FXUS63 KIWX 190605

AFDIWX



Area Forecast Discussion

National Weather Service Northern Indiana

205 AM EDT Tue Aug 19 2025



.KEY MESSAGES...



- Chances of showers and storms (30-55%) tonight into Tuesday. 

  Severe weather is not expected at this time, but a few storms 

  could produce some locally heavy rainfall and gusty winds to 

  40 mph.



- Remaining hot and humid Tuesday with heat indices in the 

  upper 80s to middle 90s.



- Confidence increasing in cooler and drier conditions mid-late

  week into early next week.



&&



.DISCUSSION...

Issued at 242 PM EDT Mon Aug 18 2025



Showers and thunderstorms that originated along the IN-IL line this 

morning have refused to diminish and continue to slide slowly 

east. This is despite a dry, easterly surface wind, weak flow 

aloft, modest instability and poor shear. Storms developed on a 

remnant outflow boundary from overnight storms and have been 

aided by an warm front nosing into Illinois. This activity is 

becoming outflow dominant which makes additional eastward 

progress questionable. Subtle low-level capping is in place as 

well. 



In far northern Illinois, thunderstorms have begun to develop on the 

interface of not only the warm front, but the outflow boundary of a 

Wisconsin MCS. This activity has flat-lined a bit and has otherwise 

been poorly modeled today. Should an organized line develop over 

Illinois this afternoon, it will encounter a stable air mass from 

the ongoing storms over far northwest IN. Instead, the area to watch 

this afternoon and evening is over eastern IA, squarely in the warm 

sector of this low moving through the upper Midwest. Satellite in 

eastern Iowa is beginning to bubble up with cumulus which could be 

the origin of tonight's storms. The best upper-level forcing will be 

north of our area and instability and shear continue to be limited 

locally. This minimizes the overall severe weather risk locally, yet 

the strongest of storms could produce damaging wind gusts. Heavy 

rain rates are expected as well, with 1" per hour rates possible. 



Decaying showers/storms linger into Tuesday morning followed by

possible reinvigoration along and east of I-69 Tuesday 

afternoon as long as instability can blossom as advertised. 

Shear will remain poor, limiting the overall severe risk, but 

the cold front will provide ample forcing. 



In the wake of the cold front, not has humid, with dew points in the 

60s Wednesday. A stretch of dry weather is anticipated 

Wednesday through at least the start of the weekend. There is 

only a slight chance of showers Saturday afternoon as a 

moisture- starved cold front moves through. This cold front will

bring a refresh dose of Canadian air resulting in Sunday high 

temperatures in the 70s.



&&



.AVIATION /06Z TAFS THROUGH 06Z WEDNESDAY/...

Issued at 151 AM EDT Tue Aug 19 2025



VFR conditions to start the TAF period, deteriorating to

MVFR/IFR, particularly at KSBN overnight into Tuesday. A

decaying line of storms is moving towards KFWA this evening,

with the outflow moving through as of this writing. Light winds

may temporarily shift north/be variable for a bit before

shifting back to the southeast. Additional storms are on Lake MI

right now and will move through KSBN around 8z-12z, with

IFR/MVFR visibilities and ceilings possible. Behind that as the

front and winds shift to the W-NW, we could see some drizzle or

light rain persist through 17z or so-with ceilings around

700-1500ft. Expect improvement to MVFR by the afternoon. KFWA

will see rain pass between 13-17z, with showers and storms

lingering in the vicinity until around 20z. VFR conditions will

then persist through the end of the TAF Period. 



&&



.IWX WATCHES/WARNINGS/ADVISORIES...

IN...None.

OH...None.

MI...None.

MARINE...None.



&&



$$



DISCUSSION...Brown

AVIATION...MCD