645
FXUS63 KIWX 302312
AFDIWX
AREA FORECAST DISCUSSION
NATIONAL WEATHER SERVICE NORTHERN INDIANA
712 PM EDT THU APR 30 2026
KEY MESSAGES
- BELOW NORMAL TEMPERATURES PERSIST THROUGH THIS WEEKEND WITH
MODERATION CLOSER TO NORMAL INTO NEXT WEEK.
- RAIN SHOWERS (50-80%) MOVE THROUGH TONIGHT INTO FRIDAY MORNING.
- FROST MAY IMPACT SENSITIVE VEGETATION FRIDAY NIGHT INTO EARLY
SATURDAY MORNING AND AGAIN ON SUNDAY MORNING. A 25 PERCENT
CHANCE FOR 30 DEGREE TEMPERATURES EXISTS IN THE I-69 CORRIDOR,
WHICH WOULD OCCUR MAINLY AFTER 2AM FRIDAY NIGHT.
DISCUSSION
ISSUED AT 200 PM EDT THU APR 30 2026
BIGGEST HAZARD TO WATCH IN THE SHORT TERM IS THE FROST AND FREEZE
POTENTIAL.
AS AN UPPER LOW SLOWLY SHIFTS EASTWARD FROM THE NORTHERN GREAT LAKES
TO SOUTHEASTERN CANADA, IT ALLOWS COOLER AIR TO FILTER DOWN INTO THE
AREA FROM CANADA ON NORTHWEST FLOW. FOR TONIGHT, STARTING AROUND 00Z
GIVE OR TAKE A FEW HOURS, A POCKET OF LOW LEVEL RH SWINGS THROUGH IN
CONJUNCTION WITH A WEAK SURFACE LOW AND MODERATELY STRONG MID LEVEL
SHORTWAVE AND DOES APPEAR TO HAVE SOME 850 MB COLD ADVECTION BEHIND
A COLD FRONT. LAV GUIDANCE DOES STILL SHOW WINDS LESS THAN 4 KTS AT
KIRS OVERNIGHT, BUT PROBABLY, CLOUD COVER IS THE LIMITING FACTOR FOR
FROST CONDITIONS, EVEN WITH BRANCH AND HILLSDALE COUNTIES DIPPING
DOWN TO 36/37 DEGREES. LAV GUIDANCE IS SHOWING LOW STRATUS (MVFR
CIGS FOR THOSE ATTUNE TO AVIATION TERMS). SATURDAY MORNING BRINGS
THE BEST CHANCE FOR 32 DEGREE, WHICH COULD BRING A SOFT FREEZE AS
850 MB TEMPS DIP DOWN TO NEGATIVE 5C. CERTAINLY WOULD LIKE TO SEE 28
TO 30 DEGREES TO HAVE MORE CONFIDENCE GO WITH A FREEZE WATCH. WITH
THE TAIL END OF A TROUGH STILL TO OUR WEST, BUT ATTEMPTING TO SWING
THROUGH, CANNOT RULE OUT SOME NUISANCE CLOUDS MOVING THROUGH, BUT
SURFACE HIGH PRESSURE IS ACROSS THE PLAINS STATES AND THAT APPEARS
TO KEEP US MOSTLY CLEAR. THIS IS EVEN WITH A COLD FRONT THAT WASHES
OUT AHEAD OF THE SURFACE HIGH TO OUR SOUTHWEST. ALL SAID AND DONE,
IT APPEARS THE BEST LOCATIONS FOR FROST AND PERHAPS A FREEZE IS IN
OUR MI COUNTIES AND IN COUNTIES EAST OF US-31. SUNDAY MORNING 850 MB
TEMPERATURES ARE A FEW DEGREES WARMER THAN SATURDAY AT NEGATIVE 1 OR
2C AS THE MAIN COLD AXIS BEGINS TO SLIDE EASTWARD. WARM ADVECTION AT
850 MB ALSO COMMENCES ON THE BACK SIDE OF THE HIGH WHICH COULD BRING
SOME SCATTERED CLOUDINESS INTO THE AREA. THIS IS PROBABLY WIDESPREAD
FROST CONDITIONS MAINLY EAST OF IN-15 AND IN OUR MI COUNTIES, BUT
COULD BRING SOME SOFT FREEZE POTENTIAL (32 OR 31 DEGREES) IN
OUTLYING AND NORTHERN LOCATIONS. NAM BUFKIT SOUNDINGS INDICATE WE
ATTEMPT TO DECOUPLE BOTH FRIDAY NIGHT AND SATURDAY NIGHT.
THE OTHER HAZARD BETWEEN SUNDAY DAYTIME AND THE MIDDLE OF NEXT WEEK
WILL BE A SERIES OF COLD FRONTS THAT PUSH THROUGH. IT IS INTERESTING
TO NOTE ON NSSL'S AI SEVERE WEATHER OUTLOOK BASED ON THE GEFS THAT
MONDAY AND TUESDAY HAVE A SEVERE WEATHER CHANCE. IT LOOKS LIKE 50
DEGREE DEW POINTS INCREASE DURING THE DAYTIME MONDAY WITH THE MAIN
AXIS STALLING ACROSS THE AREA (ESPECIALLY SOUTH OF US-24) INTO
MONDAY NIGHT. MID LEVEL LAPSE RATES STAY AROUND 6C/KM DURING THE
MONDAY TO MONDAY NIGHT PERIOD. GIVEN THE POTENTIAL FOR REMNANT
BOUNDARIES AND SLOWED FRONTS, FLOODING COULD BE A POSSIBILITY.
HOWEVER, MOISTURE PROFILES DON'T LOOK ALL THAT SATURATED WITH ONLY
AROUND 1" PWATS AND SURFACE DEW POINTS STAYING BELOW 60F AND 850 MB
DEW POINTS ONLY BETWEEN 5 AND 10C. THERE IS SOME SHEAR AND LOW LEVEL
TURNING TO WORK WITH IN THIS CHANCE, BUT IT APPEARS THAT THE THREAT
WANES WITH SUNSET AS WE LOSE INSTABILITY. TUESDAY'S SEVERE/FLOODING
CHANCE DEPENDS ON WHERE THE FRONT/OUTFLOW BOUNDARY ENDS UP.
CURRENT MODEL PROJECTIONS INDICATE THE FRONT IS DRAPED ACROSS
THE AREA BISECTING IT MEANING AREAS SOUTH OF US-24 WOULD HAVE
THE BETTER STORM INGREDIENTS, BUT IT COULD END UP OUTSIDE OF OUR
AREA ALTOGETHER.
QUITE A BIT OF DISAGREEMENT EXISTS FOR WEDNESDAY WITH BOTH THE GFS
AND ECMWF INDICATING A LOW PRESSURE SYSTEM DEVELOPS ALONG THE
STALLED FRONTAL BOUNDARY, BUT WHERE AND HOW QUICKLY IS THE QUESTION.
SOME SCATTERED INSTABILITY SHOWERS COULD BE AROUND THE AREA THURSDAY
AS COLD AIR COMES IN BEHIND THE LOW THAT DEVELOPED ALONG THE FRONT
AND VORTICITY DIPS SOUTHWARD FROM THE UPPER LOW IN CANADA.
AVIATION /00Z TAFS THROUGH 00Z SATURDAY/
ISSUED AT 712 PM EDT THU APR 30 2026
ANOTHER UPPER LEVEL SHORT WAVE IN WESTERLY UPPER FLOW REGIME
ACROSS NORTHERN IOWA WILL SHIFT ACROSS THE SOUTHERN GREAT LAKES
THROUGH DAYBREAK. A WING OF ISENTROPIC FORCING IS EXPANDING
EASTWARD THIS EVENING ACROSS FAR NORTHERN INDIANA AND SOUTHERN
LOWER MICHIGAN. RELATIVELY DRY SUBCLOUD BASES INITIALLY ARE
DELAYING PRECIP ONSET A BIT, BUT STARTING TO SEE SOME LIGHT RAIN
REPORTS ACROSS SW LOWER MICHIGAN. THIS WARM ADVECTION FORCING
QUICKLY TRANSLATES EAST OF THE TERMINALS THIS EVENING BUT WILL
BE REPLACED BY SOME LOW/MID LEVEL FGEN FORCING IN ADVANCE OF THE
IOWA SHORT WAVE. RAIN SHOWERS ARE STILL EXPECTED TO AFFECT
TERMINALS FROM LATE THIS EVENING THROUGH A GOOD PORTION OF THE
OVERNIGHT HOURS AS THE ASSOCIATED FGEN FORCING AND MID/UPPER
LEVEL FORCING WITH THE UPSTREAM SHORT WAVE AFFECT NORTHERN
INDIANA. CIGS SHOULD LOWER TO MVFR TONIGHT, WITH A POSSIBILITY
OF A PERIOD OF IFR CIGS AT KFWA PARTICULARLY IN THE 10Z-13Z
TIMEFRAME. A LAGGING MID LEVEL TROUGH WILL DIG ACROSS THE
SOUTHERN GREAT LAKES ON FRIDAY WHICH COULD AID IN SOME DIURNALLY
ENHANCED SCATTERED SHOWERS FRIDAY AFTERNOON. A SHOWER MENTION
MAY BE NEEDED EVENTUALLY, BUT GIVEN EXPECTED LIMITED COVERAGE AT
THIS FORECAST DISTANCE, WILL KEEP TAFS DRY AFTER LEAD OF
TONIGHT'S/EARLY FRIDAY MORNING ROUND OF RAIN.
IWX WATCHES/WARNINGS/ADVISORIES
IN...NONE.
OH...NONE.
MI...NONE.
MARINE...NONE.
DISCUSSION...ROLLER
AVIATION...MARSILI
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