FXUS63 KIWX 261733

AFDIWX



Area Forecast Discussion

National Weather Service Northern Indiana

133 PM EDT Thu Jun 26 2025



.KEY MESSAGES...



- Hot and humid conditions will cause heat indices to rise to

  near 100 degrees today, prompting another Heat Advisory for 

  all areas.



- Highs will be in the upper 80s to around 90 through Monday with 

  heat indices generally in the 90s to around 100 degrees.



- Scattered to numerous mainly afternoon and evening

  thunderstorms are forecast through Monday. Severe weather

  should be limited to a locally strong to severe storm wind

  gust. Locally heavy rainfall in likely with every storm.



&&



.DISCUSSION...

Issued at 257 AM EDT Thu Jun 26 2025



The upper level ridge remained over the Ohio Valley region early 

this morning. The subsidence and warming associated with this system 

was contributing to the hot and humid condition over the past 

several days over northern Indiana and surrounding areas. The 

500 mb height anomaly associated with this system was still over

100 meters above normal. The upper level ridge will gradually 

weaken and should drift east, allowing a very slow cooling trend

the next few days. Concern for the lengthening of the heat wave

that is now beginning the 6th day. Highs at both South Bend and

Fort Wayne have been between 90 and and 94 degrees every day of

this heat wave since Saturday. Caveats on the hot side include 

urban areas and locally lower elevations that may be a few to 

several degrees warmer than surrounding areas. Numerous locations

yesterday recorded heat indices between 105 and 107. The moisture

depth in the lower layers was deep enough to prevent mixing of 

drier air aloft, especially with a weak cap at the base of a 

weak subsidence inversion. We are planning to issue a Heat 

Advisory for all of our forecast area just for today. Heat 

indices Friday are more uncertain given the likelihood of outflow

boundaries and more widespread rain-cooled air.



As far as thunderstorms are concerned, conditions today should 

be very similar to yesterday with storms beginning to form after

16Z (noon EDT). Coverage of storms should be greater than 

yesterday given a decrease in subsidence and given a weak and 

diffuse front across the area. Storm movement should be slow to 

non-existant, especially considering meso-beta velocity elements

with virtually no movement - locally heavy rainfall is likely 

with every thunderstorm. 



Except for relatively brief cooling Saturday in the wake of a

weak cold front, the hot and humid conditions will persist

through Monday. Additional heat headlines are likely.



&&



.AVIATION /18Z TAFS THROUGH 18Z FRIDAY/...

Issued at 133 PM EDT Thu Jun 26 2025



Tstms have fired across southern MI between the I94 and I80

corridors while more widely sctd across nrn IN.This trend is

expected to continue through the rest of the aftn and evening

period, so will emphasize the SBN terminal site for convection 

through 00Z. Thus far, the storms have remained below svr

criteria as they are pulse in nature. The flow is predominately

SW for both sites and will carry this into the night hours then

winds turn more southerly overnight at KSBN. The heat and

elevated humidity levels continue Friday and coupled with the 

upper ridging weakening, expect a continuation of tstm 

development with daytime heating.





&&



.IWX WATCHES/WARNINGS/ADVISORIES...

IN...Heat Advisory until 8 PM EDT /7 PM CDT/ this evening for 

     INZ005>009-012>015-017-018-020-022>027-032>034-103-104-

     116-203-204-216.

OH...Heat Advisory until 8 PM EDT this evening for OHZ001-002-004-

     005-015-016-024-025.

MI...Heat Advisory until 8 PM EDT this evening for MIZ078>081-177-

     277.

MARINE...None.



&&



$$



DISCUSSION...Brown

AVIATION...MF

