Severe Thunderstorm Warning 289, NWS Jackson, MS

AREA FORECAST DISCUSSION
NATIONAL WEATHER SERVICE JACKSON MS
320 PM CDT FRI APR 7 2000

FORECAST CONFIDENCE REMAINS HIGH THROUGH THE WEEKEND AS MODELS ARE
LEAVING LITTLE TO DECIPHER IN THE DETAILS. CURRENTLY...A STRONG COLD
FRONT EXTENDS FROM CNTRL MO THRU NW AR INTO NE TX. OVER THE FORECAST
AREA...A STRONG SOUTHWEST FLOW CONTINUES TO BRING A GRADUAL INCREASE
TO LOW LEVEL MOISTURE. A STRONG MID LEVEL CAP IS ALSO IN PLACE WITH
AREAS OF CU DEVELOPING UNDER CAP...DO NOT EXPECT DEEP CONVECTION TO
BREAK OUT UNTIL APPROACH OF THE COLD FRONT WHEN ENOUGH LOW LEVEL
FORCING WILL EXIST TO BREAK THE CAP.

LATEST MESO-ETA BRINGS THE COLD FRONT INTO ERN AR AND NW LA BY 00Z.
BY THIS TIME...ENOUGH LOW LEVEL FORCING...INSTABILITY...AND MOISTURE
SHOULD BE AVAILABLE TO INITIATE RAPID THUNDERSTORM DEVELOPMENT ALONG
AND AHEAD OF THE COLD FRONT. THIS THE THUNDERSTORM ACTIVITY IS
PROGGED TO MOVE WELL INTO THE FORECAST AREA BY 03Z REACHING A
COLUMBUS TO NATCHEZ LINE BY MIDNIGHT. ACCORDING TO THE
MESO-ETA...DEEP CONVECTION WILL BEGIN EXITING SOUTHEAST PORTIONS OF
THE FORECAST AREA AFTER 09Z...AND DOWN TO THE GULF COAST BY 12Z. THE
TIMING IS CONSISTENT WITH MODEL RUNS FROM PAST SEVERAL DAYS AND WILL
LEAVE THE LIKELY POPS IN FOR TONIGHT. CONCERNING SEVERE WEATHER
THREAT...CONTINUES TO LOOK LIKE A STRAIGHT-LINE WIND/HAIL THREAT
WITH EXPECTATION OF SQUALL LINE DEVELOPMENT AND WILL ZONES AS
SUCH...BUT WILL LEAVE MENTION OF SEVERE THUNDERSTORM THREAT OUT OF
SOUTHEAST ZONE WORDING.

SATURDAY AND SATURDAY NIGHT...THE CLOCK TURNS BACK A COUPLE OF
MONTHS AS AN UNSEASONABLY STRONG COLD HIGH PRESSURE SYSTEM BUILDS IN
BEHIND THE COLD FRONT. STRONG LOW LEVEL COLD AIR ADVECTION WILL KEEP
TEMPS WELL BELOW SEASONAL AVERAGES SAT AND SAT NITE DESPITE PLENTY
OF SUNSHINE BY SAT AFTN. WILL MENTION WINDY WORDING IN ZONES FOR
SATURDAY AS STRONG MIXING WILL TAKE PLACE UP TO 875MB WITH ETA
FORECASTS LINKED WINDS OF 35 TO 40 KT WINDS. WINDS SHOULD SEE NO
PROBLEM AVERAGING 20 TO 30 MPH AT SURFACE. OTHER PROBLEM WILL BE
WITH TEMPS SATURDAY NIGHT. FWC/FAN GUIDANCE INDICATE THAT LOW
TEMPERATURES WILL DIP TO FREEZING OR JUST BELOW OVER MOST OF THE
AREA. UNLIKE THE LAST COLD EVENT THIS PAST WEEK...GROUND WILL BE A
BIT DRYER AND THE SFC HIGH WILL BE STRONGER AND IN BETTER POSITION
AS THE PRESSURE GRADIENT RELAXES RAPIDLY BY SAT EVENING BRINGING
IDEAL RADIATIONAL COOLING CONDITIONS.

SUNDAY...WILL BE DRY AND A BIT WARMER AS THE UPPER TROF PROGRESSES
EASTWARD AND THE COOL SURFACE HIGH PRESSURE MODIFIES.

QPF DISCUSSION...QPF DISCUSSION: ETA/NGM/AVN ALL AGREE ON TIMING AND
LOCATION OF PRECIP AXIS WITH FAST MOVING SQUALL LINE BUT DIFFER ON
AMOUNTS. THE AVN MODEL HAS BEEN PERFORMING WELL. PERCIPITABLE WATER
AMOUNTS WILL BE AROUND 1.30 JUST AHEAD OF THE FRONT. SO WILL GO WITH
AROUND QUARTER INCH BASIN AVERAGE QPF. THIS WILL BE SIMILAR WITH
NCEP GUIDANCE.

IN THE EXTENDED...HIGHLY CONFIDENT THAT MONDAY WILL BE DRY ACROSS
THE AREA...BUT MODEL DISCREPANCIES CONTINUE FOR TUESDAY AND BEYOND.
NCEP GUIDANCE HAS LEANED TOWARDS THE ECMWF SOLUTION OF A SLIGHTLY
WEAKER NORTH ATLANTIC BLOCK. THE ECMWF PROGS THE BEST RAIN CHANCES
FOR TUESDAY A LITTLE FARTHER NORTH THAN THE MRF...BUT THE
DISPLACEMENT IS NOT ENOUGH TO REMOVE PRECIP CHANCES FOR THE AREA.
OVERALL...FORECAST CONFIDENCE LOW FOR TUESDAY AND WEDNESDAY AND
GIVEN UNSETTLED LOOKING WEATHER PATTERN WILL CONTINUE TREND OF
PRECIP CHANCES. TEMPERATURES SHOULD BE SEASONABLE THRU THE EXTENDED
PERIOD.

PRELIMINARY NUMBERS...
JAN 48/59/32/71 6-00
MEI 50/59/30/71 6-00

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

43/17

ARZ074-075-LAZ007>009-015-016-023>026-MSZ018-019-025>066-072>074-
080500-

SPECIAL WEATHER STATEMENT
NATIONAL WEATHER SERVICE JACKSON MS
530 PM CDT FRI APR 7 2000

...UNSEASONABLY COLD AND WINDY WEATHER EXPECTED SATURDAY AND
SATURDAY NIGHT...

A COLD FRONT CURRENTLY FROM CENTRAL ARKANSAS TO EASTERN TEXAS WILL
MOVE THROUGH THE STATE DURING THE OVERNIGHT HOURS. AS THE FRONT MOVES
SOUTHEAST...STRONG HIGH PRESSURE WILL BEGIN TO BUILD IN BEHIND THE
BOUNDARY BRINGING MUCH COLDER TEMPERATURES AND WINDY CONDITIONS TO
THE REGION. WINDS WILL BEGIN TO SHIFT TO THE NORTHWEST AT 15 TO TO 25
MPH LATER TONIGHT...AND DURING THE DAY SATURDAY WINDS ARE EXPECTED TO
INCREASE TO AROUND 20 TO 30 MPH SUSTAINED WITH SOME HIGHER GUSTS.

ALONG WITH THE WINDY CONDITIONS...UNSEASONABLY COLD TEMPERATURES ARE
ALSO EXPECTED. DURING THE DAY SATURDAY...HIGHS ARE EXPECTED TO REACH
THE MID 50S IN NORTH CENTRAL MS TO AROUND 60 IN SOUTHERN SECTIONS.
SATURDAY NIGHT LOW TEMPERATURES WILL REACH NEAR FREEZING OVER
MUCH OF THE AREA WHICH WILL LIKELY ESTABLISH NEW RECORDS FOR THE
DATE.

TAKE PRECAUTIONS TO PROTECT TENDER VEGETATION FROM THE COLD
TEMPERATURES...AND REMEMBER TO SECURE ANY OUTDOOR ITEMS SUBJECT TO
STRONG WINDS.