Severe Thunderstorm Warning 293, NWS Jackson, MS

AREA FORECAST DISCUSSION
NATIONAL WEATHER SERVICE JACKSON MS
320 PM CDT SAT JUN 19 2010

.DISCUSSION...

THIS AFTERNOON THROUGH MONDAY NIGHT...

FOR THIS AFTERNOON AND EARLY EVENING...A COMPLEX OF THUNDERSTORMS
HAS BEEN DEVELOPING SOUTHWARD ACROSS ALABAMA IN ASSOCIATION WITH AN
UPPER LEVEL SHORTWAVE TROUGH AND A DEEP OUTFLOW BOUNDARY. MUCH OF
THE SHORTWAVE ENERGY IS REMAINING EAST OF THE ARKLAMISS...AND THE
RISK FOR GETTING ORGANIZED TSTM ACTIVITY IS CONFINED TO FAR ERN MS
GIVEN THAT CONVECTION ALONG THE BOUNDARY IN WRN AL IS UNABLE TO
BACK-BUILD TO THE WEST. SHOULD CONVECTIVE BACK-BUILDING INCREASE...
THEN THERE WOULD BE A CORRESPONDING RISK FOR STRONG TO SEVERE
WEATHER IN ERN MS...SO WILL CONTINUE TO KEEP A CLOSE WATCH ON THE
TRENDS. OTHERWISE...ISOLATED TO SCATTERED DIURNAL TSTM ACTIVITY HAS
DEVELOPED IN THE HOT/MOIST AND VERY UNSTABLE AIRMASS ALONG AND EAST
OF THE I-55 CORRIDOR. PULSE-TYPE STORMS HAVE ORGANIZED A BIT NOW
ALONG OUTFLOW BOUNDARIES IN AN AIRMASS CHARACTERIZED BY 4000-5000
J/KG CAPE AND ~2 INCH PRECIPITABLE WATER...BUT MID LEVEL LAPSE RATES
AWAY FROM THE SHORTWAVE TROUGH ARE FAIRLY WEAK GIVEN INFLUENCE FROM
THE MID LEVEL RIDGE...AND THAT SO FAR HAS BEEN A LIMITING FACTOR FOR
GETTING SEVERE MICROBURST ACTIVITY DESPITE DOWNDRAFT CAPES NEAR 1000
J/KG AND SFC TEMPERATURES IN THE MID 90S. FOR AREAS ALONG AND WEST
OF THE MS RIVER...IT LOOKS LIKE THE RIDGE IS WINNING OUT THIS AFTN
AND ONLY ISOLATED SHOWER/TSTM ACTIVITY IS EXPECTED AS WE GO INTO THE
EVENING.

CONCERNING HEAT ADVISORY FOR THIS AFTERNOON THROUGH SUNDAY...A HEAT
ADVISORY HAS BEEN ISSUED FOR NWRN PORTIONS OF THE ARKLAMISS. IN THIS
AREA...OVERNIGHT LOWS ARE STAYING ABOVE 75F AND HEAT INDICES HAVE
BEEN RISING TO ABOVE 105. IN CNTRL MS...TEMPERATURES HAVE BEEN FALLING
A LITTLE BELOW THE 75 DEGREE THRESHOLD...BUT TEMPERATURES IN
URBANIZED AREAS ARE REMAINING ABOVE 75...ESPECIALLY IN JACKSON AND
VICKSBURG...HENCE WE HAVE INCLUDED THOSE AREAS IN THE ADVISORY AS
WELL. THE LOW-LEVEL THERMAL RIDGE IS NOT QUITE AS PRONOUNCED OVER ERN
AND SOUTH CNTRL MS AND OVERNIGHT LOWS ARE FALLING BELOW 75 FOR THE
MOST PART WHILE AFTERNOON CONVECTION IS RESULTING IN A SHORTER
DURATION OF > 105. IT IS CERTAINLY POSSIBLE THAT THE HEAT ADVISORY
MAY NEED TO BE EXTENDED IN TIME GIVEN THE PERSISTENCE OF THE
RIDGE.

CONCERNING ADDITIONAL TSTM CHANCES FROM SUNDAY THROUGH MONDAY
NIGHT...THE RIDGE IS REBUILDING OVER THE AREA...BUT SOME OF THE
SHORTWAVE ENERGY CURRENTLY DROPPING SOUTHWARD THROUGH AL MAY ROTATE
WWD ALONG THE SRN PERIPHERY OF THE RIDGE. THIS COULD HELP TO ENHANCE
DIURNAL TSTM CHANCES FOR SUNDAY INTO EARLY SUNDAY EVENING SOUTH OF
THE INTERSTATE 20 CORRIDOR AND HAVE INCREASED MAV GUIDANCE POPS
THERE A LITTLE. THE ABOVE NORMAL SFC TEMPERATURES AND HIGH CAPE
VALUES WILL ONCE AGAIN BRING AT LEAST A SLIGHT POTENTIAL FOR SEVERE
MICROBURST POTENTIAL SUN AFTN. IT LOOKS LIKE THE RIDGE WILL EXERT
MORE FORCE ON THE WEATHER MONDAY AND THE CHANCES FOR DIURNAL
CONVECTION SHOULD BE A LITTLE SLIMMER THEN. /EC/

LONGER TERM...(TUESDAY THROUGH NEXT SATURDAY)...THE GREATEST DEEP-
LAYER MOISTURE WILL BE ACROSS THE SOUTHERN CWA...WHERE ISOLATED TO
SCATTERED AFTERNOON AND EARLY EVENING SHOWERS AND THUNDERSTORMS ARE
EXPECTED. LATER IN THE WEEK...850-500 MB LAPSE RATES ARE EXPECTED TO
STEEPEN ACROSS THE CWA AS THE RIDGE GRADUALLY WEAKENS. THIS WILL
RESULT IN GREATER AFTERNOON INSTABILITY AND SLIGHT CHANCES FOR
AFTERNOON AND EARLY EVENING SHOWERS AND STORMS AREAWIDE. NO
PARTICULARLY STRONG SYNOPTIC-SCALE FEATURES ARE EXPECTED TO
SUBSTANTIALLY ENHANCE PRECIP CHANCES ON ANY DAY FOR THE UPCOMING
WEEK.

THE CHANCE FOR PRECIPITATION WILL INCREASE TOWARD NEXT WEEKEND...AS
MULTI-MODEL CONSENSUS IS FOR AN AREA OF LOW PRESSURE TO ORGANIZE
SOUTH OF THE CWA. OPERATIONAL GFS INDICATES THAT THIS FEATURE WILL
EVOLVE OUT OF A STRONG TROPICAL WAVE THAT IS CURRENTLY WELL-DEFINED
ALONG 65W IN THE EASTERN CARIBBEAN. TIME-HEIGHT ANALYSES ACROSS THE
LESSER ANTILLES SUGGEST THAT THE SIGNATURE OF THIS WAVE EXTENDS FROM
THE SURFACE INTO THE MIDDLE TROPOSPHERE. GLOBAL MODELS INDICATE THAT
THE WAVE WILL SLOW ITS WEST-NORTHWESTWARD PROGRESS AS THE DEEP-LAYER
MEAN FLOW IN ITS VICINITY DECREASES. WHILE MODELS MOSTLY AGREE THAT
THIS FEATURE WILL EVOLVE INTO A CLOSED CIRCULATION AS IT APPROACHES
THE WESTERN CARIBBEAN LATE IN THE WEEK...THEY DISAGREE WITH REGARD TO
ITS EVENTUAL TRACK. SPECIFICALLY...THE OPERATIONAL GFS DEPICTS A
WEAKNESS IN THE SUBTROPICAL RIDGE CENTERED ALONG 80W...WHICH WOULD
ALLOW THE LOW TO TRACK NORTHWESTWARD INTO THE GULF OF MEXICO BY LATE
THIS WEEK. THIS SOLUTION WOULD YIELD GREATER COVERAGE OF PRECIP BY
NEXT WEEKEND. HOWEVER...THE ECMWF IS STRONGER WITH THE SUBTROPICAL
RIDGE...KEEPING THE LOW FURTHER TO THE SOUTH INTO THE CARIBBEAN
THROUGH SATURDAY. THIS WOULD MAINTAIN GENERALLY DRY CONDITIONS ACROSS
THE CWA INTO NEXT WEEKEND. GFS AND CMC ENSEMBLE MEMBERS ARE BETWEEN
THE OPERATIONAL GFS AND ECMWF SOLUTIONS. THUS...POPS FOR NEXT SATURDAY
FOLLOW ENSEMBLE MOS GUIDANCE...WHICH YIELDS HIGHER PRECIP CHANCES
ACROSS THE CWA THAN ON PRECEDING DAYS. /COHEN/

&&

.AVIATION...

VFR CONDS WILL PERSIST THRU THE PERIOD AS HIGH PRESSURE
REMAINS OVER THE REGION. ISOLD SHWRS/THUNDERSTORMS WILL PERSIST
THROUGH THE AFTN...DIMINISHING IN COVERAGE 01-03Z. GUSTY
WINDS/LIGHTNING/OCSNL MVFR/IFR CAN BE XPCTD INVOF THESE STORMS.
CLEARING SKIES TO DEVELOP OVRNGT. OCSNL BR REDUCING VSBY 4-6SM WILL
BE PSBL 10-13Z ALL AREAS. /BK/

&&

.PRELIMINARY POINT TEMPS/POPS...
JACKSON       74  97  74  98 /  10  10   5   6
MERIDIAN      70  97  72  96 /  13  14   5   7
VICKSBURG     72  97  74  98 /  10   9   6   6
HATTIESBURG   73  97  74  95 /  20  22  13  20
NATCHEZ       73  94  74  94 /  13  16  10  11
GREENVILLE    76 100  76  99 /   5   6   5   6
GREENWOOD     73  98  74  98 /   4   6   5   6

&&

.JAN WATCHES/WARNINGS/ADVISORIES...
MS...HEAT ADVISORY UNTIL 7 PM CDT SUNDAY FOR MSZ018-019-025>027-
     034>036-040>043-047>049.

LA...HEAT ADVISORY UNTIL 7 PM CDT SUNDAY FOR LAZ007>009-015-016-023-
     025.

AR...HEAT ADVISORY UNTIL 7 PM CDT SUNDAY FOR ARZ074-075.

&&

EC/COHEN/BK

HAZARDOUS WEATHER OUTLOOK
NATIONAL WEATHER SERVICE JACKSON MS
304 PM CDT SAT JUN 19 2010

ARZ074-075-LAZ007>009-015-016-023-025-MSZ018-019-025>027-034>036-
040>043-047>049-202015-
ASHLEY-CHICOT-MOREHOUSE-WEST CARROLL-EAST CARROLL-RICHLAND-
MADISON LA-FRANKLIN LA-TENSAS-BOLIVAR-SUNFLOWER-LEFLORE-GRENADA-
CARROLL-WASHINGTON-HUMPHREYS-HOLMES-ISSAQUENA-SHARKEY-YAZOO-
MADISON MS-WARREN-HINDS-RANKIN-
304 PM CDT SAT JUN 19 2010

THIS HAZARDOUS WEATHER OUTLOOK IS FOR CENTRAL MISSISSIPPI...
NORTHEAST LOUISIANA...AND EXTREME SOUTHEAST ARKANSAS.

.DAY ONE...TONIGHT AND SUNDAY

HOT AND HUMID WEATHER IS EXPECTED TO CONTINUE...AND A HEAT ADVISORY
IS IN EFFECT FOR THE OUTLOOK AREA THROUGH SUNDAY AFTERNOON. HEAT
INDICES WILL RISE TO NEAR OR ABOVE 105 DEGREES EACH AFTERNOON...
FOLLOWED BY OVERNIGHT LOWS ONLY FALLING INTO THE MID TO UPPER 70S.

IN ADDITION...ISOLATED THUNDERSTORMS WILL BE POSSIBLE THROUGH 9PM
THIS EVENING...AND AGAIN TOMORROW AFTERNOON DUE TO A WARM AND MOIST
AIRMASS REMAINING IN PLACE ACROSS REGION. THE STRONGEST STORMS
CAPABLE OF PRODUCING HEAVY RAINFALL...WIND GUSTS TO 60 MPH AND PENNY
SIZE HAIL.

.DAYS TWO THROUGH SEVEN...SUNDAY NIGHT THROUGH FRIDAY

AFTERNOON HEAT INDEX READINGS OF 100 TO 105 DEGREES MAY CONTINUE
INTO NEXT WEEK AS WELL.

.SPOTTER CALL TO ACTION STATEMENT...
THE ACTIVATION OF STORM SPOTTERS...HAM RADIO OPERATORS...AND
EMERGENCY MANAGEMENT PERSONNEL IN SUPPORT OF SEVERE WEATHER
OPERATIONS IS NOT EXPECTED THROUGH NEXT FRIDAY.

LAZ024-026-MSZ028>033-037>039-044>046-050>066-072>074-202015-
CATAHOULA-CONCORDIA-MONTGOMERY-WEBSTER-CLAY-LOWNDES-CHOCTAW-
OKTIBBEHA-ATTALA-WINSTON-NOXUBEE-LEAKE-NESHOBA-KEMPER-SCOTT-
NEWTON-LAUDERDALE-CLAIBORNE-COPIAH-SIMPSON-SMITH-JASPER-CLARKE-
JEFFERSON-ADAMS-FRANKLIN MS-LINCOLN-LAWRENCE-JEFFERSON DAVIS-
COVINGTON-JONES-MARION-LAMAR-FORREST-
304 PM CDT SAT JUN 19 2010

THIS HAZARDOUS WEATHER OUTLOOK IS FOR CENTRAL MISSISSIPPI...
NORTHEAST LOUISIANA...AND EXTREME SOUTHEAST ARKANSAS.

.DAY ONE...TONIGHT AND SUNDAY

ISOLATED TO SCATTERED THUNDERSTORMS WILL BE POSSIBLE THROUGH 9PM THIS
EVENING...AND AGAIN TOMORROW AFTERNOON DUE TO A WARM AND MOIST
AIRMASS REMAINING IN PLACE ACROSS REGION. THE STRONGEST STORMS
CAPABLE OF PRODUCING VERY HEAVY RAINFALL...WIND GUSTS TO 60 MPH AND
PENNY SIZE HAIL.

IN ADDITION...VERY HOT AND HUMID WEATHER IS EXPECTED TO CONTINUE WITH
HEAT INDEX VALUES RISING TO NEAR 105 DEGREES ON SUNDAY.

.DAYS TWO THROUGH SEVEN...SUNDAY NIGHT THROUGH FRIDAY

AFTERNOON HEAT INDEX READINGS OF 100 TO 105 DEGREES MAY CONTINUE
INTO NEXT WEEK AS WELL.

.SPOTTER CALL TO ACTION STATEMENT...
THE ACTIVATION OF STORM SPOTTERS...HAM RADIO OPERATORS...AND
EMERGENCY MANAGEMENT PERSONNEL IN SUPPORT OF SEVERE WEATHER
OPERATIONS IS NOT EXPECTED THROUGH NEXT FRIDAY.

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

BK

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