058
FXUS62 KCHS 160317
AFDCHS
AREA FORECAST DISCUSSION
NATIONAL WEATHER SERVICE CHARLESTON SC
1017 PM EST SAT FEB 15 2025
SYNOPSIS
A STRONG COLD FRONT WILL IMPACT THE AREA SUNDAY, FOLLOWED BY
HIGH PRESSURE FOR MONDAY AND TUESDAY. A LOW PRESSURE SYSTEM
WILL MOVE ACROSS THE REGION DURING THE MIDDLE OF NEXT WEEK.
HIGH PRESSURE WILL THEN RETURN LATE NEXT WEEK.
NEAR TERM /UNTIL 6 AM SUNDAY MORNING/
A STRONG TROUGH ALOFT WILL SWEEP EASTWARD TO THE AREA FROM
MISSOURI TO THE ARKLATEX, AS SURFACE LOW PRESSURE DEEPENS AS IT
LIFTS FROM THE TENNESSEE VALLEY INTO THE OHIO VALLEY OVERNIGHT.
A PAIR OF STRONG COLD FRONTS STRETCHING FROM THE LOW WILL
APPROACH THE APPALACHIAN MOUNTAINS LATE. AT THE SAME TIME, A
WARM FRONT ASSOCIATED WITH THE LOW, AND FOUND ACROSS GEORGIA
LATE SATURDAY, WILL LIFT NORTH AND PASS THROUGH THE ENTIRE
REGION OVERNIGHT.
AHEAD OF THE WARM FRONT, AND BEFORE A 45-55 KT LOW LEVEL JET
ARRIVES, THERE WILL BE SOME AREAS OF FOG OVER THE COASTAL
COUNTIES FROM NEAR THE SAVANNAH RIVER NORTHWARD. THIS IS DUE TO
THE COMBINATION OF STRATUS BUILD DOWN AND SEA FOG. HOWEVER, NO
DENSE FOG ADVISORY IS EXPECTED TO BE ISSUED.
THERE WILL ALSO BE A FEW SHOWERS ASSOCIATED WITH A MID LEVEL
IMPULSE, ISENTROPIC ASCENT, AND LOW LEVEL CONVERGENCE. RAIN
AMOUNTS WILL BE NO MORE THAN A FEW HUNDREDTHS, AND THE HEAVIER
RAINS WITH THE UPSTREAM COLD FRONTS DON'T ARRIVE UNTIL SUNDAY.
GIVEN THE EXTENSIVE CLOUD COVER, INCREASING SOUTHERLY WINDS,
AND ELEVATED DEW POINTS, TEMPERATURES WILL HOLD FAIRLY STEADY
THROUGH THE NIGHT. TEMPERATURES BY DAYBREAK WILL BE AROUND
15-20F WARMER THAN THE SAME TIME SATURDAY MORNING.
SHORT TERM /6 AM SUNDAY MORNING THROUGH TUESDAY/
SUNDAY: A POTENT UPPER LEVEL WAVE WILL ADVECT EAST SUNDAY
MORNING WITH A SEASONABLY STRONG 250 MB JET STREAK APPROACHING
THE AREA (140 - 150 KT). AT 500 MB, THE MID-LEVEL WAVE WILL BE
OVER THE SOUTHERN OHIO RIVER VALLEY AROUND SUNRISE WITH 200 M
HEIGHT FALLS APPROACHING. THE WAVE WILL THEN BEGIN TO TAKE ON A
NEGATIVE TILT AS IT EJECTS NORTHEAST WITH THE CORE OF THE DCVA
AND HEIGHT FALLS MOVING ALONG THE SPINE OF THE APPALACHIANS.
ACROSS SC/ GA 80/100 M HEIGHT FALLS WILL STILL MOVE EAST OVER
THE REGION. AT 850/ 925 MB, THE PGF IS FORECAST TO TIGHTEN
THROUGH THE MORNING PERIOD WITH THE LLJ PEAKING AT 50 TO 60 KT
OVERHEAD. AT THE SURFACE, A COLD FRONT AND ASSOCIATED LINE OF
SHOWERS (WITH A RUMBLE OF THUNDER POSSIBLE) WILL BE APPROACHING
THE WESTERN ZONES BETWEEN 6 AND 8 AM.
TIMING-- SEVERE WEATHER LINE:
* I-95 BETWEEN 9 - 11 AM
* THE GA/ SC COAST BETWEEN 11 AM - 1 PM.
SUNDAY SEVERE THREAT: THE MAIN CONCERN FOR SUNDAY WILL BE THE
CHANCE FOR SEVERE WEATHER/ STRONG TO LOCALLY DAMAGING WIND
GUSTS. CLOUD BEARING SHEAR VALUES ARE AROUND 50 KT ALONG THE
LINE, HOWEVER INSTABILITY IS EXTREMELY LIMITED (ONLY AROUND 100
J/KG OF MU CAPE). AS MENTIONED ABOVE THOUGH, 50 - 60 KT OF WIND
IS FORECAST TO BE IN THE 925/850 MB LAYER AND WITH ANY DOWNWARD
MOMENTUM TRANSFER, LOCALLY DAMAGING WIND GUSTS WILL BE
POSSIBLE. THE GREATEST INSTABILITY, IS TOWARDS SOUTHERN GA AND
THEREFORE SPC HAS INTRODUCED A SLIGHT RISK FOR SEVERE WEATHER
ACROSS GA, AND CONTINUED A MARGINAL RISK FOR SC.
WIND THREAT: A WIND ADVISORY IS ALSO IN EFFECT FOR ALL ZONES
FROM 5 AM THROUGH 6 PM SUNDAY. AHEAD OF THE COLD FRONT, WINDS
WILL START TO APPROACH WIND ADVISORY CRITERIA AND REMAIN GUSTY
AFTER THE LINE PASSES AND A COLD FRONT SWEEPS ACROSS THE REGION.
LATEST FORECAST SOUNDINGS SHOW WIND GUSTS BEHIND THE COLD FRONT
AROUND 30 KT (VIA MOMENTUM TRANSFER TECHNIQUES), OR JUST SHY OF
WIND ADVISORY CRITERIA. GIVEN THE STRONG CAA THOUGH, HAVE OPTED
TO KEEP THE WIND ADVISORY UNTIL 6 PM SUNDAY.
MONDAY AND TUESDAY: SURFACE HIGH PRESSURE WILL BUILD OVER THE
REGION FOR MONDAY AND TUESDAY. QUIET AND DRY WEATHER IS
EXPECTED. THERE WILL BE PLENTY OF SUNSHINE, ALTHOUGH CLOUD COVER
WILL BE ON THE INCREASE DURING THE LATTER HALF OF THE DAY
TUESDAY. SEASONALLY COOL TEMPERATURES MAINLY IN THE MID 50S ON
MONDAY WILL MODERATE CLOSER TO NORMAL FOR TUESDAY. LOWS MONDAY
NIGHT WILL RANGE FROM THE LOW 30S INLAND TO UPPER 30S/AROUND 40
CLOSER TO THE COAST.
LONG TERM /TUESDAY NIGHT THROUGH SATURDAY/
FOCUS FOR THE EXTENDED PERIOD WILL BE ON MID-WEEK AS THE NEXT
WEATHER SYSTEM IMPACTS THE REGION. SURFACE LOW PRESSURE IS EXPECTED
TO DEVELOP OVER THE NORTHERN GULF AND THEN LIFT NORTHEAST, PASSING
NEAR/ALONG THE SOUTHEAST COAST WEDNESDAY INTO WEDNESDAY NIGHT. AMPLE
FORCING FOR ASCENT ALONG WITH PWATS RISING TO WELL OVER AN INCH WILL
RESULT IN A FAIRLY WET DAY WITH WIDESPREAD SHOWERS CURRENTLY
FORECAST. THIS SYSTEM HAS THE POTENTIAL TO BRING 1-2 INCHES OF RAIN
TO THE AREA. INSTABILITY PROGS ARE PRETTY MEAGER, SO NO THUNDER IS
MENTIONED IN THE FORECAST AT THIS TIME. RAIN CHANCES SHOULD DECREASE
WEDNESDAY NIGHT.
THE AFOREMENTIONED LOW WILL LIFT AWAY FROM THE AREA ON THURSDAY,
ALLOWING CHILLY AND DRY HIGH PRESSURE TO BUILD FOR LATE WEEK.
TEMPERATURES WILL BE NOTABLY COOLER, WITH LOWS DIPPING WELL INTO THE
20S. WILL NEED TO MONITOR THE POTENTIAL FOR A COLD WEATHER ADVISORY
(WIND CHILL 20F OR COLDER) THURSDAY NIGHT.
AVIATION /03Z SUNDAY THROUGH THURSDAY/
KCHS/KJZI/KSAV: MAINLY IFR OR MVFR CONDITIONS WILL PREVAIL. GIVEN
A WEAK MID LEVEL IMPULSE PASSING THROUGH, THERE COULD STILL BE
A BRIEF SHOWER OR TWO AT ANY OF THE TERMINALS TONIGHT. FOR
OVERNIGHT INTO EARLY SUNDAY WITH THE PASSAGE OF A 45-55 KT LOW
LEVEL JET, SURFACE WINDS WILL INCREASE. BUT THERE REMAINS ENOUGH
OF A DIFFERENTIAL BETWEEN WINDS AT THE SURFACE AND 2000 FEET TO
INCLUDE LLWS FROM 06-15Z.
SUNDAY: A COLD FRONT WILL CROSS THE ZONES IN THE MORNING WITH A
LINE OF SHOWERS AND POSSIBLY A RUMBLE OF THUNDER. WIND GUSTS OF
30 TO 50 KT ARE POSSIBLE WITH THE PASSAGE OF THIS CONVECTIVE
LINE WITH SOME LOCALIZED HIGHER GUSTS. THE LINE OF SHOWERS WILL
THEN RAPIDLY CLEAR THE COAST LATE SUNDAY MORNING AND BE CLEAR OF
THE TAF SITES BY 18Z SUNDAY.
EXTENDED AVIATION OUTLOOK: VFR WILL RETURN FOR MONDAY AND TUESDAY.
FLIGHT RESTRICTIONS ARE POSSIBLE WEDNESDAY INTO WEDNESDAY NIGHT AS A
LOW PRESSURE SYSTEM PASSES ACROSS THE REGION.
MARINE
WE HAVE CANCELLED THE DENSE FOG ADVISORY FOR THE NEARSHORE
WATERS OF GEORGIA AND OFF THE LOWER SOUTH CAROLINA COAST.
HOWEVER, FOG IS SPREADING NORTH INTO THE CHARLESTON COUNTY
WATERS, INCLUDING CHARLESTON HARBOR. WE HAVE INCREASED THE
COVERAGE OF FOG TO A QUALIFIER OF "AREAS", BUT ANY VISIBILITIES
OF LESS THAN 1 NM LOOKS TO BE TOO LIMITED IN COVERAGE TO HOIST A
DENSE FOG ADVISORY. AS WINDS INCREASE OVERNIGHT DUE TO A
TIGHTENING OF THE PRESSURE GRADIENT AND BOTH THE 850 MB AND 925
MB WINDS APPROACH 40 KT, THE FOG WILL COMPLETELY DISSIPATE.
THOSE SAME WINDS HOWEVER WILL RESULT IN STRENGTHENING SURFACE
WINDS AND THE RESULTING CLIMBING SEAS. SMALL CRAFT ADVISORIES
ARE THEREFORE IN EFFECT FOR ALL WATERS.
SUNDAY: A COLD FRONT WILL BE APPROACHING THE WATERS FROM THE
WEST AND SWEEP ACROSS THE MARINE ZONES IN THE EARLY AFTERNOON.
OUT AHEAD OF THE COLD FRONT, THE CORE OF THE 60 KT JET WILL BE
JUST OFF THE SC COAST. SOME HIGH RES GUIDANCE IS INDICATING THE
POSSIBILITY OF STORM FORCE GUSTS, BUT GIVEN THE TEMPERATURES OF
THE SHELF WATERS HAVE OPTED FOR A GALE WARNING WITH GUSTS
PEAKING AT 45 KT. SEAS WILL ALSO BE DANGEROUS SUNDAY AND PEAK 8
TO 12 FT. A HIGH SURF ADVISORY WAS CONSIDERED, BUT WE OPTED TO
HOLD FOR NOW GIVEN THE COASTLINE PARALLEL WAVE ENERGY. HOWEVER
THIS MIGHT NEED TO BE RE-EVALUATED.
MONDAY THROUGH THURSDAY: MARINE CONDITIONS WILL SUBSIDE ON
MONDAY AS HIGH PRESSURE EXPANDS ACROSS THE AREA AND THE PRESSURE
GRADIENT RELAXES. WINDS WILL TURN NORTHERLY AND EVENTUALLY MORE
NORTHEASTERLY WITH NO CONCERNS THROUGH TUESDAY. A LOW PRESSURE
SYSTEM IS EXPECTED TO IMPACT THE REGION WEDNESDAY INTO WEDNESDAY
NIGHT WHICH WILL BRING THE NEXT CHANCE FOR SMALL CRAFT
ADVISORIES. WINDS COULD STAY ELEVATED ON THURSDAY BEHIND THE
SYSTEM AS HIGH PRESSURE BUILDS INTO THE AREA.
HIGH SURF: GIVEN THAT SEAS WILL BUILD TO AS HIGH AS 6-10 FEET ON
THE NEARSHORE WATERS ON SUNDAY, WE MIGHT REQUIRE A HIGH SURF
ADVISORY, ESPECIALLY FOR CHARLESTON COUNTY, WHERE THE FLOW IS
MORE ONSHORE THAN FURTHER SOUTH, WHERE IT IS MORE PARALLEL TO
THE COAST.
CHS WATCHES/WARNINGS/ADVISORIES
GA...WIND ADVISORY FROM 5 AM TO 6 PM EST SUNDAY FOR GAZ087-088-
099>101-114>119-137>141.
SC...WIND ADVISORY FROM 5 AM TO 6 PM EST SUNDAY FOR SCZ040-042>045-
047>052.
MARINE...SMALL CRAFT ADVISORY UNTIL 7 AM EST SUNDAY FOR AMZ330.
GALE WARNING FROM 7 AM TO 3 PM EST SUNDAY FOR AMZ330.
SMALL CRAFT ADVISORY UNTIL 7 AM EST SUNDAY FOR AMZ350-352-354-
374.
GALE WARNING FROM 7 AM TO 6 PM EST SUNDAY FOR AMZ350-352-354-
374.
NEAR TERM...
SHORT TERM...ETM/HAINES
LONG TERM...ETM
AVIATION...
MARINE...
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