000
FXUS64 KMEG 220437
AFDMEG

AREA FORECAST DISCUSSION
NATIONAL WEATHER SERVICE MEMPHIS TN
1137 PM CDT TUE MAY 21 2013

.DISCUSSION...

UPDATED FOR 06Z AVIATION DISCUSSION

&&

.PREV DISCUSSION... /ISSUED 807 PM CDT TUE MAY 21 2013/

UPDATE...

A LINE OF SHOWERS AND THUNDERSTORMS CONTINUES TO MOVE EAST ACROSS
WEST TENNESSEE AND NORTH MISSISSIPPI. THE ATMOSPHERE ACROSS WEST
TENNESSEE HAS BEEN WORKED OVER AND THUS FAR THE STORMS HAVE NOT
APPROACHED SEVERE LIMITS. MEANWHILE FURTHER SOUTH...THE LINE IS
JUST GETTING INTO NORTHEAST MISSISSIPPI WHERE THE ATMOSPHERE IS
MUCH MORE UNSTABLE SINCE NO RAIN HAS FALLEN ACROSS THE AREA TODAY.
IN ADDITION...THE SECOND LINE OF SHOWERS AND THUNDERSTORMS
ASSOCIATED WITH THE UPPER SHORTWAVE IS BEGINNING TO TO STREAM
NORTHWARD ACROSS SOUTHEAST ARKANSAS. DON/T KNOW WHAT THE STORMS
WILL DO WHEN THEY MOVE INTO NORTHWEST MISSISSIPPI AS THE
ATMOSPHERE HAS BEEN WORKED OVER FROM FIRST LINE. HOWEVER...SEVERE
THUNDERSTORM WARNINGS CONTINUE TO BE ISSUED ALONG PORTIONS OF THE
LINE SO WILL HANG ON TO THE WATCH FOR NORTH MISSISSIPPI AFTER THE
FIRST LINE MOVES THROUGH UNTIL WE SEE WHAT THE STORMS DO ALONG THE
SECOND LINE. HOWEVER...WILL CONTINUE TO CLEAR THE WATCH BEHIND THE
FIRST LINE ACROSS WEST TENNESSEE.

KRM

DISCUSSION... /ISSUED 304 PM CDT TUE MAY 21 2013/

VERY ACTIVE RADAR THIS AFTERNOON. OVERNIGHT/EARLY MORNING
CONVECTION MAY HAVE US FROM A MUCH MORE SIGNIFICANT SEVERE WEATHER
OUTBREAK TODAY...ALTHOUGH SEVERE POTENTIAL STILL
EXISTS...ESPECIALLY ACROSS NORTH MISSISSIPPI. FARTHER NORTH THE
AIRMASS HAS BEEN WORKED OVER...AND ABUNDANT CLOUD COVER HAS KEPT
TEMPERATURES QUITE A BIT COOLER. INSTABILITY IS HIGHEST IN NORTH
MISSISSIPPI WHERE TEMPERATURES HAVE BEEN ABLE TO CLIMB INTO THE
MIDDLE AND UPPER 80S. DEW POINTS ARE IN THE UPPER 60S TO LOWER 70S
RESULTING IN CAPES IN EXCESS OF 2500 J/KG AND LI`S BELOW -6C. JUST
ACROSS THE STATE LINE IN MOST OF TN...THE MISSOURI BOOTHEEL AND
NORTHEAST ARKANSAS...CAPES ARE GENERALLY BELOW 1500 J/KG WITH LI`S
-4C OR GREATER. DEW POINTS ARE ALSO SLIGHTLY HIGHER. IN THE PAST
COUPLE OF HOURS STORMS HAVE DEVELOPED IN NORTH MISSISSIPPI AND
HAVE SHOWN SOME SIGNS OF ROTATION. 0-3KM HELICITY IS GENERALLY
50-90M^2/S^2 WHICH WOULD CERTAINLY SUPPORT ROTATING STORMS. UPPER
LEVEL SUPPORT IS NOT CURRENTLY AS FAVORABLE FOR SEVERE
THUNDERSTORMS...ALTHOUGH BETTER SUPPORT IS EXPECTED TO MOVE IN
TONIGHT.

ANOTHER ROUND OF STORMS CAN BE SEEN OVER NORTH TEXAS INTO
OKLAHOMA. THIS LINE WILL BRING ADDITIONAL SHOWERS AND
THUNDERSTORMS TO THE MIDSOUTH OVERNIGHT. NUMEROUS OUTFLOW
BOUNDARIES WILL ONLY HELP SUPPORT FOCUS UPDRAFTS AND MAINTAIN A
SEVERE THREAT.

A SHORTWAVE TROUGH CURRENTLY OVER THE TEXAS AND OKLAHOMA
PANHANDLES WILL SHIFT TO THE EAST THIS EVENING AND APPROACH THE
MISSISSIPPI RIVER BY SUNRISE. A SURFACE LOW HAS DEVELOPED OVER
NORTH TEXAS AND SHOULD TRACK NORTHEAST ACROSS CENTRAL ARKANSAS
DURING THE NIGHT. WE WILL SEE A 40-45KT LLJ DEVELOP BY MIDNIGHT
AND MUCH OF THE MIDSOUTH WILL BE IN THE RIGHT ENTRANCE REGION OF A
70-80KT UPPER LEVEL JET. THIS ADDITIONAL DYNAMIC SUPPORT WILL MOVE
IN JUST AS WE LOSE DAYTIME THERMODYNAMIC SUPPORT. THUS FEEL LIKE
THE THREAT FOR SEVERE WEATHER WILL REMAIN ABOUT THE SAME DURING
THE NIGHT...MARGINAL BUT CERTAINLY NOT ZERO.

RESEARCHERS AT MISSISSIPPI STATE UNIVERSITY LAUNCHED A WEATHER
BALLOON MIDDAY ABOUT 30 MILES SOUTHWEST OF GREENWOOD MISSISSIPPI.
IT SHOWS A BIT OF A CAP AT 10KFT...BUT CAPE IN EXCESS OF 3500
J/KG. FARTHER NORTH AT LITTLE ROCK A MIDDAY SOUNDING WAS
INDICATIVE OF A WORKED OVER ENVIRONMENT...FEATURING ONLY 343
JOULES OF CAPE. ANY THREATS FROM STORMS IN WEST TENNESSEE AND EAST
ARKANSAS WOULD BE PRIMARILY HAIL.

A COLD FRONT WILL SWEEP ACROSS THE MIDSOUTH TOMORROW BRINGING AN
END TO THE PRECIPITATION. THE FRONT SHOULD MOVE INTO EAST ARKANSAS
BY 10 AM...CROSS THE MISSISSIPPI RIVER MIDDAY AND EXIT INTO
CENTRAL TENNESSEE/NORTH ALABAMA DURING THE MID AFTERNOON HOURS.
RAIN WILL LIKELY LIMIT TEMPERATURES AGAIN TOMORROW BUT AS RAIN
ENDS...WE COULD SEE TEMPERATURES SURGE INTO THE LOW 80S DURING THE
AFTERNOON HOURS. THE DIURNAL TEMPERATURE PROFILE WILL LIKELY BE
TRICKY TOMORROW DUE THE RAINFALL AND FRONT.

THURSDAY THROUGH THE WEEKEND LOOK MOSTLY DRY. TEMPERATURES THURSDAY
WILL BE NEAR NORMAL...WITH COOLISH FRIDAY...THEN TRENDING
GRADUALLY WARMER THROUGH THE WEEKEND. FRIDAY THROUGH THE WEEKEND
OUR WEATHER SHOULD BE PRIMARILY INFLUENCED BY A WEAK RIDGE ALOFT
AND SURFACE HIGH PRESSURE RESULTING IN DRY CONDITIONS.

&&

.AVIATION...

06Z TAF CYCLE

A LINE OF STRONG TSRAS WILL MOVE THROUGH KTUP BETWEEN 22/06Z-22/08Z
FOLLOWED BY A LARGE AREA OF STRATIFORM RAIN. THIS RAIN WILL MOVE
OUT OF KJBR SHORTLY AND OUT OF KMEM AND KMKL OVER THE NEXT COUPLE
OF HOURS. AFTER THE TSRAS MOVE THROUGH KTUP EXPECT MAINLY VFR
CONDS FOR THE REST OF THE OVERNIGHT PERIOD. LATEST MODELS
INDICATE MORE SHRAS DEVELOPING OVER ARKANSAS AND MOVING ACROSS
THE MIDSOUTH BTWN 22/10Z AT KJBR AND 22/14Z AT KTUP. A PERIOD OF
MVFR CIGS IS LIKELY ACROSS THE AREA WED MORNING AS WELL. CONDS
WILL IMPROVE TO VFR BY WED AT AROUND NOON AND CONTINUE THROUGH THE
REMAINDER OF THE PERIOD.

GENERALLY LIGHT SOUTH WINDS OVERNIGHT BECOMING SW AT 10-12 KTS WED
MORNING.

SJM

&&

.PRELIMINARY POINT TEMPS/POPS...
MEM  66  83  61  82 / 100  60  10  10
MKL  64  81  58  81 / 100  60  10  10
JBR  63  82  57  80 / 100  40  10  10
TUP  64  83  60  86 / 100  70  10  10

&&

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

$$