Area Forecast Discussion

KEY MESSAGES

- Freeze conditions expected tonight.

- Breezy with scattered rain showers this afternoon.

- After a cool start to the week, temperatures trend warmer starting Tuesday.

DISCUSSION

Issued at 134 AM EDT Sun Apr 19 2026

Skies are gradually clearing along the I-69 corridor early this morning as yesterday's cold front continues to track slowly east. Temperatures have remained somewhat elevated (low-40s) thanks to steady northwest wind due to a decent pressure gradient from the departing low. These winds diminish through the morning and there may still be enough time for at least patchy frost to develop. Dew points in the low-20s this hour suggest a quick drop of temperatures are favored once winds abate.

New for this forecast package is the inclusion of scattered showers this afternoon. A compact, mid-level wave is exiting the Dakotas this morning. Strong upper-level support, modest moisture profiles and non-zero instability point to diurnally-driven rain showers as this wave moves through. With the freezing level near 3,000 ft and - 10C around 6,000 ft, cannot rule out graupel from the strongest (tallest) showers this afternoon. This activity will diminish with sunset. Otherwise today, breezy and cool with northwest wind gusts near 30mph and high temperatures struggling to reach 50 degrees along and north of US 30.

The early Monday morning freeze watch has been upgraded to freeze warning. High pressure becomes centered over northern Illinois with 850-mb temperatures of -10C noted, good for widespread lows near 30; closer to 25 near Hillsdale, MI. With high pressure overhead, this makes high temperatures Monday the coolest of the week as highs hardly reach 50 degrees area wide.

A trough arriving onshore to the west coast shunts high pressure east by Tuesday. The result is a rapid warm up for the midweek period as an upper-level ridge develops over the Central US and eventually spreads over the Midwest. Rain chances this week are limited to a 20- 30% chance Tuesday night courtesy of shortwave aloft, and a 60% chance on Friday thanks to a cold front.

AVIATION /18Z TAFS THROUGH 18Z MONDAY/

Issued at 130 PM EDT Sun Apr 19 2026

A strong upper vort lobe will drop across the region this afternoon. Good low level mixing and dry airmass has led to sfc dew points bottoming out this afternoon. This should limit strength of surface based instability. Given strength of vort lobe and strong mid level cold pool would still expect isolated-scattered showers to progress through northeast Indiana but will be short-lived if they occur and in a brief temporal window from 19Z to 23Z. Winds will relax this evening with loss of boundary layer mixing, eventually becoming light and variable as a broad low level anticyclone drops across the Great Lakes and Ohio Valley.

IWX WATCHES / WARNINGS / ADVISORIES

IN...Freeze Warning from midnight EDT /11 PM CDT/ tonight to 11 AM EDT /10 AM CDT/ Monday for INZ005>009-012>015-017-018-020- 022>027-032>034-103-104-116-203-204-216. OH...Freeze Warning from midnight tonight to 11 AM EDT Monday for OHZ001-002-004-005-015-016-024-025. MI...Freeze Warning from midnight tonight to 11 AM EDT Monday for MIZ078>081-177-277. MARINE...Small Craft Advisory until 8 PM EDT this evening for LMZ043- 046.