115
FXUS62 KCHS 161121
AFDCHS
AREA FORECAST DISCUSSION
NATIONAL WEATHER SERVICE CHARLESTON SC
621 AM EST THU JAN 16 2025
SYNOPSIS
HIGH PRESSURE WILL PREVAIL THROUGH THE WEEK. A LOW PRESSURE
SYSTEM AND ASSOCIATED COLD FRONT WILL IMPACT THE REGION THIS
WEEKEND. ANOTHER LOW PRESSURE SYSTEM COULD IMPACT THE REGION
EARLY TO MID NEXT WEEK.
NEAR TERM /THROUGH TONIGHT/
EARLY THIS MORNING, GOES WATER VAPOR SHOWED A MID-LEVEL SHORT WAVE
RIPPLING EAST ACROSS THE DEEP SOUTH. THICK MID CLOUD WILL REMAIN
ALONG AND AHEAD OF THE DISTURBANCE. THE PASSING CLOUD COVER SHOULD
KEEP MORNING TEMPERATURES IN THE MID 30S ACROSS SE GA TO AROUND 30
ACROSS THE CHS TRI-COUNTY.
BASED ON SATELLITE TRENDS, THE BACK EDGE OF THE CLOUD COVER SHOULD
REACH THE COAST AROUND SUNRISE. THE FORECAST AREA WILL REMAIN
BETWEEN HIGH PRESSURE CENTERED OVER THE NORTHERN GULF OF MEXICO AND
LEE TROUGH ACROSS THE SOUTHERN AND MIDDLE APPALACHIANS. THIS PATTERN
WILL SUPPORT STRENGTHENING SOUTHWEST WINDS THROUGH THIS AFTERNOON.
AS TEMPERATURES PEAK AROUND 60 DEGREES THIS AFTERNOON, THE MIXED
LAYER SHOULD DEEPEN TO AROUND 5 KFT. MOMENTUM TRANSFER SHOULD RESULT
IN GUSTS BETWEEN 20-25 MPH LATE THIS MORNING THROUGH THIS AFTERNOON.
IN ADDITION, DEWPOINTS ARE FORECAST TO REMAIN IN THE UPPER 20S THIS
AFTERNOON, RESULTING IN SOME SPOTS OF RH VALUES BELOW 30 PERCENT.
THE PRESSURE GRADIENT ACROSS THE FORECAST AREA WILL RELAX TONIGHT AS
THE CENTER OF HIGH PRESSURE APPROACHES FROM THE WEST. WINDS FROM THE
WNW SHOULD FALL BELOW 5 MPH FOR MOST OF TONIGHT. THE COMBINATION OF
CLEAR SKY AND LIGHT WINDS SHOULD ALLOW FOR FAIR RADIATIONAL COOLING
CONDITIONS THROUGH MOST OF TONIGHT. LOW TEMPERATURES ARE FORECAST TO
RANGE FROM THE LOW 30S INLAND TO THE UPPER 30S ALONG THE COAST.
SHORT TERM /FRIDAY THROUGH SUNDAY/
FRIDAY: HIGH PRESSURE AT THE SURFACE WILL SHIFT OFF THE SOUTHEASTERN
COAST AS LOW PRESSURE DEVELOPS IN THE VICINITY OF ARKLATEX
ASSOCIATED WITH AN UPPER LEVEL SHORTWAVE. A QUIET DAY IS FORECAST
OVER THE LOCAL REGION, WITH PLENTIFUL SUNSHINE AND HIGH TEMPERATURES
REACHING INTO THE UPPER 50S TO LOW 60S, WARMEST IN SOUTHEASTERN GA.
CLOUDS WILL BEGIN TO INCREASE FRIDAY NIGHT AS THE LOW PRESSURE TREKS
EASTWARD ALONG WITH ITS ASSOCIATED COLD FRONT. DUE TO THE INCREASING
CLOUD COVER OVERNIGHT TEMPERATURES WILL BE NEAR NORMAL VALUES, WITH
UPPER 30S INLAND AND LOW 40S ALONG THE COASTAL COUNTIES.
SATURDAY AND SUNDAY: THE PATTERN TURNS ACTIVE ON SATURDAY AS A COLD
FRONT APPROACHES THE REGION FROM THE WEST. A RATHER MOIST AIRMASS
WILL BE USHERED INTO THE REGION EARLY SATURDAY MORNING, WITH PWATS
SURGING TO AROUND 1.3-1.5". IF THESE VALUES COME TO FRUITION THEY
WOULD RIVAL THE DAILY MAX ACCORDING TO SPC'S CLIMATOLOGY. SHOWERS
WILL INITIALLY MOVE INTO THE FAR WESTERN ZONES BY DAYBREAK SATURDAY
MORNING, OVERSPREADING THE FORECAST AREA BY SATURDAY AFTERNOON.
SHOWERS WILL LIKELY PERSIST THROUGH SATURDAY NIGHT, WANING SUNDAY
MORNING. OVERALL STORM TOTAL RAINFALL LOOKS TO BE AROUND 1-1.5
INCHES. TEMPERATURES EACH DAY WILL REMAIN NEAR NORMAL, WITH
HIGHS IN THE UPPER 50S TO LOW 60S.
LONG TERM /SUNDAY NIGHT THROUGH WEDNESDAY/
AS THE COLD FRONT PUSHES OFFSHORE, THE POTENTIAL FOR ANY SHOWERS
SUNDAY NIGHT BECOMES RATHER LOW LEAVING A MOSTLY DRY FORECAST.
HEADING INTO MONDAY AND MONDAY NIGHT, A COLD HIGH PRESSURE SYSTEM
WILL BUILD INTO THE REGION OVERHEAD AND ALLOW STRONG CAA TO DOMINATE
THE NEXT FEW DAYS.
TRANSITIONING TO TUESDAY AND BEYOND, THE FORECAST BECOMES
INCREASINGLY TRICKY AND POTENTIALLY IMPACTFUL. THE COLD TEMPERATURES
SEEM TO BE THE ONLY PART OF THE FORECAST MET WITH HIGH CONFIDENCE,
AS FOR THE REST OF FORECAST IS WHERE CONFIDENCE DECREASES
SIGNIFICANTLY. WITH THE 00Z GFS/ECMWF DETERMINISTIC MODEL RUNS
SUGGESTING A MORE SUPPRESSED SOLUTION WITH THE SURFACE HIGH PUSHED
VERY FAR SOUTH AND REMOVING ANY CHANCE OF PRECIPITATION FROM
DEVELOPING. THIS IS WILDLY DIFFERENT FROM THE LAST COUPLE MODEL RUNS
WHICH WAS SHOWING SOME SORT OF COASTAL LOW PASSING BY TO THE SOUTH
OR JUST OFFSHORE AND BRINGING A WINTRY MIX OF SNOW AND ICE ALONG
WITH IT. HOWEVER, THE GFS/ECMWF ENSEMBLE MEMBERS ARE STILL IN
AGREEMENT WITH THIS SOLUTION. THUS, CONSIDERABLE UNCERTAINTY REMAINS
WITH THIS SYSTEM AND ALL SCENARIOS ARE STILL ON THE TABLE.
AVIATION /12Z THURSDAY THROUGH MONDAY/
12Z TAFS: VFR CONDITIONS EXPECTED ACROSS THE TERMINALS THROUGH
THE TAF PERIOD. FORECAST SOUNDINGS INDICATE THAT MIXING WILL
DEEPEN TO AROUND 5 KFT DURING THIS AFTERNOON. THE COMBINATION OF
2-3 MB PRESSURE GRADIENT AND DEEP MIXING SHOULD RESULT IN GUSTS
BETWEEN 20-25 KTS BETWEEN 16-23Z. THE REST OF THE EVENING
SHOULD FEATURE SOUTHWEST WINDS BETWEEN 5 TO 10 KTS WITH CLEAR
SKY CONDITIONS.
EXTENDED AVIATION OUTLOOK: VFR CONDITIONS ARE EXPECTED TO PREVAIL
THROUGH THE END OF THE WEEK. A FRONT IS EXPECTED TO BEGIN IMPACTING
THE AREA SATURDAY, BRINGING THE POTENTIAL FOR SHOWERS AND BRIEF
PERIODS OF FLIGHT RESTRICTIONS.
MARINE
THE MARINE ZONES WILL REMAIN BETWEEN AN AREA OF HIGH PRESSURE
CENTERED TO THE SOUTH AND A BROAD AREA OF LOW PRESSURE EAST OF THE
APPALACHIANS. THIS PATTERN WILL YIELD A 2-3 MB PRESSURE GRADIENT
ACROSS THE MARINE ZONE TODAY INTO LATE TONIGHT. AS A RESULT,
SOUTHWEST WINDS SHOULD STRENGTHEN THIS MORNING. BY THIS AFTERNOON,
THE NEARSHORE SC WATERS ALONG WITH THE OUTER GA WATERS SHOULD SEE
FREQUENT GUSTS BETWEEN 25-30 KTS. IN ADDITION, SEAS WILL BUILD
THROUGH THE DAY, REACHING 3-5 FT BY THIS EVENING. AS HIGH PRESSURE
APPROACHES FROM THE WEST TONIGHT, WINDS SHOULD DECREASE TO AROUND 15
KTS. THE NEARSHORE SC WATERS (OUTSIDE THE CHS HARBOR) ALONG WITH THE
OUTER GA WATERS WILL BE HIGHLIGHTED WITH SMALL CRAFT ADVISORIES FROM
THIS AFTERNOON UNTIL 4 AM FRIDAY.
FRIDAY THROUGH TUESDAY: AS A SURFACE HIGH PRESSURE MOVES ACROSS THE
WATERS FRIDAY, CONDITIONS WILL BECOME RATHER QUITE AS WINDS DIMINISH
TO AROUND 10 KT AND SHIFT MORE EASTERLY/SOUTHEASTERLY FRIDAY NIGHT.
MOVING INTO SATURDAY, WINDS SHIFT INTO A SOUTHERLY/SOUTHWESTERLY
FLOW AND BEGIN TO INCREASE AHEAD OF THE APPROACHING COLD FRONT TO 10
TO 15 KT. BEHIND THE COLD FRONT, WINDS BECOME NORTHWESTERLY AND PICK
UP TO 15 TO 20 KT WITH GUSTS UP TO 25 KT. SMALL CRAFT ADVISORIES
APPEAR MORE LIKELY DURING THIS TIME PERIOD. SEAS WILL VARY ACROSS
THE FORECAST PERIOD, BUT MAINLY WILL BE FROM 2 TO 4 FT UNTIL TUESDAY
NIGHT WITH SEAS INCREASING TO 4 TO 6 FT (AND 7 FT IN THE OUTER
GEORGIA WATERS).
CHS WATCHES/WARNINGS/ADVISORIES
GA...NONE.
SC...NONE.
MARINE...SMALL CRAFT ADVISORY FROM 1 PM THIS AFTERNOON TO 4 AM EST
FRIDAY FOR AMZ350.
SMALL CRAFT ADVISORY FROM 4 PM THIS AFTERNOON TO 4 AM EST
FRIDAY FOR AMZ352-374.
NEAR TERM...NED
SHORT TERM...CPM
LONG TERM...DENNIS
AVIATION...DENNIS/NED
MARINE...DENNIS/NED
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