Severe Thunderstorm Warning 548, NWS Jackson, MS

AREA FORECAST DISCUSSION
NATIONAL WEATHER SERVICE JACKSON MS
345 PM CDT THU AUG 10 2000

MODELS ARE IN EXCELLENT AGREEMENT ON THE OVERALL PATTERN WITH STRONG
TROFFING TAKING PLACE OVER THE EASTERN US THUS DRIVING A "COLD" FRONT
AND SEASONABLY DRY AIRMASS SOUTHWARD THROUGH THE LOWER MS VALLEY
REGION FOR THIS WEEKEND.

FOR TONIGHT...VERY ACTIVE WEATHER WITH A HIGHLY UNSTABLE MOIST
AIRMASS IN PLACE OVER NORTHERN AND EASTERN PORTIONS OF THE FORECAST
AREA AHEAD OF THE SOUTHWARD MOVING COLD FRONT PUSHING INTO THE TN
VALLEY REGION WITH TSTM COMPLEX DEVELOPING. WILL MENTION SEVERE TSTM
POSSIBLITIES IN NRN/E ZONES TONIGHT AS FRONT AND COMPLEX CONTINUE TO
DEVELOP SOUTHWARD AND WITH WATCH CURRENTLY IN PLACE. ALSO...TSTMS
CURRENTLY OVER ERN MS/WRN AL WILL CONTINUE TO DEVELOP AND PROPAGATE
WESTWARD THRU LATE AFTN/EVENING. WILL NEED TO MAKE LAST MINUTE
ALIGNMENT OF ZONES AND POPS BASED ON LATEST CONVECTIVE TRENDS AND
MESOSCALE ANALYSES.

FOR FRIDAY...THE FRONT AND INSTABILITY AXIS ARE PROGGED TO CONTINUE
DEVELOPING SOUTHWARD WITH FOCUS ON CNTRL/SRN PORTIONS OF THE
FORECAST AREA. MINOR DIFFERENCES BETWEEN AVN/ETA IN FRONTAL/MOISTURE
PROGRESSION WITH ETA A LITTLE SLOW. GIVEN STRENGTH OF TROF
DEVELOPING OVER ERN US...BELIEVE ETA IS TOO SLOW AND WILL TREND MORE
TOWARDS AVN IN DETAILS...MEANING A QUICKER END TO ANY CONVECTIVE
CHANCES OVER NRN ZONES. STILL...CONFIDENCE IS NOT HIGH IN NORTHWARD
EXTENT OF TSTM DEVELOPMENT DURING DAY FRIDAY AND WILL REFRAIN FROM
GOING A WHOLE LOT ABOVE GUIDANCE POPS FOR CNTRL/SRN PORTIONS OF THE
AREA.

FRI NIGHT THRU SAT NIGHT...CONFIDENCE IS HIGH THAT A MUCH DRIER
AIRMASS WILL MOVE OVER THE AREA WITH SFC DEWPOINTS PROGGED TO DROP
INTO THE MID TO UPPER 50S BY SAT AFTN ALONG WITH PRECIPITABLE WATER
VALUES BELOW ONE INCH. BIGGEST QUESTION WILL BE TEMPS AS ETA PROGS
20 DEG C 850MB TEMPS SAT AFTN WHILE AVN PROGS 15 DEG C TEMPS. AVN
SEEMS A LITTLE COOL IN THIS RESPECT WITH EXPECTED VERY STRONG LOW
LEVEL MIXING AND WILL TREND CLOSER TO WARMER ETA/FWC HIGHS SATURDAY.
WILL ADD LESSER HUMIDITY WORDING TO ZONES TO REFLECT DRYING TREND.

QPF DISCUSSION...MODELS SEEM TO BE UNDERESTIMATING INSTABILITY AND
CONVECTIVE PRECIPITATION. AM LEANING TOWARDS .25 TO .50 INCH
AVERAGES OVER NRN/ERN BASINS FOR 00Z TO 06Z TONIGHT AND .25 TO .50
INCH AVERAGES OVER CNTRL/SRN BASINS FOR 18Z FRI TO 00Z SAT.

EXTENDED FORECAST...DRY AIRMASS AND SURFACE HIGH PRESSURE WILL
MAINTAIN CONTROL ON THE WEATHER SUNDAY. MODELS STILL INDICATE
DEEPENING SOUTHEAST FLOW AND MOISTURE RETURN MONDAY AND TUESDAY
CREATING A MORE FAVORABLE ENVIRONMENT FOR DIURNAL CONVECTION. WILL
KEEP SUNDAY DRY AND MENTION TSTM CHANCES FOR MONDAY AND TUESDAY.

PRELIM NUMBERS...
JAN 071/098 069/095 441-
MEI 072/098 067/093 441-

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

43

ARZ074-075-LAZ007>009-015-016-023>026-MSZ018-019-025>066-072>074-
110400-

AREA THUNDERSTORM OUTLOOK...UPDATED
NATIONAL WEATHER SERVICE JACKSON MS
300 PM CDT THU AUG 10 2000

A MOIST AND VERY UNSTABLE AIRMASS IS IN PLACE OVER THE REGION THIS
AFTERNOON. DAYTIME HEATING AND OUTFLOW BOUNDARIES WILL SERVE TO
PRODUCE SCATTERED THUNDERSTORMS ACROSS THE AREA THIS AFTERNOON AND
EVENING.

WITH THE DEGREE OF INSTABILITY AND INCREASING NORTHERLY FLOW ALOFT
IN THE ATMOSPHERE...SOME OF THE STORMS MAY BECOME SEVERE...
PARTICULARLY OVER CENTRAL AND EASTERN MISSISSIPPI. DAMAGING WIND
WILL BE THE MAIN SEVERE WEATHER THREAT. TORRENTIAL RAIN...FREQUENT
LIGHTNING...AND HAIL MAY ALSO ACCOMPANY THE STORMS.

ACTIVATION OF STORM SPOTTERS...HAM RADIO OPERATORS...AND EMERGENCY
MANAGEMENT PERSONNEL MAY BE REQUIRED THIS AFTERNOON AND EVENING.

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