Area Forecast Discussion
Issued by NWS Indianapolis, IN

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FXUS63 KIND 210809
AFDIND

AREA FORECAST DISCUSSION
NATIONAL WEATHER SERVICE INDIANAPOLIS IN
409 AM EDT THU AUG 21 2014

.UPDATE...

THE AVIATION SECTION HAS BEEN UPDATED BELOW.

&&

.SYNOPSIS...
ISSUED AT 335 AM EDT THU AUG 21 2014

A RIDGE OF HIGH PRESSURE WILL STRENGTHEN OVER THE EASTERN THIRD OF
THE NATION INTO EARLY NEXT WEEK...BRINGING THE WARMEST WEATHER OF
THE SUMMER. HOWEVER WEAK WAVES WILL ROTATE AROUND THAT
RIDGE...KEEPING CHANCES FOR SHOWERS AND THUNDERSTORMS OVER CENTRAL
INDIANA THROUGH SATURDAY. A DRY SPELL WILL COMMENCE ACROSS THE
REGION EARLY NEXT WEEK BEFORE ANOTHER DISTURBANCE IS SET TO IMPACT
THE AREA BY NEXT TUESDAY.

&&

.NEAR TERM /TODAY/...
ISSUED AT 335 AM EDT THU AUG 21 2014

THE ENVIRONMENT OVER CENTRAL INDIANA WILL DESTABILIZE RAPIDLY EARLY
TODAY AS WARM ADVECTION SPREADS OVER CENTRAL INDIANA BEHIND A WARM
FRONT LIFTING NORTH OVER INDIANA. THIS WILL SERVE TO TRIGGER
SCATTERED SHOWERS AND THUNDERSTORMS. THE HIGHEST CHANCES WILL BE
OVER THE NORTHERN HALF OF COUNTIES WHERE ADDITIONAL FORCING FROM THE
FRONT AND A SHORTWAVE MOVING ACROSS THE AREA AIDES IN CONVECTIVE
DEVELOPMENT. HAVE CONTINUED TO CARRY LIKELY POPS FOR THIS MORNING
AND AFTERNOON. SPC HAS ALSO PLACED THIS AREA IN A SLIGHT RISK FOR
SEVERE WEATHER WITH DAMAGING WINDS...LARGE HAIL...AND TORRENTIAL
RAINFALL/LOCALIZED FLOODING AS THE MAIN THREATS.

AS FOR TEMPS THERE IS QUITE A DISCREPANCY BETWEEN THE WARM MAV AND
COOLER NAM. WENT WITH A BLEND BUT SLIGHTLY CLOSER TO THE COOLER NAM
BASED ON PERSISTENCE AND CLOUDS/PRECIP CHANCES TODAY.

&&

.SHORT TERM /TONIGHT THROUGH SATURDAY NIGHT/...
ISSUED AT 335 AM EDT THU AUG 21 2014

HIGH PRESSURE WILL CONTINUE TO STRENGTHEN OVER THE AREA FOR THE
REMAINDER OF SHORT TERM PERIOD...BUT WEAK WAVES IN THE FLOW WILL
DRIFT ALONG THE RIDGE...KEEPING PESKY CHANCES FOR ON/OFF SHOWERS AND
THUNDERSTORMS IN THE FORECAST THROUGH SATURDAY. BY SATURDAY NIGHT IT
APPEARS CONDITIONS WILL FINALLY DRY OUT ACROSS THE AREA.

AS FOR TEMPERATURES...SOME OF THE HIGHEST TEMPS OF THE SEASON WILL
OCCUR DURING THIS PERIOD /AND INTO THE NEXT/ WITH HIGHS REACHING
INTO THE LOW TO MID 90S ON FRIDAY AND SATURDAY SOUTH OF INTERSTATE
70. THESE TEMPS COMBINED WITH LOW TO MID 70S DEW POINTS WILL ALLOW
HEAT INDICES TO REACH AND EXCEED THE 100 MARK IN SOME LOCATIONS
ACROSS THE AFOREMENTIONED AREA. WILL NEED TO KEEP AN EYE ON THIS
WARM UP AND SEE IF A HEAT ADVISORY IS WARRANTED FOR A FEW DAYS
THIS PERIOD AND POSSIBLY INTO EARLY NEXT WEEK. AND ACTUALLY
TRENDED ON THE LOWER SIDE OF GUIDANCE DUE TO PERSISTENCE.

&&

.LONG TERM /SUNDAY THROUGH THURSDAY/...
ISSUED AT 335 AM EDT THU AUG 21 2014

MODELS CONTINUE TO DEPICT PERHAPS THE LONGEST WARM STRETCH OF THE
SEASON THUS FAR CONTINUING THROUGH THE WEEKEND AS AN UPPER LEVEL
RIDGE DOMINATES OVER THE LOWER MISSISSIPPI AND OHIO VALLEYS. IF WE
HAVE STILL NOT MADE 90 BY THEN...THERE WILL STILL BE AT LEAST A
COUPLE OF OPPORTUNITIES EARLY IN THE LONG TERM PERIOD TO DO SO. 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 TO 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 LATE IN THE PERIOD AS THE RIDGE BREAKS
DOWN AND TEMPERATURES MODERATE/...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 ISOLATED DIURNAL CONVECTION MANAGES TO OCCUR DESPITE
THE QUITE WARM MIDLEVEL TEMPERATURES PUSHING 10 TO 12C...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 IN THE NEXT SEVERAL DAYS...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.

IT IS WORTH NOTING THAT THE ECMWF ENSEMBLE MOS REMAINS QUITE
WARM...A FEW DEGREES ABOVE WHAT WILL BE THE OFFICIAL FORECAST
NUMBERS. GFS ENSEMBLE MOS MEANS ARE MUCH COOLER AND WITH MUCH LOWER
STANDARD DEVIATION. WILL BE CURIOUS TO SEE HOW EACH PERFORMS...BUT
THE SIGNIFICANT SPREAD IN THE ECMWF MOS CONTINUES TO NOT INSPIRE
CONFIDENCE AT THIS TIME.

&&

.AVIATION /DISCUSSION FOR THE 21/09Z TAF UPDATE/...
ISSUED AT 409 AM EDT THU AUG 21 2014

HAVE MADE SOME CHANGES TO THE TAFS BASED ON RADAR AND OBS TRENDS.
SEEMS UNLIKELY THAT THUNDER OR FOG WILL BE A THREAT AT IND WITHIN
THE NEXT COUPLE OF HOURS. SOME VERY ISOLATED DEVELOPMENT OCCURRING
UPSTREAM BUT IT IS STRUGGLING. PREVIOUS DISCUSSION FOLLOWS.

ISSUED AT 1249 AM EDT THU AUG 21 2014

MVFR VISIBILITIES POSSIBLE OVERNIGHT WITH FOG. RESTRICTIONS POSSIBLE
IN ANY CONVECTION THROUGH MIDDAY.

WEAK SURFACE RIDGING ACROSS CENTRAL INDIANA WITH JUST MID/HIGH LEVEL
CLOUDS DRIFTING THROUGH. COMPLEX OF STORMS OVER SOUTHERN ILLINOIS
NEAR THE FRONTAL BOUNDARY RIDING ALONG A THETA E RIDGE AND SHOULD
REMAIN SOUTH OF THE TERMINALS OVER THE NEXT FEW HOURS. DO ANTICIPATE
AN INCREASE IN SCATTERED CONVECTION AFTER 08Z AS THE BOUNDARY LIFTS
NORTH INTO THE FORECAST AREA AND THE NEXT UPPER LEVEL WAVE OVER THE
MISSOURI VALLEY SHIFTS EAST TOWARDS THE REGION. THE COMBINATION OF
THESE FEATURES ALONG WITH A LOW LEVEL JET NOSING INTO CENTRAL
INDIANA SHOULD SUPPORT EXPANDING CONVECTIVE DEVELOPMENT TO THE
NORTHWEST TOWARDS DAYBREAK...WITH STORMS MIGRATING INTO THE REGION
DURING THE MORNING. WITH SOME UNCERTAINTY IN EXTENT TO CONVECTIVE
COVERAGE AND SPECIFIC IMPACTS TO TERMINALS...WILL CARRY A BROAD
PERIOD OF PREVAILING SHOWERS WITH VCTS THROUGH MIDDAY.

UPPER RIDGING WILL ATTEMPT TO EXPAND ACROSS THE FORECAST AREA
THURSDAY AFTERNOON AS THE UPPER WAVE DEPARTS. POTENTIAL EXISTS FOR
RENEWED CONVECTIVE DEVELOPMENT LATE THURSDAY AFTERNOON AND EVENING
AS ANOTHER UPPER WAVE RIDES OVER THE RIDGE AND INTO THE LOWER GREAT
LAKES. WITH HIGH UNCERTAINTY...WILL KEEP CONDITIONS DRY AT THIS
TIME. SOUTHWEST WINDS TO AROUND 10KTS POSSIBLE TODAY.

&&

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

&&

$$

SYNOPSIS...SMF
NEAR TERM...SMF
SHORT TERM...SMF
LONG TERM...NIELD
AVIATION...RYAN/NIELD

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