014
FXUS63 KIWX 291323
AFDIWX
AREA FORECAST DISCUSSION
NATIONAL WEATHER SERVICE NORTHERN INDIANA
923 AM EDT SAT AUG 29 2026
KEY MESSAGES
- MAINLY DRY AND TRENDING WARMER THIS WEEKEND. SLIGHT CHANCES OF
SHOWERS FAR NORTHERN INDIANA AND SOUTHERN LOWER MICHIGAN
TONIGHT AND SUNDAY.
- HEAT AND HUMIDITY INCREASES INTO NEXT WEEK WITH AFTERNOON HEAT INDICES
EXPECTED TO REACH WELL INTO THE 90S FOR MANY. HEAT INDICES
MAY APPROACH 100 DEGREES FOR PORTIONS OF THE AREA TUESDAY AND
WEDNESDAY AFTERNOONS.
- A PRIMARILY DRY PATTERN SHOULD CONTINUE INTO AT LEAST THE
FIRST HALF OF NEXT WEEK, WITH CHANCES OF SHOWERS AND
THUNDERSTORMS DURING THE MIDDLE AND LATTER PORTIONS OF THE
UPCOMING WORK WEEK.
UPDATE
ISSUED AT 917 AM EDT SAT AUG 29 2026
AREA OF SHOWERS AND THUNDERSTORMS, CURRENTLY ACROSS EASTERN IA
INTO SOUTHWEST WI, WILL KEEP MOVING ESE TODAY. THE LEADING EDGE
BEING RATHER HIGH BASED AND SHOWING UP AS LITTLE MORE THAN
SPRINKLES ON OBS. AS IT APPROACHES, IT WILL ENCOUNTER AN EVEN
DRIER AIRMASS IN THE LOW LEVELS AS WELL AS OUTRUN THE BETTER LOW
LEVEL FLOW AND INSTABILITY GRADIENT. WHILE SOME CAMS SHOW SOME
LIGHT PRECIP MAKING IT IN THIS AFTERNOON, NOT OVERLY CONFIDENT
RIGHT NOW WITH ONLY POPS CONTINUING TODAY ACROSS THE NORTH AS
SOME REDEVELOPMENT UPSTREAM COULD GRAZE OUT NORTHERN AREAS.
CLOUDS WILL STEADILY INCREASE FROM THE BLOWOFF OF THE CONVECTION
TO DIM THE SUN SOMEWHAT.
DISCUSSION
ISSUED AT 320 AM EDT SAT AUG 29 2026
OVERALL NO MAJOR CHANGES IN FORECAST THINKING FROM THE PAST SEVERAL
CYCLES. LOW CHANCES OF RAIN SHOWERS FOR NORTHERN LOCATIONS ARE
EXPECTED TONIGHT THROUGH SUNDAY. A WARMING TREND STILL REMAINS OF
HIGH CONFIDENCE THIS WEEKEND INTO EARLY NEXT WEEK. HEAT INDICES FROM
THE MID 90S TO 100 ARE POSSIBLE TUESDAY AND WEDNESDAY AFTERNOONS.
AN EXPANSIVE LOW LEVEL ANTICYCLONE PERSISTS THIS MORNING FROM
WESTERN NEW YORK INTO SOUTHERN MISSOURI. LITTLE MOVEMENT IN
THIS ANTICYCLONE IS EXPECTED THROUGH TONIGHT AS LOCAL AREA
REMAINS DOWNSTREAM OF MID/UPPER LEVEL RIDGE AXIS ACROSS THE
CENTRAL AND NORTHERN PLAINS.
A STRONG LOW LEVEL JET IN VICINITY OF THE UPPER LEVEL RIDGE AXIS
ACROSS THE NORTHERN PLAINS HAS LED TO DEVELOPMENT OF CONVECTION
EARLY THIS MORNING ACROSS EASTERN SOUTH DAKOTA. THIS CONVECTION
SHOULD AUGMENT A SMALLER SCALE SHORT WAVE PROGRESSING THROUGH THIS
RIDGE AXIS, AND UPPER LEVEL WAVE PATTERN REMAINS SUPPORTIVE OF
THIS SHORT WAVE DROPPING EAST-SOUTHEAST TO THE SOUTHERN GREAT
LAKES LATER THIS AFTERNOON/EARLY EVENING. A POCKET OF ENHANCED
MID LEVEL WESTERLIES ASSOCIATED WITH THIS CONVECTIVELY ENHANCED
SHORT WAVE SHOULD SHIFT ACROSS THE SOUTHERN GREAT LAKES REGION
TONIGHT WITH A PERIOD OF SHARP MID LEVEL MOISTURE ADVECTION. LOW
LEVEL MOISTURE ADVECTION WILL BE A BIT MORE LIMITED GIVEN WHAT
SHOULD REMAIN SOME UNFAVORABLE LOW LEVEL FLOW TRAJECTORIES
ARISING FROM THE PERSISTENCE OF THE LOW LEVEL ANTICYCLONE. THIS
EVOLUTION SHOULD ALLOW FOR SOME VERY WEAK ELEVATED INSTABILITY
TO SHIFT EASTWARD ACROSS SOUTHERN/CENTRAL LOWER MICHIGAN THIS
EVENING. PASSAGE OF THIS SHORT WAVE, BROAD ISENTROPIC UPGLIDE,
AND WEAK ELEVATED INSTABILITY ARISING FROM ELEVATED MOISTURE
TRANSPORT COULD BE ENOUGH FOR A FEW SHOWERS ACROSS THE NORTH
TONIGHT.
STRONGER SOUTHWESTERLY LOW LEVEL FLOW FROM THE PLAINS WILL MIGRATE
EASTWARD TO THE MID MS VALLEY/SOUTHERN GREAT LAKES ON SUNDAY WITH
SOME INCREASE IN ISENTROPIC LIFT. DIFFICULT TO DISCERN MUCH ELSE IN
TERMS OF MORE PRONOUNCED MID/UPPER LEVEL FORCING BY THIS TIME,
BUT OVERALL PATTERN WITH ADVECTIVE FORCING SEEMS TO SUPPORT AT
LEAST SOME SLIGHT CHANCE POPS ACROSS THE NORTHERN HALF OF THE
AREA. AN ISOLATED THUNDERSTORM IS POSSIBLE, BUT BETTER LOW LEVEL
MOISTURE TRANSPORT AND MORE PRONOUNCED MUCAPES SHOULD RESIDE
BACK ACROSS THE CORN BELT. IT WILL BE NOTICEABLY WARMER ON
SUNDAY WITH HIGH TEMPERATURES INTO THE MIDDLE 80S. WITH BETTER
MOISTURE TRANSPORT STILL DISPLACED TO THE WEST, SFC DEW POINTS
SHOULD BE LIMITED TO THE MID 60S LOCALLY.
FOR SUNDAY NIGHT INTO MONDAY, SOME SUBTLE POSITIVE HEIGHT TENDENCIES
ARE EXPECTED ACROSS THE WESTERN GREAT LAKES DOWNSTREAM OF MORE
SUBSTANTIAL UPPER TROUGH TRACKING ACROSS SOUTHERN
SASKATCHEWAN/MANITOBA. EASTWARD PROGRESSION OF THE UPPER RIDGE AXIS
AND THIS UPPER TROUGH RIDING THIS RIDGE SHOULD RESULT IN SOME
VEERING OF LOW LEVEL FLOW LATE MONDAY AND EASTWARD ADVECTION OF
RICHER LOW LEVEL MOISTURE ACROSS CORN BELT/MID MS VALLEY. THIS
PERIOD WILL ALSO MARK THE BEGINNING OF A STRONGER MID LEVEL THERMAL
RIDGE BUILDING ACROSS THE AREA. A FEW SHOWERS AND STORMS ARE
POSSIBLE AS THIS MID LEVEL THERMAL RIDGE BUILDS IN LATER MONDAY
NIGHT BUT CONFIDENCE IN PRECIP IS LOW. THE MAIN WEATHER STORY FOR
TUESDAY/WEDNESDAY WILL FOCUS ON BUILDING HEAT AND HUMIDITY WITH
A POTENTIAL OF HEAT INDICES FROM THE MID 90S TO AROUND 100 EACH
AFTERNOON.
ON WEDNESDAY, THE AFOREMENTIONED UPPER TROUGH WILL BE TRACKING
ACROSS THE WESTERN GREAT LAKES AND EVENTUALLY EASTERN GREAT LAKES
WEDNESDAY EVENING. AN ASSOCIATED FRONTAL BOUNDARY MAY BE FOCAL POINT
FOR ISOLATED-SCATTERED SHOWERS AND STORMS SOMEWHERE ACROSS GREAT
LAKES REGION, BUT QUESTIONS REMAIN AS TO INSTABILITY MAGNITUDES
GIVEN PRESENCE OF WARM MID LEVEL THERMAL PROFILES AND GOOD
POSSIBILITY THAT SFC/NEAR SFC CONVECTION IS SUPPRESSED. MAY NEED
TO WATCH FOR ANY SOUTHWARD MIGRATING OUTFLOWS FROM GREAT LAKES
CONVECTION AIDING IN CONVECTIVE DEVELOPMENT LATER WEDNESDAY.
A PERIOD OF COLD ADVECTION IS EXPECTED WED NIGHT/THU AS THIS
FRONT DROPS INTO THE REGION. MEDIUM RANGE GUIDANCE DETERMINISTIC
SOLUTIONS DIFFER SHARPLY BY NEXT THU/FRI, BUT OVERALL ENSEMBLE
MEAN TREND IS FOR SOME SUBTLE AMPLIFICATION OF LONGWAVE WESTERN
CONUS TROUGH-CENTRAL CONUS RIDGE-EASTERN CONUS TROUGH PATTERN.
MULTI-ENSESMBLE MEAN POSITION OF UPPER RIDGE AXIS IS WEST OF THE
LOCAL AREA WHICH WOULD KEEP GREATER HEAT CONCERNS WEST OF THE
LOCAL AREA THURSDAY THROUGH SATURDAY. HOWEVER, OCCASIONAL SHORT
WAVES IN NORTHWEST FLOW ALOFT AND POTENTIAL EPISODES OF POSITIVE
LOW-MID LEVEL THETA-E ADVECTION ACCOMPANYING THESE WAVES MAY
PROVIDE SOME ADDITIONAL CHANCES OF RAIN IN THE DAYS 5 TO 7
PERIOD.
AVIATION /12Z TAFS THROUGH 12Z SUNDAY/
ISSUED AT 546 AM EDT SAT AUG 29 2026
A SHORT WAVE TROUGH WILL GET SOME INCREASE IN STRENGTH THIS
MORNING FROM ONGOING CONVECTION ACROSS SOUTHERN
MINNESOTA/NORTHWEST IOWA. THIS FEATURE IS EXPECTED TO SHIFT
EAST-SOUTHEAST TO THE SOUTHERN GREAT LAKES REGION LATER THIS
AFTERNOON/EARLY EVENING. MOST OF THE NOTABLE MOISTURE TRANSPORT
IN ADVANCE OF THIS SHORT WAVE WILL BE MORE MID LEVEL IN NATURE
WITH SOME VERY WEAK ELEVATED INSTABILITY LIKELY TO DEVELOP
ACROSS FAR NORTHERN INDIANA THIS EVENING. APPROACH OF THIS SHORT
WAVE AND WEAK ELEVATED INSTABILITY COULD LEAD TO SOME ISOLATED
SHOWERS IN KSBN VICINITY LATE AFTERNOON AND TONIGHT, BUT
CONFIDENCE REMAINS TOO LOW FOR TAF INCLUSION. OTHERWISE,
INCREASING CLOUDS TODAY WITH BROAD MID LEVEL WARM ADVECTION
RESULTING IN MID LEVEL CEILINGS. WINDS WILL REMAIN LIGHT THIS
PERIOD DUE TO PERSISTENCE OF EXPANSIVE LOW LEVEL ANTICYCLONE.
IWX WATCHES/WARNINGS/ADVISORIES
IN...NONE.
OH...NONE.
MI...NONE.
MARINE...NONE.
UPDATE...FISHER
DISCUSSION...MARSILI
AVIATION...MARSILI
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