166
FXUS62 KCHS 140758
AFDCHS
AREA FORECAST DISCUSSION
NATIONAL WEATHER SERVICE CHARLESTON SC
358 AM EDT WED APR 14 2021
SYNOPSIS
DRY HIGH PRESSURE WILL PREVAIL INTO TONIGHT. A COLD FRONT WILL
ADVANCE THROUGH THE REGION THURSDAY THEN WILL STALL OFF THE
SOUTHEAST COAST FRIDAY THROUGH EARLY NEXT WEEK. A SERIES OF LOW
PRESSURES WILL TRACK ALONG THIS STATIONARY FRONT AND WILL
PRODUCE PERIODS OF INCLEMENT WEATHER THIS WEEKEND INTO EARLY
NEXT WEEK. DRIER HIGH PRESSURE WILL BUILD OVER THE REGION
DURING THE MIDDLE OF NEXT WEEK.
NEAR TERM /THROUGH TONIGHT/
SHORTWAVE UPPER RIDGING AND STRONG LOW-LEVEL WARM ADVECTION,
COMBINED WITH PLENTY OF SUNSHINE, WILL RESULT IN A WARM DAY
TODAY. BY FAR THE COOLEST AREAS WILL BE ALONG THE BEACHES DUE TO
A CONSISTENT ONSHORE FLOW OFF THE COOLER ATLANTIC. WE FOLLOWED
LOCAL CLIMO AND LOW-LEVEL THICKNESS PROGS PRETTY CLOSELY FOR
INLAND HIGHS, WHICH RESULTS IN 84-87F. A LOW-LEVEL JET WILL
DEVELOP THIS AFTERNOON AS THE 925 MB RIDGE SHIFTS SOUTHEAST IN
RESPONSE TO A DIGGING SHORTWAVE FROM THE WEST. WE SHOULD MIX TO
5,000-7,000 FEET DURING THE AFTERNOON WHICH WILL PRODUCE BREEZY
CONDITIONS.
A SERIES OF UPPER SHORTWAVES WILL MOVE THROUGH THE AREA TONIGHT,
THEN A COLD FRONT WILL APPROACH TOWARD DAYBREAK THURSDAY.
ALTHOUGH LOW-LEVEL MOISTURE ADVECTION WILL BE QUITE LIMITED
TONIGHT, THERE SHOULD BE ENOUGH FORCING TO PRODUCE AT LEAST
SCATTERED SHOWERS FROM LATE THIS EVENING THROUGH THE OVERNIGHT
HOURS. PERSISTENT 5-8 KT SW WINDS WILL RESULT IN A MILD NIGHT
WITH LOWS IN THE LOW/MID 60S.
SHORT TERM /THURSDAY THROUGH SATURDAY/
A COLD FRONT WILL STAFF OFF THE SOUTHEAST COAST, AND WAVES OF LOW
PRESSURE WILL DEVELOP AND TRACK EAST WITHIN THE ASSOCIATED
BAROCLINIC ZONE. AS A RESULT, THIS PERIOD WILL FEATURE COOLER
TEMPERATURES, MOSTLY CLOUDY CONDITIONS AND PERIODS OF SHOWERS. THE
PROSPECTS FOR MEASURABLE RAINFALL APPEAR GREATEST ACROSS SOUTHERN
COUNTIES OF THE FORECAST AREA. FARTHER NORTH, INCLUDING THE
CHARLESTON TRI-COUNTY REGION AND FAR INLAND COUNTIES, THE POTENTIAL
FOR MEASURABLE RAINFALL REMAINS UNCERTAIN AND WILL DEPEND ON THE
TRACK, STRENGTH AND MESOSCALE ENVIRONMENT/THUNDERSTORM COVERAGE OF
EACH WAVE OF LOW PRESSURE THAT WILL PASS TO OUR SOUTH.
THURSDAY: THE COLD FRONT WILL ADVANCE INTO THE REGION, AND A WEAK
SHORTWAVE TROUGH ALOFT WILL TRACK EAST ACROSS THE SOUTHEAST. WEAK
FORCING FOR ASCENT AND TRANSPORT OF PWAT VALUES AROUND 1.5 INCH WILL
SUPPORT SHOWERS. GUIDANCE HAS TRENDED WETTER AS COMPARED WITH RECENT
DAYS, AND AT LEAST LIKELY POPS ARE IN ORDER SOUTH OF INTERSTATE 16
FROM MID MORNING TO MID/LATE AFTERNOON. THE NORTHWARD EXTENT OF
DEEPER MOISTURE/PRECIPITATION REMAINS UNCERTAIN, SO POPS DECREASE
FARTHER NORTH, AS LOW AS 25-30 PERCENT FAR INLAND/NORTH. HOWEVER, IF
THE SHORTWAVE TROUGH AMPLIFIES EVEN SLIGHTLY, MORE WIDESPREAD
SHOWERS COULD SPREAD DEEPER INTO THE FORECAST AREA. INSTABILITY
COULD SUPPORT ISOLATED THUNDERSTORMS ACROSS SOUTHERN COUNTIES, BUT
NO SEVERE WEATHER IS EXPECTED. OTHERWISE, HIGH TEMPERATURES WILL
AVERAGE CLOSE TO NORMAL, IN THE MIDDLE 70S AT MOST LOCATIONS.
THURSDAY NIGHT INTO FRIDAY NIGHT: AS THE COLD FRONT AND ASSOCIATED
SHORTWAVE TROUGH ALOFT PUSH OFF THE SOUTHEAST COAST, AND THE COLD
FRONT SHOULD STALL. WEAK HIGH PRESSURE WILL PRESS INTO THE REGION
AND SHOULD PROVIDE A PERIOD OF RAIN-FREE CONDITIONS, ESPECIALLY
LATER THURSDAY NIGHT INTO EARLY AFTERNOON FRIDAY. THEN, THE NEXT
WAVE OF LOW PRESSURE WILL ADVANCE EAST ALONG THE STATIONARY FRONT
AND COULD SPREAD A FEW SHOWERS INTO FAR SOUTHERN COUNTIES BY
LATER FRIDAY, WITH AT LEAST ISOLATED/SCATTERED SHOWERS ADVANCING
INTO THE FORECAST AREA FRIDAY NIGHT. OTHERWISE, COOLER CONDITIONS
WILL PREVAIL, WITH THURSDAY NIGHT AND FRIDAY NIGHT LOWS MAINLY IN
THE 50S AND FRIDAY HIGHS IN THE LOWER 70S.
SATURDAY: THE NEXT WAVE OF LOW PRESSURE AND ASSOCIATED DEEP LAYERED
MOISTURE WILL SPREAD ADDITIONAL SHOWERS INTO THE FORECAST AREA. POPS
ARE GRADUATED FROM 30-40 PERCENT FAR NORTH/INLAND TO CATEGORICAL
SOUTH OF I-16, AND GIVEN GUIDANCE TRENDS HIGHER POPS COULD
EVENTUALLY BE REQUIRED ACROSS A WIDER SWATH OF THE REGION. SATURDAY
SHOULD ALSO BE THE COOLEST DAY OF THIS PERIOD, WITH TEMPERATURES
STRUGGLING TO CLIMB ABOUT THE UPPER 60S AT MANY LOCATIONS.
LONG TERM /SATURDAY NIGHT THROUGH TUESDAY/
UNSETTLED CONDITIONS/AT LEAST ISOLATED/SCATTERED SHOWERS WILL
PERSIST INTO TUESDAY AS ADDITIONAL WAVES OF LOW PRESSURE TRACK NEAR
THE SOUTHEAST COAST. DETAILS REGARDING TIMING, COVERAGE AND
INTENSITY OF PRECIPITATION EVENTS REMAIN UNCERTAIN, AND FORECASTS
REMAIN GENERIC. THEN, HIGH PRESSURE SHOULD FINALLY EXPEND INTO
THE REGION WITH DRIER CONDITIONS BY THE MIDDLE OF NEXT WEEK.
HIGHS IN THE 70S AND LOWS IN THE 50S SHOULD REMAIN COMMON.
HOWEVER, GREATER COVERAGE OF SHOWERS COULD RESULT IN COOLER
DAYTIME TEMPERATURES SUNDAY, MONDAY OR TUESDAY.
AVIATION /07Z WEDNESDAY THROUGH SUNDAY/
VFR. GUSTY WINDS EXPECTED THIS AFTERNOON.
EXTENDED AVIATION OUTLOOK: PERIODS OF FLIGHT RESTRICTIONS,
ESPECIALLY IN LOWER CEILINGS, COULD OCCUR AT ANY TIME THURSDAY
INTO EARLY NEXT WEEK.
MARINE
MODERATE SOUTHERLY FLOW THIS MORNING WILL INCREASE THROUGHOUT
THE AFTERNOON HOURS AS A POTENT LOW-LEVEL JET DEVELOPS OVER THE
MARINE AREA. THE CURRENT FORECAST FOR THE CHARLESTON NEARSHORE
WATERS AND CHARLESTON HARBOR HAVE SUSTAINED WINDS INCREASING TO
15-20 KT DURING THE MID AFTERNOON WITH SOME HIGHER GUSTS. WE MAY
VERY WELL NEED SMALL CRAFT ADVISORIES FOR BOTH OF THESE ZONES AT
SOME POINT THIS AFTERNOON INTO THE EVENING DUE TO 25 KT GUSTS.
AT THIS JUNCTURE WE HELD OFF ON ISSUING ADVISORIES AS WE'RE
THINKING THE GUSTS MAY STAY JUST BELOW THAT THRESHOLD. FAIRLY
POTENT WINDS WILL CONTINUE THROUGH TONIGHT ACROSS THE MARINE
AREA AS A COLD FRONT APPROACHES THE AREA.
THURSDAY THROUGH MONDAY: AHEAD OF A COLD FRONT, SOUTHWEST WINDS
15- 20 KNOTS AND AND SEAS 3-5 FEET ARE EXPECTED THURSDAY, AND A
FEW GUSTS TO 25 KNOTS WILL BE POSSIBLE. SMALL CRAFT ADVISORIES
COULD EVENTUALLY BE REQUIRED IN SOME AREAS. WINDS WILL SHIFT TO
THE WEST/NORTHWEST 10-15 KNOTS WITH GUSTS TO 20 KNOTS THURSDAY
EVENING, THEN WILL VEER TO THE NORTH/NORTHEAST AT SIMILAR SPEEDS
LATER THURSDAY NIGHT IN TO FRIDAY MORNING. SEAS WILL AVERAGE
2-4 FEET. THEN, CHANGEABLE WIND DIRECTION SHOULD REMAIN AT OR
BELOW 15 KNOTS MOST OF THE TIME THIS WEEKEND INTO EARLY NEXT
WEEK. SEAS WILL AVERAGE 1-3 FEET THROUGH THIS PERIOD. OF NOTE,
THUNDERSTORMS COULD IMPACT GEORGIA WATERS ANY TIME THIS WEEKEND
INTO EARLY NEXT WEEK.
FIRE WEATHER
RH IS EXPECTED TO DROP TO 27-30% FOR A FEW HOURS THIS AFTERNOON
ACROSS FAR INLAND SC/GA ZONES. MEANWHILE, AN APPROACHING LOW-
LEVEL JET AND WARM SURFACE TEMPERATURES WILL RESULT IN DEEP
MIXING AND SOME GUSTY WINDS. ALTHOUGH WE BUMPED UP OUR WINDS A
BIT FOR THIS AFTERNOON, WE ARE STILL JUST SHY OF FIRE DANGER
STATEMENT CRITERIA AND THE DURATION/AREA OF POSSIBLE CRITERIA
SEEMS A BIT TOO LOW TO JUSTIFY A STATEMENT AT THIS TIME.
CHS WATCHES/WARNINGS/ADVISORIES
GA...NONE.
SC...NONE.
MARINE...NONE.
NEAR TERM...JRL
SHORT TERM...SPR
LONG TERM...SPR
AVIATION...JRL/SPR
MARINE...JRL/SPR
FIRE WEATHER...
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