944
FXUS62 KCHS 260212
AFDCHS
AREA FORECAST DISCUSSION
NATIONAL WEATHER SERVICE CHARLESTON SC
1012 PM EDT SUN OCT 25 2020
SYNOPSIS
A WEAK COLD FRONT WILL SLIDE ACROSS THE REGION TONIGHT. HIGH
PRESSURE IS FORECAST TO LINGER THROUGH THE MIDDLE OF THE WEEK.
A STORM SYSTEM IS EXPECTED TO BRING IMPACTS TO THE REGION LATE
IN THE WORK WEEK. HIGH PRESSURE SHOULD RETURN TO THE REGION BY
NEXT WEEKEND, RESULTING IN FAIR WEATHER.
NEAR TERM /UNTIL 6 AM MONDAY MORNING/
THERE WILL BE A SMALL RISE IN HEIGHTS OVERNIGHT IN WAKE OF A
SUBTLE SHORT WAVE THAT CONTINUES TO MOVE FURTHER OFFSHORE, AS
THE FLOW BECOMES ZONAL. MEANWHILE, A COLD FRONT CONTINUES TO
PROGRESS SOUTH AND WILL CLEAR THE ENTIRE FORECAST REGION BY
AROUND 06Z, AS A HIGH PRESSURE WEDGE BUILDS IN ITS WAKE. THIS
WILL FINALLY ALLOW FOR THE LAST OF THE ISOLATED SOUTH CAROLINA
SHOWERS TO HAVE COME TO AN END.
THE LEADING EDGE OF THAT WEDGE WAS FOUND ACROSS MUCH OF THE
CHARLESTON QUAD-COUNTY DISTRICT AND ALLENDALE AND HAMPTON
COUNTY PRIOR TO MIDNIGHT, BUT WILL PROGRESS FURTHER SOUTH
OVERNIGHT. THIS WILL ALLOW FOR STRATUS TO DEVELOP, BUILD DOWN
WITH TIME, AND GIVEN A SATURATED BOUNDARY LAYER ENVIRONMENT WILL
LEAD TO THE FORMATION OF PATCHY DRIZZLE, PLUS PATCHY OR AREAS
OF FOG.
COOL ADVECTION IS WEAK, BUT THERE WILL BE ENOUGH OF A CHANGE IN
AIR MASS TO ALLOW FOR MIN TEMPS TO GET DOWN TO 60-65F MOST
PLACES INLAND FROM US-17, WITH MID AND UPPER 60S CLOSER TO THE
COAST.
SHORT TERM /6 AM MONDAY MORNING THROUGH WEDNESDAY/
MONDAY: THE CENTER OF A H5 RIDGE WILL SLIDE FROM FL MONDAY MORNING
EAST OVER THE WESTERN ATLANTIC BY THE AFTERNOON. H5 HEIGHTS OVER THE
FORECAST AREA WILL INCREASE TO AROUND 590 DM. AT THE SFC, THE CENTER
OF HIGH PRESSURE WILL BUILD SOUTH OVER THE WESTERN CAROLINAS DURING
THE AFTERNOON. CONDITIONS ACROSS THE FORECAST AREA ARE FORECAST TO
REMAIN DRY. HIGH TEMPERATURES ARE EXPECTED TO RANGE FROM THE UPPER
70S ACROSS THE SC LOWCOUNTRY TO THE LOW 80S ACROSS SE GA.
TUESDAY AND WEDNESDAY: THE MID-LEVEL PATTERN WILL BE DOMINATED BY A
STRONG RIDGE OVER THE WESTERN ATLANTIC AND A DEEP LOW SWINGING EAST
ACROSS THE SOUTHERN PLAINS. BETWEEN THESE TWO FEATURES, TC ZETA IS
EXPECTED TO LIFT NORTH ACROSS THE GULF OF MEXICO. BASED ON NHC
FORECAST, ZETA WILL MAKE LANDFALL NEAR THE MISSISSIPPI DELTA
WEDNESDAY PM. MOISTURE IS EXPECTED TO GRADUALLY INCREASE ACROSS THE
FORECAST AREA TUESDAY AND WEDNESDAY, APPROACHING FROM THE SOUTH.
ISOLATED TO SCATTERED SHOWERS ARE POSSIBLE EACH DAY, ESPECIALLY
DURING THE AFTERNOON AND EVENING. TEMPERATURES ARE FORECAST TO
REMAIN ABOVE NORMAL. BASED ON A BLEND OF MOS, LOW TEMPERATURES ARE
FORECAST TO RANGE IN THE LOW TO MID 60S. HIGH TEMPERATURES WILL
GENERALLY RANGE IN THE LOW TO MID 80S.
LONG TERM /WEDNESDAY NIGHT THROUGH SUNDAY/
MID-LEVEL HIGH PRESSURE LOCATED OFFSHORE WILL MOVE AWAY ON THURSDAY.
MEANWHILE, A STRONG TROUGH WILL APPROACH FROM THE WEST ON THURSDAY,
THEN PASS OVERHEAD OR JUST TO OUR NORTH ON FRIDAY. ZONAL FLOW IS
EXPECTED ON SATURDAY. AT THE SURFACE, A STORM SYSTEM WILL CROSS
THROUGH OUR REGION THURSDAY INTO THURSDAY NIGHT, BRINGING RAINFALL.
CONDITIONS DRY OUT FRIDAY AS HIGH PRESSURE BUILDS IN FROM THE WEST,
AND REMAIN DRY INTO SATURDAY. TEMPERATURES WILL BE COLDER BEHIND THE
FRONT.
AVIATION /02Z MONDAY THROUGH FRIDAY/
KCHS WILL FLUCTUATE BETWEEN VFR AND MVFR EARLY TONIGHT, WHILE
KSAV WILL TRANSITION FROM VFR EARLY TONIGHT TO MVFR OVERNIGHT.
BOTH SITES WILL EVENTUALLY DROP TO IFR OR EVEN POTENTIALLY LIFR
LATE TONIGHT INTO MONDAY MORNING. THIS OCCURS AS THE HIGH
PRESSURE WEDGE DEVELOPS IN WAKE OF A COLD FRONT, WITH A MODEST
WEDGE INVERSION TO FORM AND TRAP CONSIDERABLE MOISTURE
UNDERNEATH. EXPECT STRATUS BUILD DOWN, ALONG WITH PATCHY DRIZZLE
AND MAYBE A LITTLE FOG, WITH THE WORST CONDITIONS ROUGHLY
07-15Z MONDAY, ALTHOUGH IT CERTAINLY COULD OCCUR EARLIER AS
WELL.
VFR WILL THEN RETURN FOR MONDAY AFTERNOON, MAYBE TAKING A
LITTLE LONGER TO DO SO AT KSAV THAN AT KCHS, AS THE INVERSION
WEAKENS AND RISES, AND MOISTURE BEGINS TO SLOWLY SCOUR OUT.
EXTENDED AVIATION OUTLOOK: BRIEF RESTRICTIVE CEILINGS AND FOG MAY
DEVELOP ACROSS THE TERMINALS AROUND DAWN TUESDAY. A STORM SYSTEM IS
EXPECTED TO BRING FLIGHT RESTRICTIONS WEDNESDAY INTO THURSDAY.
MARINE
OVERNIGHT: A HIGH PRESSURE RIDGE WILL BUILD FROM THE NORTH,
BEHIND A COLD FRONT THAT PUSHES SOUTH OF THE LOCAL WATERS. THIS
WILL ALLOW FOR E AND NE WINDS TO BACK AROUND TO THE N AND NE,
WITH SPEEDS TO INCREASE TO AS HIGH AS AROUND 12-17 KT. SEAS WILL
RISE TO AS MUCH AS 3 OR 4 FEET WITHIN 20 NM AND HOLD AROUND 4 OR
5 FEET FURTHER OFFSHORE. THERE IS A CHANCE THAT AFTER THE LOWER
STRATUS MOVES IN THAT THERE COULD BE SOME MINOR REDUCTION IN
VISIBILITY IN CHARLESTON HARBOR.
MONDAY THROUGH FRIDAY: SFC HIGH PRESSURE WILL REMAIN RIDGED ACROSS
THE MARINE ZONES MONDAY AND TUESDAY. CONDITIONS WILL FEATURE A
STEADY NE WIND AND SEAS BETWEEN 2-4 FT. BASED ON NHC FORECAST, TC
ZETA WILL MAKE LANDFALL NEAR THE MISSISSIPPI RIVER DELTA WED PM,
TRACKING NE TO THE SOUTHERN APPALACHIANS ON THURSDAY. WINDS WILL
SHIFT FROM THE SE ON WEDNESDAY, SPEEDS BETWEEN 10-15 KTS. THE
PRESSURE GRADIENT WILL BEGIN TO TIGHTEN ACROSS THE MARINE ZONES
THURSDAY MORNING, WITH A COLD FRONT SWEEPING ACROSS THE REGION
THURSDAY EVENING. VEERING WINDS AND GUSTY WINDS ARE EXPECTED,
ESPECIALLY IN THE WAKE OF THE FRONT THURSDAY NIGHT AND FRIDAY
MORNING ACROSS AMZ350 AND 374.
CHS WATCHES/WARNINGS/ADVISORIES
GA...NONE.
SC...NONE.
MARINE...NONE.
NEAR TERM...
SHORT TERM...NED
LONG TERM...
AVIATION...
MARINE...
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