236
FXUS63 KIND 210204
AFDIND

Area Forecast Discussion
National Weather Service Indianapolis IN
1004 PM EDT Mon Jul 20 2026

.KEY MESSAGES...

- Dry through this evening but smoke and haze will be over the area

- Isolated strong thunderstorms possible late tonight. Locally heavy
  rain will also be possible.

- Noticeably cooler and less humid for the second half of the week

&&

.FORECAST UPDATE...
Issued at 1002 PM EDT Mon Jul 20 2026

Seasonable moderate humidity will oversee temperatures continuing to
slowly fall through the 70s amid light breezes across central
Indiana.  Meanwhile overall disorganized convective cluster spanning
from Des Moines to much of central Illinois will continue to
progress to the south-southeast...although the local region`s
northwest corner could catch light rain from the cluster`s eastern-
most extent through midnight.  Latest guidance`s significant
downward trends in coverage and intensity of late-night storms has
been reflected in latest grids update...where have kept at least
widely-scattered thunder for most zones after 10Z...with perhaps
numerous showers by 12Z. Dewpoints will continue to slowly climb to
the low 70s for most locations by daybreak...guiding lows to 69-74
across the region.

&&

.DISCUSSION (This evening through Monday)...
Issued at 703 PM EDT Mon Jul 20 2026

Surface analysis early this afternoon shows high pressure over NY
and PA while a frontal boundary was found over MN and SD, sagging
SE. This was resulting in southerly surface flow across Indiana. A
convective cluster was found over IA and Nrn IL. GOES19 shows high
cloud associated with this drifting SE into NW Indiana along with
sct CU development across Central Indiana. Haze remained present in
most observations. Aloft the upper flow continued to be dominated by
high pressure in place across the central Rockies, which was
allowing a stream of Pacific moisture to flow across the NW CONUS
across the northern plains and diving southeastward toward the Ohio
Valley.

Tonight...Quiet weather is expected this evening as the upper wave
over the upper midwest continues to approach. As daytime heating is
lost, CU will dissipate this evening leading to partly cloudy skies,
but haze and high clouds may still linger.

Overnight, the strong upper wave will dig southward, triggering
showers and storms as they pass across Central Indiana. Forecast
soundings suggest deep saturation overnight and pwats over 2 inches.
CAPE appears relatively marginal while shear values remain high
enough that a few severe storms cannot be ruled out. The main threat
from any storms will be damaging straight line winds and heavy rain
resulting in flooding. Diurnally, these showers and storms will not
be passing at favorable time of day for strong convection, so
overall confidence is medium. HRRR shows area of showers and storms
entering NW Central Indiana by 07-08Z before passing through the
Indy metro between 10Z-13Z, and exiting Central Indiana by 14Z-15Z
Tuesday. HRRR continues to focus best forcing and storm organization
over the northern and eastern parts of the forecast area, and will
focus best pops in those locations.

Tuesday afternoon through Wednesday, strong Canadian high pressure
over the northern plains will begin to build east into the Great
Lakes and Ohio Valley. This will result in cooler northerly flow
across Indiana on Tuesday afternoon through Wednesday night.
Forecast soundings show strong subsidence and a dry column, which
should result in a mostly clear nights and partly cloudy days, with
highs only in the middle 70s on Wednesday.

Thursday through Monday...

Dry and cooler weather is mainly expected until Sunday and Monday.
Models suggest strong ridging developing aloft over the western
CONUS on Thursday, persisting through Sunday. This will result in
leeside NW flow spilling from the northern Plains and upper midwest
and into the Ohio Valley. At the moment, little in the way of
forcing dynamics appear to pass until Sunday and Monday. Best
forcing looks to pass on Monday afternoon at this point, but
uncertainty with timing at this point will remain high.

Otherwise, we will look for a large surface high pressure system
lingering across Indiana on Thursday through Sunday, with subsidence
in place from the flow aloft. This Canadian air mass will be much
cooler, allowing below normal temperatures as highs will only reach
the upper 70s and lower 80s through Saturday.

Warmer and more humid southerly flow will return on Sunday and
Monday, adding moisture for the potential of storms at that time as
that previously discussed upper wave approaches on Monday.

&&

.AVIATION (00Z TAF Issuance)...
Issued at 742 PM EDT Mon Jul 20 2026

Impacts:

- Areas of HZ/smoke continuing to slightly reduce VIS this evening
- SHRA/some TSRA expected within mainly 07Z-14Z Tuesday...MVFR
  possible in heavier embedded cells
- Wind shift from WSW to NW Tuesday

Discussion:

Cirrus ceilings will continue to clear from NW to SE through 0030Z.
Bigger story will be potential strong TSRA around pre-dawn/early AM
hours, although confidence now lower following lackluster upstream
development so far today...with present stronger convection west of
Quad Cities on course to pass west of KHUF tonight.

Upper vort max to cross southern Great Lakes will drag a stronger
cold front across central Indiana terminals Tuesday morning after
13Z.  Any TSRA may produce brief IFR conditions. VFR conditions to
resume at KLAF around 13Z...and along I-70 by 17Z.

Winds, outside of any convection, will increase slightly overnight
ahead of the boundary.  Stronger breezes Tuesday will oversee the
frontal passage/zone, with flow sustained around 8-12KT as winds
slowly veer to WNW/NW by afternoon.  Expect gusts up to around 20KT
after 15Z at KIND/KLAF.

&&

.IND WATCHES/WARNINGS/ADVISORIES...None.
&&

$$

UPDATE...AGM
AVIATION...AGM
DISCUSSION...Puma