Special Weather Statement, NWS Indianapolis, IN

AREA FORECAST DISCUSSION
NATIONAL WEATHER SERVICE INDIANAPOLIS IN
626 AM EDT SUN JUN 19 2011

.UPDATE...
THE AVIATION SECTION HAS BEEN UPDATED BELOW.

&&

.SYNOPSIS...
AN ACTIVE...CHANGEABLE WEATHER PATTERN IS EXPECTED OVER
THE NEXT WORK WEEK. A LINGERING FRONTAL BOUNDARY OVER ILLINOIS AND
INDIANA WILL CONTINUE TO PROVIDE A FOCUS FOR SHOWERS AND STORMS
THROUGH EARLY THIS WEEK. ON MONDAY...THE FRONT IS EXPECTED TO PUSH
NORTH AS LOW PRESSURE DEEPENS IN THE NORTHERN PLAINS. THIS WILL
ALLOW MUCH WARMER AND VERY HUMID AIR TO SURGE INTO CENTRAL INDIANA
FROM THE SOUTHWEST. HIGH TEMPERATURES ON MONDAY AND TUESDAY WILL
REACH AROUND 90 AT MANY SPOTS...WITH HIGH HUMIDITY.

A COLD FRONT IS THEN EXPECTED TO PUSH ACROSS THE REGION ON
WEDNESDAY AND THURSDAY...BRINGING CHANCES FOR MORE SHOWERS AND
STORMS. AS HIGH PRESSURE BUILDS IN ACROSS INDIANA ON FRIDAY AND
SATURDAY...DRY WEATHER APPEARS MOST LIKELY THEN.

&&

.NEAR TERM /TODAY/...
BASED ON LATEST RADAR TRENDS...STORMS SEEM TO BE VERY SLOWLY
PROPAGATING EASTWARD INTO EASTERN ILLINOIS...CAUSING FLASH FLOODING
CONCERNS. PLAN ON ADDING HEAVY RAINFALL WORDING (MAINLY TO
SOUTHERN COUNTIES) TO GRIDS ALONG WITH HITTING THE FLOOD THREAT A
LITTLE HARDER IN OTHER PRODUCTS.

RADAR IS QUIET ACROSS INDIANA ATTM...BUT MORE CONVECTION BECKONS
TO OUR SW ACROSS MO AND WESTERN IL. A FEW ISOLATED SHOWERS MAY POP
UP AHEAD OF THIS COMPLEX OVER THE NEXT FEW HOURS BUT THE BULK OF
ACTIVITY WILL NOT ARRIVE UNTIL CLOSER TO 12Z THIS MORNING. AND
ACCORDINGLY SPC CONTINUES TO PLACE US UNDER A SLIGHT RISK WITH
DAMAGING WINDS/LARGE HAIL AND HEAVY RAINFALL THE MAIN THREATS.
BULK OF THE SHORT TERM MODEL GUIDANCE MOVES THIS CLUSTER OF
SHOWERS AND STORMS ACROSS SOUTHERN INDIANA THROUGH TODAY..SO
PAINTED IN HIGHER (LIKELY POPS) ACROSS THE SOUTHERN COUNTIES TO
30-40% FARTHER NORTH. SOUNDINGS SHOW A WEAK CAP BUT BELIEVE
FORCING WILL BE GREAT ENOUGH TO BREAK THIS. BACKED OFF SLIGHTLY
ON HIGH TEMPS CONSIDERING THE ADDITIONAL CLOUDS AND PRECIP. HIGHS
82-88.

&&

.SHORT TERM /TONIGHT THROUGH MONDAY NIGHT/...
TONIGHT LOOKS DRIER WITH ONLY SOME LINGERING CHANCES ACROSS THE
FAR SE COUNTIES. STRONGER WARM AIR ADVECTION BEGINS AS RIDGING
ALOFT CONTINUES TO BUILD ACROSS CENTRAL INDIANA. FORECAST
SOUNDINGS CONTINUE TO SHOW HIGH CAPE IN EXCESS OF 2000 J/KG AND
LI/S NEAR -6/-7...HOWEVER CONVECTIVE TEMPERATURES ARE TOO WARM
(MID 90S) AND 700MB TEMPERATURES ARE CLOSE TO 10C...PROVIDING A
CAPPING EFFECT. THIS MAY BE THE SET UP FOR MONDAY AS WELL...A
VERY WARM BUT CAPPED COLUMN...EXCEPT FOR NORTH OF I-70 WHERE CAP
APPEARS WEAKER. ADDED CHANCE POPS HERE...AND SPC SHOWS MUCH OF
CENTRAL INDIANA UNDER A SLIGHT RISK. THE ENTIRE AREA SHOULD BE
SUFFICIENTLY CAPPED BY MON NIGHT SO KEPT FORECAST DRY DURING THIS
TIME.

&&

.LONG TERM /TUESDAY THROUGH SATURDAY/...
ECMWF AND GFS AGREE IN ON MONDAY THROUGH WEDNESDAY AS AN UPPER
LOW REMAINS OVER THE WESTERN GREAT LAKES AND WARM SOUTHERLY FLOW
AND RIDGING WILL REMAIN IN PLACE ACROSS THE OHIO VALLEY AND
CENTRAL INDIANA. GIVEN THE VERY WARM AND MOIST FLOW..AFTERNOON
SHOWERS AND THUNDERSTORMS APPEAR POSSIBLE ON TUESDAY...BUT VERY
WARM 700MB TEMPERATURE NEAR 10C MAY PROVIDE A SUFFICIENT CAP TO
PREVENT PRECIPITATION. AS THE LOW EDGES AND COLD FRONT TOWARD
INDIANA ON TUESDAY AND WEDNESDAY...HAVE INCLUDED PRECIPITATION
CHANCES THEN AS THE CAP SHOULD BE WEAKENED BY THE APPROACHING
DYNAMICS. GIVE THE WARM AND HUMID FLOW HAVE TRENDED TEMPERATURES
TO THE WARMER SIDE OF MEXMOS.

DURING THE WEDNESDAY AND THURSDAY TIME FRAME...THE GFS AND ECMWF
PUSH THE COLD FRONT ACROSS INDIANA AS THE LOW PULLS NORTHEAST
ACROSS THE GREAT LAKES. THIS WILL CERTAINLY BE THE BEST WINDOW FOR
PRECIPITATION AS EARLIER RAIN APPEAR MORE DAYTIME HEATING DRIVEN
AND THIS EVENT WILL HAVE PLENTY OF DYNAMICS...NOT TO MENTION THE
VERY MOIST AIR MASS IN PLACE AHEAD OF THE FRONT.

HIGH PRESSURE IS EXPECTED TO BUILD IN THE WAKE OF THE FRONT ON
FRIDAY INTO SATURDAY AND WILL USE A DRY FORECAST FOR NOW. HOWEVER
ECMWF AND GFS DISAGREE ON LINGERING MOISTURE IN THE WAKE OF THE
COLD FRONT AND THE STRENGTH OF THE SUBSIDENCE AS THE HIGH BUILDS
IN THE REGION. GIVEN THE COOLER AND DRIER NORTHWEST FLOW EXPECTED
HAVE DECIDED TO KEEP PRECIPITATION OUT FOR NOW.

&&

.AVIATION /DISCUSSION FOR THE 191200Z TAFS/...

AREAS OF THUNDERSTORMS LOOK TO IMPACT MOST SITES EARLY IN THE
PERIOD. STILL PLENTY OF UNCERTAINTY ON HOW THE STORMS NORTH OF THE
BOW ECHO WILL BEHAVE...BUT FOR NOW WILL GO WITH A TEMPO AT ALL BUT
KLAF FOR THE FIRST COUPLE OF HOURS OF THE PERIOD.

DEPENDING ON HOW STORMS ACROSS WESTERN ILLINOIS DEVELOP...STORMS MAY
LAST LONGER THAN 14/15Z...SO WILL KEEP VCTS MENTION UNTIL 18Z OR SO.
ATMOSPHERE SHOULD THEN NEED TIME TO RECOVER...THEN ADDITIONAL STORMS
MAY DEVELOP IN THE WARM AFTERNOON. THUS WILL CONTINUE CB MENTION.

MORE STORMS MAY DEVELOP OVERNIGHT AGAIN...SO WILL KEEP CB MENTION
THROUGH THE OVERNIGHT.

MVFR FOG WILL DEVELOP AGAIN TONIGHT DUE TO RECENT RAINS.

&&

.IND WATCHES/WARNINGS/ADVISORIES...NONE.

&&

SYNOPSIS...PUMA/SMF
NEAR TERM...SMF
SHORT TERM...SMF
LONG TERM....PUMA
AVIATION...50

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