965
FXUS62 KCHS 202318
AFDCHS
AREA FORECAST DISCUSSION
NATIONAL WEATHER SERVICE CHARLESTON SC
618 PM EST WED NOV 20 2024
SYNOPSIS
A STRONG COLD FRONT WILL MOVE THROUGH THE AREA THIS EVENING.
CANADIAN HIGH PRESSURE WILL BUILD ACROSS THE AREA THURSDAY AND
WILL REMAIN THE PRIMARY FEATURE THROUGH EARLY NEXT WEEK.
NEAR TERM /UNTIL 6 AM THURSDAY MORNING/
TONIGHT: SATELLITE AND 20/2245Z MESOANALYSIS SHOWED THE COLD
FRONT WAS LOCATED ACROSS THE EASTERN MIDLANDS AND FAR INTERIOR
SOUTHEAST GEORGIA AND EXTENDING SOUTH INTO APALACHEE BAY. THE
FRONT IS MARKED BY A STRONG STABILITY GRADIENT AND WILL CONTINUE
TO MOVE RAPIDLY EAST AND OFFSHORE OVER THE NEXT FEW HOURS. STRONG
POST-FRONTAL COLD AIR ADVECTION WILL FOLLOW THE FRONT BY SEVERAL
HOURS, BUT WILL USHER IN A SLIGHTLY MODIFIED CP AIRMASS AS THE
NIGHT PROGRESSES. LOWS LOOK TO BOTTOM OUT IN THE LOWER 40S WELL
INLAND TO THE UPPER 40S/NEAR 50 AT THE BEACHES. GUSTY NORTHWEST
WINDS WILL MAKE IT FEEL EVEN COOLER BY DAYBREAK THURSDAY WITH
WIND CHILLS DROPPING INTO THE UPPER 30S/LOWER 40S.
LAKE WINDS: IMPRESSIVE AND DEEP MIXING PROFILES WILL DEVELOP ON
LAKE MOULTRIE OVERNIGHT AS STRONG POST-FRONTAL COLD AIR
ADVECTION ENSUES WITH THE PASSAGE OF THE COLD FRONT. RAP
SOUNDINGS SUPPORT AS MUCH AS 35-40 KT OF WIND AT THE TOP OF THE
MIXED LAYER BY MIDNIGHT SUPPORTING WINDS 20-25 KT WITH GUSTS AT
LEAST TO 30 KT, IF NOT A TAD HIGHER AT TIMES. WINDS WERE
SLIGHTLY WITH WAVES OVER THE OPEN LAKE WATERS BUILDING TO 2-3
FT. THE COMBINATION OF INCREASING WINDS AND BUILDING WAVES WILL
MAKE FOR DANGEROUS WAVE ACTION ON THE LAKE TONIGHT WITH THE
WORST CONDITIONS OCCURRING OVER THE CENTRAL AND EASTERN PORTIONS
OF THE LAKE. BOATERS ARE ENCOURAGED TO REMAIN OFF THE LAKE.
SHORT TERM /6 AM THURSDAY MORNING THROUGH SATURDAY/
A POWERFUL CLOSED UPPER LOW WILL SWING THROUGH THE GREAT LAKES
ON THURSDAY THEN STALL NEAR NEW ENGLAND FRIDAY INTO SATURDAY.
MEANWHILE, STRONG HIGH PRESSURE WILL EXPAND ACROSS THE SOUTHEAST
AT THE SURFACE. DRY WEATHER AND BELOW NORMAL TEMPS EXPECTED.
HIGHS WILL TOP OUT IN THE UPPER 50S TO LOWER 60S ON THURSDAY,
THEN ONLY REACH THE MID/UPPER 50S ON FRIDAY. SATURDAY SHOULD BE
A TAD WARMER WITH HIGHS IN THE LOWER 60S. LOWS BOTH NIGHTS COULD
DIP INTO THE MID TO UPPER 30S INLAND, THOUGH WE EXPECT ENOUGH
OVERNIGHT WIND TO PREVENT WIDESPREAD FROST DEVELOPMENT.
LAKE WINDS: GUSTY WEST WINDS ARE EXPECTED TO PERSIST OVER LAKE
MOULTRIE THURSDAY INTO THURSDAY EVENING DURING WHICH WE HAVE A
LAKE WIND ADVISORY IN EFFECT.
LONG TERM /SATURDAY NIGHT THROUGH WEDNESDAY/
SURFACE HIGH PRESSURE WILL MAINTAIN INFLUENCE OVER THE LOCAL
WEATHER SUNDAY THROUGH TUESDAY. NOT MUCH GOING ON UPSTAIRS WITH
RELATIVELY ZONAL FLOW. RAIN-FREE FORECAST IN PLACE WITH WARMING
TEMPERATURES THROUGH THE PERIOD. MAIN FORECAST CONCERN REMAINS
THE POTENTIAL FOR FROST LATE SATURDAY NIGHT/EARLY SUNDAY MORNING
AS IDEAL RADIATIONAL COOLING CONDITIONS ALLOW TEMPERATURES TO
FALL TO THE MID/UPPER 30S INLAND OF THE COAST. FROST IS
POSSIBLE, MAINLY OVER FAR INTERIOR LOCATIONS.
AVIATION /00Z THURSDAY THROUGH MONDAY/
21/00Z TAF DISCUSSION:
KCHS/KJZI/KSAV: THE APPROACHING COLD FRONT WILL CLEAR ALL
TERMINALS BY 02Z WITH GUSTY NORTHWEST WINDS DEVELOPING WITH ITS
PASSAGE. THESE GUSTY WINDS WILL PERSIST INTO THE DAY THURSDAY.
ANY LINGERING LOW CLOUDS SHOULD SCOUR OUT WITH FROPA. VFR WILL
PREVAIL FOR THE ENTIRE 00Z TAF PERIOD.
EXTENDED AVIATION OUTLOOK: VFR. GUSTY WEST WINDS ARE EXPECTED
THURSDAY AND FRIDAY.
MARINE
TONIGHT: STRONG POST-FRONTAL COLD AIR ADVECTION WILL OVERSPREAD
THE WATERS OVERNIGHT WITH THE PASSAGE OF A COLD FRONT.
NORTHWEST WINDS WILL INCREASE TO 25 KT WITH GUSTS TO 30 KT FOR
THE WATERS WITHIN 20 NM AND 25-30 KT WITH GUSTS 35 KT OVER
GEORGIA OFFSHORE WATERS OUT 20-60 NM. A GALE WARNING REMAINS IN
EFFECT FOR THE GEORGIA OFFSHORE WATERS BEYOND 20 NM WITH HIGH-
END SMALL CRAFT ADVISORIES FOR ALL NEARSHORE LEGS, INCLUDING
CHARLESTON HARBOR. GUSTS COULD GET CLOSE TO GALE WARNING
CRITERIA ACROSS THE NEARSHORE WATERS, MAINLY WITHIN 10-20 NM,
BUT THESE CONDITIONS LOOK INFREQUENT ENOUGH TO NOT TO JUSTIFY AN
UPGRADE TO A GALE WARNING AT THIS TIME. THIS WILL BE CLOSELY
WATCHED THIS EVENING AND OVERNIGHT, HOWEVER. FOR CHARLESTON
HABOR, NORTHWEST WINDS WILL INCREASE TO 20-25 KT WITH GUSTS TO
30 KT AND WAVES BUILDING 2-3 FT.
THURSDAY THROUGH MONDAY: GUSTY WEST WINDS WILL PERSIST OVER THE
COASTAL WATERS THURSDAY THROUGH FRIDAY NIGHT, MAINTAINING THE
ONGOING SMALL CRAFT ADVISORIES. FOR THE CHARLESTON HARBOR, GUSTS
TO 25 KNOTS ARE EXPECTED THURSDAY THROUGH FRIDAY. IMPROVEMENT
IS EXPECTED SATURDAY WITH WINDS AND SEAS REMAINING BELOW
ADVISORY LEVELS THROUGH MONDAY.
CHS WATCHES/WARNINGS/ADVISORIES
GA...NONE.
SC...LAKE WIND ADVISORY FROM 10 PM THIS EVENING TO 11 PM EST
THURSDAY FOR SCZ045.
MARINE...SMALL CRAFT ADVISORY UNTIL 6 PM EST FRIDAY FOR AMZ330.
SMALL CRAFT ADVISORY UNTIL 7 AM EST SATURDAY FOR AMZ350-352-
354.
GALE WARNING UNTIL 7 AM EST THURSDAY FOR AMZ374.
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