000
FXUS64 KMEG 171210
AFDMEG

AREA FORECAST DISCUSSION
NATIONAL WEATHER SERVICE MEMPHIS TN
710 AM CDT FRI MAY 17 2013

.UPDATE...
UPDATED TO ADD 12Z AVIATION DISCUSSION.

&&

.PREV DISCUSSION... /ISSUED 440 AM CDT FRI MAY 17 2013/

DISCUSSION...

AN UPPER LEVEL LOW PRESSURE SYSTEM POSITIONED OVER NORTHEAST
ARKANSAS EARLY THIS MORNING WILL CONTINUE TO LIFT NORTHEASTWARD
TODAY. AT THE SURFACE...A 1010MB LOW PRESSURE SYSTEM IN THE
VICINITY OF LITTLE ROCK ARKANSAS WILL ALSO LIFT TO THE NORTHEAST
THROUGH THE DAY. NUMEROUS SHOWERS AND THUNDERSTORMS HAVE DEVELOPED
IN ADVANCE OF THE SURFACE LOW OVER WESTERN PORTIONS OF THE MID
SOUTH AS OF 09Z. THIS ACTIVITY SHOULD CONTINUE TO MOVE NORTHEAST
THROUGH THE MORNING HOURS WITH ADDITIONAL DEVELOPMENT POSSIBLE
THROUGH THE DAY. PLAN TO CONTINUE WITH LIKELY WORDING THROUGH THE
DAY AT ALL LOCATIONS.

SURFACE WINDS IN ADVANCE OF THE SURFACE LOW WILL REMAIN BACKED
WITH DECENT VEERING PROFILES THROUGH THE LOWER AND MIDDLE LEVELS
OF THE ATMOSPHERE. A MID LEVEL JET STREAK ON THE ORDER OF 30-40
KTS WAS SAMPLED FROM 00Z SOUNDINGS AT KLZK...KSHV...AND KJAN.
THIS MID LEVEL JET WILL MAINTAIN A NORTHWESTERLY COMPONENT AND IS
FORECAST TO SPREAD EASTWARD ACROSS SOUTHERN PORTIONS OF THE MID
SOUTH TODAY. DEEP LAYER SHEAR PROFILES ACROSS AREAS SOUTH OF
INTERSTATE 40 SHOULD REMAIN AROUND 30 KTS THROUGH THE
DAY...ALTHOUGH LOW LEVEL SPEED SHEAR SHOULD REMAIN MEAGER. THIS
AMOUNT OF SHEAR WOULD BE SUPPORTIVE OF SOME STORM ORGANIZATION AND
AT LEAST A MARGINAL SEVERE THUNDERSTORM THREAT. A HIGHER LEVEL OF
UNCERTAINTY REMAINS THIS MORNING WITH REGARD TO THE POTENTIAL
SEVERE WEATHER THREAT AS IT WILL BE PREDICATED ON THE DEGREE OF
INSTABILITY THAT CAN DEVELOP. WIDESPREAD CLOUD COVER AND ONGOING
CONVECTION AND EXPECTED RENEWED DEVELOPMENT COULD LIMIT OVERALL
HEATING EVEN AS DEWPOINTS RISE INTO THE MID AND UPPER 60S. THIS
COMPLEX PATTERN MAKES THE POTENTIAL FOR SEVERE STORMS QUITE
UNCERTAIN AND OVERALL CONFIDENCE REMAINS LOW AT THIS TIME. PLAN TO
CONTINUE WITH THE IDEA THAT A FEW STORMS COULD APPROACH SEVERE
LIMITS OVER SOUTHERN AREAS...ESPECIALLY SINCE MUCH OF THE MODEL
GUIDANCE SUPPORTS AFTERNOON SBCAPE VALUES OVER THESE LOCATIONS
BETWEEN 1000-1500 J/KG. CURRENTLY STILL THINK THAT THESE VALUES
MAY BE OVERDONE BY THE MODEL GUIDANCE AND THAT ANY SEVERE WEATHER
THREAT WILL REMAIN ISOLATED. LATER SHIFTS WILL CONTINUE TO MONITOR
THIS POTENTIAL THROUGH THE DAY AND PROVIDE UPDATES AS NECESSARY.

AS THE UPPER LOW MOVES FURTHER NORTHEAST AND DEAMPLIFIES TONIGHT
THE GREATEST CONVECTIVE CHANCES SHOULD SHIFT TO EASTERN SECTIONS
OF THE MID SOUTH. WARM AND HUMID CONDITIONS SHOULD REMAIN IN
PLACE OVERNIGHT.

UPPER LEVEL RIDGING WILL BEGIN TO BUILD EASTWARD INTO WESTERN
PORTIONS OF THE MID SOUTH ON SATURDAY WITH LINGERING TROUGHING
OVER EASTERN SECTIONS. STRONG DAYTIME HEATING WITH TEMPERATURES
RISING INTO THE MID AND UPPER 80S COMBINED WITH DEWPOINTS NEARING
70 DEGREES AND WEAK CAPPING SHOULD RESULT IN THE DEVELOPMENT OF
ISOLATED TO SCATTERED SHOWERS AND THUNDERSTORMS BY SATURDAY
AFTERNOON. THE HIGHEST CHANCES SHOULD REMAIN ACROSS EASTERN
PORTIONS OF THE AREA WHERE THERE IS THE HIGHEST CONFIDENCE FOR CAP
EROSION. MODERATE TO STRONG INSTABILITY WITH SBCAPES IN EXCESS OF
2500 J/KG...LI/S BETWEEN -6C AND -10C...MID LEVEL LAPSE RATES IN
EXCESS OF 7.0 C/KM...COMBINED WITH WEAK DEEP LAYER SHEAR MAY
SUPPORT A FEW PULSE SEVERE STORMS SATURDAY AFTERNOON AND EARLY EVENING.
CONVECTION SHOULD WANE THROUGH THE EVENING HOURS WITH LOSS OF
DAYTIME HEATING.

THE UPPER RIDGE WILL STRENGTHEN FURTHER AND SPREAD EAST ON SUNDAY
BRINGING MAINLY DRY AND INCREASINGLY HOT WEATHER TO THE AREA.
HIGH TEMPERATURES NEARING 90 DEGREES COMBINED WITH UPPER 60S
DEWPOINTS SHOULD MAKE FOR THE HOTTEST DAY SO FAR THIS YEAR. THE
VERY WARM...HUMID...AND DRY WEATHER SHOULD PERSIST THROUGH NEXT
MONDAY.

ANOTHER MID LEVEL SHORTWAVE TROUGH AND ASSOCIATED COLD FRONT WILL
IMPACT THE WEATHER BY NEXT TUESDAY AND WEDNESDAY WITH INCREASING
CHANCES FOR SHOWERS AND THUNDERSTORMS. AS THE SHORTWAVE LIFTS OUT
TO THE NORTHEAST ON THURSDAY...EXPECT THE ASSOCIATED SURFACE FRONT
TO WASH OUT ACROSS THE AREA. UPPER RIDGING SHOULD REBUILD BY THE
END OF NEXT WEEK WITH A RETURN TO DRY WEATHER AND SEASONABLY WARM
TEMPERATURES.

JLH

&&

.AVIATION...
12Z TAF CYCLE

UPPER LEVEL LOW LOCATED ACROSS WEST TENNESSEE WILL PRODUCE SHRA
AT TAF SITES TODAY AND PERHAPS VCTS AT MKL/TUP THIS MORNING.
MVFR/IFR CONDITIONS EXPECTED TO PREVAIL THIS MORNING WITH A
GRADUAL IMPROVEMENT TO MVFR CONDITIONS BY LATE THIS AFTERNOON.
MVFR/IFR CONDITIONS DUE TO LOW STRATUS MAY DEVELOP LATE TONIGHT AT
ALL SITES. SOUTH/SOUTHEAST WINDS BETWEEN 6-9 KTS THIS MORNING WILL
GRADUALLY BECOME LIGHT TOWARDS LATE AFTERNOON/EARLY EVENING AND VEER
WEST/NORTHWEST AT JBR.

CJC

&&

.PRELIMINARY POINT TEMPS/POPS...
MEM  69  88  72  90 /  20  20  10  10
MKL  65  84  68  88 /  50  30  20  10
JBR  66  87  69  88 /  20  20  10  10
TUP  67  85  69  88 /  50  30  20  10

&&

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

$$