897
FXUS62 KCHS 210651
AFDCHS
AREA FORECAST DISCUSSION
NATIONAL WEATHER SERVICE CHARLESTON SC
151 AM EST THU FEB 21 2019
SYNOPSIS
A WARM FRONT WILL LIFT NORTH THROUGH THE AREA TONIGHT. A NEARLY
STATIONARY FRONT WILL THEN MEANDER IN THE VICINITY THROUGH
SATURDAY. A COLD FRONT WILL SWEEP THROUGH FROM THE WEST LATE
SUNDAY, FOLLOWED BY HIGH PRESSURE ON MONDAY. A LOW PRESSURE
SYSTEM COULD AFFECT THE AREA DURING THE MIDDLE OF NEXT WEEK.
NEAR TERM /UNTIL 6 AM THIS MORNING/
AS OF 145 AM: I WILL UPDATE THE FORECAST TO EXPAND DENSE FOG TO
ALL ZONES. DENSE FOG ADVISORIES HAVE BEEN ISSUED FOR ALL ZONES,
EXPECT THE OUTER GA WATERS.
PREVIOUS DISCUSSION:
LATE EVENING UPDATE: WE OPTED FOR DENSE FOG ADVISORIES ACROSS
ALL OF SOUTHEAST GA AND BORDERING ZONES IN SOUTHERN SC. THE
APPROACH OF THE WARM FRONT SHOULD RESULT IN LOWERING STRATUS
RESULTING IN A GENERAL INCREASE IN DENSE FOG. ADVISORIES FOR
THE CHARLESTON AREA WILL LIKELY BE NEEDED LATER TONIGHT.
AT MID EVENING, WARM AIR ADVECTION PROCESSES ATOP A STABLE, DAMP
AND COOL SURFACE BASED LAYER WAS RESULTING IN LOWER STRATUS
DECKS ACROSS THE REGION AND MORE REPORTS OF FOG WITH MANY AREAS
IN GA BELOW 3 NM VSBYS AT 9 PM. THE TABLE APPEARS SET FOR AREAS
OF DENSE FOG LATER TONIGHT WITH GA GETTING IN ON IT FIRST AND SC
ZONES FOLLOWING SUIT LATER IN THE NIGHT AND PERHAPS CLOSER TO
DAYBREAK AROUND THE CHARLESTON AREA. THE PROGRESSION OF THE WARM
FRONT WILL BE SLOW OVERNIGHT AND THIS SHOULD ENHANCE THE AREAL
COVERAGE OF FOG EVENTUALLY. TEMPS HAVE STILL BEEN INFLUENCE
GREATLY BY THE WEDGE PATTERN WITH READINGS IN THE MID/UPPER 40S
FAR NORTHWEST AREAS TO THE LOWER 60S TO THE SOUTH OF I-16. WE
CONTINUE TO SHOW SLOWLY RISING TEMPS SC ZONES BUT AT A MORE
MODEST CLIP OVERNIGHT. RAINS HAVE GENERALLY ENDED AND WE HAVE
REMOVED POPS MOST AREAS FOR THE REMAINDER OF THE NIGHT.
SHORT TERM /6 AM THIS MORNING THROUGH SATURDAY/
THE FORECAST AREA WILL BE IN THE WARM SECTOR ON THURSDAY FOLLOWING
THE PASSAGE OF A WARM FRONT EARLIER IN THE DAY. THE HIGHLIGHT OF THE
DAY WILL BE TEMPERATURES. ALTHOUGH NOT EXPECTED TO REACH OR EXCEED
RECORDS, HIGHS ARE FORECAST TO BE WITHIN A FEW DEGREES OF THOSE
VALUES GENERALLY IN THE UPPER 70S/LOW 80S. OTHERWISE, THERE IS SOME
WEAK ENERGY ALOFT THAT COULD HELP SPUR SOME SHOWERS INLAND, BUT
OVERALL THE RAIN POTENTIAL DOESN'T APPEAR IMPRESSIVE. KEPT POPS
LIMITED TO 20-30%. THURSDAY NIGHT, CONDITIONS APPEAR FAVORABLE FOR
FOG DEVELOPMENT GIVEN THE JUICY AIRMASS IN PLACE (SURFACE DEW POINTS
IN THE LOW 60S).
ON FRIDAY, A WEDGE OF HIGH PRESSURE WILL BUILD DOWN THE MID-ATLANTIC
STATES, SENDING A BACKDOOR COLD FRONT THROUGH THE LOCAL AREA. THIS
FRONT WILL STALL IN THE VICINITY, THEN LIFT BACK NORTH AGAIN AS A
WARM FRONT ON SATURDAY. UPPER LEVEL FORCING IS LACKING, HOWEVER
GIVEN THE BOUNDARY LINGERING NEARBY THROUGH LATE WEEK, RAIN CHANCES
WILL REMAIN IN THE FORECAST. RAINFALL TOTALS SHOULD NOT AMOUNT TO
MUCH.
LONG TERM /SATURDAY NIGHT THROUGH WEDNESDAY/
A POTENT COLD FRONT WILL SWEEP THROUGH THE AREA SUNDAY AFTERNOON
THOUGH ONLY SCATTERED SHOWERS ARE EXPECTED TO ACCOMPANY IT.
STRONG WARM AIR ADVECTION AHEAD OF THE FRONT WILL PRODUCE HIGH
TEMPS IN THE UPPER 70S ON SUNDAY. SOMEWHAT COOLER WEATHER IS IN
STORE FOR MONDAY THROUGH WEDNESDAY AS A SERIES OF HIGH PRESSURE
AREAS MOVE INTO THE AREA. A GULF LOW PRESSURE SYSTEM COULD BRING
SOME RAIN TO THE AREA TUESDAY AND TUESDAY NIGHT.
AVIATION /07Z THURSDAY THROUGH MONDAY/
STRATUS BUILD DOWN IS EXPECTED TO CONTINUE THROUGH DAYBREAK.
LIFR TO VLIFR FOG IS FORECAST TO LINGER AT KCHS AND KSAV INTO
THE EARLY DAYLIGHT HOURS. FOG IS EXPECTED TO DISSIPATE DURING
THE MID TO LATE MORNING HOURS, WITH THE CEILING IMPROVING TO VFR
BY MID DAY. DEEPENING MIXING SHOULD RESULT IN STEADY SW WINDS
DURING THE DAY. FOG AND LOW CEILINGS ARE FORECAST TO REDEVELOP
AGAIN TONIGHT.
EXTENDED AVIATION OUTLOOK: RESTRICTIONS IN LOW CEILINGS AND/OR
REDUCED VISIBILITY LIKELY THURSDAY NIGHT THROUGH SATURDAY.
MARINE
LATE EVENING UPDATE: RECENT REPORT HAD DENSE FOG AT THE SAVANNAH
RIVER ENTRANCE AND GIVEN THIS TREND AND LATEST DEW POINTS UP TO
64 DEGREES AT GRAYS REEF, MARINE DENSE FOG ADVISORIES HAVE BEEN
ISSUED. CHARLESTON COUNTY WATERS WILL LIKELY GET IN ON THE FOG
LATER TONIGHT AND WE EXPECT ADVISORIES WILL LIKELY BE HOISTED
OVERNIGHT FOR THE CHARLESTON HARBOR.
TONIGHT: A WARM FRONT OFF THE IMMEDIATE COAST THIS EVENING WILL
MOVE ONSHORE, THEN LIFT NORTH OVERNIGHT. WE HAVE LOWERED THE
SCA FOR CHARLESTON WATERS ON THE LATE EVENING UPDATE. HOWEVER,
SEAS WILL TAKE LONGER TO SUBSIDE ACROSS THE GA WATERS BEYOND 20
NM AND THAT ADVISORY WILL CONTINUE THROUGH THE NIGHT.
SEA FOG: DENSE MARINE FOG WILL LIKELY PERSIST INTO THURSDAY AND
THURSDAY NIGHT. BY MIDDAY FRIDAY THE WINDS WILL BE NORTHEAST
WHICH IS LESS FAVORABLE. EXPECT DENSE FOG ADVISORIES TO BE
ISSUED AND/OR EXTENDED TO COVER THESE TIME PERIODS ON THURSDAY.
THURSDAY THROUGH MONDAY: SOUTHERLY WINDS ON THURSDAY WILL BECOME
NORTHEAST LATE FRIDAY AS A BACKDOOR COLD FRONT DROPS THROUGH THE
AREA. A TIGHTENED GRADIENT ACROSS THE CHARLESTON COUNTY WATERS COULD
RESULT IN MARGINAL SCA CONDITIONS FOR A SHORT PERIOD FRIDAY NIGHT.
THE AFOREMENTIONED FRONT WILL THEN LIFT BACK NORTH SATURDAY, VEERING
THE WINDS TO THE SOUTH. MORE WIDESPREAD SCA CONDITIONS ARE POSSIBLE
SUNDAY AHEAD OF A COLD FRONT.
CHS WATCHES/WARNINGS/ADVISORIES
GA...DENSE FOG ADVISORY UNTIL 10 AM EST THIS MORNING FOR GAZ087-088-
099>101-114>119-137>141.
SC...DENSE FOG ADVISORY UNTIL 10 AM EST THIS MORNING FOR SCZ040-
042>045-047>052.
MARINE...DENSE FOG ADVISORY UNTIL 4 PM EST THIS AFTERNOON FOR AMZ350-
352-354.
SMALL CRAFT ADVISORY UNTIL 1 PM EST THIS AFTERNOON FOR AMZ374.
DENSE FOG ADVISORY UNTIL 11 AM EST THIS MORNING FOR AMZ330.
NEAR TERM...NED
SHORT TERM...
LONG TERM...
AVIATION...NED
MARINE...
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