329
FXUS63 KIND 300637
AFDIND

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

.KEY MESSAGES...

- Hot and humid condition expected with highs in the 90s and heat
  indices peaking at 105 to 110 degrees in the afternoons through
  Thursday

- Extreme Heat Warning in effect through Thursday evening

- Thunderstorm chances will increase Friday through the holiday
  weekend

&&

.DISCUSSION (Today through Monday)...
Issued at 237 AM EDT Tue Jun 30 2026

Muggy early this morning as with the center of the upper ridge
across the Ohio Valley. 06Z temperatures remained between 75 and 80
degrees with dewpoints well into the 70s.

A dangerous heat wave will continue for much of the rest of the week
as deep ridging sets up over much of the eastern half of the
country. The ridge will flatten by late week as the jet stream
drifts back south into the area. Scattered convection largely
prevalent on any waves rippling through the flow will increase for
the holiday weekend as a result.

The primary focus will be on the heat and humidity with at least 4
or 5 consecutive days with highs in the 90s. Monday was day one with
highs in the lower 90s and heat indices that peaked over 100
degrees. Expect warmer air temperatures and higher heat indices
today through Thursday with the core of the ridge over the area as
mid level heights peak at 596-598dm. Increased subsidence over the
Ohio Valley will limit clouds and diurnal cu as well...especially
today and Wednesday. Likely to see a slight increase in cu
development Thursday as moisture pivots around the back side of the
ridge and into the area...but it is shallow and should not have much
impact on expected highs.

Low level thermals support low to mid 90s each of the next three
days with dewpoints remaining in the 70s. Max heat indices of 105 to
110 degrees are possible each afternoon. Considering the intensity
of the heat with the compounding nature of impacts over multiple
days from the oppressive airmass have elected to upgrade the Heat
Advisory to an Extreme Heat Warning through Thursday evening. An
increase in outdoor activities in advance of the Independence Day
weekend also factored into this decision to upgrade. An argument
could be made to extend the warning into Friday even as temps and
heat indices fall back slightly from levels expected through
Thursday...but increasing uncertainty on convective potential
beginning Friday precludes an expansion in time at this point.

The ridge will slowly flatten heading into the weekend as waves
aloft drift further south into the lower Great Lakes and Ohio
Valley. Moisture lifting around the back side of the ridge may be
enough to generate more cu and perhaps isolated late afternoon and
evening convection by Thursday. Convective coverage should steadily
increase Friday into the weekend as the mid level heights begin to
fall back. Locally intense slow moving storms producing damaging
winds during the afternoon and evening will be a possibility
within the moist and highly unstable airmass. There remains the
possibility of one or more mesoscale convective systems impacting
parts of the region by the weekend as well...and there is already
CIPS analog support for this solution by Saturday and Sunday.
Very warm and humid conditions will linger into early next week.

&&

.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...
Extreme Heat Warning until 8 PM EDT Thursday for INZ021-028>031-
035>049-051>057-060>065-067>072.

&&

$$

AVIATION...Ryan
DISCUSSION...Ryan