Area Forecast Discussion
Issued by NWS Indianapolis, IN

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472
FXUS63 KIND 201930
AFDIND

Area Forecast Discussion
National Weather Service Indianapolis IN
335 PM EDT Thu Jul 20 2017

.UPDATE...
Synopsis...Near Term and Short Term sections have been updated
below.

&&

.SYNOPSIS...
Issued at 335 PM EDT Thu Jul 20 2017

A strong upper ridge over the southern and central plains and
lower Mississippi valley will produce very hot and humid conditions
through Saturday.  A frontal system over the southern great lakes
will move to the northern part of our forecast area later tonight...
then stall and move back to the north later Friday.

Another cold front will move our way by Sunday as an upper trough
digs into the great lakes.   The long term period will be not as
hot.   High pressure will dominate our weather Monday through
Wednesday.   Then another system will move our way by Thursday.

&&

.NEAR TERM /Tonight/...
Issued at 335 PM EDT Thu Jul 20 2017

The thunderstorm complex which brought storms midday has moved on
to the east.  Rather quiet weather will be the rule next few hours.
This will be followed by increasing chance of storms across our
northern sections by late evening as a cold front over the
southern great lakes moves our way.  Models indicate good low
level convergence near this front and thunderstorms should develop
this evening over the middle and upper Mississippi valley and move
our way overnight.

SPC has the northern half of our forecast area in a slight risk of
severe weather overnight.   Locally heavy rain is also possible
as precipitable water is over two inches.   Will go with high chance
POPS towards midnight across our north...while southern sections
remain dry.

Lows tonight will be in the lower to middle 70s which is close to a
MOS blend.

&&

.SHORT TERM /Friday through Sunday/...

Issued at 335 PM EDT Thu Jul 20 2017

The front across our north will move back to the southern great
lakes by Friday night....while a strong upper ridge remains across
the lower Mississippi valley and southern plains.   The main issues
next few days will be how hot and humid it gets and also
thunderstorm chances.

860 MB temperatures will be a little warmer next few days with lower
20s across our south.  This translates to highs in the lower to
middle 90s and this combined with dewpoints in the middle to upper
70s will produce index values from 105 to 108 degrees across parts
of our south.  Will add a few more counties to the heat advisory to
the heat advisory beginning tomorrow.  This includes Greene and
lawrence counties through Jennings counties across our south.  All
heat advisories will then remain in effect until 23Z Saturday.

In regards to POPS...there should be a lull tomorrow morning
followed by chance POPS most areas Friday afternoon.  With the front
farther north...southern sections should be mostly dry Friday night
and Saturday...while a chance of storms will be the rule in the
north.     Raised POPS a little most areas Saturday night as the
cold front again moves our way.

Sunday will be a tad cooler with a few storms south.

&&

.LONG TERM /Sunday night through Thursday/...

Issued at 213 PM EDT Thu Jul 20 2017

The long term begins with Indiana having an upper wave move through
along with a front moving to the south. Thus will keep the slight to
low chance pops from the Superblend, and these will move off to the
southeast late Sunday night and Monday. Cooler highs (low to mid
80s) will be in place for Monday and Tuesday, but upper ridging
begins building back in and temperatures will start warming trend on
Wednesday. Medium confidence of dry weather Tuesday through
Wednesday under building upper ridge. The next system then
approaches on Thursday as the upper ridge suppresses and more
chances for storms arrive. Looking at thicknesses and upper pattern
though would not be surprised if high temperatures wind up a little
warmer than going forecast.

&&

.AVIATION (Discussion for the 201800 TAF Issuance)...
Issued at 100 PM EDT Thu Jul 20 2017

Shower and thunderstorm complex over east central Indiana will move
on to the east.   Quiet weather should occur the rest of the
afternoon and early tonight.  Several models indicate more storms
may develop along a weak frontal system moving into northern Indiana
by late evening and affect the northern portions of central Indiana
overnight.   Confidence on timing is low and will mention a period
of VCTS at KLAF from 03Z to 06Z tonight.   Could affect IND TAF as
well...but chances and confidence on timing is too low to add at
this time.

Otherwise...It will be VFR with few to scattered CU and Scattered to
broken mid clouds.   Will mention a period of MVFR fog at KLAF very
late tonight through 12Z.

Winds will be southwest up to 8 knots this afternoon and variable
around 5 knots most other periods.


&&

Heat Advisory from noon Friday to 7 PM EDT Saturday for INZ061-
070>072.

Heat Advisory until 7 PM EDT Saturday for INZ060-067>069.
&&

$$

SYNOPSIS...JH
NEAR TERM...JH
SHORT TERM...JH
LONG TERM....CP
AVIATION...JH



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