Severe Thunderstorm Warning 435, NWS Jackson, MS

AREA FORECAST DISCUSSION
NATIONAL WEATHER SERVICE JACKSON MS
210 PM CDT SAT AUG 17 2002

FORECAST CONCERNS OVER THE NEXT SEVERAL DAYS WILL CENTER AROUND
CONVECTIVE PRECIPITATION CHANCES IN ASSOCIATION WITH WEAKENING MID
LEVEL SHEAR AXIS OVER THE LOWER MS VALLEY REGION.

VAPOR IMAGERY/IR/VIS/RUC SHOWS A MID LEVEL SHEAR AXIS  ACROSS THE
LOWER MISSISSIPPI VALLEY. THE ASSOCIATED WEAK MID LEVEL CIRCULATION
WAS NOTED OVER NORTHEAST LOUISIANA DRIFTING NORTHEAST ALONG THE MID
LEVEL SHEAR AXIS...WHICH STRETCHED FROM EASTERN TEXAS TO THE OHIO
VALLEY. THE AVN MODEL INITIALIZED THE MIDLEVEL CIRCULATION AND SHEAR
AXIS BETTER THAN THE MESO ETA MODEL/NGM. SCATTERED CONVECTION WAS
OBSERVED ACROSS THE FORECAST AREA AS A STRONG COLD FRONT WAS
NORTHWEST OF THE REGION IN THE PLAINS. DAYTIME HEATING...DEEP
MOISTURE AND BOUNDARIES LAID DOWN FROM YESTERDAYS CONVECTION WAS
AIDING IN THE DEVELOPMENT.

LOOKING AT THE SHORT TERM THE AFFECTS OF THE  FLAT UPPER RIDGE WILL
KEEP THE STRONG FRONT NORTHWEST OF THE REGION. THE MOIST AIRMASS WITH
(PRECIP WATER OF 1.8 TO 2 INCHES) WILL CONTINUE TO STREAM NORTHWARD
OUT OF THE GULF. SHEAR AXIS WILL WEAKEN SOME ON SUNDAY AND WILL
DISSIPATE BY EARLY MONDAY AS ANOTHER SERIES OF WEAK SHORTWAVES COMES
INTO THE REGION FROM THE SOUTHWEST. SO COMBINED WITH DAY TIME
HEATING WILL CONTINUE OUR CHANCES OF DIURNAL CONVECTION. THE AVN/ETA
SOLUTIONS WERE GENERALLY SIMILAR WITH THE SHEAR AXIS. SO WITH THIS
IN MIND WILL PUT IN GOOD CHANCE POPS FOR THE REGION THIS EVENING.
WILL MAKE LAST MINUTE MODIFICATIONS BASED ON RADAR TRENDS. EXPECT LESS
CONVECTIVE COVERAGE ON SUNDAY INTO MONDAY. WILL KEEP BEST POPS OVER
THE MAINLY EAST HALF FOR TONIGHT AND SCATTERED POPS THROUGH THE
PERIOD AND KEEP CLOSE TO MOS TEMPS.

EXTENDED DISCUSSION TUESDAY THROUGH SATURDAY
THE AVN GLOBAL MODEL SHOWED A BROAD UPPER RIDGE ACROSS THE REGION
WITH DIURNAL CONVECTION BECOMING ISOLATED WEDNESDAY THROUGH FRIDAY.
BY EARLY SATURDAY A TROF COMING IN FROM THE CENTRAL AND NORTHERN
PLAINS WILL BE DIGGING ACROSS THE LOWER MISSISSIPPI VALLEY. A
FRONTAL BOUNDARY WILL BE MOVING THROUGH THE REGION ON SATURDAY. THIS
WILL INCREASE THE CHANCES OF CONVECTION ON SATURDAY. THE
EUROPEAN...UKMO...CANADIAN AND THE NOGAPS WERE IN GENERAL AGREEMENT
WITH THE BROAD UPPER RIDGE THROUGH FRIDAY. SO WILL KEEP CHANCE POPS
FOR TUESDAY AND SATURDAY AS WELL AS SLIGHT CHANCES FOR WEDNESDAY
THROUGH FRIDAY. WILL GO CLOSE TO MEX TEMPS.

PRELIM NUMBERS...
JAN 73/92/72/92 5423
MEI 72/92/72/92 5423

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

17

ARZ074-075-LAZ007>009-015-016-023>026-MSZ018-019-025>066-072>074-
181200-

HAZARDOUS WEATHER OUTLOOK
NATIONAL WEATHER SERVICE JACKSON MS
202 PM CDT SAT AUG 17 2002

...THUNDERSTORMS...
SCATTERED THUNDERSTORMS CAN BE EXPECTED DURING THE EVENING
HOURS...OVER EXTREME SOUTHEAST ARKANSAS...NORTHEAST LOUISIANA...
AND MUCH OF MISSISSIPPI. THE THUNDERSTORMS WILL DECREASE AFTER
SUNSET. WHILE NO WIDESPREAD SEVERE WEATHER IS EXPECTED...A FEW
STORMS MAY APPROACH SEVERE CRITERIA. IN ANY STORM...BRIEF GUSTY
WINDS TO 45 MPH...HEAVY DOWNPOURS...AND FREQUENT LIGHTNING MAY
OCCUR.

SOUTHERLY WINDS CONTINUE TO REINFORCE THE MOISTURE IN THE
ATMOSPHERE OVER THE AREA AND AS AFTERNOON HEATING WARMS THE LOWER
LAYERS STORMS DEVELOP AND LAST UNTIL TEMPERATURES BEGIN COOLING
AFTER SUNSET.

ACTIVATION OF EMERGENCY MANAGEMENT...STORM SPOTTERS...AND HAM
RADIO OPERATORS IN SUPPORT OF SEVERE WEATHER OPERATIONS...SHOULD
NOT BE NECESSARY THROUGH TONIGHT.

...FLOODING...
LOCALLY HEAVY DOWNPOURS IN STRONG THUNDERSTORMS COULD CAUSE WATER
TO POND OVER LOW-LYING AREAS...STREETS...AND ROADWAYS JUST ABOUT
ANY AREA ACROSS SOUTHEAST ARKANSAS...NORTHEAST LOUISIANA...AND
MISSISSIPPI.

ABUNDANT MOISTURE IS ALREADY AVAILABLE OVER THE LOWER MISSISSIPPI
VALLEY...WHILE SOUTH WINDS CONTINUE TO TRANSPORT ADDITIONAL
MOISTURE FROM THE GULF OF MEXICO. IN STRONGER...EFFICIENT
THUNDERSTORMS...HEAVY DOWNPOURS WILL OCCUR. LOCAL RAINFALL
AMOUNTS OVER TWO INCHES WILL BE POSSIBLE WITHIN AN HOUR.

SOILS ARE ALREADY APPROACHING SATURATION FROM PREVIOUS HEAVY
RAINFALL. ANY DOWNPOURS COULD QUICKLY PRODUCE PONDING...SINCE THE
SOILS MAY NOT BE ABLE TO RAPIDLY ABSORB THE DELUGE. AS A
RESULT...ANY HEAVY RAINFALL COULD BECOME RUN-OFF WATER. FLASHY
CREEKS AND SMALL STREAMS MAY BE QUICKLY INUNDATED. URBANIZED
AREAS ARE ESPECIALLY SUSCEPTIBLE TO PONDING WATER AND BRIEF
FLOODING DUE TO INCREASED IMPERVIOUS SURFACES...SUCH AS PARKING
LOTS AND ROADS...WHICH FURTHER INDUCE RUN-OFF.

DRIVERS CAUGHT IN ANY HEAVY DOWNPOUR SHOULD EXERCISE EXTREME
CAUTION. REDUCE YOUR SPEED TO AVOID HYDROPLANING. AVOID DRIVING
INTO AREAS WITH STANDING WATER.

FOR MORE INFORMATION PLEASE VISIT OUR WEBSITE AT
WWW.SRH.NOAA.GOV/JAN. THIS INCLUDES THE GRAPHICAL HAZARDOUS
WEATHER OUTLOOK.