819
FXUS62 KCHS 160904
AFDCHS
AREA FORECAST DISCUSSION
NATIONAL WEATHER SERVICE CHARLESTON SC
404 AM EST SUN FEB 16 2025
SYNOPSIS
A STRONG COLD FRONT WILL IMPACT THE AREA TODAY, FOLLOWED BY
HIGH PRESSURE FOR MONDAY AND TUESDAY. A LOW PRESSURE SYSTEM
WILL MOVE ACROSS THE REGION DURING THE MIDDLE OF THE WEEK. HIGH
PRESSURE WILL THEN RETURN LATE WEEK.
NEAR TERM /THROUGH TONIGHT/
EARLY THIS MORNING, SATELLITE WATER VAPOR SHOWED A STRONG MID-LEVEL
SHORT WAVE RIPPLING ACROSS THE DEEP SOUTH. AT THE SFC, A COLD FRONT
WILL PUSHING EAST ACROSS AL. REGIONAL RADAR COMPOSITE INDICATED A
SOLID LINE SQUALL LINE OF SHOWERS/THUNDERSTORMS ALONG AND AHEAD OF
THE COLD FRONT. SO FAR TONIGHT, THIS LINE HAS BEEN HIGHLIGHTED WITH
NUMEROUS SEVERE THUNDERSTORM AND ISOLATE TORNADO WARNINGS. THE
ENVIRONMENT AHEAD OF THE LINE WILL FEATURE HIGH SHEAR AND LOW CAPE.
RECENT RUNS OF THE HRRR INDICATES THAT THE LINE WILL REMAIN SOLID AS
IT REACHES THE FORECAST AREA AROUND DAYBREAK, REACHING THE I-95
CORRIDOR BY 10 AM, THEN PUSH OFFSHORE BY NOON. FORECAST SOUNDINGS
AND SPC MESOANALYSIS INDICATE THAT EFFECTIVE BULK SHEAR OVER THE SE
GA/SC WILL REMAIN 60 KTS WITH 100-300 J/KG OF SBCAPE. SINCE
MIDNIGHT, KCLX VAD WIND PROFILE INDICATES WIND SPEED AT 1 KFT AROUND
50 KTS WITH 2 KFT BETWEEN 55 TO 60 KTS. LLVL WINDS ARE FORECAST TO
INCREASE BY 5 TO 10 KTS PRECEDING THE ARRIVAL OF THE SQUALL LINE.
ORGANIZED SEGMENTS OF THUNDERSTORMS COULD EASILY RESULT IN MOMENTUM
TRANSFER TO THE SFC, RESULTING IN DAMAGING WIND GUSTS. IT IS
INTERESTING TO NOTE THAT THE NCAR NEURAL NETWORK NETWORK GUIDANCE
FOR GREATER THAN 50 KTS RANGES BETWEEN 50 TO 70 PERCENT ACROSS SE
GA. SPC HAS HIGHLIGHTED SE GA AND PORTIONS OF THE SC LOWCOUNTRY WITH
A SLIGHT RISK FOR SEVERE THUNDERSTORMS.
ANOTHER CONCERN FOR TODAY WILL BE THE GUSTY SOUTHWEST WINDS AHEAD OF
THE COLD FRONT TODAY. NEAR TERM GUIDANCE INDICATES THAT THE PRESSURE
GRADIENT AHEAD OF THE FRONT IS EXPECTED TO TIGHTEN TO 4 TO 5 MBS
THIS MORNING. IN ADDITION, HIGH TEMPERATURES IN THE LOW 70S SHOULD
RESULT IN MIXING UP TO 2.5-3.5 KFT. THIS SHOULD SUPPORT A FEW HOURS
OF GUSTS OF 40 TO 45 MPH, WITH PEAK GUSTS NEARING 50 MPH ALONG THE
SC COAST. THESE WINDS HAVE BEEN HIGHLIGHTED WITH A WIND ADVISORY
UNTIL 6 PM THIS EVENING.
TONIGHT, DRY HIGH PRESSURE WILL SPREAD ACROSS THE FORECAST AREA,
WITH CLEAR TO MOSTLY CLEAR CONDITIONS EXPECTED THROUGH TONIGHT.
BUILDING HIGH PRESSURE SHOULD SUPPORT NORTHWEST WINDS BETWEEN 5 TO
10 MPH THROUGH MOST OF THE NIGHT. LOW TEMPERATURES ARE FORECAST TO
RANGE FROM AROUND 30 INLAND TO THE MID TO UPPER 30S ACROSS THE
COASTAL COUNTIES.
SHORT TERM /MONDAY THROUGH WEDNESDAY/
MONDAY AND TUESDAY: AT THE SURFACE, COLD CANADIAN HIGH PRESSURE WILL
EXTEND SOUTHEASTWARD ACROSS THE MIDWEST AND INTO THE SOUTHEASTERN
U.S. INTO TUESDAY. QUASI-ZONAL FLOW ALOFT WILL KEEP THE FORECAST
RELATIVELY QUIET. SOME SEMBLANCE OF A COASTAL TROUGH LOOKS TO FORM
BY EARLY TUESDAY MORNING WHICH WILL INCREASE CLOUD COVER THROUGH THE
DAY. THE TROUGH SHARPENING LATER IN THE EVENING AND OVERNIGHT COULD
RESULT IN SHOWERS OFFSHORE WHICH COULD THEN APPROACH THE COAST, BUT
FOR NOW IT LOOKS TO STAY DRY OVER LAND. HIGHS WILL ONLY REACH THE
MID TO UPPER 50S UNDER FULL SUN MONDAY, AND THEN REBOUND QUICKLY
TUESDAY TO NEAR NORMAL IN THE LOW TO MID 60S. MONDAY NIGHT WILL BE
COLD WITH MIN TEMPS IN THE LOW TO MID 30S INLAND AND LOW TO MID 40S
ALONG THE COAST. "WARMER" TEMPS ARE EXPECTED TUESDAY NIGHT; IN THE
LOW TO MID 40S INLAND AND LOW 50S ALONG THE COAST.
WEDNESDAY: THE AXIS OF AN UPPER TROUGH WILL MOVE ACROSS THE
CENTRAL/SOUTHERN PLAINS AND TOWARD THE EAST COAST. CYCLOGENESIS
ALONG THE GULF COAST WILL SPIN UP A SURFACE LOW WHICH IS PROGGED TO
MOVE OVER THE FL/GA BORDER BY THE AFTERNOON AND THEN LIFT NORTHEAST
ALONG THE CAROLINA COAST LATER IN THE EVENING. THIS WILL BRING A
ROUND OF WIDESPREAD RAINFALL TO THE AREA. LOOKS TO BE ANOTHER HIGH
SHEAR/LOW CAPE SCENARIO WITH LITTLE TO NO INSTABILITY PRESENT AND 50-
70 KT DEEP LAYER (0-6 KM) SHEAR. FOR NOW, LOW PROBABILITIES OF
THUNDER WILL KEEP ONLY MENTION OF SHOWERS IN THE FORECAST WITH THE
EXCEPTION OF EXTREME SOUTHEAST GEORGIA AND THE COASTAL WATERS.
OTHERWISE A DECENT AMOUNT OF RAINFALL COULD COME OF THIS SYSTEM, UP
TO 1 INCH, POSSIBLY MORE. HOWEVER, PLACEMENT OF THE LOW, IN ADDITION
TO HOW PROGRESSIVE THIS SYSTEM MOVES WILL LARGELY IMPACT RAINFALL
TOTALS. HIGHS WILL BE SOMEWHAT TRICKY TO PIN DOWN WITH A LARGE
TEMPERATURE GRADIENT IN PLACE. WE CURRENTLY HAVE LOWER 50S ACROSS
THE FAR INTERIOR TO UPPER 50S/LOWER 60S ALONG THE BEACHES AND
SOUTHEAST GEORGIA.
LONG TERM /WEDNESDAY NIGHT THROUGH SATURDAY/
THE MAIN CONCERN FOR THIS PERIOD WILL BE THE VERY COLD/ARCTIC HIGH
PRESSURE THAT WILL QUICKLY FILTER IN THE WAKE OF THE AFOREMENTIONED
DEPARTING SURFACE LOW. MOST OF THE RAINFALL SHOULD MOVE OFFSHORE
WEDNESDAY EVENING; HOWEVER, SOME P-TYPE CONCERNS COULD BE PRESENT
WEDNESDAY NIGHT IF SHOWERS LINGER BEHIND THE LOW, BUT AS OF NOW
THOSE CONCERNS REMAIN NORTH OF THE FORECAST AREA. LOWS IN THE LOWER
TO MID 30S INLAND TO LOW 40S ALONG THE COAST WEDNESDAY NIGHT COULD
DROP AS LOW AS THE MID 20S TO LOWER 30S BOTH THURSDAY AND FRIDAY
NIGHT. WILL NEED TO MONITOR THE POTENTIAL FOR A COLD WEATHER
ADVISORY (WIND CHILL 20F OR COLDER) THURSDAY NIGHT. ANOTHER LOW
PRESSURE SYSTEM COULD AFFECT THE AREA NEXT WEEKEND.
AVIATION /09Z SUNDAY THROUGH THURSDAY/
PRIOR TO THE 6Z TAFS, KCLX VAD PROFILE DETECTED SOUTH WINDS AT
50 KTS AT 1 KFT, EACH TAF WILL BE INITIALIZED WITH LLWS. IR
SATELLITE ALONG WITH SURFACE BASED OBSERVATIONS INDICATED MVFR
TO IFR CEILINGS ACROSS KCHS AND KJZI. KSAV WAS UNDER A PATCH OF
MID-LEVEL CEILINGS WITH FEW TO SCT IFR BASED CLOUDS, EXPECTED TO
REMAIN UNTIL 9Z. MOS AND RECENT RUNS OF THE HRRR INDICATES THAT
AT LEAST MVFR CEILINGS WILL REMAIN OVER THE TERMINALS THROUGH
DAYBREAK. GUIDANCE SHOWS THAT SOUTHWEST WINDS WILL CONTINUE TO
STRENGTHEN AS A COLD FRONT APPROACHES FROM THE WEST. WINDS ARE
TIMED TO PEAK DURING THE MID TO LATE MORNING HOURS, GUSTS AROUND
40 KTS. BASED ON RADAR TRENDS AND HIGH RESOLUTION GUIDANCE, A
SOLID LINE OF SHOWERS WITH EMBEDDED THUNDERSTORMS IS TIMED TO
PUSH ACROSS THE TERMINALS BETWEEN 14-18Z, HIGHLIGHTED WITH
TEMPOS. AFTER THE LINE OF CONVECTION AND COLD FRONT, WINDS ARE
FORECAST TO VEER FROM THE WEST BETWEEN 10 TO 15 KTS WITH GUSTS
AROUND 20 KTS. CLOUD COVER SHOULD DECREASE THROUGH THE REST OF
THE AFTERNOON AND EVENING.
EXTENDED AVIATION OUTLOOK: GENERALLY VFR TO PREVAIL THROUGH EARLY
TUESDAY NIGHT. A STORM SYSTEM COULD IMPACT THE AREA WEDNESDAY WITH
FLIGHT RESTRICTIONS POSSIBLE.
MARINE
TODAY, THE PRESSURE GRADIENT WILL TIGHTEN ACROSS THE MARINE ZONES
AHEAD OF A COLD FRONT. SOUTHWEST WINDS WILL STRENGTHEN RAPIDLY THIS
MORNING, GUSTS RANGING BETWEEN 35 TO 40 KTS. WINDS ACROSS THE
CHARLESTON COUNTY NEARSHORE WATERS MAY SEE GUSTS AROUND 45 KTS,
ESPECIALLY DURING THE MID TO LATE MORNING. ALL MARINE ZONES,
INCLUDING THE CHS HARBOR, WILL BE HIGHLIGHTED WITH A GALE WARNING
THROUGH THIS AFTERNOON. SEAS ARE FORECAST TO PEAK AROUND MID-DAY,
RANGING BETWEEN 6 TO 10 FT. A SQUALL LINE IS TIMED TO PUSH ACROSS
THE NEARSHORE WATERS EARLY THIS AFTERNOON, ENHANCING THE WIND GUST
POTENTIAL. IN THE WAKE OF THE SQUALL LINE, WINDS WILL SHIFT FROM THE
WEST-SOUTHWEST.
TONIGHT, HIGH PRESSURE IS FORECAST TO INCREASE ACROSS THE MARINE
ZONES. WINDS WILL SHIFT FROM THE NORTHWEST, SPEEDS REMAINING BETWEEN
20-25 KTS WITH GUSTS UP TO 30 KTS OUTSIDE THE HARBOR. SEAS LATE
TONIGHT ARE FORECAST TO RANGE FROM 4 TO 7 FT. A SMALL CRAFT
ADVISORY WILL BE NEEDED AFTER THE GALE WARNING.
MONDAY THROUGH FRIDAY: HIGH PRESSURE WILL BUILD OVER THE REGION
THROUGH TUESDAY WITH NO HIGHLIGHTS/CONCERNS EXPECTED. WINDS WILL
GENERALLY BE OUT OF THE NORTHEAST AROUND 10 KT OR LESS AND SEAS 2-4
FT DROPPING TO 2-3 FT. HIGH PRESSURE WILL MOVE EAST OF THE WATERS
TUESDAY NIGHT AHEAD OF A PROGRESSIVE SURFACE LOW MOVING TOWARD THE
SOUTHEAST COAST. SOUTHERLY WINDS WILL INCREASE, WITH THE POTENTIAL
FOR SMALL CRAFT ADVISORIES WEDNESDAY NIGHT INTO THURSDAY NIGHT FOR
25 KT GUSTS AND 4-6 FT SEAS. CONDITIONS WILL IMPROVE FRIDAY AS HIGH
PRESSURE SETTLES ACROSS THE REGION.
HIGH SURF: GIVEN THAT SEAS WILL BUILD TO AS HIGH AS 6-10 FEET ON
THE NEARSHORE WATERS TODAY, WE HAVE ISSUED A HIGH SURF
ADVISORY FOR CHARLESTON COUNTY. ELSEWHERE, THE FLOW IS MORE
PARALLEL TO THE COAST.
CHS WATCHES/WARNINGS/ADVISORIES
GA...WIND ADVISORY UNTIL 6 PM EST THIS EVENING FOR GAZ087-088-
099>101-114>119-137>141.
SC...WIND ADVISORY UNTIL 6 PM EST THIS EVENING FOR SCZ040-042>045-
047>052.
HIGH SURF ADVISORY FROM 7 AM THIS MORNING TO 4 PM EST THIS
AFTERNOON FOR SCZ050.
MARINE...SMALL CRAFT ADVISORY UNTIL 7 AM EST THIS MORNING FOR AMZ330-
350-352-354-374.
GALE WARNING FROM 7 AM THIS MORNING TO 3 PM EST THIS AFTERNOON
FOR AMZ330.
GALE WARNING FROM 7 AM THIS MORNING TO 6 PM EST THIS EVENING
FOR AMZ350-352-354-374.
NEAR TERM...NED
SHORT TERM...BRS
LONG TERM...BRS
AVIATION...NED
MARINE...BRS/NED
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