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000
FXUS64 KMEG 211807
AFDMEG

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

.UPDATE...

.UPDATED FOR 18Z TAF DISCUSSION..


&&

.PREV DISCUSSION... /ISSUED 1059 AM CDT TUE MAY 21 2013/

UPDATE...MORNING UPDATE.

ADJUSTED THE FORECAST BASED ON RADAR AND SATELLITE TRENDS. DOES
NOT LOOK LIKE WE WILL REALIZE THE EXPECTED AFTERNOON HIGH
TEMPERATURES DUE TO CLOUD COVER AND ONGOING PRECIPITATION. THE
EXCEPTION MAY BE IN NORTH MISSISSIPPI WHERE RAIN IS LESS
WIDESPREAD. HOWEVER CLOUD COVER IS STILL WIDESPREAD. NEW ZONES ARE
OUT. WILL LIKELY FOCUS ON SEVERE WEATHER THREAT THIS AFTERNOON. DO
NOT ANTICIPATE SIGNIFICANT CHANGES TO THE LONG TERM WITH THE
AFTERNOON PACKAGE.

PREV DISCUSSION... /ISSUED 735 AM CDT TUE MAY 21 2013/

UPDATE...

UPDATED FOR 12Z AVIATION DISCUSSION.

PREV DISCUSSION... /ISSUED 551 AM CDT TUE MAY 21 2013/

DISCUSSION...09Z SURFACE ANALYSIS PLACES A SURFACE LOW OVER
EASTERN SOUTH DAKOTA WITH A COLD FRONT EXTENDING SOUTH FROM THE
LOW ACROSS WESTERN MISSOURI...THEN BACK INTO CENTRAL OKLAHOMA AND
BACK INTO TEXAS. MEANWHILE...SHOWERS AND THUNDERSTORMS ASSOCIATED
WITH LAST NIGHT/S CONVECTIVE ACTIVITY OVER THE PLAINS AND WESTERN
SECTIONS OF THE LOWER MISSISSIPPI VALLEY PRODUCED DAMAGING WINDS
ACROSS PORTIONS OF EAST AND NORTHEAST ARKANSAS AND WEAKENED AS IT
MOVED EAST OF THE MISSISSIPPI RIVER. TEMPERATURES AS OF 4 AM CDT
ARE PREDOMINANTLY IN THE 60S AT MOST LOCATIONS. SEVERE
THUNDERSTORM POTENTIAL MAINLY LATER THIS AFTERNOON INTO TONIGHT
REMAINS THE MAIN FORECAST CONCERN IN THIS MORNING/S FORECAST
ISSUANCE.

SHORT TERM...(TODAY THROUGH WEDNESDAY NIGHT)...SHOWERS AND
THUNDERSTORMS ASSOCIATED WITH LAST NIGHTS CONVECTION HAS MOVED TO
PORTIONS OF WEST TENNESSEE NEAR THE MISSISSIPPI RIVER. REGIONAL
WSR-88D RADAR TRENDS SHOW A COUPLE OF ADDITIONAL LINES ACROSS
ARKANSAS...THE FIRST LINE ACROSS EAST AND NORTHEAST ARKANSAS...AND
A SECOND LINE BEGINNING TO APPROACH CENTRAL ARKANSAS. LATEST RADAR
TRENDS INDICATE LESS SURFACE BASED INSTABILITY ACROSS THE AREA AND
THESE TWO ADDITIONAL LINES ARE EXPECTED TO BE REMAIN ELEVATED AT
THIS TIME.

A SURFACE LOW NEAR MIDLAND TEXAS EARLY THIS MORNING WILL MOVE
INTO EASTERN OKLAHOMA BY LATE AFTERNOON...INTO NORTHWEST ARKANSAS
TONIGHT AND UP INTO THE OHIO RIVER VALLEY BY WEDNESDAY.
MEANWHILE...AN UPPER LEVEL TROUGH WILL BECOME NEGATIVELY TILTED
AS IT MOVES INTO THE MIDDLE AND LOWER MISSISSIPPI VALLEYS TONIGHT.
THE ATMOSPHERE IS EXPECTED TO RECOVER AND DESTABILIZE ONCE AGAIN
BY THIS AFTERNOON INTO TONIGHT. MODERATELY STEEP TO STEEP 700-500
MB LAYER MID LEVEL LAPSE RATES...0-6 KM BULK SHEAR VALUES BETWEEN
40 TO 50 KTS...SURFACE BASED CAPE VALUES BETWEEN 1500-2500 J/KG
ESPECIALLY DURING THE LATE AFTERNOON INTO THE EARLY
EVENING...NEARLY UNIDIRECTIONAL WINDS ALOFT...AND FAVORABLE UPPER
LEVEL DIVERGENCE PRODUCED BY THE LEFT EXIT REGION OF AN UPPER
LEVEL JET STREAK SUGGEST THE CONVECTIVE ACTIVITY WILL BE MOSTLY IN
THE FORM OF A LINE AS IT MOVES ACROSS THE MID SOUTH TONIGHT. THE
PRIMARY SEVERE WEATHER THREATS WILL BE LARGE HAIL AND DAMAGING
WINDS WITH ANY THUNDERSTORMS THAT REACH SEVERE LIMITS. A POTENTIAL
WILL ALSO EXIST FOR PERHAPS A TORNADO OR TWO EMBEDDED WITHIN THE
LINE AS IT MOVES ACROSS THE AREA. LOCALIZED FLASH FLOODING FROM
HEAVY RAINFALL WILL BE POSSIBLE AS PRECIPITABLE WATER VALUES WILL
RANGE FROM 1.5 TO 2 INCHES. WILL CONTINUE TO MONITOR TRENDS AND
CONSIDER THE POTENTIAL FOR A FLASH FLOOD WATCH MAINLY WEST OF THE
MISSISSIPPI RIVER TODAY AND TONIGHT IF SHORT TERM TRENDS SHOW AN
INCREASING POTENTIAL. WILL HIGHLIGHT SEVERE WEATHER THREATS IN THE
HAZARDOUS WEATHER OUTLOOK.

CHANCES FOR SHOWERS AND THUNDERSTORMS WILL PERSIST INTO WEDNESDAY
AS THE COLD FRONT MOVES THROUGH THE MID SOUTH AND GRADUALLY TAPER
OFF INTO WEDNESDAY NIGHT.

LONG TERM...(THURSDAY THROUGH MEMORIAL DAY)...LATEST LONG TERM
MODEL TRENDS INDICATE ANOTHER FRONT WILL MOVE THROUGH THE LOWER
MISSISSIPPI VALLEY THURSDAY. A POTENTIAL WILL EXIST FOR ADDITIONAL
SHOWERS AND THUNDERSTORMS TO DEVELOP BUT OVERALL CONFIDENCE IN
COVERAGE REMAINS LOW. HIGH PRESSURE IS EXPECTED TO BUILD INTO THE
MID SOUTH FOR THURSDAY NIGHT INTO FRIDAY WITH SLIGHTLY COOLER AIR
TEMPORARILY RETURNING BACK TO THE FORECAST AREA. LONG TERM MODELS
REMAIN IN DISAGREEMENT WITH THE OVERALL SYNOPTIC PATTERN AS THE
COLD FRONT RETURNS NORTH AS A WARM FRONT THIS WEEKEND INTO EARLY
NEXT WEEK. THE GFS REMAINS THE DRIER OF THE SOLUTIONS WITH THE
ECMWF SUGGESTING SEVERAL CHANCES FOR SHOWERS AND THUNDERSTORMS
ESPECIALLY ALONG AND NORTH OF I-40 FOR THIS WEEKEND INTO MEMORIAL
DAY. HAVE OPTED TO LEAVE POPS OUT OF THE FORECAST UNTIL MODELS
COME INTO BETTER CONSENSUS.

CJC

.AVIATION...
18Z TAF CYCLE

COMPLEX WEATHER PATTERN FOR THIS AFTERNOON AND EVENING. ONGOING
CONVECTION..MAINLY OVER NORTH MISSISSIPPI AT THIS TIME..WILL
CONTINUE TO DEVELOP AND BRIEFLY AFFECT TERMINALS THIS AFTERNOON.
WINDS OUT OF THE SOUTH AT AROUND 10KTS ARE EXPECTED AT ALL SITES
THIS AFTERNOON...WITH SOME BRIEF GUSTY WINDS GENERATED BY NEARBY
TS. OVERNIGHT..EXPECT THUNDERSTORMS TO INCREASE IN COVERAGE AND
MOVE FROM WEST TO EAST WITH STRONG WIND GUSTS TO 20KT POSSIBLE.
THUNDERSTORMS WILL MOVE EAST OF THE MIDSOUTH BETWEEN 10-12UTC
WITH ADDITIONAL SHOWERS EXPECTED THROUGH THE MORNING.

SAK

&&

.PRELIMINARY POINT TEMPS/POPS...
MEM  70  84  65  82 /  80  50  10  20
MKL  68  82  63  81 /  70  50  10  20
JBR  66  82  62  82 /  90  30  10  20
TUP  68  83  65  86 /  60  60  10  20

&&

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

$$