPER
50S TO LOW 60S.

&&

.LONG TERM /SUNDAY NIGHT THROUGH THURSDAY/...
THE MID LEVEL PATTERN WILL FLATTEN THROUGH THE EARLY AND MIDDLE
PARTS OF NEXT WEEK...ALTHOUGH A SUBTLE IMPULSE WILL MOVE THROUGH
LATE MONDAY/EARLY TUESDAY. THIS WILL FORCE A COLD FRONT THROUGH THE
FORECAST ZONES...ACCOMPANYING ONLY BY MODEST MOISTURE AND JUST
LIMITED CHANCES FOR SHOWERS. THE FRONT THEN WASHES OUT AND GIVES WAY
TO HIGH PRESSURE THROUGH MID WEEK. WARMER CONDITIONS WILL RETURN AS
EVEN THE AIR MASS BEHIND THE COLD FRONT IS OF PACIFIC ORIGIN SO
TEMPS SHOULD GET BACK NEAR OR EVEN ABOVE SEASONAL NORMS.

&&

.AVIATION /06Z FRIDAY THROUGH TUESDAY/...
KCHS...AS A SHORT WAVE PASSES ALONG THE SC COAST OVERNIGHT THERE
WILL BE A SHOWERS PASSING NEARBY OR THROUGH THE TERMINAL.
HOWEVER...ANY FLIGHT RESTRICTIONS WILL RESULT FROM DEVELOPING
STRATUS CLOUDS THAT DROP US INTO THE MVFR AFTER 09Z. ADDITIONAL
SUB-VFR CONDITIONS ALONG WITH SHOWERS AND MAYBE AN ISOLATED
T-STORM WILL ACCOMPANY A COLD FRONT...AS IT MOVES TOWARD AND
THROUGH THE AIRFIELD DURING THE LATE MORNING AND AFTERNOON. WEST
AND NW WINDS WILL BE GUSTY AT TIMES...PEAKING AROUND 20
KT...BEFORE FADING WITH SUNSET. VFR CONDITIONS WILL RETURN TONIGHT
BEHIND THE EXITING COLD FRONT...ALTHOUGH A FEW SHOWERS ARE STILL
POSSIBLE AS STRONG ENERGY ALOFT SWINGS THROUGH.

KSAV...IFR CEILINGS WILL PREVAIL AT THE AIRFIELD INTO FRIDAY
MORNING...WITH MOISTURE TRAPPED UNDERNEATH THE INVERSION AROUND
600 FT. HOWEVER...ISOLATED SHOWERS WILL SKIRT NEARBY AND COULD
OCCASIONALLY ALLOW FOR A TEMPORARY IMPROVEMENT BACK INTO THE MVFR
CATEGORY. A BETTER CHANCE FOR MVFR CONDITIONS THOUGH WILL PREVAIL
DURING AFTER 13Z AS THE INVERSION BREAKS AND SHOWERS AND MAYBE A
T-STORM MOVE THROUGH IN ASSOCIATION WITH A STRONG COLD FRONT. VFR
WEATHER WILL FINALLY RETURN LATE FRIDAY AND PERSIST INTO FRIDAY
NIGHT BEHIND THE COLD FRONT. GUSTY WESTERLY WINDS WILL PREVAIL
DURING MUCH OF THE DAYLIGHT HOURS FRIDAY...PEAKING AT 20-25 KT IN
THE AFTERNOON IN WAKE OF THE COLD FRONT.

EXTENDED AVIATION OUTLOOK...VFR WEATHER WILL PREVAIL FRIDAY NIGHT
INTO MONDAY...BEFORE POSSIBLE SUB-VFR WEATHER ACCOMPANIES ANOTHER
COLD FRONT LATE MONDAY.

&&

.MARINE...
OVERNIGHT...SOUTH WINDS WILL VEER SOUTHWEST AND INCREASE AHEAD OF
AN APPROACHING COLD FRONT. THE COMBINATION OF INCREASING WIND
GUSTS AND SLOWLY BUILDING SEAS WILL SUPPORT SMALL CRAFT ADVISORY
CONDITIONS OVER BOTH THE CHARLESTON COUNTY NEARSHORE WATERS AND
THE GEORGIA OFFSHORE WATERS EARLY FRIDAY MORNING. FLAGS WERE
RAISED FOR THESE TWO ZONES WITH THE LATE AFTERNOON FORECAST
PACKAGE. WINDS AND SEAS WILL BE A BIT LESS FOR THE REMAINING
MARINE ZONES WITH SEAS ONLY REACHING 3-5 FT WITH WINDS 15-20 KT.
SEA FOG IS STILL PREVALENT AS PER GOES-E SATELLITE IMAGERY AND
COASTAL OBSERVATIONS. SOME OF THE FOG WILL BE LOCALLY DENSE...BUT
INCREASING WINDS WILL LIKELY PREVENT IT FROM BECOMING TOO
WIDESPREAD AND THUS NO DENSE FOG ADVISORY AT THIS TIME.

FRIDAY...THE COMBINATION OF A TIGHT PRESSURE GRADIENT AHEAD AND
ALONG A COLD FRONT...AS WELL AS MIXING IN THE WAKE OF THE
FRONT...WILL SUPPORT GUSTS UP TO 25 KT AND SEAS PEAKING AT 6
FT FOR THE CHARLESTON COUNTY WATERS OFFSHORE GEORGIA MARINE
ZONES. SMALL CRAFT ADVISORIES HAVE THUS BEEN ISSUED FOR THESE
MARINE ZONES. ALTHOUGH WIND FIELDS WILL BE SOMEWHAT ELEVATED AHEAD
OF THE FRONT...SEA FOG WILL PERSIST UNTIL THE FRONT PASSES THROUGH
THE AREA. CONDITIONS WILL FALL BELOW ADVISORY THRESHOLDS FOR THE
CHARLESTON WATERS DURING THE AFTERNOON...YET PERSIST BEYOND 20 NM.

SATURDAY AND SUNDAY...SMALL CRAFT ADVISORY CONDITIONS WILL
CONTINUE FOR THE OUTER GEORGIA WATERS THROUGH THE MORNING
HOURS....ENDING BY EARLY AFTERNOON. STRONG CONTINENTAL HIGH
PRESSURE WILL BUILD FROM THE NORTHWEST AND SUPPORT A SURGE IN
NORTH/NORTHEAST WINDS AROUND DAYBREAK SUNDAY. HOWEVER...EXPECT
WINDS AND SEAS TO REMAIN BELOW ADVISORY CRITERIA. THE HIGH
PRESSURE CENTER WILL THEN SETTLE DIRECTLY OVER THE WATERS BY LATE
IN THE DAY...AND WINDS AND SEAS WILL DIMINISH ACCORDINGLY.

MONDAY AND TUESDAY...HIGH PRESSURE EARLY NEXT WEEK WILL GIVE WAY TO
A COLD FRONT THAT MOVES THROUGH BY EARLY TUESDAY...BEFORE BECOMING
DIFFUSE. MARINE CONDITIONS WILL BE AT OR LESS THAN 15 OR 20 KT FOR
WINDS AND SEAS WILL BE LESS THAN 3 TO 5 FT.

&&

.CHS WATCHES/WARNINGS/ADVISORIES...
GA...NONE.
SC...NONE.
MARINE...SMALL CRAFT ADVISORY FROM 5 AM EARLY THIS MORNING TO 1 PM EDT
     SATURDAY FOR AMZ374.
     SMALL CRAFT ADVISORY FROM 5 AM EARLY THIS MORNING TO 5 PM EDT
     THIS AFTERNOON FOR AMZ350.

&&

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


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