textproduct: Northern Indiana

KEY MESSAGES

- There is a 30-60 percent chance of rain on Sunday with a few thunderstorms possible south of US-24. Severe weather is not expected.

- Highs drop into the 40s for Monday but slowly climb back to the 60s by Thursday.

- Dry conditions are expected Monday through Wednesday but additional rain is likely on Thursday.

DISCUSSION

Issued at 145 PM EDT Sat Mar 21 2026

Main forecast concern is thunderstorm potential late tomorrow. A midlevel shortwave is currently entering the northern Great Lakes but becomes increasingly sheared with time as the mid/upper level flow briefly dampens and becomes more zonal late tonight. The most notable aspect of the system at this point is strong low level WAA. Lows tonight likely remain in the 50s given steady southwest wind/WAA. This strong W/SW flow advects modest surface dewpoints (mid/upper 50s) into the area along with a notable EML (midlevel lapse rates over 8 C/km). However, this also results in a strong capping inversion around 750mb for much of the day. The trailing surface cold front that crosses our CWA tomorrow arrives very early, reaching the US-24 corridor by 15-16Z. This significantly limits the potential for surface-based diurnal destabilization and, outside some broad low level convergence, this front doesn't have much available forcing for ascent (certainly not enough to overcome a strong cap, at least until a secondary shortwave arrives later tomorrow evening). In fact, forecast soundings show virtually no opportunity for surface-based convection with a strong cap ahead of the front and significant 1000-850mb CAA behind the front. There is still some postfrontal MUCAPE available as midlevel lapse rates remain on the high side but depth and strength of low level stable layer suggests small hail as the only potential threat. By the time the secondary shortwave arrives and diurnal destabilization is maximized (21-03Z), the surface front is already well SE of our area. Will maintain a thunderstorm mention and won't rule out some small hail south of US-24 but overall the severe risk appears very low.

Rest of the forecast is relatively quiet as Canadian high pressure settles into the region for the Mon-Wed period. Highs Monday drop into the 40s with 850mb temps near -5C. Slow but steady moderation expected on Tue with WAA really ramping up late Wed. This will be our next chance of precip, particularly into Thu as another modest wave crosses the northern Great Lakes and sends a sharp cold front through our area. This system looks very similar to Sunday with decent theta-e advection ahead of the front but lackluster mid/upper level support for ascent in our area. Still plenty of time for adjustments here though.

AVIATION /18Z TAFS THROUGH 18Z SUNDAY/

Issued at 1225 PM EDT Sat Mar 21 2026

Pesky IFR stratus deck at KFWA should mix out here shortly with mainly VFR to follow this afternoon into Sunday morning. There has also been some patches of MVFR haze across northern IN so far today. Expectations are for this to lift north by 19/20z as as winds veer to the south-southwest and pick up a bit. LLWS conditions are still anticipated in advance of a cold front tonight, with fropa anticipated around 11/12z Sun at KSBN, and toward midday at KFWA. Winds will turn northerly in it's wake with flight conditions possibly lowering into MVFR. Anafrontal forcing then generates increasing chances for showers Sunday afternoon, mainly at KFWA.

IWX WATCHES/WARNINGS/ADVISORIES

IN...None. OH...None. MI...None. MARINE...Small Craft Advisory from noon Sunday to 3 PM EDT Monday for LMZ043-046.