FXUS62 KCAE 232335
AFDCAE
AREA FORECAST DISCUSSION
NATIONAL WEATHER SERVICE COLUMBIA SC
635 PM EST WED DEC 23 2009
.SYNOPSIS...
HIGH PRESSURE OVER THE REGION TONIGHT WILL BEGIN TO MOVE EAST
THURSDAY. A STORM SYSTEM WILL APPROACH FROM THE SOUTHWEST LATE
THURSDAY AND AFFECT THE AREA CHRISTMAS EVE THROUGH CHRISTMAS DAY.
DRY HIGH PRESSURE WILL THEN RETURN OVER THE WEEKEND.
&&
.SHORT TERM /6 PM THIS EVENING THROUGH 6 PM THURSDAY/...
HIGH PRESSURE WILL KEEP DRY WEATHER OVERNIGHT. THE HIGH CLOUDS
ASSOCIATED WITH DEVELOPING LOW PRESSURE SYSTEM OFF TO THE WEST
WILL KEEP LOWS TO NIGHT SLIGHTLY WARMER THAN PREVIOUS NIGHTS.
OVERNIGHT LOWS IN THE LOWER 30S NORTH TO UPPER 30S SOUTH.
AN UPPER LEVEL LOW PRESSURE WILL MOVE OUT OF THE SOUTHERN ROCKIES
LATE TONIGHT AND INTENSIFY ON THE DAY THURSDAY. SURFACE LOW
FORECAST TO DEVELOP ACROSS THE SOUTHERN PLAINS STATES IN
ASSOCIATION WITH STRONG UPPER SYSTEM. THIS SYSTEM WILL REMAIN FAR
ENOUGH OFF TO THE WEST THURSDAY MORNING TO LIMIT RAIN.
HOWEVER...INCREASING ISENTROPIC LIFT FROM SOUTHWESTERLY WINDS
RIDING OVER TOP OF WEAK SURFACE WEDGE WILL CAUSE AN INCREASE IN
CLOUDS AND RAIN CHANCES BY THURSDAY AFTERNOON. AFTERNOON HIGHS
WILL RANGE FROM AROUND 50 NORTH TO NEAR 60 SOUTH.
&&
.SHORT TERM /THURSDAY NIGHT THROUGH FRIDAY/...
SURFACE RIDGE WILL BE PUSHED NORTH AND EAST THURSDAY NIGHT AS A
LOW PRESSURE SYSTEM LIFTS NORTHEAST INTO THE MISSISSIPPI RIVER.
ISENTROPIC LIFT WILL SPREAD ACROSS THE AREA THURSDAY NIGHT INTO
FRIDAY. NAM MODELS STILL A BIT SLOWER THAN THE GFS/ECMWF. WENT
WITH A COMPROMISE FOR FRONTAL MOVEMENT. CHRISTMAS EVE AND
CHRISTMAS DAY STILL LOOKING WET. CATEGORICAL POPS FOR THE PERIOD.
RAINFALL AMOUNTS BETWEEN 1.00 AND 1.50 INCHES. AIR MASS OVER THE
SOUTHEAST MIDLANDS FORECAST TO BECOME UNSTABLE AHEAD OF THE FRONT
FRIDAY AFTERNOON. SO...ADDED A CHANCE OF THUNDERSTORMS.
LOWS IN THE 40S THURSDAY NIGHT. SURGE OF WARM AIR WILL ALLOW
TEMPS TO WARM INTO THE MID 50S TO LOWER 60S IN SPITE OF CLOUDS AND
RAIN ON FRIDAY.
&&
.LONG TERM /FRIDAY NIGHT THROUGH WEDNESDAY/...
LARGE POLAR VORTEX OVER THE MID MS RIVER VALLEY TO SLOWLY MOVE
NORTHEAST ACROSS THE GREAT LAKE REGION INTO NEW ENGLAND THROUGH
TUESDAY. GFS A BIT FASTER TAKING THE SYSTEM NORTHEAST THAN THE
ECMWF. MEDIUM RANGE MODELS SHOWING SLIGHT UPPER LEVEL RIDGING
ACROSS THE SOUTHEAST TUESDAY AND WEDNESDAY. THE SURFACE COLD FRONT
WILL BE MAKING ITS WAY OFF THE CAROLINA COAST FRIDAY NIGHT. HIGH
PRESSURE BUILDING IN FROM THE WEST SATURDAY THROUGH TUESDAY.
WEST/NORTHWEST FLOW AT H850 WILL KEEP THE GULF CLOSED. DRY AND
COOL PERIOD EXPECTED. BY WEDNESDAY, SURFACE RIDGE MOVING OFF THE
EAST COAST AND ANOTHER LOW PRESSURE SYSTEM WILL BE CROSSING THE
GULF. GFS SHOWING ISENTROPIC LIFT AND A CHANCE OF RAIN WEDNESDAY
AS THE SURFACE LOW MOVES FROM THE NORTHERN GULF ACROSS FLORIDA.
ECMWF IS ABOUT 12 HOURS SLOWER THAN THE GFS.
SO...A RAIN-FREE AND RELATIVELY TRANQUIL PERIOD IS EXPECTED THIS
WEEKEND THROUGH MIDWEEK. HIGH TEMPERATURES WILL BE AROUND NORMAL
SATURDAY...THEN BELOW NORMAL TEMPERATURES SUNDAY THROUGH MIDWEEK.
&&
.AVIATION /00Z THURSDAY THROUGH TUESDAY/...
HIGH PRESSURE WILL CONTINUE TO WEDGE DOWN INTO THE REGION THROUGH
THE TAF PERIOD. SATELLITE LOOP SHOWS PLENTY OF MID/HIGH CLOUDS
SPREADING ACROSS THE REGION THIS EVENING AND THIS WILL CONTINUE
THROUGH THE OVERNIGHT PERIOD. TIME SECTIONS SHOW LOW LEVEL MOISTURE
TO BEGIN INCREASING ACROSS THE AREA THURSDAY MORNING. BOTH NAM/GFS
SHOW ISENTROPIC LIFT INCREASING THROUGH THE DAY ON TUE. LLJ WILL
INCREASE OVERNIGHT AND EXPECT WINDS TO REMAIN LIGHT FROM THE
NORTHEAST TONIGHT. CONDITIONS WILL REMAIN VFR TONIGHT AND INTO
THURSDAY MORNING...BUT AS ISENTROPIC LIFT INCREASES THROUGH THE DAY
EXPECT MVFR CONDITIONS DUE TO CLOUDS TO DEVELOP BETWEEN 15-16Z. NO
MENTION AT THIS TIME OF PCPN THROUGH THE TAF PERIOD.
EXTENDED AVIATION OUTLOOK...MVFR CONDITIONS POSSIBLE THURSDAY NIGHT
INTO FRIDAY AS A STORM SYSTEM MOVES THROUGH THE REGION. HIGH
PRESSURE WILL BUILD INTO THE REGION FOR FRIDAY NIGHT THROUGH MONDAY.
&&
.CAE WATCHES/WARNINGS/ADVISORIES...
SC...NONE.
GA...NONE.
&&
$$
