912
FXUS63 KIND 300421
AFDIND

Area Forecast Discussion
National Weather Service Indianapolis IN
1221 AM EDT Tue Jun 30 2026

.KEY MESSAGES...

- Hot and humid condition expected for much of this week with
  multiple days in the 90s and heat indices over 100 degrees

- Heat Advisory in effect this afternoon through Thursday

- Thunderstorm chances will increase late week into the holiday
  weekend

&&

.FORECAST UPDATE...
Issued at 944 PM EDT Mon Jun 29 2026

No significant changes to the going forecast this evening.

Day one of our midsummer heat wave went as expected, with highs
breaching the 90 degree mark in most locations, and oppressive
humidity continuing to build. Dewpoints much of the day and at this
hour remain largely in the mid to upper 70s, and latest hourly
numerical guidance suggests previous min temps were a degree or two
low, and have made this minor adjustment. The lack of overnight
relief, of course, will contribute to the impacts of this prolonged
episode of heat, and will likely keep HeatRisk values in the extreme
category across much of the area in the coming days.

&&

.DISCUSSION (This evening through Monday)...
Issued at 257 PM EDT Mon Jun 29 2026

Ensemble guidance is in excellent agreement showing anomalous
ridging this week across the Ohio River Valley. Ensemble mean 500mb
heights around 598dm are roughly 2-3 sigma above average for this
time of the year. Ridging remains roughly in place through about
Thursday, before gradually drifting eastward and weakening somewhat.
At the surface, prolonged southerly flow will continue to allow
moisture and warm air to flow northward.

The warm and deeply subsident atmosphere should act to prevent
shower or thunderstorm activity. Compressional heating combined with
modest warm air advection is expected to result in above-normal
warmth this week and likely into this weekend. High temperatures in
the low to middle 90s are probable, with lows in the 70s.
Additionally, dew points in the 70s will contribute to high heat
indices between 100-110 all of this week. A Heat Advisory has been
issued through Thursday evening.

As the ridge gradually drifts eastward later this week, subsidence
weakens allowing for the possibility of daytime / pop-up showers and
thunderstorms beginning on Friday. Severe weather is not currently
expected, since the jet stream is far to our north, but isolated
downbursts can never be ruled out in low-shear situations. Guidance
shows a weak cold front potentially arriving early next week, with
an increased risk of showers/storms. Upper-level flow remains
minimal, however, and organized severe weather does not appear
likely at this time.

&&

.AVIATION (06Z TAF Issuance)...
Issued at 1221 AM EDT Tue Jun 30 2026

Impacts:

- Patchy ground fog possible early this morning
- Wind gusts may peak at 15-20kts at times this afternoon

 Discussion:

VFR conditions are likely to prevail throughout the period.

Given the very moist airmass in place...brief visibility
restrictions near daybreak cannot be ruled out at the outlying
sites. This remains too low of a probability to mention in the TAFs.
Light southerly flow through daybreak will veer to southwest this
afternoon and increase to 10 to 15kts at times. A sporadic higher
gust is possible this afternoon as well...especially at KLAF. Winds
will diminish near sunset.

&&

.IND WATCHES/WARNINGS/ADVISORIES...
Heat Advisory until 8 PM EDT Thursday for INZ021-028>031-035>049-
051>057-060>065-067>072.

&&

$$

UPDATE...Nield
AVIATION...Ryan
DISCUSSION...Eckhoff