944
FXUS63 KIWX 272336
AFDIWX
AREA FORECAST DISCUSSION
NATIONAL WEATHER SERVICE NORTHERN INDIANA
736 PM EDT MON JUL 27 2026
KEY MESSAGES
- SHOWERS AND A FEW STORMS ACROSS NORTHERN INDIANA WILL SINK
SOUTH OF THE AREA THROUGH THE REMAINDER OF THE EVENING. SEVERE
WEATHER IS NO LONGER EXPECTED.
- HIGH SWIM RISK TUESDAY FOR SOUTHEAST LAKE MICHIGAN BEACHES.
DISCUSSION
ISSUED AT 255 PM EDT MON JUL 27 2026
THE MAIN FORECAST CONCERN WILL BE ON THE SEVERE WEATHER POTENTIAL
THROUGH THIS EVENING.
A COMPLICATED CONVECTIVE SCENARIO IS UNFOLDING ACROSS THE GREAT
LAKES REGION THIS AFTERNOON. PREFERRED REGION OF CONVECTIVE
DEVELOPMENT HAS BEEN ACROSS NORTHEAST ILLINOIS ALONG A CORRIDOR
OF LOW LEVEL WARM/MOIST ADVECTION. THIS FORCING IS COINCIDENT
WITH STRENGTHENING UPPER LOW LEVEL FLOW AND EFFECTIVE SHEAR
PROFILES. EXTREME INSTABILITY WITH MLCAPES 4-5K J/KG CAPES IS
SITUATED ACROSS NORTHEAST INDIANA WITH SHARP EASTWARD
DIMINISHMENT IN INSTABILITY ACROSS NORTHEAST INDIANA/NORTHWEST
OHIO. CELLS ACROSS NORTHEAST ILLINOIS ARE FAVORING STRONG COLD
POOLS WITH SIGNATURES OF VERY STRONG BASE VELOCITY SHIFTING
SOUTHEAST ACROSS FAR NORTHWEST INDIANA. THE COMBINATION OF
SHALLOW LOW LEVEL SOUTHWEST FLOW AND DEEPER NORTHWESTERLY FLOW
IN THE MID/UPPER LEVELS IS FAVOR SOME NORTH TO SOUTH PREFERENCE
IN PROPAGATION VECTORS WITH THE STORMS ACROSS NORTHEAST
ILLINOIS. AREAS WEST OF US ROUTE 31 ACROSS NORTHEAST INDIANA
SHOULD STAND GREATEST RISK OF SEEING HIGHER END THUNDERSTORM
WIND GUSTS (80+ MPH) AS THE STORMS ACROSS NE ILLINOIS DROP
SOUTHEAST. IN ADDITION TO THE RISK OF HIGHER END DAMAGING WIND
GUSTS, THE EXTREME INSTABILITY WILL SUPPORT SOME ISOLATED LARGE
HAIL OF 1 TO 2 INCHES IN DIAMETER. ALSO, THE AFOREMENTIONED
BACKGROUND SHEAR PROFILES WILL CONTINUE TO SUPPORT SOME EMBEDDED
SUPERCELL STRUCTURES WITH A RISK OF ISOLATED TORNADOES. 0-3KM
SHEAR VECTORS ORIENTED FROM THE NORTHWEST AT AROUND 30 KNOTS
COULD ALSO SUPPORT A FEW QLCS TORNADO SPINUPS WHERE ANY REAR
INFLOW JET CAN ORIENT IN A NW TO SE FASHION AND WHERE MORE
MATURE COLD POOLS DEVELOP.
ADDITIONAL STORMS ARE EXPECTED TO DEVELOP ACROSS THE GREAT LAKES
REGION THIS EVENING AS LOW LEVEL FRONT PUSHES SOUTHWARD WITH AN
ADDITIONAL RISK OF SCATTERED DAMAGING WIND GUSTS THROUGH AROUND 02Z.
CONFIDENCE IN SEVERE GUSTS AFTER 00Z DOES DIMINISH SOMEWHAT HOWEVER.
BY TUESDAY MORNING, THE NOSE OF THE UPPER LEVEL JET STREAK WILL
REACH THE MID ATLANTIC STATES WITH LAGGING SFC TROUGH/COOL FRONT
EXPECTED TO EXTEND FROM WESTERN PA TO SOUTHERN ILLINOIS. PASSAGE OF
THIS FRONT WILL LEAD QUIETER WEATHER CONDITIONS THROUGH THE MIDDLE
OF THE WEEK WITH TEMPERATURES/DEW POINTS CLOSER TO SEASONABLE LEVELS.
THE NEXT SYSTEM TO WATCH WILL BE TOWARD END OF THE WORK AS THE
POTENTIAL EXISTS FOR SYNOPTIC WAVE TO BECOME CONVECTIVELY ENHANCED
ACROSS THE DAKOTAS. SOME QUESTION EXISTS AS TO INSTABILITY
MAGNITUDES AS FAR EAST AS SOUTHERN GREAT LAKES/OHIO VALLEY WITH THIS
SYSTEM WITH SOME INDICATIONS OF THIS SYSTEM BECOMING MORE VERTICALLY
STACKED IN NATURE WELL TO THE WEST.
AVIATION /00Z TAFS THROUGH 00Z WEDNESDAY/
ISSUED AT 735 PM EDT MON JUL 27 2026
THE POTENTIAL OF THUNDERSTORMS HAS DIMINISHED ACROSS THE
TERMINALS THIS EVENING. SOME LINGERING LIGHT RAIN SHOULD CLEAR
THE TERMINAL BY 00Z. CANNOT COMPLETELY RULE OUT ISOLATED SHOWERS
LATE THIS EVENING/EARLY OVERNIGHT AS COLD FRONT APPROACHES FROM
THE NORTH, BUT THIS PROBABILITY APPEARS TOO LOW TO INCLUDE WITH
THE 00Z TAFS. SOME POST-FRONTAL STRATUS AND PERHAPS SOME FOG
COULD DEVELOP LATE TONIGHT INTO EARLY TUESDAY MORNING, WITH
GREATER CONFIDENCE IN STRATUS DEVELOPMENT OPPOSED TO FOG.
IFR/MVFR CIGS SHOULD GRADUALLY MIX OUT LATE TOMORROW MORNING
INTO EARLY AFTERNOON WITH NORTHWEST WINDS BECOMING GUSTY TO 15
TO 20 KNOTS.
IWX WATCHES/WARNINGS/ADVISORIES
IN...BEACH HAZARDS STATEMENT FROM 4 AM CDT TUESDAY THROUGH
WEDNESDAY MORNING FOR INZ103.
OH...NONE.
MI...BEACH HAZARDS STATEMENT FROM 5 AM EDT TUESDAY THROUGH
WEDNESDAY MORNING FOR MIZ177-277.
MARINE...SMALL CRAFT ADVISORY FROM 2 AM TUESDAY TO 2 AM EDT WEDNESDAY
FOR LMZ043-046.
DISCUSSION...MARSILI
AVIATION...MARSILI
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