249
FXUS63 KIND 210019
AFDIND

Area Forecast Discussion
National Weather Service Indianapolis IN
819 PM EDT Sat Jun 20 2026

.KEY MESSAGES...

- A few showers and possibly a stray TS far S-SE areas ending this
  evening.

- Heavy rain and severe storms are possible Sunday afternoon into
  early Monday.

- Flooding threat both river and non-river will increase with
  heavy rain on already saturated soils in some areas.

- Below normal temperatures will continue for much of the period.

- Transition to multiple heavy rain events is possible going into
  the week of 4th of July.

&&

.DISCUSSION (This evening through Saturday)...
Issued at 342 PM EDT Sat Jun 20 2026

Rest of this afternoon...

Weak surface confluence zone associated with slight T/TD gradient
will continue to shift south of I-70 over the next few hours. As a
result modest convergence and steep 0-3 KM lapse rates and residual
moisture in the 850-700mb layer will support some scattered light
showers. Recent ACARS soundings from KIND continue to support
presence of mid level inversion centered between 3-4 KM on the
backside of departing shortwave trough. Some indications are that
sufficient moistening and cooling from transport and lift below
this inversion may allow for just enough erosion to support an
isolated TS across far S-SE zones this afternoon with between 750-
1000 J/KG potentially being realized. As a result have continued to
carry slight chance of TS in these areas until 00Z.

Tonight....

Fairly quiet conditions are expected as weak area of high pressure
moves into the region. Winds will become light and variable with
increasing mid-high level clouds preventing any concerns for patchy
fog formation.

Sunday into Monday...

Lee cyclogenesis over the High Plains currently ongoing will help in
the development of an MCS over the central High Plains this evening.
This MCS will move into the lower plains/MO valley overnight
supported by a progressive mid level shortwave trough and 35-45 kt
low level jet. Exact morphology of this system into Sunday morning
remains somewhat uncertain. Recent ensemble guidance suggest that at
the very least the remnant MCV will move into Indiana during the
late afternoon. Increasing clouds and light showers are expected to
develop during the late morning on the leading WAA wing of the
MCS/MCV. As a result, instability is expected to be more limited
across areas north of I-70 and as a result severe TS threat.
Therefore, current indications are that the best threat for severe
TS will occur south of I-70 and may be a combination of
re-invigoration of ongoing convective line late Sunday morning
over the MS valley and/or combination of redevelopment of
convection along the MCV trough axis/remnant outflow boundary
during the late afternoon.

As a result of the uncertainties in the morphology of convection
Sunday morning/afternoon, storm mode is equally uncertain. With the
surface low attendant to the shortwave trough likely enhanced by
diabatic effects of tonight/s MCS, there is the potential for
isolated tornadoes, especially considering the 200-300 0-1 KM SRH
noted on forecast soundings owing to relatively strong low level
jet. Proximity of south/central Indiana to the track of the surface-
850 mb low also would support a tornado threat with any cellular
activity per pattern recognition. However if a more linear mode
remains in place/intensifies during the afternoon/evening into
southern/central Indiana, then damaging winds will likely be the
primary threat, with isolated embedded tornadoes still possible
within the line given the aforementioned low level shear profiles.
The main limiting factor for a more substantial severe threat will
be relatively marginal instability /per June standards/ with
forecast soundings suggesting between 1000-1500 J/KG of SB/MU
CAPE and mid level lapse rates near 6 C/KM.

QPF forecasts remain bullish for the most part, with average QPF
around 2 inches, with some areas near I-70 expected to receive
locally over 3 inches, owing to the proximity of expected
synoptic/mesoscale differential heating/baroclinic zone and 30-40
kts low level jet impinging on this boundary. Have maintained the
Flood Watch for most of central Indiana, except the far NE. PWAT
values remain around 1.8 inches, near the 90th percentile, and storm
training effects will likely be the main instigator for any flash
flood threat. Much of central Indiana along and 50 miles either side
of the I-70 corridor has a Moderate Risk for Flash Flood per the WPC
day 2 outlook and this seems very reasonable given aforementioned
synoptic pattern as well as antecedent high soil moisture levels for
much of the area.

Tuesday through Thursday...

Broad long wave trough will remain anchored over the eastern
Canadian provinces. In the wake of the early week shortwave, surface
high pressure will build southward through the Great Lakes on
Tuesday leading to another day of below normal temps in the 70s and
relatively dry airmass. Several SE moved shortwave troughs in NW
flow will be capable of producing scattered precip Wednesday and
Thursday.

Friday into 4th of July week...

Exceptional agreement exists in the medium range model guidance.
With the EPS, GEFS, AIFS all showing a very strong trough developing
over the intermountain west late next week into next weekend. As a
result, downstream riding will intensify over the plains supported
by near record heat. On the northern periphery of the ridge, remnant
W-NW flow combined with moderate to high instability will set the
stage for one or more severe MCS events in the corn belt region
potentially starting next Saturday in central Indiana and going into
the 4th of July week. Stay tuned on the timing and intensity of
these events.

&&

.AVIATION (00Z TAF Issuance)...
Issued at 819 PM EDT Sat Jun 20 2026

Impacts:

- Scattered thunderstorms expected late Sunday afternoon into the
overnight hours

Discussion:

Overnight, mid level clouds will begin to increase ahead of a storm
system over the plains. Weak high pressure will lead to light and
variable winds and VFR conditions.

On Sunday, expecting winds to become SE with some gust possible as
high as 15 kts by midday ahead of a developing low pressure area
over MO. Associated with this low pressure area, expecting a complex
of thunderstorms, gradually weakening, to move into central Indiana
towards the afternoon and lasting beyond 00z. Have at least showers
at all sites with at least VCTS at most sites. Exact timing of
thunder lacks confidence at IND so have stuck with PROB30 TSRA at
the end of the period for now. MVFR or lower will be possible as
storms move through.

&&

.IND WATCHES/WARNINGS/ADVISORIES...
Flood Watch from Sunday afternoon through Monday morning for
INZ028>030-035>037-039-043>048-051>057-060>065-067>072.

&&

$$

AVIATION...KF
DISCUSSION...Crosbie