520
FXUS62 KCHS 211509
AFDCHS
AREA FORECAST DISCUSSION
NATIONAL WEATHER SERVICE CHARLESTON SC
1009 AM EST SAT DEC 21 2024
SYNOPSIS
ARCTIC HIGH PRESSURE WILL BUILD ACROSS THE REGION TODAY INTO
MONDAY. A COASTAL TROUGH WILL THEN DEVELOP NEARBY AND PERSIST
THROUGH MUCH OF NEXT WEEK.
NEAR TERM /THROUGH TONIGHT/
THE WINTER SOLSTICE BEGAN AT 4:21 AM EST.
TODAY: ALOFT, A FAST MOVING SHORTWAVE WILL QUICKLY DIVE INTO
THE TENNESSEE VALLEY AND CROSS THE SOUTHERN APPALACHIANS LATE IN
THE DAY WITHIN THE BROADER NORTHWEST FLOW. AT THE SURFACE, COLD
HIGH PRESSURE WILL CONTINUE TO BUILD IN THROUGH THE DAY. OTHER
THAN A FEW MID-LEVEL CLOUDS THAT COULD ACCOMPANY THE
AFOREMENTIONED SHORTWAVE LATER IN THE DAY, SKIES WILL REMAIN
MOSTLY CLEAR WITH PLENTIFUL SUNSHINE. HOWEVER, EVEN WITH THAT
SUNSHINE, GIVEN NORTHERLY WINDS AT 10 TO 15 MPH AND GUSTY,
TEMPERATURES WILL BE ON THE CHILLY SIDE. HIGHS ARE EXPECTED TO
TOP OUT IN THE LOWER TO MID 50S, OR ABOUT 7-8 DEGREES BELOW
NORMAL FOR THIS TIME OF YEAR.
LAKE WINDS: AS MIXING HEIGHTS TAP INTO SOME OF THOSE STRONGER
WINDS LATE THIS MORNING AND EARLY AFTERNOON, NORTHERLY WINDS
ACROSS LAKE MOULTRIE WILL HIT 15-20 KT. THIS IS JUST SHORT OF
ADVISORY THRESHOLDS.
TONIGHT: THE SURFACE HIGH WILL REMAIN CENTERED ACROSS THE OHIO
VALLEY AND EASTERN GREAT LAKES REGION, PRODUCING A CLEAR AND
COLD NIGHT FOR THE FORECAST AREA. WE WILL SEE A DECENT
NORTHEASTERLY ORIENTED GRADIENT WHICH WILL ALLOW US TO MAINTAIN
AT LEAST SOME LIGHT FLOW THROUGH THE NIGHT. IT WON'T BE A
PERFECT RADIATIONAL COOLING NIGHT, BUT WE WILL STILL LIKELY SEE
SOME UPPER 20S AND LOW 30S FOR INLAND AREAS, RANGING TO THE MID
TO UPPER 30S AT THE BEACHES.
SHORT TERM /SUNDAY THROUGH TUESDAY/
HIGH PRESSURE WILL CONTINUE TO BUILD INTO THE AREA ON SUNDAY.
MID LEVEL TROUGH EXITS TO THE EAST, LEAVING NORTHWESTERLY FLOW
IN PLACE ALOFT. DESPITE FULL SUNSHINE, IT WILL BE THE COOLEST
DAY OF THE SET WITH HIGHS TOPPING OUT IN THE UPPER 40S TO LOWER
50S. LOWS SUNDAY NIGHT WILL FALL TO THE MID/UPPER 20S INLAND OF
THE COAST. THERE WILL BE A LITTLE WIND PRESENT WHICH WILL LEAD
TO WIND CHILLS IN THE 20- 25F RANGE, WITH A COUPLE SPOTS IN THE
UPPER TEENS POSSIBLE. A COLD WEATHER ADVISORY IS NOT OUT OF THE
QUESTION FOR A PORTION OF THE AREA, BUT IT SEEMS MARGINAL AT
THIS POINT.
HIGH PRESSURE WILL PERSIST INLAND MONDAY AND TUESDAY, WHILE A
COASTAL TROUGH DEVELOPS OFFSHORE. ALOFT, RIDGING WILL BRIEFLY
TRAVERSE OVERHEAD FOLLOWED BY A WEAK SHORTWAVE. ISOLATED TO
SCATTERED SHOWERS WILL BE POSSIBLE, ESPECIALLY NEAR THE COAST,
MONDAY NIGHT INTO TUESDAY. HIGHS IN THE LOW/MID 50S MONDAY WILL
GAIN A FEW DEGREES FOR TUESDAY. LOWS MONDAY NIGHT WILL RANGE
FROM THE MID/UPPER 30S FAR INLAND TO LOW/MID 40S CLOSER TO THE
COAST.
LONG TERM /TUESDAY NIGHT THROUGH FRIDAY/
HIGH PRESSURE WILL EXTEND INTO THE AREA MID TO LATE WEEK, WHILE
A COASTAL TROUGH LINGERS OFFSHORE. RIDGING LARGELY PREVAILS
ALOFT, WITH A COUPLE OF WEAKENING SHORTWAVES BRIEFLY MOVING
THROUGH THE REGION. PRECIP COVERAGE IS A BIT UNCLEAR BUT WITH
PWAT PROGS OF OVER AN INCH AND SOME SIGNS OF LIFT PRESENT,
MAINTAINED 20-30% POPS. TEMPS WILL TREND ON THE WARMER SIDE OF
NORMAL.
AVIATION /15Z SATURDAY THROUGH WEDNESDAY/
VFR CONDITIONS WILL PREVAIL AT KCHS, KJZI, AND KSAV THROUGH 12Z
SUNDAY. GUSTY NORTHERLY WINDS LATE THIS MORNING AND EARLY THIS
AFTERNOON.
EXTENDED AVIATION OUTLOOK: FLIGHT RESTRICTIONS ARE POSSIBLE IN
SHOWERS AND LOW CLOUDS ASSOCIATED WITH A COASTAL TROUGH TUESDAY
AND WEDNESDAY.
MARINE
WE EXTENDED THE SMALL CRAFT ADVISORY FOR ALL ATLANTIC WATERS
THROUGH 1 PM BASED ON LATEST TRENDS.
TODAY THROUGH TONIGHT: NORTHERLY FLOW WILL SUBSIDE A BIT
THROUGH MID MORNING, ALLOWING THE ONGOING SMALL CRAFT ADVISORIES
TO COME DOWN. WINDS WILL THEN REMAIN BELOW ADVISORY CRITERIA
THROUGH THE EVENING. WINDS WILL RAMP BACK UP LATE TONIGHT AS THE
HIGH BUILDS IN AND PRODUCES AN ENHANCED GRADIENT ACROSS THE
LOCAL WATERS. WINDS WILL SURGE BACK TO 15-20 KNOTS, WITH A FEW
GUSTS TO 25 KNOTS POSSIBLE LATE TONIGHT. CONDITIONS COULD BECOME
MARGINALLY SUPPORTIVE OF SMALL CRAFT ADVISORIES AGAIN. OVERALL,
SEAS ARE EXPECTED TO AVERAGE 3-5 FEET.
SUNDAY THROUGH THURSDAY: NORTHEAST WINDS WILL AVERAGE IN THE
15-20 KNOT RANGE SUNDAY AND MONDAY. SOME GUSTS COULD APPROACH 25
KNOTS, BUT CONDITIONS SHOULD LARGELY STAY BELOW SMALL CRAFT
ADVISORY CRITERIA. THE EXCEPTION POSSIBLY BEING THE OUTER
GEORGIA WATERS WHERE 6 FOOT SEAS ARE FORECAST. NORTHEAST FLOW
WILL PERSIST TUESDAY THROUGH THURSDAY WITH HIGH PRESSURE INLAND
AND COASTAL TROUGH NEARBY. SPEEDS WILL BE 15 KNOTS OR LESS WITH
SEAS 3-5 FT. 6 FT SEAS COULD POSSIBLY LINGER OVER THE OUTER
GEORGIA WATERS THROUGH MID WEEK.
CHS WATCHES/WARNINGS/ADVISORIES
GA...NONE.
SC...NONE.
MARINE...SMALL CRAFT ADVISORY UNTIL 1 PM EST THIS AFTERNOON FOR AMZ350-
352-354-374.
NEAR TERM...
SHORT TERM...ETM
LONG TERM...ETM
AVIATION...BSH/ETM
MARINE...
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