491
FXUS63 KIWX 251115
AFDIWX
AREA FORECAST DISCUSSION
NATIONAL WEATHER SERVICE NORTHERN INDIANA
715 AM EDT TUE AUG 25 2026
KEY MESSAGES
- SEASONABLE TEMPERATURES, DRY CONDITIONS, AND MUCH LOWER
HUMIDITY CONTINUE TODAY. PATCHY FOG THIS MORNING.
- 40-70% CHANCES FOR RAIN AND STORMS WEDNESDAY AFTERNOON AND
EVENING. THERE IS A MARGINAL TO SLIGHT RISK FOR SEVERE WEATHER
WITH ALL HAZARDS POSSIBLE. MEDIUM CONFIDENCE.
- THERE IS A 20 PERCENT CHANCE FOR SHOWERS AND STORMS THURSDAY
AFTERNOON ALONG AND SOUTH OF US 24, MAINLY EAST OF INTERSTATE
69. THERE IS A MODERATE SWIM RISK ON LAKE MICHIGAN BEACHES IN
LA PORTE CO, IN AND BERRIEN CO, MI. WAVES OF 2-3 FEET AND
CURRENTS EXPECTED.
DISCUSSION
ISSUED AT 512 AM EDT TUE AUG 25 2026
SURFACE HIGH PRESSURE/UPPER LEVEL RIDGE IN PLACE OVER MUCH OF THE
AREA TODAY AND TONIGHT WILL KEEP WEATHER QUIET. EXPECT PARTLY TO
MOSTLY CLEAR SKIES, LIGHT WINDS, AND HIGHS IN THE 70S, LOW 80S.
OVERNIGHT LOWS WILL BE IN THE 50S. PATCHY FOG IS POSSIBLE THIS
MORNING.
SPC MARGINAL TO SLIGHT RISK FOR SEVERE STORMS WED...
THE UPPER LEVEL RIDGE BREAKS DOWN AND SHIFTS EASTWARD WEDNESDAY
ALONG WITH THE SURFACE HIGH AS AN UPPER LEVEL TROUGH ENTERS INTO THE
UPPER GREAT LAKES. THIS TROUGH WILL CROSS THROUGH OUR FORECAST AREA
AND INTO THE LOWER GREAT LAKES BY THURSDAY MORNING. THE
CORRESPONDING SURFACE LOW PRESSURE CROSSES NORTHERN ONTARIO/LAKE
SUPERIOR WEDNESDAY, LIFTING INTO QUEBEC BY THURSDAY AFTERNOON. THIS
BRINGS A COLD FRONT ACROSS OUR CWA WEDNESDAY AFTERNOON INTO LATE
WEDNESDAY NIGHT/THU AM. THERE COULD BE A FEW SHOWERS/NON-SEVERE
STORMS DURING THE LATE MORNING/EARLY AFTERNOON HOURS NEAR LAKE MI
AND IN OUR MI COUNTIES BEFORE WE SEE BETTER FORCING ARRIVE WITH THE
FRONT. ONCE THAT OCCURS, MODELS DEVELOP A CONVECTIVE LINE OF STORMS
(POSSIBLY INITIALLY DISCRETE) THAT DRIFT ROUGHLY EAST-SOUTHEASTWARD
THROUGH LATE EVENING. THE EXACT TIMING AND POINT OF INITIATION IS
STILL SLIGHTLY UNCERTAIN-SOME START THE CELLS OVER LAKE MI AND DRIFT
THEM EASTWARD ALONG I 80-90 BEFORE FILLING IN FURTHER SOUTHWESTWARD
WITH TIME, OTHERS DEVELOP A BROADER LINE INITIALLY AND EVENTUALLY
WEAKEN ON THE NORTH END, PUSHING THE GREATEST THREAT FURTHER
SOUTHWEST. IN SOME CASES, IT ALMOST APPEARS THE LAKE BREEZE OF LAKE
MI ENHANCES THE DEVELOPMENT, WHICH WOULD TRIGGER STORMS FURTHER EAST
OF THE LAKESHORE COUNTIES. HOWEVER, MOST OF THE GUIDANCE HAS THE
BEST SEVERE POTENTIAL DEVELOPING BETWEEN 4 PM-12 AM EDT. FORECAST
WISE, HAVE BROAD 40-70 PERCENT POPS FOLLOWING THIS GENERAL TREND AS
A FIRST START. GIVEN THE EARLIER ONSET TIME TO COINCIDE WITH PEAK
HEATING, CONFIDENCE IS SLIGHTLY HIGHER IN SEVERE WEATHER OCCURRING
THAN PREVIOUS FORECASTS. MODELS ARE ALSO SLIGHTLY HIGHER ON MID-
LEVEL LAPSE RATES (6.5C/KM)...THOUGH THEY STILL AREN'T REALLY THAT
GREAT. STILL, MUCH OF THE GUIDANCE HAS ABOUT 1500-2500 J/KG OF MIXED
LAYER CAPE BY THE AFTERNOON (SOME SUGGEST HIGHER FURTHER SOUTHWEST).
0-6 KM BULK SHEAR IS SLIGHTLY HIGHER THAN PREVIOUS RUNS SUGGESTED AS
WELL, ON THE ORDER OF 25-40 KTS. THIS IS ENOUGH FOR SUPERCELLS TO
DEVELOP (ESPECIALLY MODELS INDICATING THE HIGHER END OF THAT RANGE).
WITH ANY SUPERCELL DEVELOPMENT, WE HAVE ALL HAZARDS ON THE TABLE,
INCLUDING TORNADOES. 0-1 KM SHEAR VALUES (20 KTS) AND SRH VALUES
(AROUND 100 OR MORE), IN COMBINATION WITH LOW LCL'S CERTAINLY
SUPPORT THAT. THESE PARAMETERS WERE ALSO PART OF THE REASON FOR
INCREASED CONFIDENCE IN SEVERE WEATHER OCCURRING (MEDIUM
CONFIDENCE).
MOSTLY DRY OUTSIDE OF A LOW CHANCE (20 PERCENT) FOR SHOWERS AND
STORMS ALONG AND SOUTH OF US 24, MAINLY EAST OF I 69 ON THURSDAY.
NORTHWEST WINDS BEHIND THE FRONT WILL KICK UP LAKE MI WAVES TO
AROUND 2-3 FEET, WHICH IS A MODERATE SWIM RISK. CURRENTS ARE
EXPECTED. MONITOR THE BEACH FORECAST FOR MORE DETAILS.
SURFACE HIGH PRESSURE AND WEAK RIDGING BUILDS IN FRIDAY INTO SUNDAY,
ALLOWING FOR MOSTLY DRY CONDITIONS. HIGHS WILL BE IN THE UPPER 70S,
LOW TO MID 80S.
AVIATION /12Z TAFS THROUGH 12Z WEDNESDAY/
ISSUED AT 714 AM EDT TUE AUG 25 2026
VFR CONDITIONS ARE EXPECTED AT THE TERMINALS THROUGH THE PERIOD,
WITH LIGHT WINDS AND MAINLY HIGH CLOUDS TO CONTEND WITH.
IWX WATCHES/WARNINGS/ADVISORIES
IN...NONE.
OH...NONE.
MI...NONE.
MARINE...NONE.
DISCUSSION...MCD
AVIATION...MCD
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