Areal Flood Warning 4, NWS St. Louis, MO

AREA FORECAST DISCUSSION...UPDATED AVIATION
NATIONAL WEATHER SERVICE ST LOUIS MO
626 AM CDT THU APR 28 2011

.DISCUSSION...
/514 AM CDT THU APR 28 2011/

MOSTLY CLEAR SKIES WILL PROMOTE GOOD MIXING TODAY...TAPPING INTO
STRONG WINDS AT THE TOP OF THE MIXED LAYER. SOME OF THIS WIND WILL
MIX DOWN TO THE SFC PRODUCING GUSTS OF 30 TO 40 MPH WHICH IS
SLIGHTLY BELOW ADVISORY CRITERIA. COLD CORE UPPER LOW DROPPING SEWD
OUT OF MN/IA WILL SUPPORT SCATTERED SHOWERS AND ISOLATED
THUNDERSTORMS TODAY ACROSS ERN MO INTO WRN/SWRN IL DUE TO STRONGER
LAPSE RATES FROM THE COMBINATION OF COOLING TEMPERATURES ALOFT AND
DIURNAL HEATING AT THE SFC. THIS SCENARIO IS SUPPORTED BY SEVERAL
MODELS WHICH CONTINUE TO SHOW 200-600 J/KG OF MUCAPE DURING THE
AFTERNOON HOURS. ANY THUNDERSTORMS THAT DEVELOP COULD PRODUCE SMALL
HAIL OR GRAUPEL SINCE BUFKIT SOUNDINGS SHOW RELATIVELY LOW FREEZING
LEVELS FOR THE AFTERNOON. IN ADDITION...THERE IS A CONCERN THAT EVEN
WEAK SHOWERS MIGHT PRODUCE STRONG GUSTY WINDS SINCE PRECIPITATION
LOADING WILL LOCALLY ENHANCE DOWNDRAFTS THAT WILL ALREADY BE MIXING
DOWN WINDS OF 30 TO 40 KTS. COVERAGE SHOULD DIMINISH WITHIN A FEW
HOURS AFTER SUNSET WITH THE LOSS OF DIURNAL HEATING.

SECONDARY COLD FRONT BRIEFLY MOVES INTO THE NERN AND ERN CWA
OVERNIGHT BEFORE LIFTING NEWD TOMORROW AS WAA SPREADS ACROSS THE
REGION. MUCH WARMER TEMPERATURES ARE EXPECTED FOR TOMORROW AS WINDS
TURN SLY TO SWLY ACROSS MO/IL. WINDS SHOULD START TO PICK UP BY MID
TO LATE AFTERNOON AS A LOW PRESSURE SYSTEM DEVELOPS OVER THE PLAINS
AND STARTS TO APPROACH THE AREA. WIDESPREAD PRECIPITATION IS THEN
EXPECTED FROM SATURDAY THROUGH SUNDAY NIGHT AS A COLD FRONT
APPROACHES THE AREA AND WAVES OF LOW PRESSURE MOVE ALONG THE FRONT.
FEW CHANGES MADE PAST 12Z SUN.

KANOFSKY

&&

.AVIATION...
/619 AM CDT THU APR 28 2011/

LARGE UPPER LEVEL VORTEX SPINNING SOUTHEAST FROM THE UPPER MIDWEST
TO THE OHIO RIVER VALLEY TODAY WILL BRING AN INCREASED THREAT OF
SHOWERS AND PERHAPS SOME THUNDERSTORMS THIS AFTERNOON. WINDS WILL
INCREASE WITH DIURNAL MIXING...AND COULD SEE GUSTS TO 35KTS.

SPECIFICS FOR KSTL...
LOOK FOR LINE OF SHOWERS AND THUNDERSTORMS TO DEVELOP AHEAD OF
UPPER LEVEL DISTURBANCE THIS AFTERNOON. APPEARS MAIN TIME FOR
CONVECTION TO AFFECT TERMINAL IS BETWEEN 20 AND 23Z. THESE STORMS
COULD PRODUCE LOCALLY STRONG WIND GUSTS TO 45KTS.

OTHERWISE...STRONG AND GUSTY WEST WIND IS EXPECTED TODAY. EXPECT GUSTS
OF 30 TO 35 KTS.

CVKING

&&

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

WFO LSX

HAZARDOUS WEATHER OUTLOOK
NATIONAL WEATHER SERVICE ST LOUIS MO
444 AM CDT THU APR 28 2011

ILZ058>060-064-065-069-070-074-079-095>102-MOZ018-019-026-027-
034>036-041-042-047>052-059>065-072>075-084-085-099-290945-
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-
444 AM CDT THU APR 28 2011

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

.DAY ONE...TODAY AND TONIGHT

SCATTERED THUNDERSTORMS ARE POSSIBLE THIS AFTERNOON ACROSS EASTERN
MISSOURI INTO WESTERN AND SOUTHWESTERN ILLINOIS. SOME OF THE
THUNDERSTORMS COULD PRODUCE GUSTY WINDS AND SMALL HAIL.

RIVERS...CREEKS...AND STREAMS WILL CONTINUE TO RISE IN SOUTHEAST
MISSOURI AND SOUTHWEST ILLINOIS DUE TO RUNOFF FROM HEAVY
RAINFALL.

.DAYS TWO THROUGH SEVEN...FRIDAY THROUGH WEDNESDAY

THERE IS A CHANCE OF THUNDERSTORMS ON SATURDAY AND SUNDAY.

.SPOTTER INFORMATION STATEMENT...

SPOTTER ACTIVATION IS NOT ANTICIPATED TONIGHT.

KANOFSKY