Severe Thunderstorm Warning 146, NWS St. Louis, MO

AREA FORECAST DISCUSSION...UPDATED AVIATION
NATIONAL WEATHER SERVICE ST LOUIS MO
1100 PM CDT FRI JUN 18 2010

.DISCUSSION...
/318 PM CDT FRI JUN 18 2010/

A LOT GOING ON IN THE SHORT TERM WITH SCATTERED STORMS POPPING UP
THIS AFTERNOON DUE TO OLD OUTFLOWS...INSTABILITY AND TONS OF
MOISTURE. ALSO...DEALING WITH HIGH HEAT INDICES WHICH WILL PERSIST
DURING THE AFTERNOON HOURS THROUGH AT LEAST MONDAY.

FOR TONIGHT...WILL HAVE TO DEAL WITH POSSIBLE RWS/TRWS OVER AT LEAST
THE NORTHERN PORTIONS OF THE FORECST AREA. NO ACTIVITY CURRENTLY
FIRING UP OVER NORTHWESTERN MO...AND THE MCS NOW OVER NORTHWESTERN
IL...DOES NOT SHOW ANY SIGNS OF BACK BUILDING TO THE SOUTH AND WEST
TOWARDS OUR AREA. FOR NOW WILL KEEP LIKELY/HIGH CHANCE POPS IN THE
FAR NORTH THROUGH 06Z...BUT MAY NEED TO BACK OFF LATER THIS EVENING
IF STUFF DOES NOT FIRE. IN THE MEANTIME...DO HAVE SCATTERED
ACTIVITY MAINLY ALONG AND SOUTH OF I-70 DUE TO RESIDUAL OUTFLOWS
FROM THE COMPLEX THAT SKIRTED THE NORTHERN PORTIONS OF OUR FORECAST
AREA EARLY THIS MORNING...SO KEEPING SLIGHT/LOW CHANCE POPS GOING.
SPC HAS BACKED OFF ON THEIR MODERATE RISK AREA...WITH IT BARELY
TOUCHING OUR FAR NORTHERN COUNTIES...BUT ENTIRE AREA IS IN A SLIGHT
RISK NOW...MAINLY FOR ISOLATED LARGE HAIL AND DAMAGING WINDS.

OTHER ISSUE FOR THIS EVENING...IS THE HEAT AND HUMIDITY. TEMPS HAVE
CLIMBED IN TO THE LOW TO MID 90S MOST LOCATIONS AND DEWPTS ARE
HOLDING IN THE 70S...SO HAVE HEAT INDEX VALUES TOPPING 100 IN A LOT
OF LOCATIONS. WILL SEE TEMPS COOL OFF OVERNIGHT...BUT REMAIN RATHER
MILD IN THE LOW TO MID 70S.

ON SATURDAY AND SATURDAY NIGHT...ANOTHER TRICKY FORECAST AS MODELS
ARE STILL TRYING TO MOVE WEAK COLD FRONT SOUTH INTO THE FORECAST
AREA. FOR NOW WILL BE A BIT PESSIMISTIC AND KEEP MOST OF ACTIVITY
ALONG AND NORTH OF I-70. ALSO...KEPT HIGH TEMPS IN THE UPPER 80S FAR
NORTH TO THE LOW TO MID 90S FOR THE REST OF THE FORECAST AREA...EVEN
UPPER 90S OVER ST. LOUIS METRO AREA. WITH SUCH HIGH TEMPS AND DEWPTS
IN THE UPPER 60S TO LOW 70S...WILL SEE HEAT INDICIES BETWEEN 100 AND
105 ONCE AGAIN. BUT IF ANY LARGE AREA OF STORMS DEVELOPS...THIS
COULD AFFECT HIGH TEMPS TOMORROW.

BY SUNDAY...FRONTAL BOUNDARY WEAKENS AND RETREATS BACK NORTH OF
FORECAST AREA. SO WE WILL STAY IN THE HOT AND HUMID AIR...WITH BEST
CHANCES OF ANY ACTIVITY OVER OUR NORTHERN SECTIONS FOR THE REMAINDER
OF THE FORECAST PERIOD. AS FOR TEMPS...90S ARE HERE TO STAY WITH
PLENTY OF HEAT AND HUMIDITY. FOR NOW HAVE HEAT ADVISORY GOING FOR
SOUTHEAST HALF OF CWA THROUGH 00Z TUESDAY...BUT IF CONDITIONS
PERSIST...WILL NEED TO EXTEND THE ADVISORY WELL BEYOND 00Z TUESDAY.

BYRD

&&

.AVIATION...
/1026 PM CDT FRI JUN 18 2010/

LINE OF TSRA ACROSS NRN MO ALONG AN OLD OUTFLOW BOUNDARY AND
AHEAD OF A CDFNT EXTENDING FROM NWRN WI SW THROUGH SERN NEBRASKA.
THESE STORMS WILL DROP SEWD THRU UIN BETWEEN 06Z-10Z SAT WITH
POSSIBLE THUNDERSTORM WIND GUSTS TO AROUND 30 KTS. A LOT OF
UNCERTAINTY WITH THE SWD PROGRESS OF THESE STORMS LATE TGT. THESE
STORMS WILL LIKELY WEAKEN AS THEY APPROACH COU...STL AND SUS. MAY
JUST HAVE VCTS AND A CB CLOUD GROUP IN THE COU...STL AND SUS TAFS
FROM ABOUT 08Z TO 12Z SAT DEPENDING ON THE LATEST RADAR TRENDS
JUST BEFORE TAF ISSUANCE TIME. OUTSIDE OF THE TSRA JUST VFR
CONDITIONS WITH HIGH LEVEL CONVECTIVE CLOUD DEBRIS LATE TGT AND
EARLY SAT MRNG. SCATTERED DIURNAL CUMULUS CLOUDS SHOULD DEVELOP
LATE SAT MRNG AND AFTN. S-SWLY SFC WINDS WILL VEER AROUND TO A
NWLY DIRECTION IN UIN SAT MRNG AND A W-NWLY DIRECTON IN COU...STL
AND SUS AS THE WEAKENING CDFNT...PREFRONTAL TROF/OUTFLOW BOUNDARY
DROPS SWD THROUGH THE AREA.

SPECIFICS FOR KSTL...HI LEVEL CONVECTIVE CLOUD DEBRIS WILL ADVECT
SEWD INTO STL LATE TGT FROM MCS ACTIVITY ACROSS NRN MO. MAY JUST
KEEP VCTS AND CB CLOUD GROUP IN TAF FROM 08Z-12Z SAT AS STORMS
DROP SEWD TOWARDS STL LATE TGT. SCATTERED DIURNAL CUMULUS CLOUDS
WILL DEVELOP AGAIN DURING LATE SAT MRNG AND AFTN AROUND 4000 FT.
S-SWLY SFC WINDS WILL BECOME W-NWLY BY LATE SAT MRNG AS WEAKENING
CDFNT ALONG WITH OUTFLOW BOUNDARIES AHEAD OF IT DROP SWD INTO THE
AREA.

GKS

&&

.LSX WATCHES/WARNINGS/ADVISORIES...
MO...HEAT ADVISORY UNTIL 7 PM CDT MONDAY FOR CRAWFORD MO-FRANKLIN MO-
     IRON MO-JEFFERSON MO-LINCOLN MO-MADISON MO-REYNOLDS MO-ST.
     CHARLES MO-ST. FRANCOIS MO-ST. LOUIS CITY MO-ST. LOUIS MO-
     STE. GENEVIEVE MO-WARREN MO-WASHINGTON MO.

IL...HEAT ADVISORY UNTIL 7 PM CDT MONDAY FOR BOND IL-CALHOUN IL-
     CLINTON IL-FAYETTE IL-JERSEY IL-MADISON IL-MARION IL-MONROE
     IL-RANDOLPH IL-ST. CLAIR IL-WASHINGTON IL.

&&

WFO LSX

HAZARDOUS WEATHER OUTLOOK
NATIONAL WEATHER SERVICE ST LOUIS MO
831 PM CDT FRI JUN 18 2010

ILZ058>060-064-065-069-070-074-079-095>102-MOZ018-019-026-027-
034>036-041-042-047>052-059>065-072>075-084-085-099-191200-
GREENE IL-MACOUPIN IL-MONTGOMERY IL-BOND IL-FAYETTE IL-CLINTON IL-
MARION IL-WASHINGTON IL-RANDOLPH IL-ADAMS IL-BROWN IL-PIKE IL-
CALHOUN IL-JERSEY IL-MADISON IL-ST. CLAIR IL-MONROE IL-KNOX MO-
LEWIS MO-SHELBY MO-MARION MO-MONROE MO-RALLS MO-PIKE MO-BOONE MO-
AUDRAIN MO-MONITEAU MO-COLE MO-OSAGE MO-CALLAWAY MO-MONTGOMERY MO-
LINCOLN MO-GASCONADE MO-WARREN MO-ST. CHARLES MO-FRANKLIN MO-
ST. LOUIS MO-ST. LOUIS CITY MO-JEFFERSON MO-CRAWFORD MO-
WASHINGTON MO-ST. FRANCOIS MO-STE. GENEVIEVE MO-IRON MO-
MADISON MO-REYNOLDS MO-
831 PM CDT FRI JUN 18 2010

THIS HAZARDOUS WEATHER OUTLOOK IS FOR PORTIONS OF EASTERN AND
CENTRAL MISSOURI AS WELL AS WEST CENTRAL AND SOUTHWEST ILLINOIS.

.DAY ONE...TONIGHT

THUNDERSTORMS WILL BE LIKELY...MAINLY FOR PARTS OF NORTHEAST
MISSOURI AND WEST CENTRAL ILLINOIS. SOME STORMS MAY BE
SEVERE...CONTAINING DAMAGING WINDS AND LARGE HAIL...FOR AREAS
NORTH OF INTERSTATE 70 WHERE THERE IS A SLIGHT RISK. FOR FURTHER
INFORMATION ON CONVECTIVE WATCHES...PLEASE REFER TO THE LATEST
STORM PREDICTION CENTER WATCH PRODUCTS.

A WARM AND MUGGY NIGHT IS EXPECTED THAT WILL OFFER LITTLE RELIEF
FROM THE HOT DAY ON FRIDAY. LOW TEMPERATURES WILL ONLY DROP INTO
THE MID TO UPPER 70S. A HEAT ADVISORY CONTINUES FOR MOST OF EAST
CENTRAL AND SOUTHEAST MISSOURI AND SOUTHWEST ILLINOIS...INCLUDING
THE SAINT LOUIS METRO AREA. FOR FURTHER INFORMATION...PLEASE REFER
TO THE ADVISORY PRODUCT.

MODERATE RIVER FLOODING IS OCCURRING ALONG PORTIONS OF THE LA
MOINE RIVER AT RIPLEY...THE MISSISSIPPI RIVER AT CHESTER...AND
PARTS OF THE MISSOURI RIVER. PLEASE SEE THE APPROPRIATE FLOOD
STATEMENTS FOR SPECIFIC DETAILS.

.DAYS TWO THROUGH SEVEN...SATURDAY THROUGH THURSDAY

THERE IS A CHANCE FOR THUNDERSTORMS ACROSS MUCH OF THE AREA
THROUGH SUNDAY NIGHT...ESPECIALLY FOR PARTS OF NORTHEAST MISSOURI
AND WEST CENTRAL ILLINOIS. SOME STORMS MAY BE SEVERE ON SUNDAY AND
SUNDAY NIGHT.

DANGEROUS LEVELS OF HEAT AND HUMIDITY WILL PERSIST INTO NEXT
WEEK...WITH HEAT INDEX VALUES EXPECTED TO TOP 100 DEGREES EACH DAY
THROUGH AT LEAST MONDAY...WITH THE POTENTIAL OF CONTINUING INTO
LATE NEXT WEEK. THIS WILL ESPECIALLY BE THE CASE FOR MOST OF EAST
CENTRAL AND SOUTHEAST MISSOURI AND SOUTHWEST ILLINOIS...INCLUDING
THE SAINT LOUIS METRO AREA...WHERE A HEAT ADVISORY REMAINS IN
EFFECT THROUGH LATE MONDAY AFTERNOON. FOR FURTHER INFORMATION...
PLEASE REFER TO THE ADVISORY PRODUCT.LITTLE RELIEF WILL OCCUR AT
NIGHT WITH WARM AND MUGGY CONDITIONS.

MODERATE RIVER FLOODING IS OCCURRING ALONG PORTIONS OF THE LA
MOINE RIVER AT RIPLEY...THE MISSISSIPPI RIVER AT CHESTER...AND
PARTS OF THE MISSOURI RIVER. PLEASE SEE THE APPROPRIATE FLOOD
STATEMENTS FOR SPECIFIC DETAILS.

.SPOTTER INFORMATION STATEMENT...

SPOTTER ACTIVATION IS LIKELY FOR PARTS OF NORTHEAST MISSOURI AND
WEST CENTRAL ILLINOIS THIS EVENING...AND MAY OCCUR AS FAR SOUTH AS
INTERSTATE 70 LATER TONIGHT.

&&

FOR A GRAPHICAL VERSION OF THIS INFORMATION SEE OUR
WEBPAGE AT (LOWERCASE)... HTTP://WWW.WEATHER.GOV/LSX/?N=HWO1

TES

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