Area Forecast Discussion
Issued by NWS Indianapolis, IN

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FXUS63 KIND 191636
AFDIND

AREA FORECAST DISCUSSION
NATIONAL WEATHER SERVICE INDIANAPOLIS IN
1236 PM EDT TUE AUG 19 2014

.UPDATE...
THE AVIATION 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 /FRIDAY THROUGH TUESDAY/...
ISSUED AT 247 AM EDT TUE AUG 19 2014

MODELS DEPICT PERHAPS THE WARMEST STRETCH OF THE SEASON THUS FAR FOR
THE COMING WEEKEND AS AN UPPER LEVEL RIDGE STRENGTHENS OVER THE
LOWER MISSISSIPPI AND OHIO VALLEYS. THIS MAY BE THE CLOSEST CALL YET
THIS SUMMER FOR THE ELUSIVE 90 DEGREE MARK AT INDIANAPOLIS. THAT
SAID...SEVERAL FACTORS WILL HAVE A HAND IN DETERMINING WHETHER OR
NOT WE GET THERE. WHILE SUMMER BEGAN ON QUITE A WET NOTE WITH ONE OF
THE TOP 15 WETTEST JUNES...WHICH HAS LIKELY CONTRIBUTED AT LEAST IN
SOME SMALL PART TO THE LACK OF HEAT THUS FAR...THE ATMOSPHERE HAS
REVERSED ITSELF SOMEWHAT SINCE THE START OF JULY...AND INDIANAPOLIS
IS ROUGHLY TWO AND A HALF INCHES BELOW NORMAL ON PRECIP SINCE
THEN...OR AROUND THE SAME AMOUNT THAT JUNE WAS ABOVE NORMAL.
HOWEVER...THE GUIDANCE DEPICTS A MOIST AIRMASS WITH DEWPOINTS
PUSHING THE LOW TO MID 70S AT TIMES. ADDITIONALLY...WHILE THE
FORECAST WILL ONLY CARRY POPS INTO SATURDAY...THE PERIPHERY OF THE
RIDGE...WHERE CONVECTION MAY OCCUR IN A RING OF FIRE STYLE...AND THE
CORRIDOR WHERE ANY ORGANIZED CONVECTIVE COMPLEXES MAY TRACK...WILL
NOT BE THAT FAR NORTH OF THE AREA...AND THIS COULD COMPLICATE
MATTERS AS WELL. IF SOME DIURNAL CONVECTION MANAGES TO OCCUR DESPITE
THE QUITE WARM MIDLEVEL TEMPERATURES PUSHING 10C...THAT WOULD ALSO
POTENTIALLY WORK AGAINST THE HEAT. WILL BE INTERESTING TO SEE HOW
CLOSE WE GET TO 90 OR IF WE MANAGE TO FINALLY BREACH THE MARK. IF IT
OCCURS THIS WEEKEND...IT WILL BE THE LATEST FIRST 90 DEGREE DAY
SINCE 1960...WHEN 90 WAS NOT REACHED UNTIL SEPTEMBER FIRST. THIS IS
OF COURSE EXCLUDING 2004...THE ONLY YEAR ON RECORD THUS FAR WITHOUT
A 90 DEGREE READING.

&&

.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...NIELD
AVIATION...JP

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