912
FXUS62 KCHS 191135
AFDCHS
AREA FORECAST DISCUSSION
NATIONAL WEATHER SERVICE CHARLESTON SC
635 AM EST TUE NOV 19 2024
SYNOPSIS
HIGH PRESSURE WILL PREVAIL UNTIL A STRONG COLD FRONT MOVES
THROUGH LATER WEDNESDAY. CANADIAN HIGH PRESSURE WILL BUILD
ACROSS THE AREA THURSDAY INTO SUNDAY.
NEAR TERM /THROUGH TONIGHT/
TODAY: ALOFT, THE UPPER RIDGE AXIS WILL SHIFT OFF TO THE EAST
THIS MORNING AS SHORTWAVE ENERGY SPREADS IN ACROSS THE REGION
WITH THE ARRIVAL OF SOUTHWESTERLY FLOW AHEAD OF A STRENGTHENING
TROUGH ACROSS THE CENTRAL CONUS. AT THE SURFACE, HIGH PRESSURE
WILL BE POSITIONED OVER THE SOUTHWEST ATLANTIC AS A COLD FRONT
GRADUALLY TRACKS EASTWARD ACROSS THE DEEP SOUTH. THE DAY WILL
START OFF WITH AN AREA OF CONVECTION ALONG AND AHEAD OF THE
FRONT WELL TO OUR WEST. THIS CONVECTION IS EXPECTED TO GRADUALLY
WEAKEN AS IT PROGRESSES EASTWARD THROUGH MIDDAY AND ALSO BEGIN
TO FOCUS FURTHER SOUTH ALONG THE GULF COAST AND OVER THE GULF OF
MEXICO. THIS TIMING SHOULD KEEP THE AREA DRY THROUGH ABOUT
MIDDAY BEFORE RAIN CHANCES INCREASE THROUGH THE AFTERNOON.
THROUGH SUNSET, THE HIGHEST RAIN CHANCES ARE EXPECTED FOR
INTERIOR SOUTHEAST GEORGIA (AND WEST OF I-95 MORE GENERALLY)
WHERE THE WEAKENING CONVECTION WILL ARRIVE FIRST. RAINFALL
AMOUNTS ARE EXPECTED TO BE LIGHT, IN THE 0.10-0.20" RANGE FOR
THE FAR WESTERN ZONES AND MOSTLY A TENTH OF AN INCH OR LESS
ELSEWHERE. WE DO EXPECT ANOTHER WARM DAY ACROSS THE AREA,
DESPITE PLENTY OF CLOUD COVER. HIGHS ARE FORECAST IN THE MID TO
UPPER 70S FOR MOST OF THE AREA, EXPECT LOW 70S IN AREAS WHERE
RAIN ARRIVES THIS AFTERNOON.
TONIGHT: FOR THE EVENING, THE LEFTOVER AREA OF SHOWERS IS
EXPECTED TO GRADUALLY MOVE EASTWARD ACROSS THE FORECAST AREA,
AIDED BY VORTICITY ALOFT AND THE PRESENCE OF UPPER-LEVEL
DIVERGENCE IN THE RIGHT ENTRANCE REGION OF THE UPPER JET.
COVERAGE OF SHOWERS SHOULD PEAK IN THE EVENING WITH THE BEST
OVERLAP OF MOISTURE (1.5-2" PRECIPITABLE WATER) AND FORCING.
MODEL CONSENSUS IS FOR THE SHOWER ACTIVITY TO DWINDLE THROUGH
THE LATE NIGHT HOURS AS THE BETTER FORCING AND MOISTURE SHIFTS
OFF THE COAST. THERE ISN'T ANY SUPPORT FOR INTENSE RAINFALL, AND
AMOUNTS ARE FORECAST TO BE A TENTH OF AN INCH OR LESS, AND NO
MORE THAN A FEW HUNDREDTHS IN MOST LOCATIONS. WITH THE COLD
FRONT STILL BACK TO THE WEST, EXPECT A VERY MILD NIGHT. LOWS ARE
FORECAST TO ONLY FALL INTO THE LOW 60S FOR MOST AREAS, WHICH
WOULD ONLY BE AROUND 5-7 DEGREES BELOW CLIMO HIGH TEMPERATURES
FOR THIS TIME OF YEAR.
SHORT TERM /WEDNESDAY THROUGH FRIDAY/
A DEEPENING MID LEVEL TROUGH WILL SHIFT INTO THE EASTERN U.S.
ON WEDNESDAY. AT THE SURFACE, A STRONG COLD FRONT WILL APPROACH
FROM THE WEST AND SWEEP THROUGH THE AREA LATER IN THE DAY INTO
WEDNESDAY EVENING. ISOLATED TO SCATTERED SHOWERS WILL BE
POSSIBLE, ESPECIALLY DURING THE MORNING AND INTO EARLY
AFTERNOON, BEFORE DRIER AIR MOVES IN AND BRINGS AN END TO
PRECIP. ALL AREAS SHOULD BE RAIN-FREE BY WEDNESDAY NIGHT. ONE
MORE WARM DAY WITH HIGHS LARGELY IN THE MID 70S. COLD AIR
ADVECTION WILL BEGIN WEDNESDAY NIGHT. LOWS ARE CURRENTLY
FORECAST TO SPAN THE 40S, COOLEST INLAND.
MID LEVEL LOW INITIALLY OVER THE GREAT LAKES WILL ROTATE TO THE
NORTHEAST THURSDAY INTO FRIDAY, WITH LARGER SCALE TROUGH
EXTENDING DOWN THE ENTIRE EAST COAST. SURFACE LOW WILL CONTINUE
TO MEANDER OVER THE NORTHEASTERN PART OF THE COUNTRY WHILE HIGH
PRESSURE BEGINS TO BUILD. TIGHT PRESSURE GRADIENT WILL LEAD TO
GUSTY WEST WINDS BOTH DAYS. GUSTS TO AROUND 25 MPH WILL BE
COMMON. DESPITE FULL SUN, HIGHS WILL BE SEASONALLY COOL,
GENERALLY IN THE UPPER 50S TO AROUND 60. LOWS THURSDAY NIGHT
WILL BE CHILLY WITH MANY INLAND LOCATIONS DROPPING INTO THE 30S.
TEMPS AND WINDS SHOULD STAY A BIT TOO ELEVATED FOR FROST.
LAKE WINDS: GUSTY WEST WINDS ARE EXPECTED TO DEVELOP OVER LAKE
MOULTRIE WEDNESDAY NIGHT INTO THURSDAY BEHIND A COLD FRONT. A
LAKE WIND ADVISORY IS LIKELY, WHICH COULD PERSIST INTO FRIDAY.
LONG TERM /FRIDAY NIGHT THROUGH MONDAY/
HIGH PRESSURE WILL CONTINUE TO BUILD OVER THE AREA OVER THE
WEEKEND AND REMAIN THE DOMINANT FEATURE THROUGH MONDAY. NO
THREAT FOR RAIN WITH A DRY FORECAST THROUGH THE ENTIRE PERIOD.
MAIN FORECAST CONCERN WILL BE THE POTENTIAL FOR FROST EARLY
SATURDAY MORNING AND AGAIN SUNDAY MORNING. PERHAPS THE BETTER
CHANCE WOULD BE SUNDAY MORNING AS WINDS COULD STAY A BIT TOO
HIGH FOR FROST DEVELOPMENT FRIDAY NIGHT/SATURDAY MORNING.
AVIATION /12Z TUESDAY THROUGH SATURDAY/
VFR CONDITIONS WILL PREVAIL AT KCHS, KJZI, AND KSAV THROUGH MOST
OF THE 12Z TAF PERIOD. THE POTENTIAL FOR RAIN SHOWERS WILL
INCREASE FROM THE WEST LATE IN THE TAF PERIOD AND WE HAVE
INTRODUCED A MENTION OF VCSH AT ALL 3 SITES IN THE LAST 3-6
HOURS. THIS AREA OF SHOWERS IS EXPECTED TO MOVE AWAY FROM KSAV
LATE AND MODEL GUIDANCE SUGGESTS THAT MVFR OR LOWER CEILINGS
WILL SPREAD IN FROM THE WEST. THEREFORE, WE HAVE INTRODUCED MVFR
CEILINGS INTO KSAV AT 07Z. AT KCHS AND KJZI, THE AREA OF SHOWERS
WILL IMPACT THE TERMINALS THROUGH THE END OF THE TAF PERIOD AND
THEN THE CHANCES FOR CEILINGS TO SPREAD IN WILL INCREASE AFTER
12Z.
EXTENDED AVIATION OUTLOOK: BRIEF FLIGHT RESTRICTIONS ARE
POSSIBLE IN SHOWERS AND LOW CLOUDS WEDNESDAY IN ADVANCE OF A
COLD FRONT. VFR WILL PREVAIL THEREAFTER. GUSTY WEST WINDS ARE
EXPECTED THURSDAY AND FRIDAY.
MARINE
TODAY AND TONIGHT: HIGH PRESSURE OVER THE SOUTHWEST ATLANTIC
WILL STILL BE THE PRIMARY FEATURE THROUGH TODAY DRIVING A MODEST
SOUTH TO SOUTHWEST FLOW THAT SHOULD INCREASE TO AROUND 10 KNOTS
BY SUNSET. OVERNIGHT, A COLD FRONT WILL BEGIN TO APPROACH FROM
THE WEST AND THE LOCAL WATERS WILL BE SITUATED BETWEEN THE FRONT
AND THE HIGH. THE RESULT WILL BE INCREASING SOUTH TO SOUTHWEST
FLOW LATE TONIGHT, PEAKING AROUND 15-20 KNOTS IN THE GEORGIA
WATERS BY SUNRISE WEDNESDAY. SEAS WILL AVERAGE 1-2 FEET THROUGH
TODAY, THEN INCREASE LATE TONIGHT. BY SUNRISE WEDNESDAY WE
SHOULD SEE 2-3 FEET ACROSS ALL THE WATERS, WITH 3-4 FEET IN THE
OUTER GEORGIA WATERS.
WEDNESDAY THROUGH SUNDAY: A STRONG COLD FRONT WILL MOVE THROUGH
LATER WEDNESDAY WITH INCREASING WINDS AND SEAS IN ITS WAKE.
SMALL CRAFT ADVISORIES ARE EXPECTED FOR ALL WATERS, INCLUDING
THE CHARLESTON HARBOR, BEGINNING WEDNESDAY NIGHT AND POTENTIALLY
CONTINUING THROUGH FRIDAY. WHILE A FEW GUSTS NEAR OR AT GALE
FORCE ARE POSSIBLE BOTH WEDNESDAY NIGHT AND THURSDAY NIGHT, IT
APPEARS TO BE BRIEF AND MARGINAL, SO NO GALE WATCH ANTICIPATED
AT THIS TIME. IMPROVEMENT IS EXPECTED ON SATURDAY AS THE
PRESSURE GRADIENT EASES.
CHS WATCHES/WARNINGS/ADVISORIES
GA...NONE.
SC...NONE.
MARINE...NONE.
NEAR TERM...BSH
SHORT TERM...ETM
LONG TERM...ETM
AVIATION...BSH/ETM
MARINE...BSH/ETM
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