Severe Thunderstorm Warning 644, NWS Jackson, MS

AREA FORECAST DISCUSSION
NATIONAL WEATHER SERVICE JACKSON MS
320 PM CDT SAT SEP 23 2000

IN THE SHORT TERM...DEEPEST TROPICAL MOISTURE HOLDING OVER SRN MS
THIS EVENING HOWEVER A JET LEVEL IMPULSE BRINGING THE REMAINING
MOISTURE FROM "NORMAN" ACROSS CENTRAL TX COULD ALLOW A FEW SHOWERS
TO PERSIST OVERNIGHT. LIGHT SLY FLOW WILL KEEP TEMPERATURES VERY
WARM AS REFLECTED IN MOS NUMBERS IN M70S.

OTHERWISE...MID-UPPER LEVEL RIDGE OVER NWRN GULF OF MEXICO SHOULD
REMAIN IN TACT THROUGH MIDDAY SUNDAY WHEN A STRONG CENTRAL ROCKIES
CLOSED LOW HEADS EWD INTO THE PLAINS. SOME WEAK UPPER LEVEL IMPULSES
SHOULD TRIGGER ADDITIONAL SHOWERS AS FLOW ALOFT GRADUALLY INCREASES
DURING DAYTIME HEATING SUNDAY AFTERNOON. ALSO...AN E-W LOW LEVEL
THETAE RIDGE AND INSTABILITY AXIS LIFTS NWD ACROSS THE CWFA AHEAD OF
A VERY JUICY(2.25" PWATS) PRE-FRONTAL AXIS APPROACHING THE DELTA
SUNDAY NIGHT.

NEXT...THE PRIMARY STORM SYSTEM FORCES CYCLOGENESIS ALONG OUR
SLOW-MOVING POLAR FRONTAL BOUNDARY EXITING THE OZARKS LATE SUNDAY.
MODELS(ETA/AVN/NGM) QUITE SIMILAR ON WHERE THIS LOW SPINS UP AS IT
CROSSES NRN MS SUNDAY NIGHT. THE LOW DEEPENS MORE QUICKLY ONCE INTO
THE TN VALLEY WHICH ALLOWS THE SURFACE FRONT TO PLOW SEWD QUICKLY
ACROSS LOWER MS VALLEY BETWEEN 06Z AND 18Z MONDAY MORNING.

EXPECT A SUBSTANTIAL SQUALL LINE TO FORM ALONG THE FRONT SUNDAY
EVENING FROM ERN AR INTO NE TX. THE LINE GETS SMASHED FROM BEHIND BY
INTENSIFYING MID LEVEL JET DIVING ACROSS SRN AR. THE SQUALL LINE
WILL BOW RAPIDLY EWD OVERNIGHT WITH DAMAGING TSTM WIND POTENTIAL
MAINLY ALONG AND N OF I-20. INCREASING VERTICAL MOTION FIELDS...
SHARP SURFACE-850MB THETA-E AXIS...A VERY IMPRESSIVE DRY PUNCH AT 700MB
DRYING FROM 90% TO 10% IN 6HRS...AND PRESENCE OF M70S SURFACE
DEWPOINTS LEADS ME TO CONCLUDE THAT SEVERE WEATHER MAY STILL OCCUR
EVEN WITH LOSS OF DAYTIME HEATING. WILL WORD FORECAST FOR TSTMS
LIKELY IN HIGHEST THREAT AREA AND GIVE NEXT FORECAST CYCLE A CHANCE TO
PIN THINGS DOWN.

FINALLY...MUCH COOLER AND DRIER AIRMASS BY MIDDAY MONDAY WITH
CLEARING PROBABLY LATE IN THE DAY FROM NW TO SE AS POST-FRONTAL
STRATO CU FIELD MAY BE A LITTLE STUBBORN.

QPF DISCUSSION...ETA/AVN/NGM IN GENERAL AGREEMENT ON AXIS OF
HEAVIEST QPF NEXT 48 HOURS OVER NW MS/SE AR DELTA COUNTIES. THIS
APPEARS REASONABLE AS MODEL DEPICTION OF JET HAS BEST UPPER SUPPORT
REMAINING OVER THIS REGION COMBINING WITH UNSEASONABLY HIGH PW
VALUES...WHICH COULD BE ENHANCED BY MOISTURE FROM "NORMAN". OVERALL
NCEP VALUES APPEAR FAIRLY REASONABLE WITH A TIGHT GRADIENT FROM N TO
S AS POTENTIAL FOR HEAVIER QPF WILL DIMINISH LATE IN THE PERIOD FROM
NW TO SE AS FRONTAL SPEED INCREASES AND BEST JET SUPPORT PASSES TO
THE E AND NE.

IN THE EXTENDED...A CLEAR AND DRY PERIOD UNDER NWLY FLOW ALOFT UNTIL
NEXT WEEKEND WHEN UPPER RIDGE REBUILDS PER MRF/CANADIAN ENSEMBLES. COOL
NIGHTS SHOULD PREVAIL WITH TEMPERATURES IN THE 40S AND 50S...MAINLY
70S IN THE DAYTIME.

PRELIM NUMBERS...

JAN 74/90/71/76 2366
MEI 73/92/72/78 2347

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

ARZ074-075-LAZ007>009-015-016-023>026-MSZ018-019-025>066-072>074-
240400-

AREA THUNDERSTORM OUTLOOK
NATIONAL WEATHER SERVICE JACKSON MS
1025 AM CDT SAT SEP 23 2000

SCATTERED THUNDERSTORMS WILL DEVELOP ACROSS MUCH OF MISSISSIPPI...
NORTHEAST LOUISIANA AND SOUTHEAST ARKANSAS THIS AFTERNOON. WHILE A
COUPLE OF ISOLATED SEVERE STORMS ARE POSSIBLE...THE LIMITED NATURE
OF ANY SEVERE ACTIVITY SHOULD PRECLUDE THE ACTIVATION OF STORM
SPOTTERS...HAM RADIO OPERATORS...OR EMERGENCY MANAGEMENT PERSONNEL
THROUGH TONIGHT.

A VERY MOIST AIRMASS WAS IN PLACE ACROSS THE LOWER MISSISSIPPI
VALLEY THIS MORNING. DAYTIME HEATING WILL ALLOW THE DEVELOPMENT OF
SCATTERED THUNDERSTORMS WITH HEAVY DOWNPOURS AND FREQUENT LIGHTNING
ACROSS THE REGION THIS AFTERNOON AND EVENING. THE AIRMASS WILL BE
THE MOST UNSTABLE OVER NORTHERN MISSISSIPPI AND SOUTHEAST ARKANSAS.
THIS WILL MAKE THIS AREA THE MOST VULNERABLE TO THE DEVELOPMENT OF A
FEW SEVERE STORMS WITH LARGE HAIL AND DAMAGING WIND...BUT ANY SEVERE
ACTIVITY SHOULD REMAIN VERY ISOLATED IN NATURE.

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

MSZ001>082-240100-

FIRE DANGER STATEMENT
NATIONAL WEATHER SERVICE JACKSON MS
310 PM CDT SAT SEP 23 2000

...HIGH FIRE DANGER CONDITIONS WILL REDEVELOP ACROSS THE STATE...

SCATTERED SHOWERS AND THUNDERSTORMS OVER THE LAST SEVERAL DAYS HAS PROVIDED
SOME TEMPORARY RELIEF TO THE HIGH FIRE DANGER CONDITIONS ACROSS THE
STATE. RAINFALL AMOUNTS HAVE AVERAGED FROM AROUND QUARTER UP TO ONE
INCH...WITH LOCALLY ISOLATED SPOTS OF 2 TO 3 INCHES.

ACCORDING TO THE MISSISSIPPI FORESTRY COMMISSION...THE DROUGHT
CONDITIONS HAVE MADE ANY BURNING EXTREMELY HAZARDOUS. CONDITIONS ARE
SUCH THAT A SPARK FROM EQUIPMENT, THE HEAT FROM A CATALYTIC
CONVERTER OR ANY HEAT SOURCE WILL START A FIRE. WITH WINDY
CONDITIONS THERE ARE NO PRECAUTIONS A HOMEOWNER CAN TAKE THAT WILL
PREVENT BURNING DEBRIS OR TRASH FROM ESCAPING. THESE FIRES PLACE THE
MISSISSIPPI FORESTRY COMMISSION AND VOLUNTEER FIRE DEPARTMENT
PERSONNEL IN LIFE THREATENING SITUATIONS...TRYING TO CONTROL THEM AS
WELL AS ENDANGERING THEIR NEIGHBORS LIVES AND PROPERTY. LIGHTNING
STRIKES FROM THUNDERSTORMS CAN ALSO QUICKLY START FIRES. PLEASE USE
CAUTION IN PREVENTING FOREST AND GRASS FIRES.

THE MISSISSIPPI FORESTRY COMMISSION DOES NOT FEEL THAT ANY REASON
FOR BURNING CAN BE JUSTIFIED AT THIS TIME. UNDER THESE CONDITIONS WE
URGE THE PUBLIC TO COMPLY WITH THE GOVERNOR'S BAN AND FORGO ANY OUTDOOR
BURNING. WHEN BARBECUING TAKE THE UTMOST CARE, DO NOT DUMP ASHES UNLESS
YOU ARE CERTAIN THAT THEY ARE DEAD OUT. LIVE COALS CAN REMAIN AS
LONG AS ONE OR TWO DAYS AFTER BEING USED FOR COOKING.

SOME MORE TEMPORARY RELIEF IS ON THE WAY...AS GULF MOISTURE WILL
CONTINUE ACROSS THE REGION...AHEAD OF AN APPROACHING STRONG COLD
FRONT. SCATTERED SHOWERS AND THUNDERSTORMS WILL CONTINUE THIS EVENING
AND ON SUNDAY. A LINE OF STRONG TO POSSIBLY SEVERE STORMS WILL
DEVELOP SUNDAY NIGHT...AS A STRONG COLD FRONT PASSES THROUGH THE
REGION. AFTER THE PASSAGE OF THE COLD FRONT BREEZY CONDITIONS OF 15
TO 25 MPH NORTHWEST WINDS WITH SOME HIGHER GUSTS WILL PUSH THROUGH
THE STATE ON MONDAY...DRYING OUT THE THE MOISTURE FROM THE
THUNDERSTORMS. THIS WILL REVIVE THE HIGH FIRE DANGER CONDITIONS.