182 
FXUS63 KLSX 090012
AFDLSX

AREA FORECAST DISCUSSION...UPDATED AVIATION
NATIONAL WEATHER SERVICE ST LOUIS MO
712 PM CDT FRI APR 8 2011

.DISCUSSION...
/305 PM CDT FRI APR 8 2011/

WELL-DEFINED WARM FRONT CURRENTLY SITS VERY CLOSE TO THE MISSOURI
RIVER...THOUGH TEMP GRADIENT HAS BEEN LESSENED DUE TO LOSS OF
DIFFERENTIAL HEATING WHERE SKIES CLEARED NORTH OF THE BOUNDARY.
AIRMASS SOUTH OF THE WARM FRONT HAS BECOME MODERATELY UNSTABLE
WITH MLCAPE VALUES APPROACHING 2500 J/KG ACROSS THE FAR SOUTHERN
CWA. HOWEVER...STOUT ELEVATED MIXING LAYER HAS OVERSPREAD THE WARM
SECTOR...AND SHOULD EFFECTIVELY CAP ANY SFC-BASED CONVECTION UNTIL
BOUNDARY LAYER HEATING IS LOST LATER THIS EVENING. 

WARM FRONT WILL SURGE NORTHWARD LATE TONIGHT AS SOUTHWESTERLY LOW
LEVEL WIND FIELD STRENGTHENS AHEAD OF A DEEPENING UPPER LOW OVER
THE SIERRA NEVADA. THIS WILL BRING A SURGE OF HIGH THETA-E AIR
AROUND THE 900-800 HPA LAYER WHICH SHOULD TRANSLATE INTO MUCAPES
IN EXCESS OF 2000 J/KG GIVEN STEEP MIDLEVEL LAPSE RATES. THIS WILL
BE COINCIDENT WITH MODERATE CONVERGENCE AT THIS LEVEL AT THE NOSE
OF AN INCREASING LLJ. AT THE SAME TIME...A WEAK MIDLEVEL
SHORTWAVE...CURRENTLY EVIDENT ON WV IMAGERY OVER THE OK/TX
PANHANDLES...WILL SWING THROUGH SOUTHERN MISSOURI AFTER DARK. THIS
FEATURE SHOULD PROVIDE ENOUGH DEEP ASCENT SO THAT ELEVATED
CONVECTION IS ABLE TO DEVELOP OVER SOUTHWEST MISSOURI LATER THIS
EVENING...AND INCREASE IN COVERAGE AS IT OVERSPREADS AREAS SOUTH
OF THE MISSOURI RIVER OVERNIGHT. LARGE HAIL WILL BE POSSIBLE WITH
THIS ACTIVITY...ESPECIALLY GIVEN CAPE IN EXCESS OF 1000 J/KG IN
THE MAX HAIL GROWTH REGION AND WBZ VALUES BELOW 10KFT. CANNOT RULE
OUT DAMAGING WIND POTENTIAL...ESPECIALLY ACROSS THE FAR SOUTHERN
CWA WHERE SFC-BASED CIN WILL BE LESS. MIDLEVEL WINDS WILL BE
WEAKENING IN THE PRESENCE OF MIDLEVEL RIDGING...BUT WILL STILL BE
SUPPORTIVE OF ROBUST UPDRAFTS AND A POTENTIALLY WELL-ORGANIZED
CONVECTIVE COMPLEX PUSHING INTO SOUTHERN ILLINOIS INTO THE EARLY
MORNING.

ATTENTION THEN TURNS TO THE DEEPENING SYSTEM OUT WEST AS THE
ENTIRE CWA BECOMES WARM-SECTORED ON SATURDAY...AND ANOMALOUSLY
WARM 850-HPA TEMPS SURGE INTO EASTERN MISSOURI AND WESTERN
ILLINOIS. MOST SHORT AND MED-RANGE MODELS INDICATE 850 TEMPS WILL
LIKELY RISE NEAR OR ABOVE 20C BY LATE SATURDAY AFTERNOON ACROSS
MUCH OF CENTRAL AND EASTERN MISSOURI...A DEPARTURE OF ABOUT 2.5
STANDARD DEVIATIONS FOR THIS TIME OF YEAR. MIXING TO THIS LEVEL
IS SUPPORTIVE OF AT LEAST UPPER-80S TEMPS...POTENTIALLY PUSHING 90
IF MIXING IS DEEP ENOUGH. THIS COULD PUSH TEMPS CLOSE TO RECORD
TERRITORY /SEE CLIMATE SECTION BELOW/. THIS HEAT WILL CAUSE THE
AIRMASS TO BECOME MODERATELY TO STRONGLY UNSTABLE ON
SATURDAY...THOUGH THIS INSTBY WILL HAVE A HARD TIME GETTING TAPPED
AS DEEP ASCENT WILL BE VERY WEAK IF NOT NON-EXISTENT. THE
PRESENCE OF ANY CAPPING VERSION AT ALL...AS MOST MODELS
INDICATE...SHOULD KEEP THINGS DRY THROUGH SATURDAY NIGHT.

ANOTHER UNSEASONABLY WARM DAY IS ON TAP FOR SUNDAY AS WAA
CONTINUES AHEAD OF A DEEPENING TROUGH. MODELS ARE COMING INTO
AGREEMENT THAT THIS SYSTEM WILL HAVE A SLIGHT POSITIVE TILT TO
IT...WHICH SPELLS A SLIGHTLY FASTER SOLUTION BRINGING COLD FRONTAL
PASSAGE INTO THE WESTERN LSX CWA BY 00Z. DEEP FORCING AND VERY
STRONG SHEAR PROFILES POINT TO THE POTENTIAL OF AN ORGANIZED
CONVECTIVE LINE WITH EMBEDDED SUPERCELLS...ESPECIALLY IF ENOUGH
INSTABILITY IS PRESENT.

STRONG COLD AIR ADVECTION BEHIND THE FRONT WILL BRING ABOUT A
20-DEGREE DROP IN TEMPS ON MONDAY. FLATTENING UPPER RIDGE BUILDS
INTO THE REGION FOR TUES AND WEDS WHICH WILL BRING DRY WEATHER AND
A SLOW WARMING TREND BEFORE THE NEXT SYSTEM ARRIVES MID TO LATE
WEEK. PREFERRED THE SLOWER ECMWF FOR THIS SYSTEM...BRINGING BEST
PRECIP CHANCES ON THURS.

HAWBLITZEL

&&

.AVIATION...
/700 PM CDT FRI APR 8 2011/
PRIMARY CONCERN TONIGHT WILL BE THUNDERSTORMS SPREADING EAST
ACROSS THE AREA AS THE LOW LEVEL JET INTERACTS WITH A STATIONARY
FRONT. STORMS HAVE ALREADY BLOWN UP OVER THE PLAINS...AND THIS
ACTIVITY IS EXPECTED TO CONTINUE MOVING EAST-NORTHEAST THROUGH THE
EVENING. SOME QUESTION YET HOW FAR NORTH THE STORMS WILL
REACH...BUT IT LOOKS LIKE SCATTERED STORMS WILL BE POSSIBLE ACROSS
MOST OF THE AREA...HOWEVER MAIN THREAT FOR STORMS WILL LIKELY STAY
ALONG AND SOUTH OF THE I-70 CORRIDOR. UNTIL THEN...SOME CIGS
AROUND 2000FT IN NORTHEAST MO/WEST CENTRAL IL SHOULD MOVE NORTH
AND AWAY FROM THE AREA THIS EVENING...ELSEWHERE AND
OTHERWISE...VFR CONDITIONS AND LIGHT EAST-NORTHEAST FLOW WILL
PREVAIL EXCEPT NEAR THUNDERSTORMS. WIND WILL TURN TO THE SOUTH ON
SATURDAY AS THE FRONT FINALLY LIFTS FURTHER NORTH.

SPECIFICS FOR KSTL...
PRIMARY CONCERN AT LAMBERT WILL BE THUNDERSTORMS LATE TONIGHT.
UNSURE YET HOW WIDESPREAD THE STORMS WILL BE...AND THE PRIMARY
THREAT FOR RAIN WILL LIKELY STAY SOUTH OF THE TERMINAL.
HOWEVER...THINK THERE'S AT LEAST A 50/50 CHANCE SOME STORMS WILL
GET AS FAR NORTH AS THE ST LOUIS METRO AREA. OTHERWISE...EXPECT
VFR CONDITIONS AND LIGHT NORTHEAST WIND TO PREVAIL THROUGH THE
EVENING. WIND WILL BECOME SOUTHERLY ON SATURDAY MORNING...AND THE
THUNDERSTORM THREAT SHOULD END AROUND 12Z AS THE WARM FRONT LIFTS
NORTHWARD AWAY FROM THE TERMINAL.


CARNEY

&&

.CLIMATE...
RECORD HIGH TEMPERATURES THIS WEEKEND

                         SATURDAY          SUNDAY
SAINT LOUIS (KSTL)       91/2001          93/1930
COLUMBIA    (KCOU)       90/1905          93/1930
QUINCY      (KUIN)       85/2001          92/1930


&&

.LSX WATCHES/WARNINGS/ADVISORIES...
MO...NONE.
IL...NONE.
&&

$$

WFO LSX