Area Forecast Discussion
Issued by NWS Indianapolis, IN

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000
FXUS63 KIND 191814
AFDIND

AREA FORECAST DISCUSSION
NATIONAL WEATHER SERVICE INDIANAPOLIS IN
214 PM EDT TUE AUG 19 2014

.UPDATE...
THE LONG TERM SECTION HAS BEEN UPDATED BELOW.

&&

.SYNOPSIS...
ISSUED AT 259 AM EDT TUE AUG 19 2014

A FRONTAL SYSTEM WILL MOVE INTO THE AREA TONIGHT AND EVENTUALLY
STALL OUT. THIS WILL SERVE TO KEEP THE WEATHER UNSETTLED OVERALL
THROUGH MOST OF THE UPCOMING WEEK. A RIDGE OF HIGH PRESSURE WILL
BUILD BACK OVER THE REGION FOR THE LATTER HALF OF THE WEEKEND AND
INTO EARLY NEXT WEEK.

&&

.NEAR TERM /REST OF TODAY AND TONIGHT/...
ISSUED AT 1007 AM EDT TUE AUG 19 2014

FOG HAS BURNED OFF FOR THE MOST PART...SO HAVE LET THE DENSE FOG
ADVISORY EXPIRE ON SCHEDULE.

STILL UNCLEAR HOW CONVECTIVE POTENTIAL WILL EVOLVE LATER
TODAY...EITHER FROM THE CONVECTIVE CLUSTER CURRENTLY MOVING THROUGH
WESTERN ILLINOIS...OR FROM THE APPROACHING COLD FRONT. IF THE
CLUSTER OVER ILLINOIS HOLDS TOGETHER...IT COULD REACH THE LOCAL AREA
BY 191800Z-191900Z. HOWEVER...IF THE MAIN THREAT COMES FROM THE COLD
FRONT...IT COULD BE MORE TOWARDS EVENING BEFORE ANYTHING GETS INTO
THE AREA. MOST THE MODEL DATA SUGGEST THE CLUSTER OVER ILLINOIS WILL
WEAKEN...HOWEVER THERE IS A DECENT INSTABILITY AXIS AHEAD OF THIS
FEATURE...SO NOT TOTALLY SOLD ON THE WEAKENING TREND YET.

ALL IN ALL...WILL LEAVE THE FORECAST GENERALLY AS IS FOR
NOW...ALTHOUGH THE LIKELY POPS LATE THIS AFTERNOON MAY BE TOO FAR
SOUTHEAST. THIS MORNING/S UPPER AIR INDICATES FAIRLY GOOD LAPSE
RATES OVER THE AREA...ALTHOUGH DEEP SHEAR IS A LITTLE WEAK. SHEAR
SHOULD INCREASE LATER THIS AFTERNOON/EVENING WITH THE APPROACH OF
THE UPPER SYSTEM.

PREVIOUS DISCUSSION FOLLOWS.

0900Z UPDATE...BASED ON RECENT OBSERVATIONS AND TRENDS ACROSS
CENTRAL INDIANA OPTED TO ISSUE A DENSE FOG ADVISORY FOR ALL
COUNTIES UNTIL 10AM. NPWIND ALREADY OUT ALONG WITH UPDATED
PRODUCTS. PREVIOUS DISCUSSION FOLLOWS.

FIRST THIS MORNING...LIGHT/CALM WINDS COMBINED WITH A HUMID AIR
MASS HAS ALLOWED AREAS OF FOG TO FORM ALREADY THIS MORNING. FOR
NOW WILL CONTINUE WITH AN SPS STATEMENT MENTIONING AREAS OF FOG
WITH VISIBILITIES AROUND HALF A MILE. IN ADDITION WILL CONTINUE
TO MONITOR TO SEE IF PARTS OF CENTRAL INDIANA WILL WARRANT A DENSE
FOG ADVISORY LATER THIS MORNING.

AS FOR THE REST OF TODAY AND TONIGHT...AN UPPER TROUGH AND
ASSOCIATED FRONTAL SYSTEM WILL MOVE INTO THE AREA BY TONIGHT. BEST
LIFT AND HIGHEST PRECIPITATION THREAT WILL BE FROM MID AFTERNOON
UNTIL MIDNIGHT TONIGHT. MODELS APPEAR TO BE VERY CONSISTENT WITH
THIS TIMING SO HAVE INCREASED POPS TO LIKELY DURING THIS TIME. FIRST
STARTING ACROSS THE NORTHWEST COUNTIES OF THE CWA MID
AFTERNOON...AND THEN MOVING TO THE SOUTHEAST THROUGH THIS EVENING.
THIS SYSTEM STILL LOOKS STRONG ENOUGH TO WARRANT A SLIGHT RISK FOR
SEVERE /PER SPC DAY ONE OUTLOOK/ WITH THE MAIN THREATS BEING
DAMAGING WIND GUSTS AND HAIL.

BY THIS AFTERNOON LOW LEVEL WINDS WILL BECOME SWLY AHEAD OF THE
UPPER TROUGH WHICH WILL MAINTAIN RICH LOW LEVEL MOISTURE /UPPER
60S-LOW 70F DEWPOINTS/ IN THE PRE-FRONTAL WARM SECTOR. STEEPER
MID-LEVEL LAPSE RATES ARE FORECAST TO SPREAD ACROSS THE AREA THUS
CONTRIBUTING TO 2500-3000 J/KG MLCAPE WHERE DIABATIC WARMING OF THE
SFC LAYER OCCURS.

FRONTAL BOUNDARY APPEARS TO SIGNIFICANTLY WEAKEN AS IT DROPS ACROSS
THE AREA THIS EVENING AND EVENTUALLY STALL OUT OVER SOUTHERN INDIANA
BY 12Z WEDNESDAY MORNING.

AS FOR TEMPERATURES...STUCK WITH A MOS BLEND FOR TODAY...EVEN
CONSIDERING THE CLOUDS AND PRECIPITATION CHANCES...DECENT WARM SWLY
FLOW SHOULD HELP TEMPERATURE ACHIEVE HIGHS IN THE MID TO UPPER 80S.
WENT SLIGHTLY WARMER FOR LOWS TONIGHT IN THE UPPER 60S.

&&

.SHORT TERM /WEDNESDAY THROUGH THURSDAY NIGHT/...
ISSUED AT 259 AM EDT TUE AUG 19 2014

THE SHORT TERM PERIOD..AND ACTUALLY THROUGH MUCH OF THE END OF THE
WEEK WILL BE PLAGUED BY A PESKY MEANDERING FRONTAL BOUNDARY THAT
WILL CONTINUALLY DRIFT NORTH AND SOUTH OF THE FORECAST AREA AS
ONE UPPER LEVEL DISTURBANCE AFTER ANOTHER RIDES
THROUGH...PROVIDING ON/OFF SCATTERED SHOWER AND THUNDERSTORMS.
WEDNESDAY ACTUALLY LOOKS LIKE THE DRIEST DAY OF THE PERIOD WITH
THE BOUNDARY FORECAST TO BE FAR ENOUGH SOUTH OF THE AREA THAT ONLY
COUNTIES ACROSS THE SOUTHERN HALF OF THE CWA HAVE A SLIGHT CHANCE
FOR STORMS THAT DAY. HIGHER CHANCES RETURN WEDNESDAY NIGHT AND
THURSDAY AS THE BOUNDARY LIFTS BACK NORTHWARD.

LAPSE RATES/DEEP LAYER SHEAR CONTINUE TO SUGGEST ORGANIZED
CONVECTION POSSIBLE WEDNESDAY AND THURSDAY WITH HEAVY RAINFALL ALSO
A THREAT WITH PRECIPITABLE WATERS APPROACHING 2 INCHES BY THURSDAY.
BASED ON GOOD MODEL CONTINUITY AND CONSENSUS BUMPED UP POPS TO JUST
SHY OF LIKELY DURING THIS TIME.

&&

.LONG TERM /SATURDAY NIGHT THROUGH TUESDAY/...

ISSUED AT 207 PM EDT TUE AUG 19 2014

ONLY CERTAINTY WITH THIS FORECAST DURING THIS PERIOD IS THE
CONTINUATION OF SOME VERY WARM SUMMER WEATHER DURING THE WEEKEND.
GFS AND ECMWF CONTINUE TO KEEP THE STRONG RIDGE IN PLACE ALOFT
DURING THIS PERIOD AND NOW HAVE BACKED OFF ON THE FLATTENING OF
THE RIDGE UNTIL TUESDAY AS A COLD FRONT GOES THROUGH THE AREA AND
RETURNS TEMPERATURES CLOSER TO SEASONAL NORMALS. PRIOR TO
TUESDAY...MODELS AND ALLBLEND CONTINUE TO INDICATE POPS ON
SATURDAY NIGHT THROUGH SUNDAY NIGHT AS SEVERAL BOUNDARIES LOOK TO
REMAIN IN PLACE NEAR CENTRAL INDIANA. THUS WILL CONTINUE WITH LOW
CHC POPS FOR NOW DURING THAT TIME AS A VERY WARM AND HUMID AIR
MASS WILL REMAIN IN PLACE.


&&

.AVIATION /DISCUSSION FOR THE 191800Z TAFS/...

ISSUED AT 1225 PM EDT TUE AUG 19 2014

VFR CONDITIONS EXPECTED FOR MUCH OF THIS AFTERNOON. CONVECTIVE
COMPLEX OVER CENTRAL ILLINOIS IS EXPECTED TO PROGRESS EAST ACROSS
CENTRAL INDIANA LATE THIS AFTERNOON. RAPID REFRESH DEPICTS A
DECAYING CONVECTIVE COMPLEX WORKING ACROSS THE TAF SITES LATE THIS
AFTERNOON. WITH CONDITIONAL INSTABILITY IN PLACE AND MARGINAL
SHEAR...THE INTENSITY OF THE APPROACHING STORMS REMAINS IN
QUESTION. THUS FOR NOW WILL USE SOME TEMPO GROUPS FOCUSING THE
PRIME WINDOW OF SHRA/TSRA PASSAGE. ANY TSRA MAY PRODUCE BREIF IFR
OR WORSE CONDITIONS.

IFR CONDITIONS ARE EXPECTED AGAIN OVERNIGHT AT LAF...BMG AND HUF
AS HIGH DEW POINTS...EARLIER LIGHT RAIN AND LIGHT WINDS SHOULD
RESULT IN ANOTHER MORNING OF FOG FORMATION. HEAT ISLAND EFFECTS AT
IND SHOULD KEEP MVFR CONDITIONS AT INDIANAPOLIS.

AFTER SUN UP ON WEDNESDAY...FOG WILL ONCE AGAIN BURN OFF...QUICKLY
LEADING TO SCT DIURNAL CU.


&&

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

$$

SYNOPSIS...SMF
NEAR TERM...SMF/JAS
SHORT TERM...SMF
LONG TERM....PUMA
AVIATION...JP

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