Area Forecast Discussion
Issued by NWS Charleston, SC

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000
FXUS62 KCHS 042121
AFDCHS

AREA FORECAST DISCUSSION
NATIONAL WEATHER SERVICE CHARLESTON SC
421 PM EST WED MAR 4 2015

.SYNOPSIS...
ATLANTIC HIGH PRESSURE WILL EXTEND ACROSS THE REGION TONIGHT. A
STRONG COLD FRONT WILL APPROACH FROM THE NORTHWEST ON THURSDAY AND
PASS OFF THE COAST EARLY THURSDAY EVENING. COLDER HIGH PRESSURE
WILL BUILD OVER THE AREA INTO SATURDAY...WITH A COASTAL TROUGH TO
DEVELOP OFFSHORE LATE IN THE WEEKEND. ANOTHER STORM SYSTEM COULD
IMPACT THE AREA EARLY NEXT WEEK.

&&

.NEAR TERM /UNTIL 6 AM THURSDAY MORNING/...
LOOKS LIKE A WARM AND HUMID NIGHT ACROSS THE REGION AHEAD OF THE
APPROACHING COLD FRONT AS THE LOW-LEVELS SHOULD REMAIN WELL MIXED
GIVEN THE PRE-FRONTAL JET TRAVERSING THE REGION. DO NOT
ANTICIPATE FOG TO BE A SIGNIFICANT PROBLEM OTHER THAN SEA FOG NEAR
THE COAST. HOWEVER...WILL HAVE TO WATCH FOR SOME LOW CLOUDS AND
POSSIBLE FOG MOVING IN FROM THE SOUTHWEST. AS FOR LOWS WE WENT ON
THE WARMER SIDE OF MOS GUIDANCE...MAINLY LOWER TO MID 60S MOST
LOCALES.

NOTE...SAVANNAH AIRPORT REACHED 84 DEGREES SO FAR TODAY WHICH TIES
THE RECORD HIGH FOR THE DATE.

&&

.SHORT TERM /6 AM THURSDAY MORNING THROUGH SATURDAY/...
THURSDAY...SURFACE HIGH PRESSURE WILL BE CENTERED OVER THE ATLANTIC
WHILE A COLD FRONT APPROACHES FROM THE WEST...AND EVENTUALLY PASSES
THROUGH THE FORECAST AREA IN THE AFTERNOON INTO THE EVENING.
TIGHTENING PRESSURE GRADIENT WILL ALLOW FOR BREEZY CONDITIONS TO
DEVELOP WITH SOUTHWEST WINDS EXPECTED TO GUST UP TO AROUND 25 MPH.
COMPRESSIONAL HEATING AHEAD OF THE FRONT AND DEEP SOUTHWEST FLOW
WILL ALLOW TEMPERATURES TO SOAR WELL ABOVE NORMAL AGAIN. HIGHS WILL
WILL BE IN THE UPPER 70S/AROUND 80 WITH CURRENT RECORDS EXPECTED TO
STAY SAFE. GIVEN UPPER FORCING AND INCREASING
MOISTURE...PRECIPITATION WILL ACCOMPANY THE FRONT. WEAK INSTABILITY
AND UNIMPRESSIVE LAPSE RATES WILL KEEP THUNDER TO A
MINIMUM...HOWEVER COULD NOT RULE OUT A COUPLE RUMBLES IN THE
AFTERNOON. THURSDAY NIGHT...NORTH/NORTHEAST FLOW WILL HELP USHER
MUCH COLDER AIR INTO THE REGION. LOW TEMPERATURES WILL DROP TO THE
MID 30S/LOW 40S. FAVORABLE MIXING PROFILES WILL ALLOW FOR GUSTY
WINDS OVER LAKE MOULTRIE. A LAKE WIND ADVISORY MAY BE NEEDED LATE
THURSDAY NIGHT INTO FRIDAY.

FRIDAY...HIGH PRESSURE WILL BUILD IN FROM THE NORTHWEST WHILE THE
FRONT REMAINS NEARLY STATIONARY WELL OFF THE SOUTHEAST COAST. GIVEN
FORECAST AREA IS SITUATED IN THE FAVORABLE RIGHT ENTRANCE REGION OF
UPPER JET AND FORCING FROM WEAK MID LEVEL DISTURBANCE EMBEDDED
WITHIN SOUTHWEST FLOW ALOFT...PRECIPITATION WILL BE POSSIBLE. ONE
FORECAST CONCERN WILL BE PTYPE FRIDAY MORNING INTO EARLY AFTERNOON.
SURFACE WET BULB PROGS SHOW THE FREEZING LINE NUDGING DOWN INTO OUR
NORTHERN SC ZONES. MOISTURE WILL BE ONE OF THE BIGGER
QUESTIONS...BUT FORECAST SOUNDINGS DO HINT AT A WINDOW WHERE
FREEZING DRIZZLE/LIGHT FREEZING RAIN WILL BE POSSIBLE. WILL
CERTAINLY NEED TO CONTINUE TO MONITOR TRENDS. TEMPERATURES WILL BE
WELL BELOW NORMAL WITH HIGHS EXPECTED TO BE 30-40 DEGREES COLDER
THAN PREVIOUS DAYS. FRIDAY NIGHT...MOISTURE WILL QUICKLY START TO
DRY OUT WITH TEMPERATURES EXPECTED TO DROP AROUND FREEZING. A FREEZE
WATCH MAY EVENTUALLY BE NEEDED.

SATURDAY...HIGH PRESSURE WILL REMAIN THE DOMINANT WEATHER FEATURE AT
THE SURFACE...WHILE NEARLY ZONAL FLOW REMAINS ALOFT. LACK OF
SIGNIFICANT FORCING AND MOISTURE WILL KEEP A DRY FORECAST IN TACT.
TEMPERATURES WILL BE MODERATE A BIT ALTHOUGH STILL BE BELOW NORMAL.
HIGHS WILL BE IN THE UPPER 50S.

&&

.LONG TERM /SATURDAY NIGHT THROUGH WEDNESDAY/...
THERE REMAINS A GOOD BIT OF UNCERTAINTY IN THE LONG TERM PERIOD
AS AN ACTIVE BAROCLINIC ZONE IS EXPECTED TO WAVER FROM THE
NORTHERN GULF COAST REGION AND FLORIDA LATE IN THE WEEKEND TO
GEORGIA AND THE CAROLINAS DURING EARLY TO MID WEEK. GLOBAL MODELS
DIFFER ON TIMING AND STRENGTH OF THESE IMPULSES MOVING THROUGH THE
SE STATES DURING THIS TIME. WITH PERIODS OF CLOUDS AND SHOWERS
POSSIBLE FROM TIME TO TIME...TEMPS WILL PROBABLY BE NEAR OR
SLIGHTLY BELOW CLIMO.

&&

.AVIATION /21Z WEDNESDAY THROUGH MONDAY/...
EXPECT VFR TO PERSIST THROUGH ABOUT 08Z WHEN LOW CLOUDS DEVELOP
AND/OR ADVECT IN FROM THE SOUTHWEST. SOME SEA FOG COULD ALSO
IMPACT THE TERMS...ESPECIALLY KCHS. WE KEPT CONDS NO WORSE THAN
MVFR FOR NOW BUT THEY COULD GO LIFR TOWARD DAYBREAK...ESPECIALLY
CIGS. THE OTHER ISSUE WILL BE GUSTY WINDS...MAINLY IN THE
AFTERNOON...DUE TO THE STRONG LOW- LEVEL JET OVER THE AREA AHEAD
OF AN APPROACHING COLD FRONT...AS WELL AS MARGINAL LOW LEVEL WIND
SHEAR TONIGHT AS SFC WINDS SUBSIDE TO LESS THAN 10 KT.

EXTENDED AVIATION OUTLOOK...ADDITIONAL FLIGHT RESTRICTIONS
POSSIBLE THURSDAY NIGHT INTO FRIDAY ALONG WITH GUSTY N TO NE
SURFACE WINDS. CONDITIONS EXPECTED TO IMPROVE OVER THE WEEKEND
WITH HIGH PRES AND VFR.

&&

.MARINE...
TONIGHT...WINDS WILL REMAIN ELEVATED GIVEN THE ENHANCED PRESSURE
GRADIENT/LOW-LEVEL JET AHEAD OF AN APPROACHING COLD FRONT.
HOWEVER...CONDITIONS WILL BE BELOW ADVISORY LEVELS...MAINLY DUE TO
THE LIMITED MIXING OVER THE COOL NEARSHORE WATERS. MAIN CONCERN IS
SEA FOG WHICH HAS ALL BUT DISIPATED THIS AFTERNOON EXCEPT ALONG
THE CHARLESTON COUNTY COAST. SINCE WE EXPECT MORE LOW CLOUDS/FOG
TO DEVELOP THIS EVENING AS LOW-LEVEL MOISTURE INCREASES AGAIN WE
CONTINUED WITH A DENSE FOG ADVISORY FOR ALL NEARSHORE WATERS BUT
THE BEST CHANCES OF DENSE FOG SHOULD REMAIN CLOSE TO THE COAST.

THURSDAY THROUGH MONDAY NIGHT...MARINE CONDITIONS ARE EXPECTED TO
DETERIORATE EARLY IN THE PERIOD AS A COLD FRONT APPROACHES AND
PASSES THROUGH THE WATER THURSDAY EVENING. WARM MOIST FLOW AHEAD OF
THE FRONT WILL BE FAVORABLE FOR SEA FOG DEVELOPMENT... THUS HAVE
MAINTAINED MENTION IN THE FORECAST. AS FRONT PASSES THROUGH THE
WATERS...STRONG COLD ADVECTION WILL ENSUE PROVIDING FAVORABLE MIXING
PROFILES. THIS WILL ALLOW FOR STRONGER WINDS ALOFT TO BE MIXED TO
THE SURFACE. HAVE ISSUED A GALE WATCH FOR NEARSHORE CHARLESTON
COUNTY WATERS AND OUTER GA WATERS LATE THURSDAY NIGHT INTO FRIDAY
MORNING...AND SMALL CRAFT ADVISORIES FOR THE REMAINING COASTAL
WATERS INCLUDING THE CHARLESTON HARBOR. CONDITIONS WILL SUBSIDE ON
FRIDAY AFTERNOON AS HIGH PRESSURE BUILDS IN AND THE PRESSURE
GRADIENT RELAXES. MARINE CONDITIONS WILL REMAIN FAIRLY BENIGN THE
REMAINDER OF THE WEEKEND INTO EARLY NEXT WEEK WITH WINDS/SEAS BELOW
SMALL CRAFT ADVISORY CRITERIA.

&&

.CLIMATE...
RECORD HIGHS FOR 4 MARCH...
KCHS... 83/2004
KCXM... 80/1899
KSAV... 84/1955 /RECORD TIED TODAY/

RECORD HIGHS FOR 5 MARCH...
KCHS... 85/1997
KCXM... 84/1923
KSAV... 86/1955

RECORD LOW MAXIMUMS FOR 6 MARCH...
KCHS... 43/1960
KCXM... 43/1960
KSAV... 42/1901

&&

.CHS WATCHES/WARNINGS/ADVISORIES...
GA...NONE.
SC...NONE.
MARINE...SMALL CRAFT ADVISORY FROM 10 PM THURSDAY TO 1 PM EST FRIDAY
     FOR AMZ330.
     DENSE FOG ADVISORY FROM 7 PM THIS EVENING TO 11 AM EST
     THURSDAY FOR AMZ352-354.
     SMALL CRAFT ADVISORY FROM 10 PM THURSDAY TO 4 PM EST FRIDAY
     FOR AMZ352.
     DENSE FOG ADVISORY UNTIL 11 AM EST THURSDAY FOR AMZ350.
     GALE WATCH FROM THURSDAY EVENING THROUGH FRIDAY MORNING FOR
     AMZ350.
     GALE WATCH FROM LATE THURSDAY NIGHT THROUGH FRIDAY MORNING FOR
     AMZ374.
     SMALL CRAFT ADVISORY FROM 1 AM TO 4 PM EST FRIDAY FOR AMZ354.

&&

$$
SYNOPSIS...
NEAR TERM...RJB
SHORT TERM...ECT
LONG TERM...
AVIATION...ECT/RJB
MARINE...ECT/RJB
CLIMATE...


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