Severe Thunderstorm Warning 379, NWS Jackson, MS

AREA FORECAST DISCUSSION
NATIONAL WEATHER SERVICE JACKSON MS
230 PM CDT SUN JUN 25 2000

SUBTROPICAL UPPER RIDGE WAS NOTED OVER NORTHERN MEXICO WITH A LOWER
LEVEL BERMUDA HIGH OVER THE WESTERN ATLANTIC WHICH WAS KEEPING THINGS
HOT AND HUMID. SOME UPPER LEVEL FEATURES TO NOTE WERE THE LONGWAVE
700-500 MB SHEAR AXIS MOVING THROUGH THE TN VALLEY/EAST MS/AL...
SHORTWAVE RIDING OVER TOP OF MEXICAN UPPER RIDGE IN KS/OK IN
ASSOCIATION WITH 40-50KT 250 MB JET MAX AND WELL-DEFINED SHORTWAVE
OVER S GA/N FL. ALL SEEN CLEARLY ON WATER VAPOR IMAGERY. ALL MODELS
GENERALLY CAUGHT THESE FEATURES WITH DISCREPANCIES ON MOISTURE
FIELDS. ETA HAS CONVECTIVE FEEDBACK PROBLEMS ONCE AGAIN PAINTING QPF
DURING LATE NOCTURNAL HOURS WITH AVN HANDLING QPF/TRENDS THE BEST
AGAIN. WILL GENERALLY RIDE THE AVN/S FORECAST WITH AVERAGE
CONFIDENCE ON POPS WITH NUMEROUOS MESOSCALE FEATURES ABOUND.

BOUNDARY SEEN ON SATELLITE/RADAR ASSOCIATED DRIVING SOUTH THROUGH E
MS/W AL. IT WAS ALREADY TRIGGERING SCATTERED THUNDERSTORMS EAST OF
1-55 WITH A WEAK SEABREEZE BOUNDARY NOTED MOVING SLOWLY UP FROM THE
GULF COAST. CHANCE POPS EXPECTED ACROSS E/SE SECTIONS THIS EVENING
WHERE SURFACE BOUNDARIES COMBINED WITH UPPER DIVERGENCE IN NEAR MID
LEVEL DEFORMATION ZONE HELPING PROVIDE AMPLE LIFT. FARTHER NW...
MOISTURE BECOMES MORE SHALLOW PER UPPER AIR PRECIPITABLE WATER
ANALYSIS WITH JUST ISOLATED POPS EXPECTED TOWARDS THE MS RIVER. WET
MICROBURST ANALYSIS INDICATES GOOD POTENTIAL FOR DOWNBURST WINDS
ACROSS THE EAST HALF OF MS AGAIN WHERE LI/S APPROACHING -9...MID
LEVEL LAPSES RATES AROUND 6.5 DEG C/KM AND CAPES NEAR 4000 J/KG
ALREADY HELPING TO PRODUCE ISOLATED...SEVERE DOWNBURSTS. LOSS OF
INSOLATION AFTER SUNSET SHOULD HELP PUT AN END TO CONVECTION AS
SKIES CLEAR. MAY HAVE TO INTRODUCE SOME OVERNIGHT FOG IN EAST.

A COLD FRONT IN THE PLAINS STATES WILL SLOWLY MAKE IT/S WAY SE INTO
THE ARK-LA-TEX REGION BY MON AFTERNOON AS A VIGOROUS SHORTWAVE MOVES
INTO MISSOURI. THE COLD FRONT AND TAIL END OF SHORTWAVE TO START
AFFECTING NW SECTIONS MON NIGHT AND REST OF THE FORECAST AREA
TUES/TUES NIGHT. SLIGHTLY COOLER TEMPS BY TUESDAY AS INCREASE IN
MOISTURE/CLOUDS/PRECIP OCCURS OVER THE REGION. FAN/FWC CLOSE FOR
BOTH POPS/TEMPS AND WILL HOLD CLOSE.

EXTENDED DISCUSSION: CONSENSUS ON MEDIUM RANGE MODELS IS THAT COLD
FRONT WILL MOVE SLOWLY SOUTHEAST ACROSS THE FORECAST AREA THROUGH
FRIDAY. SHORTWAVES ARE ALSO EXPECTED TO CONTINUE RIDING OVER TOP OF
THE TX/MEXICAN SUBTROPICAL RIDGE INTO THE REGION. FRONT SHOWN TO PUSH
THE COAST BY FRI...BUT NOT CONFIDENT WITH THIS HAPPENING AND FOR NOW
WILL CONTINUE CHANCE OF SHOWERS/STORMS THROUGH THE PERIOD.

QPF DISCUSSION: VARIOUS OUTFLOWS ALREADY OCCURRING EAST OF I-55.
DIURNAL HEATING THIS EVENING AND MONDAY WITH HIGH INSTABILITIES AND
DEFORMATION LIFT SHOULD RESULT IN SCATTERED SHOWERS/STORMS ONCE
AGAIN...MAINLY EAST OF I-55 WITH ISOLATED CONVECTION POSSIBLE
FARTHER TO THE WEST. GENERALLY FOLLOWED AN AVN/HPC BLEND FOR
0.10-0.20 AMOUNTS EAST LITTLE IN THE WEST FOR THE 24 HR PD.

PRELIMINARY NUMBERS...
JAN 073/092 073/090 072 2324
MEI 071/093 071/091 07^0 3424

.JAN...
MS...NONE.
AR...NONE.
LA...NONE.
/05

ARZ074-075-LAZ007>009-015-016-023>026-MSZ018-019-025>066-072>074-
260400-

AREA THUNDERSTORM OUTLOOK
NATIONAL WEATHER SERVICE JACKSON MS
950 AM CDT SUN JUN 25 2000

A MOIST AND UNSTABLE AIRMASS WILL COMBINE WITH DAYTIME HEATING AND
SOME IMPROVED LOCALIZED CONVERGENCE THIS AFTERNOON TO PRODUCE
SCATTERED THUNDERSTORMS. THE STORMS SHOULD BE MOST NUMEROUS ACROSS
SOUTH AND EAST PORTIONS OF THE AREA WITH A GENERAL SLOW SOUTH DRIFT IN
STORM MOTION EXPECTED. ISOLATED STORMS MAY REACH SEVERE LIMITS WITH
DAMAGING DOWNBURST WIND GUSTS... PARTICULARLY SOUTHEAST OF A
BROOKHAVEN TO MERIDIAN LINE BETWEEN 1 PM AND 9 PM.

SINCE OVERALL WIND SHEAR WILL BE VERY WEAK AND THUNDERSTORM
ORGANIZATION LIMITED...NO WIDESPREAD SEVERE WEATHER IS EXPECTED.

ACTIVATION OF STORM SPOTTERS...HAM RADIO OPERATORS...AND EMERGENCY
MANAGEMENT PERSONNEL SHOULD NOT BE REQUIRED THROUGH TONIGHT.

FOR MORE INFORMATION...PLEASE VISIT OUR INTERNET WEB SITE AT
HTTP://WWW.SRH.NOAA.GOV/JAN WHICH INCLUDES AN EXPERIMENTAL GRAPHICAL
HAZARDOUS WEATHER OUTLOOK.