Severe Thunderstorm Warning 29, NWS Jackson, MS

AREA FORECAST DISCUSSION
NATIONAL WEATHER SERVICE JACKSON MS
300 AM CST SAT MAR 9 2002

THE CHALLENGES OF THIS FORECAST WILL BE TO ASSESS THE SEVERE
POTENTIAL FOR EARLY THIS MORNING IN THE NORTHWEST...CHANCES OF
THUNDERSTORMS DURING THE DAY...POSSIBLE WIND ADVISORY FOR MAINLY
POST FRONTAL WINDS FOR TODAY...AND TEMPS FOR THE SHORT TERM. IN THE
LONG TERM WILL ASSESS THUNDERSTORM POTENTIAL FOR LATE MONDAY INTO
TUESDAY AND TAKING OUT RAIN FOR WEDNESDAY.

ON SATELLITE VAPOR IMAGERY A STRONG TROF WAS MOVING THROUGH THE
PLAINS WITH CONVECTION NOTED FROM NORTH LOUISIANA THROUGH ARKANSAS. BEST
UPPER DIVERGENCE WAS OVER THE SOUTHERN PLAINS...APPROACHING THE OHIO
VALLEY. MID LEVEL WARM CAP OR RIDGE WAS LIMITING THE SEVERE
POTENTIAL FOR THE NORTHWEST EARLY THIS MORNING. HOWEVER SHEAR WAS
STILL IMPRESSIVE WITH HELICITY NUMBERS RANGING FROM 400 TO 600 AHEAD
OF THE APPROACHING STRONG COLD FRONT COMING OUT OF THE PLAINS.
SPEAKING OF THE FRONT...WINDS WERE GUSTING FROM 30 TO AROUND 40
MPH BEHIND THE FRONT.

LOOKING AT THE SHORT TERM ALL MODELS DID FAIRLY WELL IN INITIALIZING THE
LOWER AND UPPER LEVELS. LOOKING AT THE SEVERE POTENTIAL HELICITY NUMBERS
WILL RUN 400-600 ACROSS THE REGION THIS MORNING...BEFORE UPPER
DYNAMICS QUICKLY PUSHES SHEAR NORTHEAST OF THE REGION BY NOON
TODAY. THE AVN WAS SLIGHTLY FASTER IN MOVING THE FRONT THROUGH THE
REGION TODAY. BOTH MODELS BRING THE FRONT TO EAST/SOUTHEAST
MISSISSIPPI BY NOON BEFORE EXITING THE COUNTY WARNING AREA BY MID
AFTERNOON. SO WILL KEEP CHANCES OF THUNDERSTORMS ACROSS THE ENTIRE
REGION AND LEAVE A FEW POSSIBLY SEVERE IN THE NORTHWEST FOR THIS
MORNING...JUST IN CASE A FEW DEVELOP SOME GOOD ROTATION WITH ALL THE
SHEAR IN PLACE. LOOKING AT JET DYNAMICS A 110 KNOT JET WILL MOVE
ACROSS THE REGION THE NORTHWEST WILL BE UNDER THE LEFT FRONT
QUAD...ALONG WITH A BRIEF 60 KNOT LOW LEVEL JET THERE THIS MORNING.
THE LOW LEVEL JET WEAKENS BY NOON AS AXIS OF JET MOVES ACROSS THE
SOUTH PART OF THE FORECAST AREA. AS FAR AS SURFACE WINDS ARE CONCERN
WILL GO WITH 15-25 WITH GUSTS TO 35 MPH...ALONG WITH CAUTION ADVISED
ON AREA LAKES. BELIEVE THAT WE WILL GET BRIEF STRONG WINDS WITH THE
INITIAL FRONTAL PASSAGE THEN IT WILL TAPER OFF SOME AFTERWARDS. WILL
DECIDE WHETHER AN ADVISORY IS NECESSARY JUST AFTER DAWN. CLOUDS WILL
DECREASE AFTER THE FRONT AND TEMPS WILL FALL INTO THE 50S AS COLD
AIR ADVECTION PUSHES INTO THE REGION.  FOR TONIGHT THE RAINS SHOULD
END IN THE EAST/SOUTHEAST EARLY THIS EVENING...THEN SKIES SHOULD
BECOME PARTLY CLOUDY THERE...WHILE MOSTLY CLEAR ELSEWHERE. HIGH
PRESSURE WILL BEGIN TO BUILD ACROSS THE REGION FOR OVERNIGHT LOWS IN
THE 30S. FOR SUNDAY THE CENTER OF HIGH PRESSURE WILL MOVE NORTH OF
THE FORECAST AREA. IT WILL BE COOLER WITH HIGHS FROM THE MIDDLE 50S
TO LOWER 60S. FOR SUNDAY NIGHT THE ETA SHOWS SOME MARGINAL MEAN
MOISTURE WILL BE BUILDING ACROSS THE WEST HALF AS HIGH PRESSURE
RETREATS TOWARD THE EASTERN SEABOARD. CROSS SECTIONS SHOW MOISTURE
DEVELOPING IN THE UPPER LEVELS THEN DESCENDING TO THE MIDLEVELS BY
EARLY MONDAY WEST OF THE MISSISSIPPI RIVER.

LOOKING AT TEMPS AND POPS...WILL GO WITH A COMPROMISE OF THE MESO 2M/MAV
MOS GUIDANCE.

EXTENDED DISCUSSION MONDAY THROUGH FRIDAY
LOOKING AT THE ENSEMBLES THE AVN EXTENDED HAS A COLD FRONT PUSHING THROUGH
ON MONDAY NIGHT ALONG WITH AN UPPER TROUGH. IT HAS THE RAIN CLEARING
THE REGION BY EARLY TUESDAY IN THE EAST. LOOKING AT INSTABILITY IT
HAS SOME UPPER JET DYNAMICS BUT NO REAL LOW LEVEL JET FOR GOOD THUNDERSTORM
SUPPORT. CHECKING AREA SOUNDINGS INSTABILITY DOES NOT SEEM CONDUCIVE FOR
THUNDERSTORMS AS WELL. WILL JUST WORD IN SHOWERS FOR LATE MONDAY FOR
THE REGION AND EARLY TUESDAY FOR THE EAST.  THE EUROPEAN MODELS  AND
NOGAPS WERE SIMILAR WITH BRINGING THE FRONT THROUGH ON MONDAY
NIGHT...BUT THE EUROPEAN MODEL WAS A LITTLE FASTER IN THE PROCESS.
THE UK MODEL BUILDS A SHORTWAVE RIDGE OVER THE REGION BY THURSDAY AS
THE EUROPEAN CONTINUES WEST-SOUTHWEST FLOW. LOW PRESSURE WILL
DEVELOP IN THE PLAINS AS THE GULF BEGINS TO OPEN UP ACROSS THE LOWER
MISSISSIPPI VALLEY ON THURSDAY INTO FRIDAY. LOOKING AT THE CANADIAN
MODEL IT WEAKENS THE FRONT BEFORE IT HAS A CHANCE TO MOVE THROUGH ON
MONDAY NIGHT. LOOKS LIKE MOST OF THE UPPER DYNAMICES WILL BE WELL
NORTH OF THE REGION. IT WAS SIMILAR WITH EUROPEAN MODELS ON
WEDNESDAY THROUGH FRIDAY. THE MRF SHOWS GOOD INFLOW FOR THURSDAY
INTO FRIDAY HEAD OF SOUTHERN PLAINS SYSTEM...SO WILL GO WITH PARTLY
CLOUDY THERE.

PRELIM NUMBERS
JAN 62/31/62/30/67 6000
MEI 64/30/61/28/65 7000

.JAN...
AR...NONE.
LA...NONE.
MS...NONE.

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