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 270142
AFDCHS

AREA FORECAST DISCUSSION
NATIONAL WEATHER SERVICE CHARLESTON SC
942 PM EDT THU MAR 26 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 FRIDAY MORNING/...
A MID LEVEL SHORT WAVE LIFTING NE FROM THE SE GULF COAST REGION
THIS AFTERNOON WAS SLIDING THROUGH SE GEORGIA THIS EVENING AND
WILL MOVE OFFSHORE OVERNIGHT. LIGHT RAINS FALLING FROM A THICKER
MID DECK WERE DWINDLING AS THEY PASS OVER THE FORECAST AREA. THE
00Z KCHS SOUNDING INDICATED SOME DEEP LAYERS OF DRY AIR IN THE
SUB-CLOUD REGION WHICH WERE TENDING TO DIMINISH PCPN AS IT
EVAPORATES ON THE WAY DOWN. WE HAVE MADE SOME SIGNIFICANT CHANGES
LATER TONIGHT AS PRE-FRONTAL RAINS APPEAR TO STILL BE MAINLY OFF
TO THE WEST AT DAYBREAK. WE MAINTAINED 20-30 POPS OVERNIGHT WITH
NOT MUCH PROSPECT OF ANY SIGNIFICANT RAINS ANYWHERE. 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.

&&

.SHORT TERM /6 AM FRIDAY 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 /02Z FRIDAY THROUGH TUESDAY/...
VFR THROUGH THE EVENING...WITH INCREASING CHANCES FOR MVFR/IFR
CIGS LATER TONIGHT...ESPECIALLY CLOSING IN ON DAYBREAK. IN THE
NEAR TERM...LIGHT RAINS FALLING FROM RELATIVELY HIGH ALTOCUMULUS
MAY PRODUCE A PERIOD OF VERY LIGHT RAINS AROUND SAVANNAH THROUGH
MID EVENING AND PERHAPS LATER THIS EVENING AT KCHS. LATE TONIGHT
THERE COULD BE ADVECTION STRATUS IN WARM AIR ADVECTION AHEAD OF A
COLD FRONT. MVFR TO OCCASIONAL IFR CIGS ARE LIKELY ON FRIDAY AFTER
MID MORNING AS SHOWERS MOVE INTO THE COASTAL CORRIDOR. LATER IN
THE DAY SOME ENHANCED DRYING BEHIND THE FRONT COULD RESULT IN VFR
CONDITIONS AT KSAV WITH GUSTY WEST WINDS. AT KCHS...HIGH MOISTURE
CONTENT IN THE 1000-850 MB LAYER LIKELY TO KEEP LOWER CLOUDS MORE
RESILIENT TO SHIFTING WINDS IN THE LOWER LEVELS.

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

&&

.MARINE...
WE ALLOWED THE DENSE FOG ADVISORY TO EXPIRE AT 6 PM PER DISCUSSIONS
WITH BOTH THE CHARLESTON AND SAVANNAH PILOT DISPATCH OFFICES. THE
RISK FOR AT LEAST PATCHY DENSE FOG WILL LINGER THROUGH THE NIGHT
AS WINDS EVENTUALLY VEER AHEAD OF THE COLD FRONT.

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.

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 FRIDAY TO 1 PM EDT SATURDAY FOR
     AMZ374.
     SMALL CRAFT ADVISORY FROM 5 AM TO 5 PM EDT FRIDAY 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.