FXUS62 KCHS 261723
AFDCHS

AREA FORECAST DISCUSSION
NATIONAL WEATHER SERVICE CHARLESTON SC
1223 PM EST SAT DEC 26 2009

.SYNOPSIS...
HIGH PRES WILL BUILD INTO GEORGIA AND THE CAROLINAS TODAY AND
PERSIST FOR THE REMAINDER OF THE WEEKEND. BY EARLY MON...A DRY
COLD FRONT WILL PUSH THROUGH THE REGION...FOLLOWED BY STRONGER
HIGH PRES WHICH WILL BUILD OVER THE REGION THROUGH TUE. LOW
PRES WILL IMPACT THE REGION FOR THE LATTER HALF OF THE WEEK.

&&

.NEAR TERM /UNTIL 6 PM THIS EVENING/...
DRY HIGH PRESSURE WILL SLOWLY BUILD EAST INTO THE AREA TODAY. THE
LINGERING LOW CLOUDS FROM THIS MORNING HAVE MOSTLY ERODED HOWEVER
A SUBSTANTIAL VEIL OF CIRRUS ASSOCIATED WITH A 140 KT UPPER JET
WILL CONTINUE THROUGHOUT THE DAY. UPDATED FORECAST GRIDS WITH THE
LATEST OBS BUT NO SIGNIFICANT CHANGES WERE NECESSARY.

&&

.SHORT TERM /6 PM THIS EVENING THROUGH 6 PM SUNDAY/...
THE FAST JET ALOFT WILL STEER AN ELONGATED SHORT WAVE THROUGH
THE NE GULF AND SE STATES TONIGHT BRINGING FURTHER INCREASES IN
MID AND UPPER LEVEL MOISTURE AND CLOUDINESS. OUR LOWER LEVELS
REMAIN DRY AND DESPITE THE HIGH CLOUDS COMBATING RADIATIONAL
COOLING...LOW TEMPERATURES ARE STILL GOING TO BE SUB-FREEZING
OVER OUR COLDER NW INLAND TIER AREAS. WE NUDGED LOW TEMPERATURES
UP A DEGREE OR TWO ALONG AND E OF THE U.S. 17 CORRIDOR WHERE
THICKER MID CLOUDS ARE EXPECTED TO ALIGNED OVERNIGHT.

00Z GUIDANCE CONTINUES TO DEPICT A SHORTWAVE EJECTING NE ACROSS THE 
REGION SUNDAY INTO SUNDAY NIGHT...WITH ASSOCIATED ENHANCED MID LEVEL
MOISTURE SURGING NE AHEAD OF AN APPROACHING COLD FRONT. MODEL 
SOUNDINGS DEPICT A VERY DRY LOW LEVEL AIRMASS ACROSS THE 
REGION...THE TYPE OF AIRMASS THAT WOULD SUPPORT NOTHING MORE THAN 
A FEW SPRINKLES/ICE PELLETS EARLY SUNDAY MORNING THEN ISOLATED 
SPRINKLES FOR THE BALANCE OF THE DAY INTO SUNDAY EVENING. PER 
COLLABORATION WITH JAX OPTED TO LOWER POPS BELOW 15 PERCENT/REMOVE 
ALL MENTION OF PRECIPITATION FROM SUNDAY/SUNDAY EVENING FORECASTS.
OTHERWISE...MID/HIGH LEVEL CLOUDS SHOULD PRODUCE MOSTLY CLOUDY 
SKIES. DESPITE THE CLOUD COVER...AHEAD OF THE APPROACHING COLD FRONT 
TEMPERATURES SHOULD RECOVER TO AROUND 60F MOST LOCATIONS SUNDAY 
AFTERNOON...CLOSE TO NORMAL FOR LATE DECEMBER.

&&

.LONG TERM /SUNDAY NIGHT THROUGH FRIDAY/...
LATE SUNDAY NIGHT...A DRY COLD FRONT WILL PUSH THROUGH THE 
REGION...FOLLOWED BY BUILDING HIGH PRESSURE/A SURGE OF COLD 
ADVECTION AND BEGINNING A PERIOD OF BELOW NORMAL TEMPERATURES THAT 
WILL MOST LIKELY PERSIST THROUGH LATE WEEK AND BEYOND. THE HIGH 
PRESSURE WILL ALSO ENSURE RAIN-FREE CONDITIONS THROUGH TUESDAY 
NIGHT. 

AS THE HIGH EXPANDS OVER THE REGION MONDAY NIGHT...CONDITIONS 
APPEARS FAVORABLE FOR FREEZING TEMPERATURES TO PUSH TO THE COAST.

BY MIDWEEK...ANOTHER SOUTHERN BRANCH LOW PRESSURE WILL TAKE SHAPE 
OVER THE N/W GULF OF MEXICO...AND OVERRUNNING MOISTURE/PRECIPITATION 
WILL EXPAND E/NE ACROSS THE SOUTHEAST. RECENT GUIDANCE HAS TRENDED 
TOWARD A FASTER ONSET OF PRECIPITATION...THUS INTRODUCED CHANCE POPS 
WEDNESDAY AND CONTINUED CHANCE POPS THROUGH THURSDAY AS THE LOW 
PRESSURE PASSES OVER OF JUST S/E OF THE FORECAST AREA. 

MODEL AGREEMENT REGARDING THE TRACK/INTENSITY OF THE SURFACE LOW 
REMAINS POOR...AND FORECAST UNCERTAINTY REGARDING MANY FORECAST 
DETAILS REMAINS HIGH. DUE TO THIS UNCERTAINTY...MAINTAINED SLIGHT 
CHANCE POPS FRIDAY.

&&

.AVIATION /18Z SATURDAY THROUGH THURSDAY/...
WITH HIGH PRESSURE ACROSS THE AREA...VFR CONDITIONS ARE EXPECTED TO 
CONTINUE FOR KCHS AND KSAV. SCATTERED TO BROKEN JET-INDUCED CIRRUS 
WILL CONTINUE TO SPREAD ACROSS THE AREA THIS AFTERNOON AND 
OVERNIGHT. DON/T SEE POTENTIAL FOR LOW CEILINGS AS MODEL SOUNDINGS 
KEEP LOW LEVELS DRY. LESS THAN 10 KT WEST TO NORTHWEST WINDS WILL 
PREVAIL THROUGH SUNDAY.

EXTENDED AVIATION OUTLOOK...VFR THROUGH TUE. MVFR OR LOWER POSSIBLE
IN RAIN WED.

&&

.MARINE...
RESIDUAL SWELL FROM THE DEPARTING SYSTEM WILL KEEP SEAS IN SMALL
CRAFT ADVISORY THRESHOLDS THROUGH THIS AFTERNOON OVER THE OFFSHORE
GA WATERS. OTHERWISE AN OFFSHORE FLOW WILL CONTINUE TO DECREASE
WAVE HEIGHTS OVER THE NEARSHORE WATERS AND NO OTHER FLAGS WILL BE
CARRIED.

MODERATE OFFSHORE SURGING WILL CONTINUE TONIGHT AS HIGH PRES BUILDS
FROM THE W. SEAS SHOULD AVERAGE 2-3 FT NEAR SHORE AND 3-5 FT
BEYOND 20 NM. OFF THE GEORGIA COAST THERE COULD BE SOME GUSTS TO
20 KT AT TIMES BUT WE THINK SCA 

WINDS/SEAS WILL REMAIN BELOW SMALL CRAFT ADVISORY LEVELS SUNDAY INTO 
SUNDAY NIGHT. THEN...ANOTHER SURFACE OF COLD ADVECTION WILL SUPPORT 
STRONGER W/NW WINDS AND BUILDING SEAS BY MONDAY MORNING...AND SMALL 
CRAFT ADVISORY CONDITIONS WILL LIKELY DEVELOP THROUGH MONDAY NIGHT 
ESPECIALLY BEYOND 20 NM. THEN...00Z GUIDANCE SUGGESTS THAT WINDS 
WILL VEER TOWARD THE NORTHEAST TUESDAY/WEDNESDAY...TEMPORARILY 
SLACKENING TUESDAY BEFORE THE SURFACE PRESSURE GRADIENT TIGHTENS 
WEDNESDAY BETWEEN HIGH PRESSURE CENTERED NORTH OF THE WATERS AND
LOW PRESSURE APPROACHING FROM THE SOUTHWEST WEDNESDAY. THUS...BUMPED 
UP WINDS/SEAS SOMEWHAT FROM PREVIOUS FORECASTS FOR TUESDAY/
WEDNESDAY...AND SMALL CRAFT ADVISORY CONDITIONS COULD DEVELOP AROUND 
MIDWEEK. BEYOND WEDNESDAY...LOW PRESSURE WILL TRACK TOWARD THE 
SOUTHEAST COAST. FORECAST UNCERTAINTY REMAINS HIGH REGARDING THE 
TRACK/STRENGTH OF THE LOW PRESSURE AND ASSOCIATED IMPACTS ACROSS THE 
COASTAL WATERS. THE POTENTIAL EXISTS FOR HAZARDOUS WINDS/SEAS BUT 
FORECAST DETAILS COULD REMAIN ELUSIVE UNTIL SOMETIME NEXT WEEK.

&&

.CHS WATCHES/WARNINGS/ADVISORIES...
GA...NONE.
SC...NONE.
MARINE...SMALL CRAFT ADVISORY UNTIL 5 PM EST THIS AFTERNOON FOR AMZ374.

&&

$$