350
FXUS63 KIWX 122343
AFDIWX
AREA FORECAST DISCUSSION
NATIONAL WEATHER SERVICE NORTHERN INDIANA
743 PM EDT TUE MAY 12 2026
KEY MESSAGES
- SHOWERS AND SCATTERED THUNDERSTORMS ARE EXPECTED THIS EVENING.
WIDESPREAD SEVERE WEATHER IS NOT EXPECTED BUT A FEW SHOWERS
AND STORMS MAY PRODUCE WIND GUSTS TO 40 TO 50 MPH THIS
EVENING.
- MAINLY DRY CONDITIONS CAN BE EXPECTED FOR WEDNESDAY AND
THURSDAY
- PERIODIC SHOWERS AND THUNDERSTORMS FRIDAY AND SUNDAY, BUT
BETTER CHANCES FOR SEVERE WEATHER LIKELY HOLD OFF UNTIL
MONDAY AS OUR FIRST OPPORTUNITY FOR 90 DEGREE HIGHS COME INTO
VIEW.
DISCUSSION
ISSUED AT 220 PM EDT TUE MAY 12 2026
A VIGOROUS SHORTWAVE ENTERS THE GREAT LAKES NORTH OF THE AREA AND
DEVELOPS INTO AN UPPER LOW PRESSURE SYSTEM. IT DOES APPEAR TO
PROVIDE PLENTY OF LIFT OVER LK MI WHERE LOW LEVEL CONVERGENCE SITS
UNDERNEATH A GOOD AREA OF UPPER DIVERGENCE. THE MAIN SHORTWAVE MOVES
WEST TO EAST AND THE BETTER VORTICITY SWINGS SOUTHEASTWARD INTO THE
AREA TONIGHT. BETWEEN 00 AND 6Z, THE BETTER LARGE SCALE ASCENT
CONNECTS OVERHEAD AND SLIDES EASTWARD. ONE OF THE MAIN ISSUES IS
THAT THE SURFACE HIGH PRESSURE SYSTEM BROUGHT PLENTY OF DRY AIR TO
THE AREA YESTERDAY AND THIS MORNING AND THIS AFFECTS NOT ONLY
MOISTURE CONTENT, BUT ALSO INSTABILITY. SFC DEW POINTS IN THE LOW
30S WEST OF IN-15 VS IN THE MID 30S IN THE EAST AND THIS REALLY
CAUSES AN INVERTED-V STYLE SOUNDING FOR ANYTHING OUT IN FRONT OF THE
COLD FRONT. BUT WITH INVERTED-V SOUNDINGS, IT USUALLY NEEDS WEAKER
SHEAR TO GET THOSE DOWNBURSTS TO OCCUR WITH THE EVAPORATION. THE
NORMALLY MOIST-BIASED NAM HAS AROUND 500 J OF MUCAPE OUT IN FRONT OF
THE PRE-FRONTAL TROUGH AND ANOTHER 500 J CLOSER TO THE COLD FRONT
BACK IN WISCONSIN AROUND 00Z THIS EVENING. IT APPEARS THAT ONCE THE
COLD FRONT CATCHES UP TO THE PRE-FRONTAL TROUGH IN THE I-69
CORRIDOR, BETTER MOISTURE AND LINGERING MUCAPE AROUND 500 J MAY BE
ENOUGH TO ALLOW FOR SOME STORMS, BUT AT THAT POINT, WE'VE LOST THE
BETTER LOW LEVEL LAPSE RATES AND WITH THAT SETUP, IT'S PROBABLY
GOING TO BE HARDER TO GET A DOWNBURST. SFC DEW POINTS FINALLY REACH
55F IN THE I-69 CORRIDOR AROUND 6Z. SOME SMALL HAIL MAY BE POSSIBLE.
AS FAR AS A TORNADO THREAT GOES, OUR LIMITING FACTOR IS DRY AIR.
LCLS ARE ABOVE 1000M FOR A GOOD PORTION OF THE PERIOD. PERHAPS AS
THOSE DEW POINTS RISE ABOVE 50F MAYBE WE CAN GET BETTER LCLS, BUT WE
LOSE INSTABILITY AT NIGHT AND LOW LEVEL TURNING IS MARGINAL TO TOO
LOW THROUGHOUT. STILL THINK THE MOST PROBABLE IS SUB-SEVERE STORMS
40 TO 50 MPH GUSTS WITH AN ISOLATED SEVERE STORM. HAIL IS A LOW
THREAT, BUT NOT NON-EXISTENT. THE HRRR HAS THE CONVECTION THROUGH
LIMA BY AROUND 8Z.
THE WARM/MOIST THETA-E PLUME VACATES THE AREA BY 12Z WEDNESDAY AND
NEGATIVE THETA-E ADVECTION ENSUES. THIS BRINGS COOLER AND DRIER AIR
INTO THE AREA. THERE COULD BE ENOUGH INSTABILITY AROUND, HOWEVER,
FOR SCATTERED TO ISOLATED CELLS OF SPRINKLES OR LIGHT SHOWERS ON
WEDNESDAY. HIGH TEMPERATURES ALSO DROP 15 DEGREES FROM THE LOW 60S-
LOW 70S TO LOW 50S-AROUND 60. THIS LOW THETA-E PLUME STICKS AROUND
THROUGH THURSDAY. GIVEN THE DEEPENING OF THE LOW OVER THE
NORTHEASTERN CONUS ON FRIDAY, RAIN SORT OF HITS A WALL AND HAS TO
SLIDE SOUTHWARD. THEREFORE, THE FIRST PART OF FRIDAY, AS A COLD
FRONT ARRIVES, PROBABLY HAS THE BEST CHANCE FOR RAIN BETWEEN FRIDAY
AND SATURDAY. THAT'S NOT TO SAY IT WON'T RAIN, BUT THAT CHANCES ARE
MORE DOWN AROUND 15 TO 20 PERCENT AS OPPOSED TO 25 TO 30 PERCENT.
RAIN COMES IN FRIDAY NIGHT AND THEN SATURDAY NIGHT INTO SUNDAY. WE
KIND OF END UP IN THIS SQUEEZE PLAY BETWEEN THE RIDGE TO OUR EAST
AND THE ARRIVING THETA-E PLUME TRYING TO BETTER MOISTURE IN HERE
AHEAD OF NIGHTFALL AND IT SWINGING THROUGH THE AREA FOR SATURDAY.
ALL OF THIS LINGERING MOISTURE AND STALLED LOW PRESSURE SYSTEM
ARRIVAL HAS STALLED THE ARRIVAL OF THE WARMER AIR ORIGINALLY SLATED
FOR FRIDAY.
ONE THING OF NOTE IS THAT AS THE UPPER LOW THAT STALLS OVER THE
NORTHEASTERN US LEAVES, A HIGH PRESSURE SYSTEM SETS BACK UP
SOUTHEAST OF THE CONUS. THIS ALLOWS A BETTER CONNECTION TO THE GULF
ESPECIALLY BY LATER SUNDAY AND SUNDAY NIGHT. THEREFORE, MONDAY HAS A
BETTER AIRMASS FOR THUNDERSTORMS.
AVIATION /00Z TAFS THROUGH 00Z THURSDAY/
ISSUED AT 741 PM EDT TUE MAY 12 2026
AHEAD OF A SOUTHEASTERLY MOVING COLD FRONTAL BOUNDARY LIGHT
RAIN AND SHOWERS ARE MOVING STEADILY EASTWARD INTO NORTHERN
IN/SOUTHERN MI AND WILL CONTINUE OVER THE NEXT SEVERAL HOURS.
SOME LLWS WILL BE POSSIBLE FOR KSBN EARLY IN THIS PERIOD. VFR
CONDITIONS WILL BEGIN TO DEGRADE TO MVFR CONDITIONS IN LOWERED
CIGS AND SLIGHT REDUCTIONS IN VSBYS IN THE HEAVIER SHOWERS AND
SOME MIST. AS THE COLD FRONT PUSHES CLOSER THERE IS THE
EXPECTATION THAT SOME EMBEDDED THUNDERSTORMS WILL ACCOMPANY THE
FRONTAL BOUNDARY MAINLY FOR KSBN BETWEEN 00Z AND 04Z WED. THERE
IS LESS CONFIDENCE FOR THUNDERSTORMS FOR KFWA AS ANY WARMING AT
THE SURFACE WILL BE LOST IN THE OVERNIGHT PERIOD AND LENDING TO
MORE OF JUST CONVECTIVE RAIN SHOWERS. WINDS WILL BECOME MORE
NORTHWESTERLY WITH AND BEHIND THE COLD FRONT AND GUSTS AROUND 25
KTS WITH THE SHIFT. MVFR CIGS AROUND 2500-3000 FEET BUILDS IN
BEHIND THE FRONT WITH THE LOW CIRCULATION CENTERED JUST TO OUR
NORTH FOR WEDNESDAY MORNING/EARLY AFTERNOON. PERHAPS A LITTLE
DRIZZLE WITH THE LOWERED CIGS BUT CONFIDENCE NOT HIGH IN THIS
WITH THE DRIER AIRMASS POST FRONTAL.
IWX WATCHES/WARNINGS/ADVISORIES
IN...NONE.
OH...NONE.
MI...NONE.
MARINE...SMALL CRAFT ADVISORY UNTIL 11 PM EDT WEDNESDAY FOR LMZ043-046.
DISCUSSION...ROLLER
AVIATION...ANDERSEN
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