Area Forecast Discussion
Issued by NWS Jackson, MS

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000
FXUS64 KJAN 250951
AFDJAN

AREA FORECAST DISCUSSION
NATIONAL WEATHER SERVICE JACKSON MS
351 AM CST THU DEC 25 2014

.DISCUSSION...CHRISTMAS DAY THROUGH FRIDAY NIGHT...MERRY CHRISTMAS
FROM THE MIDNIGHT SHIFT HERE AT NWS JACKSON! LOOK FOR A NICE
CHRISTMAS DAY ACROSS THE REGION AS HIGH PRESSURE AT THE SURFACE
BUILDS THROUGH THE LOWER MISSISSIPPI RIVER VALLEY. AFTER A CHILLY
START THIS MORNING...HIGHS WILL WARM INTO THE 50S UNDER SUNNY SKIES.
SOUTHERLY FLOW OVER THE AREA TODAY WILL ALLOW FOR SLIGHTLY WARMER
OVERNIGHT LOWS... RANGING FROM THE MID 30S TO AROUND 40 UNDER MOSTLY
CLEAR SKIES.

CONDITIONS WILL CONTINUE TO WARM FRIDAY AND FRIDAY NIGHT UNDER
PERSISTENT LOWER AND MID-LEVEL SOUTHERLY FLOW.  THE COMBINATION OF
AN APPROACHING MID/UPPER TROUGH FROM THE WEST AND INCREASING WARM
ADVECTION...WITH RESULT IN INCREASING CLOUDS AND RAIN CHANCES FROM
LATE FRIDAY AFTERNOON THROUGH FRIDAY NIGHT.  HIGHS FRIDAY WILL RANGE
FROM THE UPPER 50S TO MIDDLE 60S.  LOWS FRIDAY NIGHT WILL BE ON THE
MILD SIDE AS THEY ONLY RANGE FROM THE MID 40S TO UPPER 50S. /19/

SATURDAY THROUGH THURSDAY...AT THE ONSET OF THE PERIOD MID LEVEL
FLOW WILL HAVE ALREADY BEEN AMPLIFIED BY WAVE MOVING OUT OF THE PAC
NW INTO THE SOUTHERN ROCKIES. MOIST LOW LEVEL SOUTHERLY FLOW WILL BE
ONGOING AS SURFACE HIGH HAS SHIFTED TO THE EAST COAST. MEANWHILE...
DEEP SW FLOW ALOFT WILL HAVE ALREADY TAPPED INTO THE HIGH PW AIR
(VALUES AROUND 1.75) POISED OVER THE NW GULF OF MEXICO. ALL OF THIS
ACTING AS A PRELUDE TO ISENTROPIC RAINS BREAKING OUT OVER THE AREA.

RETREATING BAROCLINIC ZONE AHEAD OF SURFACE COLD FRONT OVER AR/LA
SATURDAY LOOKS TO ALLOW WARM SECTOR AND MID 60 DEWPOINTS TO SURGE AS
FAR NORTH AS THE HIGHWAY 84 CORRIDOR SATURDAY AFTERNOON INTO
SATURDAY NIGHT. WHILE NEAR MOIST ADIABATIC LAPSE RATES ARE NOT THAT
IMPRESSIVE...ML CAPES OF 300-500 J/KG ARE MORE THAN ADEQUATE FOR
THUNDER. GFS/ECMWF HAVING DIFFICULTIES FORECASTING 0-3KM SRH WITH
CONSIDERABLE DIFFERENCES BETWEEN THE TWO. HOWEVER...THEY ARE IN
AGREEMENT WITH DEEP LAYER SHEAR VALUES VALUES OF AROUND 50 KNOTS
OVER THE WARM SECTOR. WHILE THERE ARE POSITIVES AND NEGATIVES FOR
ORGANIZED CONVECTION...FEEL THERE IS ENOUGH OF A SIGNAL IN THE MODEL
DATA TO POSE A LIMITED THREAT OVER SOUTHERN SECTIONS OF THE CWA.

WHILE SURFACE COLD FRONT WILL HAVE MOVED OUT OF THE AREA BY SUNDAY
NIGHT...SW FLOW ALOFT WILL CONTINUE THE ANAFRONTAL ISENTROPIC RAIN
REGIME UNTIL MID LEVEL SHORT WAVE CAN PASS MONDAY AFTERNOON.
MEANWHILE...STRONG WAVE WILL BE DIGGING SOUTH THROUGH THE WESTERN US
AND CREATE A FAST PACED ZONAL FLOW OVER THE SOUTHERN CONUS. AS THE
MID LEVEL SYSTEM MOVES INTO THE FOUR CORNERS BY WEDNESDAY/
THURSDAY...ISENTROPIC RAINS LOOK TO BREAK OUT AGAIN OVER THE
REGION. /26/

&&

.AVIATION...VFR FLIGHT CATEGORIES ARE BEGIN OBSERVED AT ALL TAF
LOCALES...AND WILL CONTINUE THROUGH THE COURSE OF CHRISTMAS DAY AND
INTO EARLY FRIDAY MORNING.  WINDS TODAY WILL BE SOUTHERLY BETWEEN
5-10 KNOTS...AND WILL GRADUALLY SUBSIDE TO LIGHT TO CALM HEADING
INTO CHRISTMAS NIGHT. /19/

&&

.PRELIMINARY POINT TEMPS/POPS...
JACKSON       55  37  61  53 /   0   0  13  43
MERIDIAN      55  33  60  48 /   0   0  13  35
VICKSBURG     57  37  62  54 /   0   0  14  45
HATTIESBURG   57  37  62  53 /   0   0  12  44
NATCHEZ       56  42  63  57 /   0   0  24  61
GREENVILLE    54  37  60  51 /   0   0  12  38
GREENWOOD     54  37  60  51 /   0   0  12  33

&&

.JAN WATCHES/WARNINGS/ADVISORIES...
MS...NONE.
LA...NONE.
AR...NONE.
&&

$$

19/26





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