Indiana’s Weather For Wednesday

HEADLINES
– Bad news: cooler than average, still spotty showers today and tomorrow.
– Good news: done with storms TFN.
– Wind gusting to 35 mph today and tomorrow.
– Some sun Friday and Parade Day.
– Scattered showers from around midnight to 9am Race Morning.

TODAY’S MAP

NWS TECHNICAL DISCUSSION

A dreary and cool weather pattern continues over the next several
days for Central Indiana as the region remains under the influence
of a deep trough and area of low pressure.

.Today...

Satellite imagery early this morning shows the low over Northern
Illinois with widespread stratus wrapping around it and into Central
Indiana. ACARs soundings indicate a nocturnal inversion setting up,
trapping low level moisture near the surface. This should result in
stratus becoming more widespread and possibly lowering through the
morning hours. Cold air advection pushing in aloft will steepen low
level lapse rates through the day despite minimal surface heating. A
strong low level jet aloft combined with steeper lapse rates will
also lead to a breezy day as gusts 25 to 35 mph mix down to the
surface, beginning mid to late morning and persisting through around
sunset. Still expect elevated winds of 10 to 20 mph to persist into
the late evening and overnight hours tonight, but gusts should begin
to diminish. Highs for today are expected to remain well below
average for late May, only in the 60s.

Weak waves of energy rounding the trough should spark off isolated
to scattered showers later this morning and into the afternoon. The
best chance for any showers is along and north of I-70, closer to
the surface low where better forcing is. Not expecting widespread
rainfall or a complete washout though.

.Tomorrow...

Similar weather conditions expected on Thursday as Indiana remains
in a cyclonic flow pattern under the influence of a deep trough over
the Great Lakes and a quasi-stationary low over Lake Ontario.
Reinforcing waves of energy coming down from Canada will wrap around
the backside of the trough and into Indiana providing just enough
lift within a the moist airmass to spark off showers. Continued cold
air advection aloft, steep low level lapse rates, and sufficient low
level shear will make for an environment conducive for scattered
shower activity much of the day Thursday as well, with the potential
for a few low topped convective showers and an isolated lightning
threat. No severe weather is expected.

Depending on how widespread the showers are on Thursday, highs may
not get out of the upper 50s for portions of North Central Indiana.
Elevated winds of 10-20 mph with higher gusts will make it feel even
colder, a pattern more similar of early Spring, rather than late
May.

The low begins to pull away by Thursday night as high pressure over
the Plains nudges eastward. Expect a drying trend during the
overnight hours with clouds beginning to clear. Surface winds should
remain elevated enough to keep temperatures from plummeting,
however with such a cold airmass in place, expect lows in the low to
mid 40s.

&&

.LONG TERM (Wednesday night through Tuesday)...
Issued at 258 PM EDT Tue May 20 2025

Friday and Saturday...

Relatively drier, yet still cooler weather arrives for the end of
the week and into the weekend for Central Indiana as lower pressure
finally exists to the northeast and high pressure becomes the
dominant weather influence over the region.

An elongated area of high pressure drops south from Canada Friday
and moves overhead as it slowly nudges eastward this weekend. The
source region of this high is from Central and Northern Canada, so
despite drier conditions and increasing sunshine, the airmass is
still going to be quite chilly. Good conditions for radiational
cooling set up both Friday and Saturday morning, allowing
temperatures to quickly drop by sunrise into the low to mid 40s. Low
lying wind sheltered areas will be the coldest spots each morning.
Would not be surprised to see isolated pockets of upper 30s in these
lower lying locations outside of urban areas. Not too concerned with
a frost threat though.

Went a little above guidance for highs Friday and Saturday as strong
solar heating and the high late May sun angle will likely lead to
very steep low level lapse rates and deep mixing during the
afternoon hours. Increased highs a few degrees into the upper 60s
for most locations.

Sunday through early next week...

A wetter weather pattern returns by early next week as the storm
track sets up across the Ohio Valley once again. By Sunday, a trough
begins to dig southward over the Front Range, inducing surface
cyclogenesis over the Southern Plains by Monday. The main storm
track and associated thermal gradient/boundary should extend from
South Dakota southeastward into Kentucky, with Central Indiana being
on the northern fringe. High pressure to the north and northeasterly
low level flow will keep a cooler airmass across the region, while
warm, moist air is confined to south of the warm front within the
Southern and Central Plains. Will have to watch where the strongest
thermal gradient sets up along with associated frontal boundaries,
as this will be the likely area for complexes of storms to track.

Confidence is increasing for a high rainfall threat for Southwest
and Southern Indiana during this period, so have increased PoPs to
Likely end of the weekend and into early next week. Most guidance
shows a few complexes of storms developing over The Plains and
weakening as they propagate ESE. While there are discrepancies
between models, the general agreement is for the storm track to
favor the southwest half of central IN or locations further south
around Sunday morning. Will continue to watch for trends as this
track is slightly further northeast compared to yesterday. There may
be a sharp SW to NE precip gradient in this pattern, with PoPs
diminishing quickly as one goes further NE. Keeping PoPs at or below
30 percent for the Indianapolis area as confidence is rather low at
the moment in precipitation making it up to the I-70 corridor Sunday
and Monday. Watching the Monday night into Wednesday for increasing
rainfall chances for all of Central Indiana as as area of low
pressure rides along the aforementioned boundary into the region.

Temperatures during this time will remain below normal for this time
of year with highs only in the 60s. Increasing clouds and moisture
should allow for slightly more mild lows in the 50s, compared to low
to mid 40s earlier in the period. &&

.AVIATION (06Z TAF Issuance)...
Issued at 148 AM EDT Wed May 21 2025

Impacts:

- MVFR/IFR ceilings at times through the period

- Winds becoming westerly, increasing to 15-20 kts after 14z

Discussion:

Satellite and radar imagery shows the majority of the showers and
storms weakening and pushing south of the region at this hour. ACARs
sounding shows a weak nocturnal inversion setting up just above the
surface, which may trap leftover moisture in the boundary layer and
result in low stratus. Cigs widely vary over Central Indiana tonight
with a few locations already reporting IFR cigs. Lower confidence in
how widespread low ceilings will be; however satellite is showing
more widespread MVFR/VFR stratus already developing. Keeping cigs at
Bkn035 at the moment as upstream observations indicate the stratus
deck around this level. Would not be surprised to see lowering cloud
bases by sunrise to MVFR levels or lower.

Central Indiana remains under the influence of an area of low
pressure over the next 24 hours, which will keep lower clouds and
scattered showers around. Expect another wave to rotate into the
state within the 13-15z timeframe this morning, bringing widespread
MVFR cigs and scattered showers. This pattern should persist through
the day. Brief periods of MVFR or worse cigs and vis possible under
any shower, however coverage of shower activity should be far less
than what has been observed the past few days.

Forecast soundings indicate steepening low level lapse rates as cold
air moves in aloft later today. With a strong low level jet
overhead, expect westerly wind gusts of 25-30 kts to mix down to the
ground beginning shortly after sunrise and persisting into the
evening hours.

&&

INDY SEVEN DAY FORECAST
Today: Mostly cloudy, with winds gusting to 35 mph. Scattered showers at times. High 63.

Tonight: Mostly cloudy. Isolated shower possible. Low 49.

Thursday: Mostly cloudy and breezy, with spotty showers, mainly in the morning. High 57.

Thursday Night: Clouds decrease. Low 43.

Friday: Partly sunny. High 63.

Friday Night: Partly cloudy. Low 44.

Saturday: Partly sunny. High 67.

Saturday Night: Partly to mostly cloudy. Scattered showers overnight. Low 50.

Sunday: Mostly cloudy, with spotty showers, mainly in the morning. High 65.

Sunday Night: Mostly cloudy. Low 47.

Memorial Day: Partly to mostly cloudy. High 68.

Monday Night: Mostly cloudy. Low 51.

Tuesday: Mostly cloudy. Scattered showers. High 70.

NWS CHARTS FOR TODAY/TONIGHT