FXUS62 KCAE 111730
AFDCAE
AREA FORECAST DISCUSSION
NATIONAL WEATHER SERVICE COLUMBIA SC
1230 PM EST FRI DEC 11 2009
.SYNOPSIS...
DRY HIGH PRESSURE WILL DOMINATE THROUGH TONIGHT. MOISTURE WILL
INCREASE SATURDAY AHEAD OF LOW PRESSURE FROM THE GULF OF MEXICO.
THE LOW WILL BE NEAR THE AREA SATURDAY NIGHT...AND LIFT NORTH OF
THE REGION SUNDAY. RAIN MAY BE MIXED WITH SLEET SATURDAY BECAUSE
OF THE COLD AIR IN PLACE AHEAD OF THE LOW PRESSURE SYSTEM.
&&
.NEAR TERM /UNTIL 6 PM THIS EVENING/...
STRONG AND COLD HIGH PRESSURE CENTERED OVER TENNESSEE IS CURRENTLY
DOMINATING THE WEATHER. VISIBLE SATELLITE IMAGERY SHOWING HIGH
CLOUDS STREAMING OVER THE AREA FROM THE SOUTHWEST...TAPPING
MOISTURE FROM THE EASTERN PACIFIC. CLOUDS SHOULD CONTINUE TO
INCREASE IN COVERAGE THROUGH THE AFTERNOON HOURS AND THIS SHOULD
INHIBIT TEMPERATURES FROM RISING MUCH TODAY. AS THE HIGH SHIFTS TO
THE EAST TODAY...WINDS WILL ALSO SHIFT AROUND TO THE
NORTHEAST...WHICH IS NOT A WARMING FLOW FOR THE FORECAST AREA.
WILL UPDATE FORECAST TO LOWER TEMPERATURES A DEGREE OR TWO ACROSS
THE NORTHERN HALF OF THE CWA WITH A GRADIENT TO SLIGHTLY WARMER
TEMPERATURES ACROSS THE SOUTH. NO CHANCE FOR PRECIPITATION TODAY.
&&
.SHORT TERM /6 PM THIS EVENING THROUGH SATURDAY NIGHT/...
THE DRY AIR MASS SHOULD REMAIN IN PLACE TONIGHT. ALL OF THE MODELS
KEEP DEEP MOISTURE SUPPRESSED SOUTH OF THE FORECAST AREA. LIGHT
WIND AND JUST HIGH CLOUDINESS SUPPORTS STRONG RADIATIONAL COOLING
AT LEAST EARLY TONIGHT. EXPECT LOW TEMPERATURES SIMILAR TO THIS
MORNING. THE MODELS SHOW AN INCREASE IN ISENTROPIC LIFT AND
MOISTURE FROM SOUTH TO NORTH SATURDAY. THE NAM IS SLOWER WITH THE
TIMING OF THE MOISTURE INCREASE...BUT BOTH MODELS INDICATE
SIGNIFICANT PRECIPITATION SHOULD HOLD OFF UNTIL THE AFTERNOON.
THIS APPEARS REASONABLE BECAUSE OF THE INITIAL DRYNESS AND THE
MODEL FORECAST OF WEAK ISENTROPIC LIFT EARLY. THE THREAT OF
FREEZING RAIN APPEARS LOW BECAUSE OF AN EXPECTED START LATER IN
THE DAY. THE INITIAL DRYNESS AND EVAPORATIVE COOLING POTENTIAL IN
LAYERS ALOFT SUPPORTS POSSIBLE SLEET. ANY SLEET SHOULD END FROM
SOUTH TO NORTH DURING THE AFTERNOON. MAINTAINED THE SLEET
POTENTIAL A LITTLE LONGER THAN INDICATED BY FORECAST THICKNESSES
AND SOUNDINGS BECAUSE THE MODELS ARE PROBABLY TOO FAST WITH THE
WARMING IN THE WEDGE PATTERN. STRONG ISENTROPIC LIFT AND DEEP
MOISTURE SUPPORTS CATEGORICAL POPS SATURDAY NIGHT INTO SUNDAY
MORNING. THE TEMPERATURE GUIDANCE APPEARS TOO WARM SATURDAY AND
SUNDAY BECAUSE OF THE WEDGE PATTERN AND CLOUDINESS.
&&
.LONG TERM /SUNDAY THROUGH THURSDAY/...
PLAN LITTLE CHANGE TO THE PREVIOUS FORECAST WHICH IS IN GOOD
AGREEMENT WITH THE LATEST OPERATIONAL GFS. THE GFS SHOWS DRY
RIDGING EARLY MONDAY...BUT A RETURN TO ISENTROPIC LIFT WITH AN
INCREASE IN MOISTURE LATER IN THE DAY. THE CONTINUED MOISTURE
INCREASE SUPPORTS A CHANCE OF RAIN MONDAY NIGHT WITH A CHANCE
REMAINING TUESDAY ASSOCIATED WITH A COLD FRONT. THE GFS SHOWS
DRYING BEHIND THIS FRONT DOMINATING FOR WEDNESDAY AND THURSDAY.
THE ECMWF IS IN CLOSE AGREEMENT WITH THE GFS. HOWEVER...THE GFS
ENSEMBLES INDICATE HIGH SPREAD SO CONFIDENCE IS LOW DURING THE
EXTENDED PERIOD.
&&
.AVIATION /18Z FRIDAY THROUGH WEDNESDAY/...
STRONG HIGH PRESSURE WILL KEEP DRY CONDITIONS AND VFR CIGS/VSBYS
THROUGH THE 24 HOUR TAF FORECAST. HIGH CLOUDS WILL CONTINUE TO
BLANKET THE TERMINALS THIS AFTERNOON AND OVERNIGHT. MOISTURE WILL
INCREASE EARLY SATURDAY AHEAD OF AN APPROACHING STORM SYSTEM AND
CIGS WILL LOWER DURING THE 12/12Z-12/18Z TIME FRAME. SIGNIFICANT DRY AIR
IN PLACE WILL PREVENT PRECIPITATION FROM REACHING THE SURFACE
DURING THE INITIAL HOURS OF PRECIPITATION ONSET...WHICH IS
EXPECTED TO ARRIVE BETWEEN 12/18Z-13/00Z. WINDS WILL BE GENERALLY
LIGHT OUT OF THE NORTHEAST THIS AFTERNOON BEFORE GOING NEARLY CALM
OVERNIGHT AND THEN PICK UP OUT OF THE EAST ON SATURDAY.
EXTENDED AVIATION OUTLOOK...EXPECT WIDESPREAD SIGNIFICANT
PRECIPITATION WITH MVFR/IFR CIGS/VSBYS LATE SATURDAY THROUGH
SUNDAY. SOME LOW CIGS MAY LINGER INTO MONDAY. A COLD FRONT IS
EXPECTED TO COME THROUGH TUESDAY WITH A CHANCE OF SHOWERS AND
ASSOCIATED RESTRICTIONS TO CIGS/VSBYS.
&&
.CAE WATCHES/WARNINGS/ADVISORIES...
SC...NONE.
GA...NONE.
&&
$$
AVIATION...HC
