Indiana’s Weather For Memorial Day

HEADLINES
– After the coolest Indy 500 in decades, Memorial Day will be warmer.
– Rainy Tuesday, spotty chances Wednesday morning, and late Thursday and Friday.
– Warmup begins Wednesday into the weekend.

TODAY’S MAP

NWS TECHNICAL DISCUSSION

High pressure over the Great Lakes keeps the cooler airmass in place
over the surface today, while an area of low pressure and associated
frontal boundary slowly nudge northeastward by tonight. Increasing 
moisture advection aloft will lead to thickening cloud cover the 
latter half of the day from south to north. Temperatures
will still be below normal for this time of year; however drier
conditions today and a few peaks of sunshine should result in highs
in the upper 60s to lower 70s. Winds remain elevated through the day
as the pressure gradient tightens ahead of the approaching low.
Afternoon surface heating and low level mixing should result in wind
gusts of 15-25 mph this afternoon before diminishing around sunset.

Low pressure tracks out of the southern Plains today, reaching the
Missouri bootheel by Monday evening. Deeper moisture will expand
towards the Ohio Valley in advance of the surface low but remnant
dry air within the boundary layer will keep any showers from lifting
into the lower Wabash Valley until early Tuesday morning. Expect
lows tonight a bit warmer than the past several nights as clouds and
elevated winds keep temperatures in the mid 50s.

&&

.LONG TERM (Tuesday through Sunday)...
Issued at 305 AM EDT Mon May 26 2025

An end is in sight to the extended stretch of cooler weather the
entire region has been experiencing over the last 7-10 days...but
first we have to get through at least the first half of this coming
week before the real warming trend begins toward the weekend

For the long term period, a broad trough over the North Central US
deepens and meanders over the Upper Great Lakes region through the
end of the week, keeping a cooler and wetter weather pattern over
Central Indiana. Waves rotating about the low within the jet and
their associated surface reflections increase rainfall chances
locally early Tuesday through Wednesday.

.Tuesday through Thursday...

Early Tuesday, low pressure rides along the warm front slowly
pushing northward into Southern Indiana bringing the best
opportunity for widespread rain and embedded thunderstorms to most
of the region. The focus for greatest convective coverage is south
of the I-70 corridor, in closest proximity to the warm front and
track of the surface low. Forecast soundings indicate a fairly
stable atmosphere, with little to no chance of severe weather
locally. Would not be surprised to see isolated thunder and
lightning, especially for the southern half of the state closer to
the warm front. The surface low lifts through Indiana Tuesday night,
maintaining at least the potential for scattered showers through the
night. Widespread clouds and rain with easterly flow keeps
temperatures below normal again with highs stuck in the 60s.

Indiana remains in a cyclonic flow pattern the remainder of the work
week as the surface low pushes northeast into Canada and the upper
trough hangs back over the Great Lakes region with weak waves
passing by overhead. Mid range guidance has been consistent with
showing a weak wave/jet streak rounding the trough and moving
overhead on Wednesday. Forecast soundings show just enough moisture
near the surface under a low/mid level inversion to keep clouds and
at least a chance for light showers around. A similar situation is
also possible Thursday afternoon. High pressure slowly approaching
from the west advects in a drier airmass by then, but a similar mid
and upper level pattern with another wave riding through the jet may
provide enough lift to spark off a few afternoon showers Thursday
afternoon as well. Keeping highs a few degrees cooler on Wednesday
in the upper 60s to near 70 due to thicker low level clouds, but by
Thursday most areas should at least reach the low to mid 70s with
increasing sunshine. Fortunately, the cooler airmass in place will
be slowly eroding mid to late week as strong ridging over the
Central US shifts a much warmer airmass closer to Indiana.

.Late Week into Next Weekend...

The forecast becomes more uncertain for toward next weekend with
widespread run to run inconsistencies among various model guidance.
Models have been hinting at another wave/low tracking across the mid-
south late week bringing a threat for more widespread showers and
storms for portions of the Ohio Valley. There has been some
consistency in keeping precipitation chances south of the Ohio
River, keeping Central Indiana relatively dry.

Confidence is moderate to high that a pattern should develop in the
extended range which supports warmer temperatures closer to normal.
Lower confidence exists in the actual evolution of smaller waves,
which could impact sensible weather locally going into next weekend
and beyond. Latest guidance shows a northwest flow pattern
developing aloft over Indiana while stronger ridging builds over the
Central US, with the core of the heat remaining west of the region.
For now, keeping a warming trend toward the upper 70s to lower 80s
through this weekend as this seems to be the most plausible
scenario. Although as forecast confidence increases on more subtle
features, more detail will be added regarding any rain or storm
chances in this period.

NWS CHARTS FOR TODAY/TONIGHT