Severe Thunderstorm Warning 1, NWS Jackson, MS

AREA FORECAST DISCUSSION
NATIONAL WEATHER SERVICE JACKSON MS
300 AM CST MON JAN 3 2000

DEWPTS IN 60S THIS MORNING WITH MID 60S SRN HALF OF FORECAST AREA.
THESE TO INCREASE DURING THE MORNING AS LOW LEVEL JET APPOROACHES.
MODELS DISAGREE SOMEWHAT IN SPEED OF FEATURES TODAY BUT GENERAL
FORECAST PICTURE IS FOR COLD FRONT TO MOVE TO VICINITY OF MS RIVER
BY 00Z TUE...PRECEEDED BY STG 850 MB JET MAX RANGING FROM 40 TO 50
KTS AVN TO 55 TO 65 KTS ETA. THIS ASSOCIATED WITH 850 MB THETAE
RIDGE AND UVV MAX. ALTHOUGH BEST DYNAMICS...INCLUDING SHORTWAVE
TRACK..SURFACE LOW CENTER AND STRONGEST UVV BULLSEYE... PIVOTING NE
OF THE FORECAST AREA WE WILL SEE STRONG ENOUGH DYNAMICS ALONG SRN
EDGE OF FEATURES TO BRING THREAT OF SEVERE THUNDERSTORMS TO AREA...
PARTICULARLY NRN ZONES. MAX 250 MB JET CORE SHIFTING TO THE NE THIS
MORNING BUT BY 00Z TUE..CDFNT POSITIONED IN VICINITY OF OF RIGHT
REAR QUAD OF TAIL OF JET STREAM WHERE UPPER WIND REMAINS IN EXCESS
OF 100 KTS. BEST 200-250MB DIVERGENCE ALSO NOTED FROM 18Z MON TO 00Z
TUE WITH STRONGEST VALUES NRN ZONES. CURRENT SPC CONVECTIVE OUTLOOK
PLACES NRN HALF OF MS IN MDT RISK WITH REST OF FORECAST AREA IN
SLIGHT RISK TODAY.

CROSS SECTIONS SHOW GOOD UVV AND SUFFICIENT MOSITURE PERSISTING ERN
ZONES THROUGH 06Z TUE BUT AMS STABILIZES QUICKLY WRN SECTIONS
TONIGHT. UVV FORECAST TO CONTINUE ACROSS AREA INTO TUE MORNING AS
SECOND LOBE OF SURFACE LOW SWINGS THROUGH BUT AMS DRIES ALL BUT
LOWEST LEVELS. 850 MB TROF FORECAST INTO WRN MS TUE MORNING WITH
NWLY 850 MB WIND ENTIRE AREA BY 00Z WED. ISENTROPIC SUBSIDENCE NOTED
IN MOIST LOWER LAYER BY TUE AFTERNOON BUT FORECAST SOUNDINGS SHOWING
LOW LEVEL INVERSION SETTING UP BY 18Z TUE AND PERSISTING INTO THE
EARLY EVENING SO WILL WORD TUESDAY PARTLY CLOUDY AT THIS TIME. WILL
SEE MUCH COOLER TEMPS TUE AND TUE NIGHT AS 500 MB COLD CORE SWINGS
THROUGH DURING THE DAY AND SURFACE RIDGE MOVES OVER FORECAST AREA BY
WED MORNING.

FORECAST LOOKS DRY WED AND THU UNTIL NEXT SHORTWAVE AND SURFACE TROF
APPROACH EARLY FRIDAY.

QPF DISCUSSION: MAIN EVENT SHOULD BE IN THE FORM OF AN EASTWARD
MOVING SQUALL LINE CROSSING THE CWFA ROUGHLY FROM NOON TO MIDNIGHT.
MODELS GENERALLY AGREE WITH THE OVERALL SCENARIO...BUT ETA QPF LOOKS
WOEFULLY UNDERDONE AND WILL GO WITH NGM/AVN. THIS AGREES WITH NCEP
AS WELL.

PRELIM NUMBERS:
JAN 74/47/52/28 8510
MEI 75/48/54/27 8610

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

ARZ074-075-LAZ007>009-015-016-023>026-MSZ018-019-025>066-072>074-
040400-

AREA THUNDERSTORM OUTLOOK
NATIONAL WEATHER SERVICE JACKSON MS
1000 AM CST MON JAN 3 2000

...TORNADO WATCH FOR NORTHWEST MISSISSIPPI AND SOUTHEAST ARKANSAS
UNTIL 4 PM...

A STRONG COLD FRONT OVER OKLAHOMA AND TEXAS WILL APPROACH THE
MISSISSIPPI RIVER THIS EVENING. THE AIRMASS AHEAD OF THIS FRONT IS
VERY WARM AND MOIST. IN ADDITION...THERE ARE STRONG SOUTH WINDS IN
THE LOWER LEVELS OF THE ATMOSPHERE AND STRONG WEST WINDS IN THE
UPPER LEVELS. THESE INGREDIENTS WILL COMBINE TO POSE A RISK OF
SEVERE WEATHER FOR NORTHEAST LOUISIANA...SOUTHEAST ARKANSAS...AND
MISSISSIPPI THROUGH TONIGHT.

SEVERE WEATHER IS EXPECTED TO THREATEN SOUTHEAST ARKANSAS AND
NORTHEAST LOUISIANA BY LATE MORNING OR EARLY AFTERNOON. THESE
STORMS WILL MOVE ACROSS MISSISSIPPI THIS AFTERNOON AND THIS EVENING.
THE AREA AT GREATEST RISK FOR SEVERE WEATHER IS SOUTHEAST ARKANSAS
AND NORTH MISSISSIPPI...GENERALLY NORTH OF A LINE FROM
CROSSETT...ARKANSAS TO GREENVILLE TO KOSCIUSKO TO STARKVILLE.
HOWEVER STRONG THUNDERSTORMS ARE POSSIBLE THROUGHOUT THE FORECAST
AREA THROUGH THIS EVENING.

THE SEVERE WEATHER THREAT INCLUDES TORNADOES...DAMAGING WIND
GUSTS...AND LARGE HAIL.

ACTIVATION OF STORM SPOTTERS...EMERGENCY MANAGEMENT PERSONNEL AND HAM
RADIO OPERATORS WILL LIKELY BE REQUIRED LATER TODAY.

FOR MORE INFORMATION...PLEASE VISIT OUR INTERNET WEB SITE AT:
HTTP://WWW.JANNWS.STATE.MS.US    /IN LOWER-CASE LETTERS/