860
FXUS63 KIWX 151852
AFDIWX
AREA FORECAST DISCUSSION
NATIONAL WEATHER SERVICE NORTHERN INDIANA
252 PM EDT FRI AUG 15 2025
KEY MESSAGES
- HOT AND HUMID THIS WEEKEND WITH HEAT INDICIES IN THE 90S TO
NEAR 100 DEGREES.
- THERE IS A MARGINAL RISK OF SEVERE THUNDERSTORMS SATURDAY
AFTERNOON AND EVENING (20-40% CHANCE OF STORMS).
- ADDITIONAL CHANCES (20-50%) FOR STORMS PERSIST EARLY NEXT
WEEK.
DISCUSSION
ISSUED AT 249 PM EDT FRI AUG 15 2025
MESOSCALE FACTORS WILL BE AT PLAY WITHIN THE NEXT 24 HOURS,
DICTATING HOW OUR THUNDERSTORM CHANCES EVOLVE INTO SATURDAY
AFTERNOON. A SHORTWAVE TROUGH IS SEEN ON WATER VAPOR MOVING ACROSS
MINNESOTA. THUNDERSTORMS ARE DEVELOPING OVER IOWA THIS AFTERNOON AND
ADDITIONAL DEVELOPMENT IS ANTICIPATED INTO SOUTHWEST WISCONSIN BY
THIS EVENING PER HREF MEMBERS. UPSTREAM ACTIVITY WILL WEAKEN AS IT
TRACKS EAST DUE TO OUR LINGERING RIDGE AND SUBSEQUENT CAPPING ALOFT.
THIS OUGHT TO MAKE FOR A SOMEWHAT CLOUDY START TO SATURDAY
(ESPECIALLY IN CENTRAL AND WESTERN INDIANA/MICHIGAN) FOLLOWED BY
INCREASING CHANCES FOR AFTERNOON THUNDERSTORMS SO LONG AS THE
ATMOSPHERE DESTABILIZES. STORMS APPEAR MOST LIKELY AS EARLY AS ABOUT
2 TO 5 PM EDT. AS MENTIONED IN THE PREVIOUS DISCUSSION, DAMAGING
WIND GUSTS FROM THUNDERSTORMS WILL BE THE PRIMARY HAZARD. HOW
WIDESPREAD SEVERE STORMS ARE IS UNCERTAIN AND CONFIDENCE IN SEVERE
WEATHER OCCURRING IS MEDIUM (FAVORABLE ENVIRONMENT, BUT
RECOVERY FROM THE MORNING WILL BE ESSENTIAL).
NORTHWEST FLOW ALOFT PERSISTS INTO SUNDAY RESULTING IN ANOTHER
CLUSTER OF STORMS RIDING ATOP THE RIDGE AND SPILLING INTO OUR AREA.
DETAILS ARE SPARSE IN SUCH A MESOSCALE-HEAVY ENVIRONMENT. BUT POPS
HERE SUNDAY MORNING, WANING INTO THE AFTERNOON, ARE REASONABLE.
HOT A HUMID THIS WEEKEND WITH HEAT INDICIES WELL INTO THE 90S
AND EVEN 100 DEGREES SOUTH OF US 24. IN CONTRAST, NOT AS HOT IN
SOUTHERN MICHIGAN ESPECIALLY SUNDAY WITH ANTICIPATED
THUNDERSTORM CLOUD COVER.
ADDITIONAL UPPER-LEVEL IMPULSES MOVE THROUGH OUR AREA MONDAY AND
TUESDAY BRINING AN ADDITIONAL CHANCE FOR STORMS. THIS ACTIVE, HOT
PATTERN EASES BY MIDWEEK WITH COLLAPSING HEIGHTS AMID A DEEPENING
UPPER-LEVEL LOW OFF THE NORTHEAST US COAST. THIS WILL PERMIT
TEMPERATURES CLOSER TO NORMAL, IF ONLY SLIGHTLY ABOVE THE NORMAL
HIGH IN THE LOW-80S. ADDITIONAL RELIEF FROM THE HEAT IS ON THE
WAY FOR NEXT WEEKEND THANKS TO A CANADIAN COLD FRONT.
AVIATION /18Z TAFS THROUGH 18Z SATURDAY/
ISSUED AT 1254 PM EDT FRI AUG 15 2025
MAJORITY OF THE TAF PERIOD IS ANTICIPATED TO BE TROUBLE-FREE
AMID LINGERING HIGH PRESSURE AND UPPER-LEVEL RIDGING. GENERALLY
LIGHT WIND WITHIN THIS PATTERN. CANNOT RULE OUT PATCHY GROUND
FOG NEAR DAYBREAK SATURDAY. MESOSCALE FACTORS WILL BE AT PLAY
FOR THE RISK OF THUNDERSTORMS JUST BEYOND THIS TAF PERIOD.
THUNDERSTORMS ACROSS IA AND WI THIS EVENING WILL WEAKEN AS THEY
TRACK EAST AND ANY OUTFLOW BOUNDARY FROM THOSE STORMS WILL BE
THE FOCUS FOR SATURDAY AFTERNOON AND EVENING STORMS LOCALLY.
IWX WATCHES/WARNINGS/ADVISORIES
IN...NONE.
OH...NONE.
MI...NONE.
MARINE...NONE.
DISCUSSION...BROWN
AVIATION...BROWN
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