789
FXUS63 KIND 010946
AFDIND

Area Forecast Discussion
National Weather Service Indianapolis IN
546 AM EDT Wed Jul 1 2026

.KEY MESSAGES...

- Heat index values up to 110 daily through Thursday

- Extreme Heat Warning in effect through Thursday evening

- Thunderstorm chances will increase Friday through the holiday
  weekend

&&

.FORECAST UPDATE...
Issued at 545 AM EDT Wed Jul 1 2026

Expanded the area of patchy fog to include all of central Indiana
with several sites hovering between a half mile and 2.5 miles. There
have been a few observations of a quarter mile, but those have been
brief and transient. If fog coverage increases, a brief Special
Weather Statement may be issued.

&&

.DISCUSSION (Today through Tuesday)...
Issued at 135 AM EDT Wed Jul 1 2026

Overview.

An intense heat wave will continue across central Indiana through
Thursday, bringing dangerously hot and humid conditions with
afternoon heat index values peaking between 105 and 110 degrees.
Relief will slowly arrive over the holiday weekend and into early
next week as temperatures pull back slightly, though this transition
will also bring daily chances for scattered showers and
thunderstorms.

Wednesday Through Thursday.

The synoptic pattern will remain dominated by a highly anomalous,
expansive 595dm sub-tropical ridge anchored over the Ohio and
Tennessee Valley regions. Strong large-scale subsidence and robust
mid-level thermal capping, evidenced by 700 mb temperatures hovering
near +12C to +15C, will effectively suppress deep vertical
development and keep diurnal convection negligible. Persistent low-
level south-southwesterly flow will continue to tap into a direct
Gulf moisture plume, sustaining an exceptionally moist planetary
boundary layer with surface dew points securely in the mid to upper
70s. In combination with intense diabatic heating, afternoon maximum
temperatures in the low to mid 90s will drive peak heat index values
up to 105 to 110 degrees across central Indiana. Consequently, the
Extreme Heat Warning remains well justified through Thursday
evening. By Thursday afternoon, a slight increase in shallow,
diurnal cumulus is anticipated as low-level moisture pivots around
the western periphery of the retreating ridge axis, though
substantial convective initiation remains inhibited by the lingering
capping inversion.

Friday Through Tuesday.

Medium-range guidance is in good agreement regarding the gradual
deamplification and southward suppression of the upper-level heat
dome heading into Friday and the holiday weekend. As the ridge
flattens, the synoptic flow over the Great Lakes and Ohio Valley
will transition to a progressive northwest flow regime aloft. This
structural shift will allow a series of mid-level shortwave troughs
and convective impulses to track into the region. Weakening large-
scale subsidence paired with an anomalously moist boundary layer
will support escalating chances for diurnal convection from Friday
through Tuesday. The Extreme Heat Warning in effect may need to be
extended into Friday, but until confidence on rain coverage and
timing increases, will hold off on any decisions regarding heat
headlines.

Given high precipitable water values and rich low-level moisture,
robust thermodynamic instability will develop each afternoon. While
weak deep-layer vertical wind shear will severely limit organized
storm structures or widespread severe weather, this low-shear, high-
CAPE environment will be highly conducive to localized pulse-type
storms capable of producing intense microbursts and heavy downpours.
By Monday and Tuesday, long-range model ensembles depict a more
organized northern stream shortwave digging into the Great Lakes,
driving a weak surface cold front southward across Indiana. While
exact frontal timing discrepancies persist between the GEFS and EPS,
this boundary will reinforce convective chances while providing much-
needed cold air advection, bringing temperatures back down toward
seasonal averages by the end of the period.

&&

.AVIATION (12Z TAF Issuance)...
Issued at 545 AM EDT Wed Jul 1 2026

Impacts:

-Patchy fog early through 13Z

Discussion:

VFR conditions expected through the TAF period outside of patchy fog
through 13Z with winds near calm and dewpoint depressions near zero.
Clear to mostly clear skies expected through the remainder of the
TAF period after fog dissipates. Winds will generally be southerly
at 7-12kts through tonight outside of the near calm winds this
morning.

&&

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

&&

$$

UPDATE...White
AVIATION...White
DISCUSSION...White