Indiana’s Weather For Thursday

HEADLINES
– Near-record high today, with increasing humidity.
– Severe storms threat after sunset tonight.
– Another threat Friday evening, especially south of I-70
– Nice weekend!

TODAY’S MAP

NWS TECHNICAL DISCUSSION

Going into the day, a cap should keep much of the day dry. Can`t

rule out something breaking through though if an area of the cap is

weaker than the rest, so will keep some slight chance PoPs in the

afternoon.

The air will be very warm for mid-May, with highs today in the mid

80s to near 90. Given the expected lack of convection, there will be

enough sunshine to boost temperatures to near record levels.

However, some areas that saw a lot of rain yester may have a harder

time reaching these levels thanks to the wet ground.
---Severe potential on Thursday---
A pronounced and pristinely maintained elevated mixed layer capping

a warm/moist PBL will lead to strong instability across our region

today. This EML is being carried eastward from its source region in

the central Rockies by strengthening westerlies at the base of

closed/deep low migrating across the northern Plains. There is about

a 75-mile spread in the position of the attendant Pacific front that

will serve as an initiating boundary and this is one element of

uncertainty in the severe thunderstorm risk. The other is whether or

not the trough`s geometry, position, and timing will be enough to

effectively lift the capping EML this far south. If convection does

form, the parameter space would support severe thunderstorms,

including supercells with the potential for significant severe.

Scenarios, and reasonable best- and worst-case scenarios are covered

below.
Scenario #1 Little/no convection forms this far south precluding a

convective hazard threat.
Analysis: Either, (1) diurnal destabilization and frontal

convergence are not a match for the magnitude of the capping EML,

and/or (2) trough lags and is less amplified (there has been a

slight multi-run trend toward this).
Scenario #2 Convection initiates, likely well west of our area near

the Mississippi River, and sustains eastward into central Indiana.

(Subjectively, this has the highest chance of occurance between the

scenarios, but still just 50-60% occurance)
Analysis: Once convection initiates, as midlevel thermal ridge moves

eastward and slight ascent/cooling overspread the area, residual

strong instability into the evening would sustain convection. There

may be a tendency for storm mode to be less organized and rooted

within moist/ascent layer aloft, atop the EML, thereby limiting the

severe magnitude some. With any convection that can overcome

inhibition from strong capping EML and remain deeply rooted in the

PBL, a more substantive severe threat would be possible with very

large hail the primary threat, though all hazards are possible.
Scenario #3 Intense/mature supercells sustain into central Indiana

during the evening with accompanying significant magnitude severe.
Analysis: If strong capping EML weakens sufficiently and supercells

are more easily able to deeply root in the PBL traversing central

Indiana well into the evening, all severe hazards are possible,

including a tornado threat. Elongated middle portion of the

hodograph favor very large hail in this scenario. This is a less

likely scenario since ascent needed to lift the capping EML appears

insufficient given the characteristics and timing of the parent

trough and so the higher-end scenario will likely be confined to the

Great Lakes region, north of our area.
In scenario #2 or #3, convection may persist into late evening or

even overnight along the trailing and decelerating Pacific front

across roughly the southern one half to one third of Indiana. Later

in the night, convection should mostly or completely diminish as

forcing for ascent isn`t particularly robust and some capping may

remain. Further, the front will become ill-defined as low-level flow

veers, and there is a weak warm/moist advection signal at best.

There is a low probability scenario of warm/moist advection being

just sufficient enough to interact with trailing boundary keeping

some convection going over southern Indiana into the pre-dawn hours.

More likely, expecting any lingering showers and storms to move off

to the SE prior to daybreak Friday.
&&
.LONG TERM (Friday through Wednesday)...

Issued at 330 AM EDT Thu May 15 2025
Friday and Friday night...
Severe storm potential to continue into the early long term as the

parent system continues to spin in a near-stationary position over

the Upper Midwest...with the corresponding cold front/boundary

slowly approaching and then only crossing central Indiana during the

Friday night period.  This will present a longer residence of again

very warm and somewhat humid air that will be maintained by

southwesterly surface flow gusting to 20-25 mph for most locations

Friday afternoon.  While, by the numbers, overall theta-e will be

lower than the Thursday set-up, better forcing between the

approaching boundary and mid-level differential PVA (mainly during

the late day and early evening hours) will present an equal to

perhaps greater overall chance for strong to severe storms for the

24 hours through Friday night.
High to inordinate instability in the afternoon along with moderate

to high mid-level lapse rates will fuel convective initiation.

Instability drops markedly with sunset, yet continuation of 40-60 kt

of bulk shear should help maintain any established cells into

evening hours.  Supercells will be most likely south of I-70 in

afternoon-late day hours, perhaps originating to the southwest of

the region.  Large hail will certainly be on the table, as will at

least a brief window for tornadoes in any rotating cells, although

the somewhat scattered/transient areas of higher low-level helicity

may partially mitigate this threat.  Faster storm motion around 40-

50 kt to the east-northeast will hopefully limit any flooding threat

to strongest supercells...with strong/severe winds becoming the

greatest concern as storms perhaps mature towards a QLCS habit into

the evening hours.  Given some uncertainty on timing/proximity of

approaching/crossing boundary, all severe weather modes will be on

the table for all portions of the CWA...with along/south I-70

overall favored for greatest density of severe weather...and the

modes most likely exhibiting a trend from more to less hail/tornado

and from less to more damaging winds.  Stay tuned for updates to

this evolving situation today through Friday.
Saturday through Wednesday...
This weekend will see a return to quieter conditions as weak ridging

builds into central Indiana under a kicking mid-level zonal flow.  A

stray shower can`t be ruled out as the late-week storm system

finally departs eastward across the Great Lakes, with mainly FEW/SCT

decks amid lower precipitable water and near-seasonable dewpoints

around 50F.  Most noteworthy weekend feature will likely be robust

westerly gusts Saturday courtesy of the gradient along the belly of

the trough passing to the north.
Noticeable change in most recent guidance looking ahead to next

Monday-Wednesday as what had been looking like favorable conditions

under broad central US ridging...may not be instead trending to a

more progressive weather system spreading an elongated west-east

warm/stationary frontal zone near the Midwest for at least several

periods as corresponding surface low pressure gradually ejects from

the central Plains to the Midwest/Ohio Valley.  This will bring both

chances for RW/TRW across the region...but also less confidence in

where potentially greater rainfall/stronger storms may occur with

uncertainty in both frontal position and timing of any better

forcing crossing the region.  Overall greater chances for perhaps

occasional rounds of storms towards southern counties which would

have potentially more frequent/longer residence in the warm sector

plus greater deep moisture.
Temperatures perhaps overall near normal with considerable

cloudiness keeping afternoon highs subdued despite above normal

heights.  The next overall rainy period should continue through the

end of the long term given the supporting wave`s quasi-cut-off

geometry and lack of any northern stream kicker until perhaps the

late week.  The normal max/min at Indianapolis through the long term

is 74/54.

&&

 
INDY SEVEN DAY FORECAST

Today: Partly sunny , hot and humid. Isolated afternoon shower possible. High 87.
Tonight: Spotty showers or storms in the evening, possibly severe. Low 68.
Friday: Mostly sunny and hot. Not as humid. High 86.
Friday Night: Scattered showers and storms. Some strong to severe. Low 62.
Saturday Mostly sunny. High 75.
Saturday Night: Partly cloudy. Low 54.
Sunday: Partly sunny. High 77.
Sunday Night: Partly cloudy. Low 52.
Monday: Partly sunny. High 74.
Monday Night: Partly cloudy.. Low 56.
Tuesday: Partly to mostly cloudy. Scattered showers and storms, mainly in the afternoon. High 76.
Tuesday Night: Scattered showers and storms. Low 62.
Wednesday: Partly to mostly cloudy, with scattered showers and storms. High 76.

NWS CHARTS FOR TODAY/TONIGHT










			
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