Area Forecast Discussion
Issued by NWS Indianapolis, IN

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000
FXUS63 KIND 150218
AFDIND

Area Forecast Discussion
National Weather Service Indianapolis IN
1018 PM EDT Mon Aug 14 2017

.UPDATE...
The AVIATION section has been updated below.

&&

.SYNOPSIS...
Issued at 303 PM EDT Mon Aug 14 2017

Overall pattern this week is slightly better with precipitation
chances than last week as dewpoints return to near 70. However
boundary in the Gulf States remains focus for torrential rains there
and keeps our chances here very low for any flooding rains. We are
now currently 8th driest start for an August.

A weak upper trough in the Upper Great Lakes will sweep a frontal
boundary into central Indiana Tuesday with low coverage of showers
and thunderstorms possible into Tuesday evening. Another somewhat
stronger system in the central and northern Rockies today will bring
more widespread showers and thunderstorm to central Indiana starting
Wednesday with more widespread coverage late Wednesday night into
Thursday. Ridging will build in Thursday night before another weaker
trough moves across Saturday bringing a slight chance of showers.
Drier weather returns Sunday and Monday with diverging model
solutions on rain or no rain Tuesday.

Temperatures and humidity this week will be slightly above normal,
certainly a more summer-like feel for August. A brief return to
cooler and drier than normal weather will occur Friday and Saturday.

&&

.NEAR TERM /Rest of Tonight/...

Issued at 950 PM EDT Mon Aug 14 2017

Forecast is in good shape. Upped sky cover some in the north based
on latest observations and satellite images. Latest hi res short
term model data keep any rain chances from an approaching front to
12Z or later, which the ongoing forecast reflects well. Low
temperatures look good too.

Previous discussion follows...

Scattered showers continue to run up the East Fork White River at
mid afternoon but still expect this to shift south of the river by
this evening.

Growing cumulus back in Iowa and Missouri near the surface front
should reach shower and storm stage this evening with remnants
possibly reaching our northern counties toward daybreak. Otherwise
dry, partly cloudy and mild conditions are expected tonight. With
rising dewpoints, some patchy late night fog is expected.

Min temperature guidance followed with mid 60s common to all.

&&

.SHORT TERM /Tuesday through Thursday/...

Issued at 303 PM EDT Mon Aug 14 2017

As the Great Lakes upper trough moves east, it will continue to
slowly push a frontal boundary south into our northern counties
Tuesday afternoon. The front will settle to southern counties
Wednesday morning. The boundary will have increased dewpoint pooling
ahead of it but convergence and dynamics will be somewhat lacking.
Still do expect isolated to scattered thunderstorms to fire at peak
heating near the boundary and last into early Tuesday evening across
north half of the area.

Tuesday and Tuesday night temperatures look pretty good, above
normal, given the continued return of more humid air.

Wednesday...the frontal boundary will begin lifting back north as
upper the trough to the west approaches. This results in at least
low chances for a few storms Wednesday.

Wednesday night and Thursday, the main upper trough and surface
front push into and across the area. With the continual feed of
moist air ahead of this system, and decent dynamics, showers and
storms are likely. Rain amounts at a half inch look pretty good for
most areas with a few one inch soakers for some.

With cloudy skies and warm advection, we will be hard pressed to
fall below 70 Thursday morning except in areas where rain occurs.
Fairly cloudy skies, wet ground and high humidity should limit max
temperatures Thursday to seasonal values outside of the southern
counties which will have enough daytime heating to reach the upper
80s one more time.

&&

.LONG TERM /Thursday night through Monday/...
Issued at 210 PM EDT Mon Aug 14 2017

Timing of pops will be the main concern for this forecast as models
generally having issues timing various shorts waves in fast flow
aloft. Consensus has an upper wave moving over the lower Great Lakes
and a cold front dropping southeast across central Indiana Thursday
night. Good confidence there will be enough synoptic forcing for
convection and models are showing plenty of instability for thunder.
The activity should end toward Friday morning with the frontal
passage. After that, an amplifying trough may bring more
thunderstorms to parts of the area Saturday afternoon through
Sunday. However, confidence in timing and coverage is low for this
weekend system, so just accepted the blotchy low blend pops.

Near normal blend pops look ok based on low level thermals and
partly cloudy skies. Look for highs in the lower to mid 80s and lows
in the 60s per the blend.

&&

.AVIATION /Discussion for 150300Z TAF Update/...
Issued at 1018 PM EDT Mon Aug 14 2017

Made minor adjustment to sky cover.

Previous discussion follows...

VFR conditions expected throughout the forecast period.

Diurnal cu field already beginning to diminish this evening as the
peak heating period has passed. Cirrus continues to drift across
the region from the upper level wave currently tracking through
Arkansas.

Central Indiana remains within an area of weak high pressure with
an approaching frontal boundary generating convection over the
Great Lakes and the aforementioned upper wave and moisture plume
present from the Ozarks E/NE through the Ohio and Tennessee
Valleys. Expect another quiet night under high pressure with just
high clouds present. While localized fog cannot be entirely ruled
out closer to daybreak with the deeper moisture advecting into the
area...but overall higher level clouds should limit fog. With low
confidence in coverage...will not place any restrictions in the
terminals at this time.

The upper wave over Arkansas will move east into the Tennessee
Valley Tuesday shifting the moisture plume associated with it
away from central Indiana. The approaching front from the north
will drop into north central Indiana before stalling and washing
out by Tuesday evening. Could see isolated convection get into
northern portions of the forecast area and possibly impact KLAF on
Tuesday afternoon...but again overall coverage and confidence too
low for inclusion in the forecast at this time.

Light west-southwesterly flow is anticipated for much of the
forecast period.

&&

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

&&

$$

SYNOPSIS...Tucek
NEAR TERM...Tucek/50
SHORT TERM...Tucek
LONG TERM...MK
AVIATION...Ryan/50



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