000 
FXUS63 KLSX 100858
AFDLSX

AREA FORECAST DISCUSSION
NATIONAL WEATHER SERVICE ST LOUIS MO
358 AM CDT SUN MAY 10 2009

.DISCUSSION...
/358 AM CDT SUN MAY 10 2009/

ZONAL FLOW AT THE MID LEVELS WILL CONTINUE THRU TONIGHT BEFORE A
WEAK H500 RIDGE THEN BUILDS IN FOR MONDAY AND TUESDAY. THE ZONAL
FLOW REGIME WILL USHER THRU A PAIR OF RELATIVELY WEAK AND QUICK
MOVING VORT CENTERS WITH A QUIET PERIOD TO THEN FOLLOW UNDER THE
RIDGE FOR EARLY IN THE WORK WEEK. ACTIVE WX WILL THEN RETURN WITH
A VENGEANCE ON LATE TUESDAY THRU WEDNESDAY NIGHT WHEN FIRST A
WRMFNT MOVES THRU LATE TUESDAY WITH ONE SHOT OF TSRA...AND THEN A
CDFNT THEN SLIDES SEWD THRU THE FA ON WEDNESDAY NIGHT WITH ANOTHER
ROUND OF TSRA. AT THE SFC...HI PRES WILL REMAIN OVER THE FA TO
SOME EXTENT THRU MONDAY NIGHT WHEN IT WILL THEN SLIDE OFF TO THE E
ALLOWING SLY FLOW TO BEGIN ON TUESDAY...AND STRENGTHEN ON TUESDAY
NIGHT AND INTO WEDNESDAY AS THE WRMFNT MOVES THRU. 

MAIN PCPN CHCS WILL BE CENTERED AROUND THE VORT CENTERS MOVING
THRU LATER TODAY AND TONIGHT...AND WITH THE FRONTAL SYSTEM MOVING
THRU LATE TUESDAY THRU WEDNESDAY NIGHT.

PCPN CHCS TODAY SHOULD HOLD OFF UNTIL AFTN WHEN THE BETTER
FORCING AT MID AND UPPER LEVELS WORKS ITS WAY IN...WITH EVEN
STRONGER FORCING MOVING IN AFTER SS TO MAINTAIN THE PCPN PROBS
THRU THE EVENING HOURS...AND PERHAPS ALL NIGHT. INSTABILITY WILL
BE DOWNRIGHT MEAGER...SO KEPT THUNDER OUT OF THE FORECAST...
ALTHOUGH WITH MINIMAL MUCAPE OF AROUND 50 J/KG...COULD NOT
ENTIRELY RULE OUT A BRIEF RUMBLE OF THUNDER. 

MOS BLEND USED FOR TODAY/S MAX TEMPS...AS THEY SHOULD BE CLOSE TO
PERSISTENCE MOST AREAS...BUT EARLY ARRIVAL OF CLOUDS IN THE NRN
AND WRN FA WILL RESULT IN COOLER THAN PERSISTENCE THERE. QUIET WX
ON MONDAY WITH AMPLE SUNSHINE SHOULD SEND TEMPS INTO THE LOWER 70S
WHICH FAVORS THE WARMER MAV NUMBERS. STRENGTHENING SELY FLOW ON
TUESDAY AS CLOUDS BEGIN TO INCREASE SHOULD STILL ALLOW TEMPS TO BE
A BIT WARMER THAN ON MONDAY...AND LIKE AT OR JUST ABOVE MOS VALUES
THIS DAY. 

FOCUS THEN SHIFTS TO PCPN CHCS AS WE HEAD INTO LATE TUESDAY WITH
APPROACHING WRMFNT. MOISTURE AND INSTABILITY RETURN IS IMPRESSIVE
BY LATE TUESDAY AFTN OVER CNTRL MO...BUT MUCH OF THE BETTER LIFT
IS STILL UPSTREAM AND SO LIMITED POPS TO 30PCT OR LESS UNTIL
TUESDAY NIGHT. LIFT DEEPENS THRU THE COLUMN AS PWATS TO NEAR
200PCT OF NORMAL AND INSTABILITY INCREASES SUBSTANTIALLY. BUMPED
POPS TO 50PCT...AND DEPENDING ON WHEN WE GET A BETTER HANDLE ON
WHERE CONVECTION WILL INITIATE AND TRACK THRU...THERE IS A VERY
GOOD CHC OF PCPN SOMEWHERE IN OUR FA AND HIGHER POPS WILL BE
REQUIRED EVENTUALLY. 

PCPN CHCS WILL REMAIN HI THRU WEDNESDAY NIGHT...WITH PERHAPS A
SMALL LULL DURING THE DAY ON WEDNESDAY FOLLOWING PASSAGE OF WRMFNT
BUT BEFORE THE CDFNT GETS TOO CLOSE. KEPT THE LIKELY POPS
SURROUNDING PASSAGE OF THE CDFNT ON WEDNESDAY NIGHT AS THAT STILL
LOOKS LIKE A GOOD BET. MODELS THEN DIVERGE ON HOW DRY TO MAKE IT
FOR THE END OF THE WORK WEEK...BUT NO CHANGES MADE TO THAT PERIOD
FOR NOW. 

TES

&&

.AVIATION...
/958 PM CDT SAT MAY 9 2009/

FOR THE 06Z TAFS...HIGH PRESSURE OVER THE AREA WITH LIGHT WINDS
AND MOSTLY CLEAR SKY. SOME CI LIKELY FROM STORM TO THE SOUTH AND
ADVANCING SHORT WAVE. MDLS CONSISTENT IN TRYING TO PRODUCE LOW
CHANCES OF PRECIP SUN AFTERNOON. SOME SHRA POSSIBLE BUT WILL GO
WITH AC DECK WHICH MAY PRODUCE SOME SPRINKLES. SOME FOG GROUND FOG
POSSIBLE AT SUS BUT NOT CONVINCED GIVEN DRYING THAT TOOK PLACE
TODAY.

JPK

&&

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

$$

WFO LSX