493
FXUS62 KCHS 190209
AFDCHS
AREA FORECAST DISCUSSION
NATIONAL WEATHER SERVICE CHARLESTON SC
1009 PM EDT MON MAR 18 2019
SYNOPSIS
A DRY COLD FRONT WILL MOVE THROUGH TONIGHT, FOLLOWED BY HIGH
PRESSURE. A TROUGH WILL DEVELOP OFFSHORE WEDNESDAY THEN MOVE
NORTHEAST AWAY FROM THE AREA. HIGH PRESSURE WILL THEN PREVAIL
THROUGH EARLY NEXT WEEK.
NEAR TERM /UNTIL 6 AM TUESDAY MORNING/
THE DRY COLD FRONT WILL PUSH INTO THE OCEAN BY MIDNIGHT NORTH
AND BEFORE 1 OR 2 AM SOUTH, ALLOWING FOR STRONGER HIGH PRESSURE
TO BUILD OUT OF THE ALLEGHENY PLATEAU REGION OF OHIO AND WEST
VIRGINIA. A STEADY SUPPLY OF COLDER AIR WILL FILTER IN THROUGH
THE NIGHT, ALLOWING FOR THE H85 0C ISOTHERM TO PENETRATE TO NEAR
THE NORTHERN TIER OF THE CWFA BY DAYBREAK. THE COLD ADVECTION
WILL BE OFFSET SOMEWHAT BY VARYING AMOUNTS AND THICKNESS OF
CIRRIFORM CLOUDS DUE TO THE UPPER JET THAT MOVES THROUGH THE
AREA. BECAUSE OF THESE CLOUDS WE CONTINUE TO SLOW OUR DECLINE IN
HOURLY TEMPS FROM PREVIOUS FORECASTS, AND HAVE ALSO KEPT MORE
CLOUD COVER THAN EARLIER.
THERE IS TOO MUCH MIXING FOR ANY FROST, ALTHOUGH LOWS WILL GET
DOWN TO THE UPPER 30S AND LOWER 40S MOST COMMUNITIES INLAND FROM
US-17 AND THE MID AND UPPER 40S ON THE BARRIER ISLANDS AND IN
DOWNTOWN CHARLESTON AND DOWNTOWN SAVANNAH.
LAKE WINDS: AS COLDER AIR MOVES ACROSS LAKE MOULTRIE THROUGH
THE NIGHT, AND STEADY ISALLOBARIC PRESSURE RISES SET IN, BETTER
MIXING WILL DEVELOP. WE HAVE N-NE WINDS AT A SOLID 15-20 KT, OR
JUST SHY OF ISSUING A LAKE WIND ADVISORY.
SHORT TERM /6 AM TUESDAY MORNING THROUGH THURSDAY/
COOL AND DRY HIGH PRESSURE WILL PERSIST NORTH OF THE AREA
TUESDAY INTO WEDNESDAY, KEEPING HIGHS IN THE LOW TO MID 60S AND
LOWS IN THE UPPER 30S TO LOWER 40S. MOSTLY CLEAR SKIES ARE
EXPECTED ASIDE FROM POSSIBLE STRATOCU ON WEDNESDAY AS A WEAK
COASTAL TROUGH DEVELOPS OFF THE SC COAST.
A CONSIDERABLE WARM-UP IS IN STORE FOR THURSDAY AS THE COLD AIR
ADVECTION DIMINISHES AND A MODERATE DOWNSLOPE FLOW SETS UP. HIGH
TEMPS WILL CLIMB INTO THE LOWER 70S.
LONG TERM /THURSDAY NIGHT THROUGH MONDAY/
A RATHER QUIET WEATHER PATTERN IS EXPECTED. STRONG CONTINENTAL HIGH
PRESSURE WILL PREVAIL ACROSS THE REGION THROUGH THE WEEKEND. MODELS
THEN HINT AT A SYSTEM APPROACHING FROM THE WEST LATE SUNDAY.
AVIATION /02Z TUESDAY THROUGH SATURDAY/
VFR THROUGH 00Z WEDNESDAY. N-NE WINDS WILL INCREASE BEHIND A
COLD FRONT OVERNIGHT AND CONTINUE GUSTY AT TIMES THROUGH MUCH OF
TUESDAY S STRONG HIGH PRESSURE BUILDS INTO THE AREA.
EXTENDED AVIATION: VFR.
MARINE
THE SURFACE PRESSURE GRADIENT WILL TIGHTEN TONIGHT AS HIGH
PRESSURE BUILDS INTO THE AREA BEHIND A COLD FRONT THAT MOVES
INTO THE WATERS AROUND MIDNIGHT NORTH AND BEFORE 2 AM SOUTH.
THIS WILL LEAD TO ELEVATED N AND NE WINDS AS HIGH AS 20-25 KT
WITH STRONGER GUSTS IN THE ATLANTIC OVERNIGHT. SMALL CRAFT
ADVISORIES REMAIN IN EFFECT FOR ALL WATERS WITH THE EXCEPTION
OF THE CHARLESTON HARBOR. WIND GUSTS IN THE HARBOR WILL GET
CLOSE TO ADVISORY CRITERIA AFTER 06Z, BUT THE FREQUENCY LOOKS
LIMITED ENOUGH NOT TO RAISE AN ADVISORY. WE WILL CONTINUE TO
EVALUATE WITH FUTURE FORECAST ISSUANCES. SEAS WILL BUILD TO 4-6
FEET BY DAYBREAK FOR THE NEARSHORE WATERS, 5-7 FT IN THE OFFSHORE
ZONE.
A RATHER PERSISTENT STRONG NORTHEAST GRADIENT IS EXPECTED
TUESDAY INTO WEDNESDAY AS HIGH PRESSURE REMAINS NORTH OF THE
WATERS. SMALL CRAFT ADVISORIES EXPECTED TO CONTINUE INTO AT
LEAST WEDNESDAY FOR ALL WATERS OUTSIDE CHARLESTON HARBOR.
LINGERING 6 FT OR GREATER SEAS WILL KEEP THE CHARLESTON
NEARSHORE WATERS IN ADVISORY TERRITORY THROUGH WEDNESDAY EVENING
AND THE OFFSHORE GA WATERS THROUGH THURSDAY AFTERNOON.
A PERIOD OF MODERATE OFFSHORE WINDS IS THEN EXPECTED THURSDAY
INTO FRIDAY AS HIGH PRESSURE BUILDS FROM THE WEST. AT THIS POINT
IT APPEARS WINDS/SEAS WILL REMAIN BELOW ADVISORY LEVELS EXCEPT
FOR THE AFOREMENTIONED SCA FOR THE OFFSHORE GA WATERS.
TIDES/COASTAL FLOODING
THE COMBINATION OF THE PERIGEE AND FULL MOON MIDWEEK ALONG WITH
MODERATE TO STRONG NORTHEAST WINDS THROUGH WEDNESDAY WILL
RESULT IN ELEVATED TIDES. COASTAL FLOOD ADVISORIES FOR MINOR OR
MAYBE MODERATE FLOODING ARE LIKELY WITH EACH HIGH TIDE TUESDAY,
WEDNESDAY, AND MAYBE THURSDAY IF THE ANOMALIES LINGER.
CHS WATCHES/WARNINGS/ADVISORIES
GA...NONE.
SC...NONE.
MARINE...SMALL CRAFT ADVISORY UNTIL 6 PM EDT WEDNESDAY FOR AMZ352-354.
SMALL CRAFT ADVISORY UNTIL 9 PM EDT THURSDAY FOR AMZ374.
SMALL CRAFT ADVISORY UNTIL MIDNIGHT EDT WEDNESDAY NIGHT FOR
AMZ350.
NEAR TERM...
SHORT TERM...JRL
LONG TERM...
AVIATION...
MARINE...
TIDES/COASTAL FLOODING...
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