Area Forecast Discussion
Issued by NWS Charleston, SC

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000
FXUS62 KCHS 221230
AFDCHS

AREA FORECAST DISCUSSION
NATIONAL WEATHER SERVICE CHARLESTON SC
730 AM EST MON DEC 22 2014

.SYNOPSIS...
UNSETTLED WEATHER IS EXPECTED TODAY THROUGH TUESDAY NIGHT AS
SEVERAL DISTURBANCES MOVE OVER THE REGION. A STRONG COLD FRONT
WILL THEN MOVE THROUGH THE AREA WEDNESDAY EVENING. DRY HIGH
PRESSURE WILL SETTLE OVER THE SOUTHEAST INTO THE WEEKEND. ANOTHER
COLD FRONT COULD SHIFT THROUGH THE AREA EARLY NEXT WEEK.

&&

.NEAR TERM /THROUGH TONIGHT/...
NEAR DAWN...CLOUDY AND COOL CONDITIONS PREVAILING OVERNIGHT AS
THE SURFACE WEDGE PATTERN REMAINS ENTRENCHED OVER GEORGIA AND THE
CAROLINAS. SINCE MIDNIGHT...PATCHES OF LIGHT RAIN...DRIZZLE...AND
EVEN SOME SMALL CONVECTIVE ELEMENTS HAVE BEEN PASSING NE OVER THE
REGION. AN AXIS OF DEEP GULF MOISTURE EXTENDS ACROSS NORTH FLORIDA
AND OUR GEORGIA ZONES CLOSER TO THIS RICH MOISTURE SOURCE SHOULD
CONTINUE TO SEE MORE WIDESPREAD LIGHT RAINS. TEMPS UNIFORM IN THE
WEDGE IN THE MID TO UPPER 40S. STRATUS WAS DOWN TO A COUPLE
HUNDRED FEET OFF THE DECK ALONG THE COAST AND FOG WAS RUNNING 1-2
MILES FROM SAVANNAH TO CHARLESTON...LOCALLY DOWN TO 1/2 MILE OR
LESS NEAR THE INTRA-COASTAL.

A REGION OF CONCENTRATED UPPER DIFLUENCE ACROSS THE FORECAST AREA
EARLY THIS MORNING NOTED ON MODEL PROGS A MID LEVEL SHORT WAVE
RACES OVER THE CAROLINAS. UPPER FORCING APPEARS TO BE WEAKER LATER
TODAY BUT WE CONTINUE TO SEE STEADY ISENTROPIC ASCENT. FORECAST
SOUNDINGS SHOW CLASSIC WEDGE PROFILES WITH MOISTURE DEEP ENOUGH
FOR DRIZZLE AND LIGHT RAINS AT TIMES ACROSS ZONES BORDERING THE
MIDLANDS AND CSRA. MOISTURE PROFILES MUCH DEEPER TO THE SOUTH
OF SAVANNAH AND THESE AREAS SHOULD CONTINUE TO SEE STEADIER
MEASURABLE RAINS PERIODICALLY IN PROXIMITY TO THE DEEPER MOISTURE.
THE CLOUDY DAMP AND OFTEN RAINY WEATHER WILL BE ACCOMPANIED BY
HIGH TEMPS IN THE LOW TO MID 50S MOST AREAS TODAY.

SOUNDINGS SHOW LOW-MID 50S AIR AT THE SURFACE TODAY AND THIS EVENING
AND MID 60S AIR AT 300-400 FT WHICH IS PRIME FOR STRATUS BUILDING
DOWN GIVEN A SETUP WITH LIGHTER WINDS IN THE BOUNDARY LAYER. THE
BIG QUESTION IS WHETHER FOGGY CONDITIONS SET IN EVEN EARLY THAN
EXPECTED WHICH APPEARS TO BE OCCURRING ALREADY ON MONDAY MORNING.
THE STORY TONIGHT SHOULD BE FOG AND PROBABLY DENSE IN MANY AREAS.
WE HAVE ADDED DENSE FOG POTENTIAL TO THE HAZARDOUS WEATHER OUTLOOK.
OTHERWISE...THE WARM FRONT MAY MOVE INTO THE OUR SOUTHERN GEORGIA
ZONES BY DAYBREAK ON TUE AND A CONTINUATION OF PERIODIC DRIZZLE
AND MAINLY LIGHT RAIN SHOWERS. MID LEVELS LOOK PRETTY UNSTABLE BUT
ELEVATED THUNDER RISK IS PRETTY LOW AS MODELS SHOW MID LEVEL NVA
AND SOMEWHAT DRIER AIR ALOFT. TEMPS OVERNIGHT SHOULD BE STEADY AND
EVEN RISE LATE. POPS MAINLY IN THE CHANCE RANGE.

&&

.SHORT TERM /TUESDAY THROUGH THURSDAY NIGHT/...
TUESDAY AND WEDNESDAY...A LARGE SYNOPTIC SCALE TROUGH OF LOW PRESSURE
WILL DIG OVER THE CENTRAL UNITED STATES...SPAWNING A SFC LOW OVER
THE NORTHERN GULF OF MEXICO TUESDAY THAT QUICKLY DEEPENS AND LIFTS
NORTH/NORTHEAST WITH A COLD FRONT EXTENDING SOUTHWARD INTO WEDNESDAY.
A STRONG H5 SHORTWAVE ROUNDING THE BASE OF THE HIGH AMPLITUDE TROUGH
AS WELL AS A STRONG LOW/MID/UPPER LVL JET WILL LIKELY FORCE THE
SOUTHWARD EXTENDING COLD FRONT TO THE EAST...EVENTUALLY PUSHING IT
THROUGH THE FORECAST AREA LATE WEDNESDAY AFTERNOON INTO EARLY
WEDNESDAY NIGHT.

AHEAD OF THE COLD FRONT...A DEEP PLUME OF MOISTURE CHARACTERIZED BY
PWATS UP TO 1.8-1.9 INCHES WILL ADVECT TO THE AREA AS A WARM FRONT
BEGINS TO LIFT NORTH AND ENCOUNTERS THE PERSISTENT WEDGE INLAND.
WIDESPREAD SHOWERS WILL THEREFORE REMAIN IN THE FORECAST FOR MOST
AREAS. MODELS NOW SUGGEST THE WARM FRONT WILL LIFT A BIT FURTHER
NORTH ON TUESDAY THAN PREVIOUSLY NOTED...TRYING TO SCOUR OUT WHAT IS
LEFT OF WEDGE OF HIGH PRESSURE INLAND. HOWEVER...WE STILL BELIEVE
THIS IS A BIT AGGRESSIVE WITH THE WEDGE CURRENTLY IN PLACE SO HAVE
MAINTAINED TEMPS A FEW DEGREES BELOW GUIDANCE...ESPECIALLY INLAND
WHERE THE WEDGE SHOULD HOLD DURING PEAK HEATING HOURS TUESDAY
AFTERNOON. GIVEN THIS SCENARIO...SLIGHT CHANCES OF THUNDERSTORMS
WILL REMAIN IN THE FORECAST TUESDAY AFTERNOON/EVENING WHERE SBCAPES
APPROACH 800 J/KG AND MODEST MID LVL LAPSE RATES OCCUR SOUTH OF THE
WARM FRONT. WE COULD SEE SOME ENHANCEMENT TO THUNDERSTORM ACTIVITY
AS SEVERAL MID LVL WAVES OF ENERGY ADVANCE OVER THE AREA TUESDAY
AFTERNOON AND/OR EVENING. THUNDERSTORMS MAY ALSO NEED TO BE INCLUDED
IN FUTURE FORECASTS FOR INLAND AREAS SHOULD ELEVATED INSTABILITY
CONTINUE TO INCREASE OVER THE WEDGE. IN GENERAL...AFTERNOON HIGH
TEMPS SHOULD RANGE IN THE LOW/MID 60S INLAND TO UPPER 60S IN
SOUTHEAST GEORGIA TUESDAY AFTERNOON.

AS DIURNAL HEATING IS LOST TUESDAY NIGHT...THUNDERSTORM CHANCES
SHOULD MAINLY OCCUR OFFSHORE...BUT DEEP MOISTURE WILL LIKELY
MAINTAIN WIDESPREAD SHOWERS WHILE FORCING INCREASES FROM THE
WEST. TUESDAY NIGHT TEMPS WILL BE MILD WITHIN A SOUTHERLY FLOW AHEAD
OF THE APPROACHING COLD FRONT...WITH LOWS ONLY DIPPING INTO THE
UPPER 50S TO LOWER 60S.

WIDESPREAD CLOUD COVER AND ONGOING SHOWERS SHOULD LIMIT THE OVERALL
THERMODYNAMIC ENVIRONMENT ON WEDNESDAY. HOWEVER...STRONG WIND FIELDS
JUST OFF THE SFC COULD RESULT IN SOME GUSTY WINDS CONDITIONS AS
TEMPS APPROACH 70 DEGREES WEDNESDAY AFTERNOON. A SLIGHT CHANCE OF
THUNDERSTORMS WILL REMAIN IN THE FORECAST FOR ALL AREAS GIVEN THE
AMOUNT OF MID/UPPER LVL FORCING SHIFTING OVER THE REGION. HOWEVER
THE BEST CHANCES OF THUNDERSTORMS SHOULD OCCUR AS THE COLD FRONT
PUSHES INTO THE AREA WEDNESDAY EVENING INTO EARLY WEDNESDAY NIGHT.
GUSTY WINDS SHOULD CONTINUE FOR A FEW HOURS WEDNESDAY NIGHT AS
STRONG COLD AIR ADVECTION OCCURS BEHIND THE FRONT. CONDITIONS WILL
THEN QUICKLY DRY OUT FROM WEST TO EAST LATE WEDNESDAY NIGHT AS HIGH
PRESSURE BEGINS TO PUSH INTO THE REGION.

THURSDAY...MUCH DRYER/QUIET WEATHER CONDITIONS ARE EXPECTED AS THE
MID LVL TROUGH AXIS SHIFTS OFFSHORE AND HIGH PRESSURE SETTLES OVER
THE SOUTHEASTERN UNITED STATES. DESPITE A RETURN TO MOSTLY SUNNY
SKIES...TEMPS WILL REMAIN COOLER AS COLD AIR ADVECTS OVER THE AREA.
IN GENERAL...AFTERNOON TEMPS SHOULD RANGE IN THE MID TO UPPER 50S
OVER MOST AREAS.

&&

.LONG TERM /FRIDAY THROUGH SUNDAY/...
QUIET WEATHER WILL PREVAIL INTO THE WEEKEND AS HIGH PRESSURE BECOMES
CENTERED OVER THE SOUTHEASTERN UNITED STATES. OVERALL HIGH TEMPS
SHOULD GRADUALLY WARM EACH DAY AS HIGH PRESSURE CONTINUES TO SLIDE
EAST LATE WEEKEND...ALLOWING A LIGHT SOUTHERLY FLOW TO RETURN TO THE
AREA. IN GENERAL...TEMPS WILL REACH THE LOWER 60S ON FRIDAY...THEN
TO THE MID 60S ON SATURDAY. OVERNIGHT LOWS SHOULD RANGE IN THE THE
LOW/MID 40S INTO THE WEEKEND. THE NEXT BEST CHANCE OF PRECIP SHOULD
OCCUR EARLY NEXT WEEK WITH A COLD FRONT THAT APPROACHES THE REGION.
HOWEVER...CONFIDENCE IN TIMING AND STRENGTH OF PATTERN IS QUITE LOW
GIVEN LARGE DISCREPANCIES IN MODEL SOLUTIONS.

&&

.AVIATION /12Z MONDAY THROUGH FRIDAY/...
KSAV...THE TERMINAL MOST LIKELY WILL REMAIN TANKED AS A STRONG WEDGE
INVERSION PERSISTS JUST OFF THE DECK AND GENERATES IFR OR LOWER
CONDITIONS THROUGH 06Z TUESDAY. IN ADDITION...MID AND UPPER LEVEL
ENERGY AND THE PROXIMITY TO A COASTAL WARM FRONT NEAR THE GULF
STREAM WILL PRODUCE PERIODS OF RAIN OR DRIZZLE.

KCHS...LIFR CONDITIONS DEVELOPING AT 09Z...DENSE FOG MAY ENSUE
AS CIGS DOWN TO 200 FT AND VSBYS AT 1 NM. THE NEXT 24 HOURS WILL
SEE LOW CIGS AND PERHAPS PERIODS OF FOGGY CONDITIONS AS STRATUS
CLOUDS REMAINED PINNED IN THE FIRST FEW HUNDRED FEET OF THE
ATMOSPHERE. OCCASIONAL DRIZZLE LIKELY WITH A CHANCE OF SHOWERS.
IFR OR LOWER CONDITIONS PREVAIL THROUGH THE TAF PERIOD.

EXTENDED AVIATION OUTLOOK...PERIODS OF MVFR OR LOWER CONDITIONS ARE
LIKELY LIKELY TUESDAY AFTERNOON INTO WEDNESDAY AFTERNOON AS A STRONG
COLD FRONT APPROACHES FROM THE WEST WITH SHOWERS AND THUNDERSTORMS.
LLWS WILL BE A POSSIBILITY TUESDAY NIGHT AS STRONGER WIND FIELDS
SHIFT OVER THE AREA IN ADVANCE OF THE FRONT. MVFR OR LOWER
CONDITIONS AND GUSTY WINDS ARE EXPECTED UNTIL THE TIME OF FRONTAL
PASSAGE SOMETIME WEDNESDAY EVENING INTO EARLY WEDNESDAY NIGHT. VFR
CONDITIONS SHOULD THEN PREVAIL BY DAYBREAK THURSDAY.

&&

.MARINE...
ALL SMALL CRAFT ADVISORIES HAVE BEEN LOWERED AS OF 7 AM. SEAS STILL
3-5 FT NEAR SHORE. WATCHING CIGS COME DOWN ON SAVANNAH WEB CAMS
EARLY THIS MORNING AS WELL. FOG ADVISORIES MAY BE NEEDED ALONG THE
GEORGIA COAST. WINDS WILL BE LIGHTER AS A COASTAL FRONT NUDGES CLOSER
THROUGH TONIGHT. THERE WILL RESIDUAL 3 TO 4 FT SEAS LATER THIS MORNING
SUBSIDING TO 2-4 FT BY TONIGHT.

TUESDAY...CONDITIONS SHOULD REMAIN JUST BELOW SMALL CRAFT ADVISORY
LEVELS AS A WEDGE OF HIGH PRESSURE PERSISTS INLAND WHILE A WARM
FRONT TRIES TO LIFT NORTH DURING THE AFTERNOON. SHOWERS AND/OR
THUNDERSTORMS ARE ANTICIPATED OVER THE WATERS THROUGH THE DAY. IN
GENERAL...WINDS SHOULD PEAK BETWEEN 15-20 KT WITH SEAS UP TO 3-4
FT...HIGHEST IN OFFSHORE GEORGIA WATERS.

TUESDAY NIGHT THROUGH WEDNESDAY NIGHT...CONDITIONS WILL LIKELY
DETERIORATE LATE TUESDAY NIGHT INTO EARLY WEDNESDAY AS THE PRESSURE
GRADIENT TIGHTENS AND WARMER AIR PROMOTES MIXING AHEAD OF A COLD
FRONT THAT EVENTUALLY SHIFTS OVER THE WATERS WEDNESDAY
EVENING/NIGHT. SHOWERS AND THUNDERSTORMS WILL BE POSSIBLE OVER MOST
WATERS AHEAD OF THE FRONT...WHILE WINDS AND SEAS INCREASE/BUILD
WITHIN A SOUTHERLY FLOW. AT THIS TIME...CONDITIONS SHOULD REACH
SMALL CRAFT ADVISORY LEVELS FOR ALL WATERS STARTING LATE TUESDAY
NIGHT. SEAS WILL ALSO BUILD UPWARDS TO 5-8 FT INTO WEDNESDAY
AFTERNOON BEFORE THE COLD FRONT SHIFTS OFFSHORE. THERE IS STILL A
CHANCE OF GALE FORCE WIND GUSTS LATE WEDNESDAY NIGHT INTO EARLY
THURSDAY AS STRONG COLD AIR ADVECTION OCCURS BEHIND THE FRONT...BUT
CHANCES APPEAR HIGHEST IN OUTER GEORGIA WATERS. A GALE WATCH/WARNING
COULD EVENTUALLY BE NEEDED AS WINDS GUST TO 30-35 KT AWAY FROM THE
COAST.

THURSDAY AFTERNOON THROUGH SATURDAY...CONDITIONS WILL IMPROVE
QUICKLY OVER ALL WATERS AS HIGH PRESSURE BECOMES CENTERED OVER THE
SOUTHEAST. WINDS/SEAS SHOULD LOWER BELOW SMALL CRAFT ADVISORY LEVELS
FOR ALL WATERS THURSDAY AFTERNOON...THEN CONTINUE TO IMPROVE
THROUGH THE WEEKEND AS THE CENTER OF HIGH PRESSURE SLIDES OFFSHORE.

SEA FOG...MARINERS ARE ADVISED THAT LOW STRATUS DECKS AND PERIODS OF
RAIN OR DRIZZLE WILL EQUATE TO REDUCED VISIBILITIES UNTIL WEDNESDAY...
BUT THE BEST CHANCE OF CLASSIC SEA FOG COULD DEVELOP AS WARMER AIR
ARRIVES ATOP MID/UPPER 50 SHELF WATER TEMPS EARLY TUESDAY PRIOR TO
WINDS INCREASING ENOUGH TO SCOUR IT OUT TUESDAY NIGHT.

&&

.TIDES/COASTAL FLOODING...
GIVEN THE PERIGEAN SPRING TIDES AND PERSISTENT NORTHEAST WINDS THE
MORNING TIDE AT DOWNTOWN CHARLESTON HAS ALREADY REACHED 7.1 FT MLLW
AND WAS STILL RISING. TUESDAY MORNING/S TIDE DOES NOT LOOK AS
SUBSTANTIAL BUT WILL MONITOR FOR POSSIBLE SHALLOW COASTAL FLOODING.

&&

.CHS WATCHES/WARNINGS/ADVISORIES...
GA...NONE.
SC...COASTAL FLOOD ADVISORY UNTIL 9 AM EST THIS MORNING FOR SCZ050.
MARINE...DENSE FOG ADVISORY UNTIL 11 AM EST THIS MORNING FOR AMZ330-350.

&&

$$

NEAR TERM...
SHORT TERM...DPB
LONG TERM...DPB
AVIATION...
MARINE...DPB
TIDES/COASTAL FLOODING...





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