472
FXUS63 KIWX 180515
AFDIWX
AREA FORECAST DISCUSSION
NATIONAL WEATHER SERVICE NORTHERN INDIANA
115 AM EDT TUE AUG 18 2026
KEY MESSAGES
- THE NEXT CHANCE OF RAIN ARRIVES TONIGHT AND PERSISTS THROUGH
WEDNESDAY.
- SEVERE WEATHER IS NOT EXPECTED BUT A FEW STRONG STORMS MAY BE
POSSIBLE IN FAR NW IN/SW MI LATE THIS EVENING. HEAVY RAIN IS
ALSO NOT EXPECTED.
- AFTER PLEASANT CONDITIONS THURSDAY AND FRIDAY, MORE LIGHT RAIN
IS EXPECTED ON SATURDAY.
DISCUSSION
ISSUED AT 115 AM EDT TUE AUG 18 2026
OVERALL A PLEASANT DAY TODAY AS HIGH PRESSURE AND THETA-E TROUGH
REMAIN OVER INDIANA. AFTER A COOL START, HIGHS TOP OUT AROUND 80F
WITH DEWPOINTS IN THE LOW/MID 60S. ATTENTION THEN TURNS TO AN UPPER
LOW ACROSS NORTHERN ONTARIO WITH EMBEDDED VORT MAX CROSSING THE
NORTHERN GREAT LAKES THAT WILL SEND A COLD FRONT THROUGH THE AREA
LATE TONIGHT INTO WED. AHEAD OF THIS FRONT, A WEAK SHORTWAVE
CURRENTLY SEEN ON WATER VAPOR EXITING THE BLACK HILLS WILL MOVE INTO
OUR AREA THIS EVENING. A MODEST LOW LEVEL THETA-E SURGE IS NOTED AS
WESTERLY 850MB FLOW INCREASES TO 25-30 KTS. BEST MIDLEVEL LAPSE
RATES REMAIN LOCKED WELL TO OUR WEST THOUGH AND MUCAPE VALUES REMAIN
MEAGER THIS FAR EAST (ONLY 1000-1500 J/KG IN OUR FAR NW). 0-6KM BULK
SHEAR IS OF COURSE IMPRESSIVE GIVEN 50+ KT MIDLEVEL JET AT THE BASE
OF THE CANADIAN TROUGH BUT BOTH INSTABILITY AND FORCING APPEAR TOO
MEAGER TO SUPPORT AN ORGANIZED SEVERE WEATHER THREAT THIS FAR EAST.
THUNDERSTORMS WILL NO DOUBT ENTER OUR NW ZONES RIGHT AROUND 00Z AND
MAY CARRY AN ISOLATED THREAT FOR GUSTY WINDS THERE IN THE 00-03Z
WINDOW BUT SEVERE WEATHER CHANCES APPEAR VERY LOW IN OUR AREA.
FURTHER, DIURNALLY-DRIVEN STABILIZATION EXPECTED AFTER 03Z AND THE
PRIMARY COLD FRONT BECOMES INCREASINGLY ORPHANED FROM PARENT TROUGH
BY WED MORNING. VAST MAJORITY OF 00Z CAM'S END ALL PRECIP BY 06-09Z
AND INDICATE ONLY WIDELY SCATTERED REDEVELOPMENT WED AFTERNOON GIVEN
EXTREMELY LIMITED INSTABILITY AND POOR MID/UPPER LEVEL SUPPORT. KEPT
SOME LOW CHANCE POP'S GOING THROUGH WED MORNING BUT SUFFICE IT TO
SAY NOT EXPECTING ANY HEAVY RAIN OR SEVERE WEATHER LATE TONIGHT OR
ON WED.
PRECIP EXITS BY WED EVENING AND CANADIAN HIGH PRESSURE RETURNS TO
THE GREAT LAKES THROUGH FRI. THU AND FRI WILL BE VERY PLEASANT WITH
HIGHS IN THE UPPER 70S, LOW HUMIDITY AND MOSTLY SUNNY SKIES. THE
NEXT MIDLEVEL TROUGH AND ASSOCIATED COLD FRONT THEN CROSS LATE FRI
NIGHT INTO SAT. HEALTHY CVA FORCING WILL LIKELY RESULT IN NUMEROUS
SHOWERS ON SAT BUT MOISTURE AND INSTABILITY APPEAR VERY LIMITED AND
SEVERE WX/HEAVY RAIN IS NOT EXPECTED. THIS WILL BE FOLLOWED BY
STRONG NORTHERLY FLOW AND EVEN COOLER AIR EARLY NEXT WEEK RESULTING
IN HIGHS ONLY IN THE MID 70S.
AVIATION /06Z TAFS THROUGH 06Z WEDNESDAY/
ISSUED AT 115 AM EDT TUE AUG 18 2026
VFR CONDITIONS EXPECTED TO PERSIST THROUGH THE BULK OF THIS PERIOD.
THERE IS SOME LOW CHANCE FOR PATCHY GROUND FOG/BR THIS MORNING BUT
LATEST GUIDANCE CAME IN DRIER AND HIGH CLOUDS ARE ALSO HELPING TO
LIMIT ITS DEVELOPMENT. COLD FRONT APPROACHES THE REGION LATE IN THE
PERIOD. THUNDERSTORMS POSSIBLE AT KSBN AFTER 00Z BUT CONFIDENCE IN
COVERAGE REMAINS LOW SO WILL HOLD WITH JUST A PROB30 FOR NOW.
IWX WATCHES/WARNINGS/ADVISORIES
IN...NONE.
OH...NONE.
MI...NONE.
MARINE...NONE.
DISCUSSION...AGD
AVIATION...AGD
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