Special Weather Statement, NWS Jackson, MS

AREA FORECAST DISCUSSION...UPDATED
NATIONAL WEATHER SERVICE JACKSON MS
1105 AM CDT MON AUG 13 2012

..STRONG TO SEVERE STORMS STILL POSSIBLE AS AIR MASS RELOADS FOR
NORTH HALF LATE AFTERNOON AND EVENING...

.UPDATE...MORNING MCS SLIDING EWD ALONG HWY 82 CORRIDOR WILL BE
LEAVING A SUBSTANTIAL OUTLFOW BOUNDARY TO SET UP THE MID AFTERNOON
DEVELOPMENT ALONG I-20 AND HIGHWAY 49 BACK INTO THE DELTA WHERE
RELOADING WARM SECTOR RETURNS. THE SURFACE COLD FRONT NOW BISECTING
AR FROM NE TO SW WAS LAGGING OUR RAIN SHIELD AND SHOULD HELP TRIGGER
NEW STORMS BY LATE AFTERNOON THROUGH THIS EVENING WHEN BEST RISK FOR
STRONG/SEVERE STORMS WILL EXIST FOR OUR NWRN CWFA QUARTER. SYNOPTIC
PATTERN SUPPORTS THE STEADILY ADVANCING EARLY AUTUMN FRONT WHICH WILL
HELP MAINTAIN SHRA/TSRA ACTIVITY INTO THE NIGHTTIME HOURS AS IT SAGS
INTO THE CENTRAL CWFA BY TUESDAY MORNING.

CONVECTIVE PARAMETERS IN THE 2 INCH PWAT AIR MASS REMAIN ADEQUATE FOR
3500J/KG SBCAPES AND MID LEVEL LAPSE RATES STILL IMPRESSIVE AT KSHV-
KLIT RAOBS. HAVE ADJUSTED POPS/TEMPS FOR CURRENT TRENDS AND LOWERED
MAXES FOR NERN PORTIONS OF OUR AREA. UPDATES SHOULD BE POSTED./40/

&&

.AVIATION...AN UNSEASONABLY STRONG SHORTWAVE TROUGH WILL MOVE ACROSS
THE FORECAST AREA TODAY AND SUPPORT A COLD FRONT THAT WILL MOVE NEAR
GLH BY 03Z TUE. TSTMS ARE ONGOING THIS MORNING FOR GTR...BUT HAVE
CURRENTLY ENDED FOR GLH/GWO. THERE WILL CONTINUE TO BE A RISK OF
TSTMS FOR JAN/MEI/HKS THIS AFTERNOON AND THIS WILL BRING TEMPO
MVFR/IFR CONDITIONS. THIS ACTIVITY WILL CONTINUE THIS EVENING AS THE
COLD FRONT SLOWLY DROPS INTO THE AREA. THIS FRONT IS EXPECTED TO BE
OVER THE CENTRAL PORTIONS OF THE AREA BY 18Z TUE AND STALL ACROSS
THE SOUTH BY 00Z WED. /15/

&&

.PREV DISCUSSION... /ISSUED 350 AM CDT MON AUG 13 2012/

SHORT TERM...TODAY THROUGH TUESDAY NIGHT...AFTER A RATHER DRY
WEEKEND...RAIN CHANCES RETURN TODAY. WATER VAPOR IMAGERY/RUC ANALYSIS
SHOWS A SHORTWAVE TROUGH AXIS OVER THE CENTRAL PLAINS THAT WILL SWING
EAST ACROSS THE MS VALLEY AND TO THE OH/TN VALLEYS TODAY. THIS TROUGH
WILL SUPPORT A SURFACE LOW NOTED OVER MISSOURI EARLY THIS MORNING
THAT WILL TRACK TO THE SOUTHERN GREAT LAKES REGION BY TUESDAY
MORNING. THE TRAILING COLD FRONT WILL APPROACH OUR NW ZONES BY THIS
EVENING AND SLOWLY MOVE ACROSS OUR CWA TONIGHT AND TUESDAY. WAA AHEAD
OF THE SYSTEM WILL INCREASE OVER OUR AREA TODAY AND BRING AN INCREASE
OF DEEP MOISTURE BACK ACROSS OUR WHOLE CWA. A RATHER DRY AIRMASS WITH
MID 60 DEW POINTS AND A PW BELOW AN INCH AND A HALF STILL RESIDED
OVER THE NORTHEAST HALF OF OUR CWA EARLY THIS MORNING. BY AFTERNOON
LOWER 70 DEW POINTS AND A PW CLOSER TO TWO INCHES IS EXPECTED TO BE
BACK ACROSS THE CWA.

DAYTIME HEATING WILL CONTRIBUTE TO MLCAPES OF 2000-2500J/KG...6.5C
MID- LEVEL LAPSE RATES AND VERTICAL TOTALS NEAR 27C OVER OUR DELTA
REGION AHEAD OF THE FRONT. STRONG TO SEVERE STORMS WILL BE POSSIBLE
LATE THIS AFTERNOON AND EARLY EVENING MAINLY OVER THE DELTA REGION
BUT ALSO ALONG THE HIGHWAY 82 CORRIDOR AND AS FAR SOUTH AS INTERSTATE
20. DAMAGING WIND GUSTS WILL BE THE MAIN RISK WITH NICKEL TO QUARTER
SIZED HAIL SECONDARY. THERE WILL BE A NOTED DECREASE IN CONVECTION
WITH THE LOSS OF DAYTIME HEATING AND THE EASTWARD SHIFT OF THE UPPER
TROUGH AXIS BUT...ACTIVITY WILL BE POSSIBLE THOUGH THE NIGHT INTO
TUESDAY AS THE COLD FRONT DRIFTS SOUTH THROUGH THE CWA. THE GFS IS
FARTHEST SOUTH WITH THE FRONT TUESDAY AFTERNOON...BUT THE FRONT IS
STILL EXPECTED TO STALL NEAR THE I-20 CORRIDOR BY TUESDAY EVENING.
DAYTIME HEATING WILL CONTRIBUTE TO DEVELOPMENT OF STORMS ALONG AND
SOUTH OF THE BOUNDARY TUESDAY. A FEW STRONG STORMS WILL BE POSSIBLE
AT LEAST ACROSS OUR SOUTHEAST MOST ZONES TUESDAY AFTERNOON. NW FLOW
ALOFT WILL REMAIN ACROSS OUR AREA THROUGH TUESDAY NIGHT. MODELS
INDICATE ANOTHER SHORTWAVE IN THE FLOW ALOFT AND THE DEVELOPMENT OF
CONVECTION ALONG THE STALLED BOUNDARY UPSTREAM OF OUR CWA. WL CARRY
GFS MOS POPS FOR NOW AS THE CONVECTION LOOKS TO HOLD OFF UNTIL
WEDNESDAY. /22/

LONG TERM...WEDNESDAY THROUGH NEXT MONDAY...PERIODS OF SHRA/TSRA
EXPECTED WITH ACTIVITY LINGERING INTO PORTIONS OF THE OVERNIGHTS
DURING THE LONG TERM. RAIN/TSTORM CHANCES GO UP FRIDAY AS AN
APPROACHING COOL FRONT IMPACTS THE REGION.

GOOD AGREEMENT AMONGST THE NWP SUITE THIS MORNING WITH LONG TERM
CHARACTERIZED BY ERN CONUS TROUGHING /WITH SUBTLE EMBEDDED S/WV'S
ACROSS LOWER MS VALLEY/ THAT WILL AID IN EXTENDING DIURNAL
SHOWER/TSTORM ACTIVITY INTO OVRNGT HOURS. WEDNESDAY WILL BE A
RECOVERY DAY AS SLY MOISTURE RETURN INFILTRATES NORTH ACROSS SW/W
ZONES WHERE GREATEST POPS HAVE BEEN PLACED. ENHANCED ZONAL TO WNW
FLOW WED INTO THURS ALONG WITH AN PROGGED EMBEDDED S/WV WILL ALLOW
FOR SOME DIURNAL ACTIVITY (ALSO ASSOCIATED WITH A WEAK WARM FRONT
MOVING NORTH) TO LINGER OVRNGT. AN ACTIVE SEA-BREEZE LOOKS ON TAP
FOR THURS WITH PULSE AIRMASS TSTORMS EXPECTED DURING AFTN ACROSS THE
REST OF THE REGION WITH SOME PSBL ENHANCEMENT OF STRENGTH/ LONGEVITY
FROM A PROGGED S/WV PER GFS/EC.

PWATS OF 1.8-2.0" WILL BE IN PLACE ACROSS ENTIRE REGION BY FRIDAY AS
SFC LOW ACROSS OHIO RIVER VALLEY CREATES STRONG SLY FLOW. ATTENDANT
COOL FRONT WILL APPROACH REGION BY FRI AFTN-FRI NGT, ALLOWING FOR
GREATEST COVERAGE OF SHOWERS/TSTORMS OF THE PERIOD. LAPSE
RATES/SHEAR/WIND FLOW APPEAR LOW AT THIS TIME FOR ANY ORGANIZED
SEVERE RISK AND WILL KEEP LONG-TERM HWO CLEAR. TEMPS SHOULD BE
COOLER FRI/SAT GIVEN GREATER CLOUD/RAIN COVERAGE WITH HIGHS IN UPPER
80S. DEPENDING OF COVERAGE, SOME AREAS MAY ONLY MAKE IT LOW TO MID
80S, WHICH WOULD BE 3-7F BELOW AVERAGE FOR MID AUGUST.

EXPECT RAIN/TSTORMS TO CONTINUE THROUGH THE OVRNGT FRI INTO SAT AS
FRONT SLOWLY SHIFTS SOUTH TOWARDS HWY-82/I-20 CORRIDOR. GFS NOT AS
BULLISH IN BRINGING THE FRONT ALL THE WAY THROUGH WITH EC AGREEING.
HAVE UPPED/EXTENDED POPS FORWARD IN TIME FOR SAT. ISO/SCT ACTIVITY
COULD BE PSBL ALONG AND SOUTH OF I-20 SAT/SUN AFTNS BUT OVERALL
PWATS COULD BE REDUCED TO 1.5-1.7" RANGE. MODELS DIVERGE SUN/MON
WITH EC BEING MORE AMPLIFIED WITH ANOTHER S/WV TROUGH DROPPING DOWN
ON THE BACK SIDE OF THE ERN CONUS L/WV TROUGH AND PUSHES THE
AFOREMENTIONED FRONT THROUGH BY MON/MON NGT. NOT HIGHLY CONFIDENT ON
THIS SOLUTION AND PLACE MORE WEIGHT TOWARDS GFS TO AND WAIT FOR A
SOLID TREND.

FOR FORECAST ELEMENTS...MAV POPS WERE UPPED 10-20% FRIDAY AND
EXTENDING FORWARD IN TIME INTO SAT MRNG WITH THE SLOWER/NEARLY
STALLING FRONT. LOWS WERE TWEAKED UPWARD AS DEWPOINTS INCREASE
WHILE UNDER BLANKET OF NOCTURNAL CLOUDS. MEXMOS HIGHS WERE GENERALLY
ACCEPTED WITH SOME MINOR TWEAKS DOWN ON FRIDAY. /ALLEN/

&&

.PRELIMINARY POINT TEMPS/POPS...
JACKSON       91  72  90  70 /  72  44  21   9
MERIDIAN      91  72  91  69 /  68  51  45  12
VICKSBURG     91  70  90  68 /  51  22  17   6
HATTIESBURG   93  75  93  71 /  40  36  49  13
NATCHEZ       91  73  89  70 /  43  24  20   7
GREENVILLE    89  69  88  68 /  51  21   8   8
GREENWOOD     85  70  88  66 /  81  29  11  10

&&

.JAN WATCHES/WARNINGS/ADVISORIES...
MS...NONE.
LA...NONE.
AR...NONE.
&&

HAZARDOUS WEATHER OUTLOOK
NATIONAL WEATHER SERVICE JACKSON MS
514 AM CDT MON AUG 13 2012

ARZ074-075-LAZ007>009-015-016-MSZ018-019-025>050-141015-
ASHLEY-CHICOT-MOREHOUSE-WEST CARROLL-EAST CARROLL-RICHLAND-
MADISON LA-BOLIVAR-SUNFLOWER-LEFLORE-GRENADA-CARROLL-MONTGOMERY-
WEBSTER-CLAY-LOWNDES-CHOCTAW-OKTIBBEHA-WASHINGTON-HUMPHREYS-
HOLMES-ATTALA-WINSTON-NOXUBEE-ISSAQUENA-SHARKEY-YAZOO-MADISON MS-
LEAKE-NESHOBA-KEMPER-WARREN-HINDS-RANKIN-SCOTT-
514 AM CDT MON AUG 13 2012

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

.DAY ONE...TODAY AND TONIGHT

STRONG TO SEVERE STORMS ARE POSSIBLE THIS MORNING IN THE DELTA AND THEN
AGAIN GENERALLY NORTH OF INTERSTATE 20 THIS AFTERNOON AND EVENING.
WIND GUSTS OF 50 TO 60 MPH AND NICKEL TO QUARTER SIZED HAIL WILL BE
POSSIBLE. THE STORMS WILL DEVELOP AHEAD OF A SHORTWAVE AND
APPROACHING COLD FRONT. THE ACTIVITY IS EXPECTED TO WEAKEN IN
INTENSITY AS THE EVENING PROGRESSES.

.DAYS TWO THROUGH SEVEN...TUESDAY THROUGH SUNDAY

THE PROBABILITY FOR WIDESPREAD HAZARDOUS WEATHER IS LOW.

.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 SUNDAY.

LAZ023>026-MSZ051>066-072>074-141015-
FRANKLIN LA-CATAHOULA-TENSAS-CONCORDIA-NEWTON-LAUDERDALE-
CLAIBORNE-COPIAH-SIMPSON-SMITH-JASPER-CLARKE-JEFFERSON-ADAMS-
FRANKLIN MS-LINCOLN-LAWRENCE-JEFFERSON DAVIS-COVINGTON-JONES-
MARION-LAMAR-FORREST-
514 AM CDT MON AUG 13 2012

THIS HAZARDOUS WEATHER OUTLOOK IS FOR PORTIONS OF CENTRAL
AND SOUTH MISSISSIPPI.

.DAY ONE...TODAY AND TONIGHT

THE PROBABILITY FOR WIDESPREAD HAZARDOUS WEATHER IS LOW.

.DAYS TWO THROUGH SEVEN...TUESDAY THROUGH SUNDAY

A FEW STRONG THUNDERSTORMS CAPABLE OF WIND GUSTS OF 40 TO 50 MPH
WILL BE POSSIBLE TUESDAY ALONG AND SOUTH OF THE COLD FRONT THAT IS
EXPECTED TO STALL JUST SOUTH OF THE INTERSTATE 20 CORRIDOR.

.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 SUNDAY.

FOR MORE INFORMATION PLEASE VISIT OUR WEBSITE AT
WWW.SRH.NOAA.GOV/JAN.

22

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