Area Forecast Discussion
Issued by NWS Indianapolis, IN

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000
FXUS63 KIND 121824
AFDIND

AREA FORECAST DISCUSSION
NATIONAL WEATHER SERVICE INDIANAPOLIS IN
224 PM EDT SAT JUL 12 2014

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

&&

.SYNOPSIS...
ISSUED AT 146 PM EDT SAT JUL 12 2014

ACTIVE WEATHER IS EXPECTED THE REST OF THE WEEKEND AS A SLOW
MOVING FRONTAL BOUNDARY OVER WISCONSIN AND IOWA SLOWLY SAGS
SOUTHWARD THROUGH CENTRAL INDIANA ON SUNDAY. THIS WILL RESULT IN
SHOWER AND THUNDERSTORM CHANCES ON TONIGHT WITH BEST CHANCES FOR
PRECIPITATION ON SUNDAY.

A SECONDARY COLD FRONT WILL PASS THROUGH THE REGION ON SUNDAY
NIGHT AND MONDAY...ONCE AGAIN RESULTING IN MORE CHANCES FOR
SHOWERS AND ISOLATED STORMS.

COOL...CANADIAN HIGH PRESSURE WILL ARRIVE IN THE OHIO VALLEY IN
THE WAKE OF THAT COLD FRONT...PROVIDING TEMPERATURES WELL BELOW
SEASONAL NORMALS. HIGHS THROUGH MUCH OF THE NEXT WORK WEEK WILL
ONLY REACH THE 70S...MAKING TEMPERATURES FEEL LIKE LATE SEPTEMBER
RATHER THAN MID JULY.

&&

.NEAR TERM /TONIGHT/...

ISSUED AT 146 PM EDT SAT JUL 12 2014

SURFACE ANALYSIS SHOWS A FRONTAL BOUNDARY STRETCHING FROM UPPER
MICHIGAN SOUTHWEST ACROSS WISCONSIN TO IOWA AND NEBRASKA. A
DECAYING CONVECTIVE COMPLEX OVER WESTERN INDIANA WAS SLOWLY
DRIFTING EAST...ALTHOUGH IR SHOWS TOPS WARMING AND RADAR COVERAGE
CONTINUES TO LESSEN. CLOUD COVERAGE ACROSS CENTRAL INDIANA WAS
LIMITING HEATING AS WELL AS KEEPING A CAP ON STABILITY. A MORE
MOIST AIR MASS WAS NOW IN PLACE ACROSS CENTRAL INDIANA HAS DEW
POINT TEMPS WERE NOW IN THE MIDDLE 60S AMID SOUTH TO SOUTHWEST
SURFACE FLOW.

MAIN FORECAST CHALLENGE TONIGHT WILL BE POPS.

TWO PHASES TO TONIGHTS FORECAST. EVENING HOURS LOOK TO BE ON THE
DRIER SIDE AS ONGOING CONVECTION SHOULD COME TO AN END AND CLOUDS
HAVE LIMITED HEATING AND INSTABILITY. RAPID REFRESH WITH APPEARS
OVERDONE IN THE NEXT FEW HOURS...FAILS TO DEVELOP ANYTHING DURING
THE EVENING HOURS ACROSS INDIANA. WILL NEED TO WATCH FOR BREAKS IN
THE CLOUDS OVER ILLINOIS AND POSSIBLE DEVELOPMENT LATE THIS
AFTERNOON...HOWEVER ANY PROPAGATION SHOULD PROBABLY LEAD INTO A
STABLE COLUMN OVER INDIANA. THUS MAY CARRY ONLY SLIGHT OR SMALL
CHC POPS THIS EVENING TO ACCOUNT FOR A STRAY SHOWER.

GFS AND NAM SUGGEST A SHORT WAVE OVER THE OVER THE UPPER MIDWEST
WILL EJECT EAST...OVER THE GREAT LAKES AND NORTHERN PARTS OF
INDIANA OVERNIGHT. GOOD CONVERGENCE IS EXPECTED OVER NORTHERN
INDIANA AND NW ILLINOIS AHEAD OF THE FRONT AND PROPAGATION
SUGGESTS THESE FEATURES WILL SAG SOUTHEAST TOWARD CENTRAL INDIANA.
A FEW TIMING DIFFERENCES HERE AS THE GFS IS A BIT QUICKER THAN
NAM. THUS WILL TREND POPS OVERNIGHT HIGHEST ACROSS THE NORTHWEST
PARTS OF THE FORECAST AREA WHERE PROXIMITY IS BEST AND TREND
TOWARD THE DRYER NAM ACROSS THE SOUTHERN FORECAST AS IN PART FOR
THE SAME REASONS. GIVEN THE EXPECTED RAIN AND DEWPOINTS...A BLEND
OF MAVMOS AND METMOS WORKS FINE.


&&

.SHORT TERM /SUNDAY THROUGH TUESDAY/...

ISSUED AT 146 PM EDT SAT JUL 12 2014

ITS GONNA RAIN!

GFS AND NAM BOTH AGREE THAT THE FRONTAL BOUNDARY OVER THE UPPER
MIDWEST WILL BE SAGGING SOUTH ACROSS CENTRAL INDIANA ON
SUNDAY...RESULTING IN PRECIP. 310K GFS ISENTROPIC SURFACE EVEN
SHOWS GOOD UPGLIDE ALONG WITH SPECIFIC HUMIDITIES OVER 9.9 G/KG.
TIME HEIGHT SECTIONS SHOW DEEP SATURATION THROUGH THE
COLUMN...MAINLY DURING THE MORNING HOURS. FORECAST SOUNDINGS ALSO
SHOW A SATURATED COLUMN. MEANWHILE LOWER LEVEL Q VECTORS SHOW GOOD
CONVERGENCE. THUS WITH ALL OF THESE FACTORS POINTING TOWARD PRECIP
WILL TREND POPS HIGHER ON SUNDAY AS THESE FEATURES PASS. GIVEN THE
EXPECTED CLOUDS AND RAIN...WILL TREND HIGH TEMPS LOWER THAN THE MAV.

BEST DYNAMICS AND FORCING APPEAR TO EXIT THE AREA ON SUNDAY NIGHT
AS ISENTROPIC FORCING IS LOST AND DRYER AIR BEGINS TO MOVE INTO
THE AREA FROM THE WEST. FORECAST SOUNDINGS AND TIME HEIGHTS ALSO
DRY OUT CONSIDERABLY BY SUNDAY NIGHT. MAY CARRY A SMALL CHANCE
DURING THE EVENING HOURS IN THE CASE THE SYSTEM IS A BIT SLOWER TO
PROGRESS...BUT WILL TREND TOWARD A DRY FORECAST AFTER 06Z MONDAY.
GIVEN THE STAR OF COLD AIR ADVECTION IN THE WAKE OF THE FRONTAL
BOUNDARY WILL TREND LOWS AT OR BELOW MAVMOS.

ON MONDAY A SECONDARY COLD FRONT WILL PUSH ACROSS THE AREA AS MUCH
COOLER TEMPERATURES BEGIN TO PUSH INTO CENTRAL INDIANA FRONT THE
NW. MOISTURE WILL BE MORE LIMITED WITH THIS
BOUNDARY...HOWEVER WITH A STRONG CHANGE IN AIR MASS BEGINNING WILL
CARRY SOME LOW CHC POPS FOR LIGHT PRECIP ON MONDAY AS THESE
FEATURES PASS. PRECIP NOT EXPECTED TO BE HEAVY.

DRY AND COLDER WEATHER EXPECTED ON MONDAY NIGHT AND TUESDAY AS
CANADIAN HIGH PRESSURE NOSES INTO THE OHIO VALLEY. STRONG COLD AIR
ADVECTION IS SET TO BUILD ACROSS THE AREA BY MONDAY NIGHT AS 850MB
TEMPS FALL TOWARD 8C BY 12Z TUESDAY. FORECAST SOUNDINGS DRY OUT
DRAMATICALLY AMID ASSOCIATED SUBSIDENCE. THUS WILL TREND TOWARD
PARTLY CLOUDY MONDAY NIGHT AND TUESDAY WITH TEMPS AT OR BELOW
MAVMOS/MEXMOS.

&&

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

ISSUED AT 224 PM EDT SAT JUL 12 2014

MODELS ARE CLOSE ENOUGH THAT THE ALLBLEND INITIALIZATION WAS
ACCEPTED FOR MOST FORECAST PARAMETERS.

THE UPPER LOW THAT WILL BRING THE COLDER AIR WILL LIFT TO THE
NORTHEAST DURING THE LONG TERM...BUT THE AREA WILL REMAIN IN A
LARGER TROUGH ALOFT. THIS WILL ALLOW TEMPERATURES TO MODERATE...BUT
STILL REMAIN BELOW AVERAGE FOR MOST OF THE PERIOD.

MODELS CONTINUE TO HINT AT SOME INSTABILITY SHOWERS ON WEDNESDAY BUT
STILL FEEL THE ODDS OF THESE ARE TOO LOW TO MENTION AT THIS TIME.
SOME ALSO SHOW SOME RAIN ON SATURDAY IN WARM ADVECTION PATTERN...BUT
UNCERTAINTY IS TOO HIGH TO MENTION THIS EITHER. THUS KEPT LONG TERM
DRY.

&&

.AVIATION /DISCUSSION FOR THE 121800Z TAF ISSUANCE/...
ISSUED AT 1257 PM EDT SAT JUL 12 2014

MVFR CONDITIONS IN SHOWERS WILL GIVE WAY TO VFR CONDITIONS EARLY IN
THE PERIOD. VFR SHOULD THEN CONTINUE OUTSIDE OF ANY ADDITIONAL
CONVECTION.

SHOWERS ASSOCIATED WITH AN UPPER WAVE WILL CONTINUE TO DIMINISH AS
THEY MOVE ACROSS THE TAF SITES. MVFR CONDITIONS WILL GENERALLY BE
THE RULE IN THE RAIN. THUNDER HAS DIMINISHED SO WILL LEAVE OUT OF
TAFS. EXPECT RAIN TO END AND VFR TO RETURN BY ABOUT 20Z.

CANNOT RULE OUT POP UP CONVECTION LATER THIS AFTERNOON AND EARLY
EVENING BUT ODDS ARE TOO LOW TO MENTION. BEST CHANCES FOR ADDITIONAL
CONVECTION WILL BE LATE TONIGHT INTO SUNDAY WITH A COLD FRONT. HAVE
PUT IN PROB30S FOR NOW. WILL LIKELY ADJUST TIMING WITH LATER
ISSUANCES.

WINDS SHOULD STAY UP ENOUGH EARLY TONIGHT TO PREVENT FOG FORMATION.

&&

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

$$

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

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