Indiana’s Weather For Wednesday

HEADLINES
– Showers this morning and midday, mainly along and north of I-70.
– Additional rain chances Friday, mainly early and late.
– Drier and warmer for the weekend. Mid 70s! Into 80s next week.

TODAY’S MAP

NWS TECHNICAL DISCUSSION

The synoptic pattern has been dictated by an Omega Block over
Western North America over the last 5-6 days, with central Indiana
positioned just upstream of a quasi-stationary upper level trough.
This has led to weakly forced, broad cyclonic flow over the Ohio
Valley, of which has resulted in cooler than normal conditions and
sporadic showers.

This upper level trough will remain upstream of Indiana today with a
mid level vorticity lobe within this trough expected to push off to
the NW of central Indiana later this morning into the afternoon.
Initially, this will lead to a corridor of confluence, aiding in
moisture convergence and lift with numerous showers moving eastward
from central IL to northern IN. Forecast soundings show 3-6km
lapse rates around 6.5 C/km near this area of moisture
convergence. Although this instability will be weak and elevated,
any strongly forced shower may be able to tap into this, and
therefor isolated thunder will be added for NW areas of central
Indiana between 14-19Z.

Following the mid level shortwave passage, central Indiana will be
placed in an elevated warm sector with 700-500mb winds shifting
towards the West. Surface winds will remain more out of the WNW with
a surface low just to the NE. On the backside of the mid-level
shortwave, 600-400mb winds will increase rapidly in reponse to
modest height falls, leading to fairly strong speed shear from 850-
500mb. Lift will be present on the upstream side of this mid level
jet, and lingering surface moisture will likely still be present.
However, large amounts of dry air advection in the mid levels will
likely be a strong limiting factor in any precipitation development,
especially if updrafts are not strong enough to withstand dry air
intrustions. With that said, PBL mixing may allow for a corridor
of weak surface based instability and a few isolated stronger
updrafts, mostly over southern portions of central Indiana. Given
the moderate speed shear, any cells that do initiate and are able
to sustain themselves through the mid level dry air, will likely
be able to develop lightning, with some potential for isolated
small hail and gusty winds.

&&

.LONG TERM (Thursday through Tuesday)...
Issued at 306 AM EDT Wed May 28 2025

As mentioned in the short term, an Omega Block pattern has dictated
central Indiana`s weather over the last week. However, this will
begin to change late Thursday onward as a strong supergeostrophic
jet streak is able to push through the periphery of the Omega Block
inducing height falls south of the upper level trough. This is
expected to lead to a low pressure system by Thursday night over the
Mid-Mississippi Valley, of which will help aid in progression of the
upper level pattern.

Initially, this will lead to a conducive corridor for precipitation
development Thursday night into Friday. Ensemble still have some
variability on where the greatest coverage of showers and
thunderstorms will occur, but generally this is expected to be most
prevalent over the southern Wabash Valley through the lower Ohio
Valley. Based on ensemble probabilities, the most likely scenario is
for the surface based instability ahead of this low to remain
generally south of the central Indiana, however there is enough
variability to not completely rule out surface based convection over
southern portions of the forecast area Thursday evening/night.
Effective bulk shear of around 50 kts, will be plenty enough to
support updraft organization, with CAMs starting to realize the
potential of upscale growth and MCS development. This will be
closely watched for severe wind potential within convection that
remains surface based. With how strong the surface low will be for
late May, elevated convection to the NE of the low may also pose a
marginal severe threat for wind and hail.

The aforementioned system should shift east by Friday night, but
additional impulses pivoting across the region will keep low chances
for rain in the forecast at times over the weekend. Saturday appears
to be the most favorable time for precipitation as some guidance
depicts a shortwave approaching, but diverging model solutions leads
to lower confidence. Available moisture is also rather subtle which
limits rain chances. POPs remain capped at 20% or lower for these
reasons. Temperatures are likely going to moderate slightly over the
weekend once the initial shortwave shifting east allows for warmer
850mb temperatures to filter in.

Despite larger model spread towards the end of the extended,
guidance generally depicts upper ridging building over the central
CONUS. Large scale subsidence from the upper ridge will likely
provide quiet weather early next week. Temperatures are also
expected to warm into the 80s due to warm air advection.

INDY SEVEN DAY FORECAST
Today: Mostly cloudy. Scattered showers in the morning and midday. High 72.

Tonight: Partly cloudy. Low 54.

Thursday: Partly sunny. High 75.

Thursday Night: Partly cloudy. Spotty showers possible overnight. Low 56.

Friday: Partly to mostly cloudy. Spotty showers possible, especially in the early morning and late afternoon. High 73.

Friday Night: Scattered showers possible. Low 57.

Saturday: Mostly sunny. High 77.

Saturday Night: Partly cloudy. Low 52.

Sunday: Mostly sunny. High 77.

Sunday Night: Mostly clear. Low 55.

Monday: Mostly sunny. High 82.

Monday Night: Clear. Low 61.

Tuesday: Sunny. High 85.

NWS CHARTS FOR TODAY/TONIGHT