565
FXUS63 KIND 301728
AFDIND

Area Forecast Discussion
National Weather Service Indianapolis IN
128 PM EDT Thu Apr 30 2026

.KEY MESSAGES...

- Spotty showers and possibly a rumble of thunder this afternoon and
  evening

- Below normal temps to continue through the weekend with frost
  likely Saturday and Sunday

- Slow warm up with rain returning early next week, potential for
  heavy rain at times

&&

.DISCUSSION (This evening through Thursday)...
Issued at 127 PM EDT Thu Apr 30 2026

Overview.

Central Indiana will experience a persistent period of below-normal
temperatures through the upcoming weekend as a deep upper-level
trough remains anchored over southeast Canada. While scattered light
showers and isolated rumbles of thunder are possible through this
evening, the primary focus shifts toward a significant frost threat
for Saturday and Sunday mornings as surface high pressure settles
over the region. Looking into next week, a transition to a more
active and humid pattern is expected as the synoptic flow shifts,
bringing an increasing threat of heavy rainfall by midweek.

This Evening through Saturday Night.

The current mesoscale environment is defined by a lingering
northwesterly flow behind a departing frontal boundary, with high-
resolution model guidance such as the HRRR and NAM indicating a weak
shortwave ripple moving along the broader cyclonic flow. While low-
level moisture is limited, a narrow window of mid-level saturation
and modest lapse rates around 7 C/km will support spotty showers and
perhaps a few isolated thunderstorms late this evening, though
instability remains too meager for any severe concern. As the
shortwave exits, residual mid-level moisture will keep clouds across
the area through near daybreak which will keep temperatures slightly
more mild with lows in the low to mid 40s. Friday will be dry and
seasonably cool, but by Saturday morning, the proximity of a surface
high-pressure ridge will promote better radiational cooling
conditions. With areas of frost expected along and north of the I-74
corridor with a low-end potential for a freeze near Muncie and areas
to the northeast. Radiational cooling becomes most favorable on
Sunday morning as the axis of the surface high pressure moves
directly over central Indiana, resulting in nearly calm winds and
clear skies. This setup will allow the boundary layer to decouple
efficiently, with high confidence in widespread frost as
temperatures bottom out in the lower 30s across most of the forecast
area with the main uncertainty being the timing of the shift to
stronger southerly flow which could advect just enough warm air to
limit frost formation.

Sunday through Thursday.

Another dry day is expected for Sunday with southerly flow gradually
strengthening ahead of the pattern shift for early next week.
Transitioning into Monday and Tuesday, the high pressure departs to
the east, allowing for a slow warming trend as low-level flow turns
southerly and begins to draw moisture from the Gulf of Mexico. Broad
ensemble runs, including the GEFS and ECMWF, highlight a deepening
longwave trough over the Central Plains by Wednesday, which will
significantly increase precipitable water (PWAT) values toward 1.40
to 1.60 inches. This surge in moisture, combined with a quasi-
stationary frontal boundary draped across the Ohio Valley, creates a
notable threat for heavy rain and training convection toward the end
of the period. Current probabilistic guidance suggests a 20-30%
chance of rainfall totals exceeding 2 inches in some basins,
necessitating a close watch on river levels and potential flash
flooding concerns for the middle of next week.

&&

.AVIATION (18Z TAF Issuance)...
Issued at 127 PM EDT Thu Apr 30 2026

Impacts:

- Showers tonight at times, a rumble of thunder possible
- MVFR cigs after 06Z, IFR possible towards 10Z
- Isolated gusts to 20kts towards LAF this afternoon

Discussion:

VFR conditions with mostly clear skies expected through the
remainder of the day with only an isolated gust towards 20kts
possible at times. Rain chances begin to increase after 00Z with
best chances from 04Z to 09Z. As the rain arrives, cigs will drop to
MVFR with IFR possible towards 10Z. Vsbys will generally remain MVFR
during showers, but a rumble of thunder or two will be possible
along with brief IFR vsbys. Any showers should end by 12Z with cigs
becoming VFR shortly after. WInds will remain northwesterly to
westerly through the period at 7-13kts outside of the isolated gusts
this afternoon.

&&

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

$$

AVIATION...White
DISCUSSION...White