249
FXUS63 KLSX 041149
AFDLSX
AREA FORECAST DISCUSSION...UPDATED AVIATION
NATIONAL WEATHER SERVICE ST LOUIS MO
649 AM CDT SAT JUL 4 2009
DISCUSSION
/415 AM CDT SAT JUL 4 2009/
MODELS HAVING A VERY DIFFICULT TIME PINNING DOWN CONVECTION TRENDS
OVER REGION THIS MORNING...SO MUCH OF THE FORECAST FOR TODAY IS
IS BASED ON EXTRAPOLATION OF CURRENT TRENDS. PRIMARY AREA OF MOST
ACTIVE CONVECTION...AND HEAVY RAIN...HAS BECOME FOCUSED ON THE
INTERSTATE 70 CORRIDOR OVER THE LAST FEW HOURS. EXPECT THIS TREND
TO CONTINUE DURING THE MORNING...WITH PERHAPS A BIT OF A SWD SHIFT
AS ACTIVITY BECOMES A BIT MORE OUTFLOW DOMINATED. CONTEMPLATED
ISSUING A FLASH FLOOD WATCH FOR THE I-70 CORRIDOR BUT GROUND
CONDITIONS ARE FAIRLY DRY WITH 3 HOUR FFG RUNNING IN THE 2.5-3
INCH RANGE...HOWEVER LOCALLIZED WATER PROBLEMS ARE CERTAINLY NOT
OUT OF THE QUESTION AND WILL CONTINUE TO MONITOR THIS DURING THE
MORNING. WITH THIS SWD SHIFT OF THE RAIN AXIS IT APPEARS THAT THE
FLASH FLOOD THREAT HAS DIMINISHED FOR OUR N AREAS...WILL CANCEL
THE FFA FOR THIS AREA BUT WILL CONTINUE MENTION OF HEAVY RAIN FOR
A WHILE THIS MORNING.
THIS AFTERNOON AND EVENINGS CONVECTIVE TRENDS WILL BE HEAVILY
INFLUENCED BY THE REMNANTS OF THIS MORNINGS ACTIVITY. ITS
CERTAINLY POSSIBLE THAT THE OUTFLOW BOUNDARY COULD BECOME THE
PRIMARY FOCUS FOR THIS AFTERNOONS ACTIVITY...AND IF THAT OCCURS
THE REDEVELOPMENT COULD OCCUR WELL SOUTH OF THE SYNOPTIC BOUNDARY
AS INDICATED BY THE MODELS...WHICH MAY ALSO MEAN THAT THE PRECIP
WILL EXIT OUR AREA THSI EVENING SOONER THAN SUGGESTED BY FROPA.
BECAUSE OF THIS I STAYED A LITTLE BIT CONSERVATIVE WITH POPS IN
OUR S AREAS FOR THIS AFTERNOON AND EVENING. ALSO DON'T KNOW HOW
MUCH AMS WILL BE ABLE TO DESTABLIZE DUE TO ALL OF THE RAIN AND
CONVECTIVE CLOUD DEBRIS AND OF COURSE THIS WILL HAVE A HUGE IMPACT
ON SVR TSRA THREAT THIS AFTERNOON AND EVENING...BUT CERTAINLY FAR
S AREAS SHOULD HAVE THE BEST CHANCE OF MAXIMIZING AFTERNOON HEATING.
ALONG THIS LINE...ITS INTERESTING TO NOTE THAT BOTH MET AND MOS
GUID ARE FORECASTING A RECORD LOW MAX FOR TODAY IN STL.
NO MAJOR CHANGES IN THE FORECAST AFTER TONIGHT. HOWEVER...DID ADD
SOME SLIGHT CHC POPS IN N AREAS FOR MON AS MODELS ARE HINTING THAT
RESIDUAL LO LVL INSTABILITY AND A BIT OF SHORTWV ENERGY MAY KICK
OFF A FEW AFTERNOON TSRA IN THE DEVELOPING NW FLOW PATTERN.
TRUETT
AVIATION
/641 AM CDT SAT JUL 4 2009/
FOR THE 12Z TAFS...
PRIMARY CONCERN FOR THIS MORNING IS THE AREA OF HEAVY RAIN AND
THUNDERSTORMS MOVING FROM CENTRAL INTO EAST CENTRAL AND SOUTHEAST
MISSOURI...AND SOUTHWEST ILLINOIS. IFR/LIFR CONDITIONS CAN BE
EXPECTED AT LEAST 50NM NORTH AND SOUTH OF I-70 THIS MORNING
BOUNDED BY MARGINAL CONDITIONS. LOW CONDITIONS WILL BE LIFTING
FROM WEST TO EAST THROUGH LATE MORNING...BUT THE LOW PRESSURE SYSTEM
CAUSING THIS RAIN AND ITS TRAILING COLD FRONT WILL PASS THROUGH
THE REGION THIS AFTERNOON POSSIBLY BRINGING MORE SHOWERS AND
STORMS THIS AFTERNOON. ADDITIONALLY IT WILL BRING DOWN A LARGE
AREA OF IFR CONDITIONS OVER EASTERN NEBRASKA AND WESTERN IOWA
WHICH WILL SETTLE OVER THE REGION THIS EVENING.
CARNEY
CLIMATE
RECORD LOW MAXIMUM TEMPERATURES FOR JULY 4
STL 82 IN 1990
COU 76 IN 1980
LSX WATCHES/WARNINGS/ADVISORIES
MO...NONE.
IL...NONE.
WFO LSX
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