Hail in Mississippi, January 4, 2009

AREA FORECAST DISCUSSION
NATIONAL WEATHER SERVICE JACKSON MS
1115 AM CST SUN JAN 4 2009

.DISCUSSION...LATEST SURFACE ANALYSIS HAS THE COLD FRONT APPROACHING
SOUTHEAST ARKANSAS. THE FRONT IS EXPECTED TO DRIFT INTO OUR CWFA
THIS AFTERNOON AND STALL OVER SOUTHEAST MISSISSIPPI TONIGHT. VISIBLE
SATELLITE IMAGERY HAS BEEN SHOWING BREAKS IN THE CLOUD COVER AHEAD
OF THE FRONT OVER LOUISIANA AND SE ARKANSAS. THIS HAS ALLOWED
TEMPERATURES TO WARM INTO THE LOWER 70S ALREADY. MOISTURE WAS
POOLING JUST AHEAD OF THE COLD FRONT AS WELL...THUS OUR TEMPERATURES
AND DEW POINTS ARE RUNNING HIGHER IN THE WEST THAN EXPECTED. CLOUD
COVER AND A LITTLE DRIER AIR WERE HOLDING TEMPERATURES AND DEW
POINTS LOWER IN OUR EAST. THE PROXIMITY OF THE FRONT ALONG WITH
GREATER HEATING AND MOISTURE SHOULD RESULT IN GREATER COVERAGE OF
SHOWERS AND STORMS IN OUR WEST THIS AFTERNOON. REGIONAL RADARS ARE
SHOWING AN INCREASING TREND SOUTHWEST OF OUR PARISHES AND HAVE
INCREASED POPS THIS AFTERNOON OVER OUR SOUTHWEST COUNTIES AND
PARISHES. HAVE ALSO RAISED HIGHS A COUPLE OF DEGREES IN THE WEST AND
ADJUSTED TEMP CURVES TO MATCH CURRENT TRENDS. CONSIDERING CLOUD
COVER AND RAINFALL...THINK RECORD HIGHS TODAY...UPPER 70S TO NEAR 80
WILL REMAIN IN TACK. /22/

&&

.PREVIOUS DISCUSSION...SHORT TERM...TODAY THROUGH MONDAY...LATEST
SATELLITE IMAGERY SHOWS A STRONG SOUTHERN STREAM SHORT WAVE MOVING
THROUGH THE SOUTHWEST CONUS. SOUTHWEST FLOW ALOFT WAS NOTED ACROSS
THE LOWER MISSISSIPPI VALLEY. LOW CLOUDS WERE MOVING ACROSS THE
REGION. A COOL AIRMASS WAS NOTED ACROSS THE CENTRAL AND SOUTHERN
PLAINS BEHIND AN APPROACHING COLD FRONT...WHICH STRETCHED FROM
ARKANSAS THROUGH NORTHEAST TEXAS.

FOR TODAY...A COLD FRONT WILL MOVE INTO THE REGION...BUT SOUTHWEST
FLOW ALOFT WILL SLOW THE FRONT DOWN AND MAKE IT BECOME NEARLY
STATIONARY ACROSS THE SOUTHEAST BY THIS EVENING. THERE WILL BE
ENOUGH INSTABILITY FOR SHOWERS AND THUNDERSTORMS TO DEVELOP...BUT
INCREASING 500 MB HEIGHTS...LACK OF SHEAR...FLOW AND HELICITY WILL
PREVENT STORMS FROM BECOMING STRONG TODAY. THERE WILL BE ENOUGH
UPPER JET ENERGY FOR THUNDERSTORMS TO MAINTAIN UNTIL EARLY THIS
EVENING. TODAY HIGHS WILL RANGE FROM THE MIDDLE 60S NORTHWEST TO THE
MIDDLE 70S SOUTHEAST.

FOR TONIGHT...THE QUASI-STATIONARY FRONT WILL STAY ACROSS THE REGION.
EXPECT SHOWERS WITH ISOLATED THUNDERSTORMS FOR EARLY THIS EVENING AS
INSTABILITY DECREASES...THEN IT WILL BECOME ALL SCATTERED SHOWERS
BY MID EVENING. EXPECTING ONLY ISOLATED SHOWERS AFTER MIDNIGHT.
NORTH OF THE BOUNDARY LOWS WILL BE IN THE 40S...TO THE SOUTH
LOWS WILL BE IN THE 50S.

FOR MONDAY...A SOUTHERN STREAM SHORT WAVE WILL CROSS THE
REGION...WHICH WILL ENHANCE SOME LIFT FOR WIDESPREAD SHOWERS AND
THUNDERSTORMS. WE WILL GET SOME BULK SHEAR AND SOME HELICITY WITH
THIS SHORT WAVE. SURFACE INSTABILITY WILL BE LIMITED. THETA E
POTENTIAL WILL BE AROUND 327K. PRECIPITABLE WATER WILL BE AROUND 1.5
INCHES.

AS FAR AS TEMPS ARE CONCERN WENT WITH MOS GUIDANCE ON DAILY HIGHS
AND ADJMAV ON SUNDAY NIGHTS LOWS. AS FAR AS POPS ARE CONCERN ADJUSTED
HIGHER MAV POPS FOR TODAY...KEPT CURRENT POPS FOR TONIGHT AND CURRENT
HIGH POPS FOR MONDAY./17/

.LONG TERM...SEVERE WEATHER SCENARIO SETTING UP FOR MONDAY NIGHT AND
TUESDAY...ESPECIALLY TUESDAY AS A DEEPENING SURFACE LOW LIFTS ACROSS
THE REGION.

THE STALLED BOUNDARY LIFTS BACK INTO THE FORECAST AREA MONDAY
NIGHT...TRENDING FARTHER N THAN THE PAST COUPLE OF RUNS. DEEP
MOISTURE AND ISENTROPIC LIFT DEVELOP ALONG AND N OF THE FRONT AS 850
MB FLOW INCREASES. FORCING INTENSIFIES SIGNIFICANTLY TUESDAY. LOW
LEVEL JET FLOW IS FORECAST TO REACH 60 KTS BY TUESDAY AFTERNOON
AHEAD OF THE DEEPENING SURFACE LOW CENTER AND ASSOCIATED FRONTAL
SYSTEM. LOW LEVEL MOISTURE STREAMS IN TO HELP DESTABILIZE THE AIR
MASS WITH SURFACE DEWPOINTS IN THE 65-67 DEG RANGE AND 850 MB THETAE
VALUES AROUND 330. STRONG DEEP LAYER SHEAR AROUND 60 KTS WILL
ACCOMPANY HELICITY VALUES FROM 200-300 WITH 70-80 KT WINDS AT 500
MB. THE SEVERE WEATHER RISK IS BECOMING MORE ORGANIZED AS IS THE
RISK FOR PERIODS OF HEAVY RAIN IN INTENSE UPPER DIV IN THE RIGHT
REAR QUADRANT OF AN INTENSE UPPER JET. PRECIPITABLE WATER VALUES ARE
ALSO BEGINNING TO TREND SLIGHTLY HIGHER WITH TIME. WILL CONTINUE THE
MENTION OF SEVERE STORMS AND HEAVY RAINFALL IN THE HWO.

CONVECTION DIMINISHES TUESDAY NIGHT BUT RAIN CHANCES CONTINUE WHEN
THE SECOND LOBE OF THE SURFACE LOW LIFTS ACROSS THE REGION. THE COLD
LONG WAVE TROUGH PUSHES INTO THE AREA LATE TUESDAY NIGHT AND CROSSES
THE REGION WEDNESDAY. MOS TEMPERATURES LOOK A BIT TOO WARM
CONSIDERING THE STRENGTH OF THE UPPER TROUGH AND HAVE TRENDED TEMPS
COOLER FOR TUESDAY NIGHT THROUGH WEDNESDAY NIGHT. AFTER SURFACE/850
MB HIGH PRESSURE THURSDAY...LOW LEVEL WARM AIR ADVECTION REDEVELOPS
IN SWLY 850 MB FLOW THURSDAY NIGHT AHEAD OF THE NEXT FRONT.
SIGNIFICANT MODEL DIFFERENCES NOTED ON FRONTAL SPEED FRIDAY AND
SATURDAY WITH THE GFS AND EURO ALMOST 12 HOURS DIFFERENT IN FRONTAL
PLACEMENT FOR SATURDAY. FOLLOWED COOLER GFS MOS FOR NOW WHICH
REFLECTED FASTER GFS SOLUTION BUT THIS WILL LIKELY BE ADJUSTED WITH
TIME.

&&

.AVIATION...LOW IFR-MVFR CEILINGS WERE NOTED ACROSS THE REGION PRIOR
TO DAWN. A COLD FRONT COMBINED WITH AN UPPER DISTURBANCE WILL SET
OFF SOME SHOWERS AND THUNDERSTORMS FOR TODAY AND TONIGHT. EXPECT
IFR-MVFR RESTRICTIONS IN SHOWERS AND THUNDERSTORMS FOR THE PERIOD.
THE SHOWERS WILL DECREASE IN COVERAGE AND BE LIGHT AFTER MIDNIGHT
AND WILL HAVE LITTLE AFFECT ON AVIATION OPERATIONS./17/

&&

.PRELIMINARY POINT TEMPS/POPS...
JACKSON       75  50  57  53 /  53  45  85  90
MERIDIAN      73  53  60  55 /  54  50  77  86
VICKSBURG     73  49  54  47 /  51  45  88  92
HATTIESBURG   76  57  66  60 /  61  44  76  61
NATCHEZ       74  51  57  51 /  52  58  85  90
GREENVILLE    67  42  45  43 /  43  23  85  92
GREENWOOD     68  44  48  48 /  49  21  81  93

&&

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

17/03

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