Severe Thunderstorm Warning 271, NWS Memphis, TN

AREA FORECAST DISCUSSION
NATIONAL WEATHER SERVICE MEMPHIS TN
817 PM CDT SAT JUL 11 2009

.DISCUSSION...00Z SURFACE ANALYSIS PLACES A QUASI-STATIONARY
BOUNDARY STRETCHING ACROSS SOUTHERN MISSOURI WHILE UPPER AIR
PROFILERS/WATER VAPOR SATELLITE TRENDS SHOW ADDITIONAL CONVECTIVE
ACTIVITY HAS FORMED ACROSS THE NORTHERN PERIPHERY OF THE UPPER
LEVEL RIDGE ACROSS SOUTH CENTRAL MISSOURI. TEMPERATURES ACROSS
THE MID SOUTH AS OF 7 PM CDT RANGE FROM THE UPPER 70S TO LOWER 80S
WHERE CONVECTIVE ACTIVITY/CLOUD COVER HAS OCCURRED EARLIER TODAY
AND MID 80S TO NEAR 90 ALONG THE MISSISSIPPI RIVER DELTA. MAIN
FORECAST CHALLENGE IS CONVECTIVE/SEVERE WEATHER POTENTIAL ACROSS
THE MID SOUTH DURING THE LATE EVENING AND OVERNIGHT HOURS.

SHORT TERM RUC ANALYSIS INDICATES THE ACTIVITY WILL GRADUALLY
BEGIN TO PROPAGATE TOWARDS THE EASTERN PERIPHERY OF THE UPPER
LEVEL RIDGE AND INTO THE MID SOUTH OVER THE NEXT COUPLE OF HOURS.
FREEZING LEVELS REMAIN QUITE HIGH OVER 15 KFT AND MAIN THREAT
WOULD BE DAMAGING WINDS IF A THUNDERSTORM OR TWO IS ABLE TO BECOME
SEVERE THIS EVENING INTO THE OVERNIGHT HOURS ACROSS PORTIONS OF
WEST TENNESSEE NEAR THE KENTUCKY BORDER AND ALONG THE TENNESSEE
RIVER. HEAVY RAINFALL ALSO A POSSIBILITY AS PRECIPITABLE WATER
VALUES ACROSS THE REGION THIS EVENING ARE AT OR ABOVE 2 INCHES.
WILL MAKE ADJUSTMENTS TO GRIDS BASED ON LATEST CONVECTIVE TRENDS.

UPDATED GRIDS WILL BE AVAILABLE SHORTLY...

CJC

&&

.PREV DISCUSSION... /ISSUED 641 PM CDT SAT JUL 11 2009/

UPDATE...

UPDATED AVIATION DISCUSSION FOR 00Z TAFS.

DISCUSSION...

/ISSUED 142 PM CDT SAT JUL 11 2009/

UPPER RIDGE WILL BEGIN TO BREAK DOWN OVER THE MIDSOUTH ON SUNDAY.
ANOTHER MCS IS EXPECTED TO DEVELOP TONIGHT ACROSS MISSOURI AND
MOVE SOUTH. WITH THE RIDGE WEAKENING OVER THE AREA TOMORROW AS THE
REMNANTS OF THE MCS MOVES INTO THE MIDSOUTH...EXPECT MORE SHOWER
AND THUNDERSTORM ACTIVITY THAN WHAT IS CURRENTLY ON RADAR FROM
TODAY/S MCS. HIGHS WILL LIKELY BE SIMILAR TO TODAY WITH READINGS
IN THE LOWER 90S. THE REMNANTS OF THE MCS COULD MOVE INTO THE AREA
LATE TONIGHT THUS WILL CONTINUE WITH POPS FOR NORTHERN AREAS
TONIGHT.

ON MONDAY...A FRONT WILL MOVE SOUTH AND HANG UP ALONG THE MO/AR AND
KY/TN BORDER AS THE UPPER RIDGE CONTINUES TO WEAKEN OVER THE AREA.
SHOWER AND THUNDERSTORMS MAY DEVELOP ALONG THIS FRONT AND MOVE
SOUTH. HIGHS WILL BE COOLER WITH READINGS IN THE UPPER 80S TO LOWER
90S.

TUESDAY INTO WEDNESDAY...UPPER RIDGE BEGINS TO BUILD BACK OVER THE
MIDSOUTH ON TUESDAY BRINGING WARMER TEMPERATURES BACK TO THE AREA.
WEDNESDAY WILL LIKELY BE THE HOTTEST DAY WITH READINGS IN THE MID TO
UPPER 90S. THE HOT TEMPERATURES COMBINED WITH DEWPOINTS IN THE 70S
WILL LIKELY PRODUCE HEAT INDICES ABOVE 105 DEGREES. HEAT ADVISORIES
MAY BE NEEDED TUESDAY AND WEDNESDAY.

WEDNESDAY NIGHT INTO THURSDAY...COLD FRONT WILL SLIDE SOUTH AS THE
UPPER RIDGE WEAKENS OVER THE AREA. THE FRONT WILL BRING CHANCES FOR
SHOWERS AND THUNDERSTORMS TO THE AREA AND COOLER TEMPERATURES.

BY FRIDAY INTO SATURDAY...COLD FRONT WILL STALL OUT POSSIBLY OVER
THE SOUTHWESTERN PORTIONS OF THE CWA AS SFC HIGH PRESSURE BUILDS
INTO NORTHWEST TENNESSEE. RAIN CHANCES WILL CONTINUE TO OCCUR TO THE
SOUTHWEST WHILE THE NORTHEAST PORTION OF THE CWA WILL SEE COOLER AND
DRIER WEATHER.

KRM

&&
.AVIATION...

00Z TAFS

MAINLY EXPECT VFR CONDITIONS AT ALL TAF SITES EXCEPT KMKL
WHERE MVFR VISIBILITIES SHOULD QUICKLY DEVELOP BY 03Z THEN
CONTINUE THROUGH 14Z. BRIEF MVFR VISIBILITIES ARE POSSIBLE
10-13Z AT KJBR AND KTUP...SO KEPT TEMPO FOR THIS OCCURRENCE.

WILL MONITOR TSRA COMPLEX DEVELOPING OVER MISSOURI. THINK THIS
WILL ORGANIZE AND MOVE SOUTHEAST. ADDED VCTS AT KMKL 09-14Z TO
ACCOUNT FOR THIS COMPLEX WHERE CHANCES OF IMPACT IS HIGHEST.
WOULD NOT BE SURPRISED IF TSRA/SHRA AFFECTED THE OTHER TAF SITES
AFTER 09Z. IF COMPLEX DIRECTLY AFFECTS A GIVEN SITE...BRIEF
IFR CONDITIONS AND GUSTY WINDS WOULD BE POSSIBLE. WILL AMEND IF
NECESSARY.

ADDITIONAL ISOLATED TO SCATTERED TSRA/SHRA WILL BE OVER THE
AREA AFTER 14Z...PARTICULARLY NEAR KMKL AND KTUP...SO KEPT VCTS
AT THESE SITES. KEPT VCTS AT KJBR...THOUGH CONFIDENCE IS LOWER
AT THIS SITE. KEPT VCTS MENTION OUT OF KMEM TAF THINKING MOST
TSRA/SHRA AFTER 14Z WILL BE NORTH AND EAST OF THIS SITE.

GENERALLY LIGHT SOUTH WINDS WILL PREVAIL.

MBS

&&

.PRELIMINARY POINT TEMPS/POPS...
MEM  78  93  78  93 /  20  20  10  20
MKL  72  90  73  88 /  20  40  20  40
JBR  76  92  76  91 /  30  30  20  20
TUP  74  92  74  92 /  10  20  10  30

&&

.MEG WATCHES/WARNINGS/ADVISORIES...
AR...NONE.
MO...NONE.
MS...NONE.
TN...NONE.
&&

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