FXUS64 KJAN 271014
AFDJAN
AREA FORECAST DISCUSSION
NATIONAL WEATHER SERVICE JACKSON MS
414 AM CST FRI NOV 27 2009
.SHORT TERM...FRIDAY THROUGH SATURDAY NIGHT...HIGH PRESSURE WILL
CONTINUE BUILDING OVER THE REGION TODAY KEEPING CLEAR SKIES IN THE
FORECAST...ALONG WITH COLD MORNING LOWS. MOST AREAS REPORTING AT OR
BELOW FREEZING TEMPERATURES AS OF THIS WRITING WITH AREAS NORTH
HOLDING ON JUST ABOVE FREEZING. NOT EXPECTING THIS TO LAST LONG
THOUGH AND WILL CONTINUE THE FREEZE WARNING FOR ALL AREAS THROUGH
8AM THIS MORNING.
A PLEASANT BUT COOL DAY CAN BE EXPECTED TODAY AS TEMPS WARM TO NEAR
60 ACROSS THE ARKLAMISS. NORTHWESTERLY FLOW ALOFT WILL GRADUALLY
BECOME WESTERLY AND EVENTUALLY SOUTHWESTERLY BY THIS TIME TOMORROW
AS A WEAK SOUTHERN STREAM S/WV CROSSES THE GULF COAST. ONLY IMPACTS
WILL BE SOME MID/UPPER LEVEL CLOUDINESS INTRUDING THE SKY STARTING
LATE THIS AFTERNOON. DRY LOW LEVEL CONDITIONS WILL PRECLUDE ANY RAIN
CHANCES. TOMORROW'S MORNING LOWS WILL NOT BE AS COLD AS THEY ARE
TONIGHT AS A SLIGHT INCREASE IN CLOUD COVER COMBINES WITH DEVELOPING
SOUTHERLY FLOW AS THE SFC HIGH PRES THAT IS IN PLACE SLIDES EAST. MAY
STILL SEE FREEZING CONDITIONS OVER FAR EASTERN ZONES TOMORROW NIGHT
BUT CONSIDERING AS LATE AS IT IN THE SEASON...AND THAT WE HAD A GOOD
FREEZE TONIGHT...WILL OMIT RAISING A FREEZE WARNING FOR THESE AREAS.
WILL REMOVE MENTION OF FROST AS WELL FOR THE SAME REASONS.
CONTINUING LOW LEVEL SOUTHERLY FLOW IN WAKE OF THE HIGH WILL MEAN
WARMER DAYTIME HIGHS ON SATURDAY WITH TEMPS REACHING THE MID 60S.
UPPER LEVEL CLOUD COVER WILL INCREASE LATE IN THE DAY AS THE JET
STRENGTHENS OVER THE SOUTHERN STATES AHEAD OF A S/WV CROSSING THE
DESERT SOUTHWEST. THIS WILL CONTINUE INTO THE MORNING HOURS ON
SUNDAY...AND WILL HELP KEEP TEMPS IN THE UPPER 30S EAST TO UPPER 40S
WEST DUE TO INCREASED INSULATION. MAV GUIDANCE WAS ON THE HIGH END OF
THE ENVELOPE THROUGH SUNDAY MORNING AND MADE SLIGHT DOWNWARD
ADJUSTMENTS ALL PERIODS AS A RESULT. /BK/
.LONG TERM...SUNDAY THRU THURSDAY...THE FORECAST PROBLEM DURING THIS
PERIOD IS THE EVOLUTION OF MID LEVEL CUTOFF LOW OVER THE NRN BAJA OF
CA AT 12Z SUNDAY AND THE DISASSOCIATED MID LEVEL TROF PULLING AWAY
OVER THE NRN PLAINS.
ALTHOUGH SUBTLE DIFFERENCES DO EXIST...GFS...GFS ENSEMBLE AND ECMWF
ARE ALL IN REASONABLE GOOD AGREEMENT DURING THIS TIME PERIOD.
DISASSOCIATED MID LEVEL TROF PULLING AWAY FROM THE CUTOFF LOW WILL
CONTINUE TO TRANSITION EAST...DEEPENING AS IT DOES SO. THIS FEATURE
WILL DRAG A FRONT INTO THE AREA BY SUNDAY NIGHT/MONDAY. UNTIL IT DOES
SO...PERSISTENT SWLY FLOW WILL SLOWLY MOISTEN THE ATMOSPHERE IN
STEADILY INCREASING DEEP LAYER WARM AIR ADVECTION. BEST ISENTROPIC
LIFT LOOKS TO GET GOING JUST ALONG AND BEHIND THE FRONT AS IT ENTERS
THE AREA MOVING INTO MONDAY MORNING. WHILE OVERALL OMEGA INCREASES
DURING THIS TIME FRAME...MAGNITUDES AND LACK OF INSTABILITY SUGGEST
ADIABATIC MOTIONS WILL DOMINATE WITH A LACK OF DEEP CONVECTION. HAVE
REMOVED THUNDER WORDING PREVIOUSLY IN THE FORECAST.
PRECIP WANES DURING LATE MONDAY NIGHT/TUESDAY MORNING AS FRONT
STALLS ALONG THE COAST...WINDS VEER AND ISENTROPIC LIFT SHUTS DOWN.
THIS IS SHORT-LIVED...HOWEVER AS BACKING WINDS DURING THE AFTERNOON
ALLOW BOUNDARY TO LIFT RAPIDLY BACK NORTH IN RESPONSE TO THE
APPROACHING COLD CORE LOW MOVING OUT OF TX BY THIS TIME. A SURFACE
LOW LOOKS TO DEVELOP OVER THE NRN GULF IN INCREASING WAR
ADVECTION/ISENTROPIC LIFT WHICH WILL GIVE THE AREA ANOTHER SHOT AS
SOME SHOWERY ACTIVITY TUESDAY NIGHT ESPECIALLY SOUTH. SHOWERS WILL
ONCE AGAIN BE POSSIBLE WEDNESDAY AS THE COLD CORE LOW ACTUALLY MOVES
ACROSS THE CWA. /GRG/
&&
.AVIATION...VFR CONDS XPCTD TO CONTINUE THRU TOMORROW AS HIGH
PRESSURE DOMINATES THE REGION. WINDS WILL REMAIN LGT AND WRLY THIS
AFTN BECOMING SRLY OVERNIGHT. /BK/
&&
.PRELIMINARY POINT TEMPS/POPS...
JACKSON 60 37 64 43 / 0 0 0 3
MERIDIAN 60 32 65 38 / 0 0 0 0
VICKSBURG 61 40 65 46 / 0 0 1 8
HATTIESBURG 62 34 64 43 / 0 0 0 0
NATCHEZ 61 40 66 48 / 0 0 2 8
GREENVILLE 60 40 65 46 / 0 0 2 6
GREENWOOD 59 38 66 44 / 0 0 0 3
&&
.JAN WATCHES/WARNINGS/ADVISORIES...
MS...FREEZE WARNING UNTIL 8 AM CST THIS MORNING FOR MSZ018-019-
025>066-072>074.
LA...FREEZE WARNING UNTIL 8 AM CST THIS MORNING FOR LAZ007>009-015-
016-023>026.
AR...FREEZE WARNING UNTIL 8 AM CST THIS MORNING FOR ARZ074-075.
&&
$$
BK/GRG
