507
FXUS63 KIWX 011740
AFDIWX
AREA FORECAST DISCUSSION
NATIONAL WEATHER SERVICE NORTHERN INDIANA
140 PM EDT FRI MAY 1 2026
KEY MESSAGES
- A FEW SHOWERS MOVING THROUGH THIS AFTERNOON, LOOK TO DISSIPATE
BY THIS EVENING.
- A COMBINATION OF A FREEZE WARNING AND FROST ADVISORY HAS BEEN
ISSUED FOR OUR AREA FOR TONIGHT AS TEMPERATURES SETTLE IN THE
30S AND POTENTIALLY INTO THE UPPER 20S.
- ADDITIONAL FROST/FREEZE CONDITIONS POSSIBLE EARLY SUNDAY AS WELL
BEFORE WARMER TEMPERATURES ARRIVE SUNDAY INTO MONDAY.
- OPPORTUNITIES FOR SHOWERS AND STORMS RETURN EARLY NEXT WEEK.
DISCUSSION
ISSUED AT 102 PM EDT FRI MAY 1 2026
THE MAIN UPPER LOW ACROSS THE NORTHERN GREAT LAKES/SOUTH-CENTRAL
CANADA SLOWLY LIFTS NORTHEASTWARD SATURDAY INTO SATURDAY NIGHT. THIS
ALLOWS OCCASIONAL SPOKES OF VORTICITY TO SWING THROUGH THE AREA WITH
THE FIRST ONE PUSHING EASTWARD THIS MORNING. SOME REMNANT
INSTABILITY HELPED ALONG BY THE COLDER AIR ARRIVING ALOFT, AS
OPPOSED TO WHAT HAS BEEN ENHANCED SURFACE WARMING, CONTINUES TO
ENHANCE LIGHT SHOWERS OR DRIZZLE THIS AFTERNOON.
WITH THE UPPER LOW PLACED WHERE IT IS, IT'S ALSO IN A GOOD SPOT TO
CONTINUE PUSHING COOL AIR INTO THE AREA. WITH 850 MB TEMPERATURES
DOWN AROUND -5C TONIGHT, HINTS AT DECOUPLING IN NAM BUFKIT
SOUNDINGS, AND WINDS GOING LIGHT TO CALM BETWEEN 00Z AND 06Z, AN
ATTEMPT AT A FREEZE WILL BE MADE. MODEL PROBABILITIES OF 30F ACROSS
THE AREA APPEAR SLIGHTLY LOWER THAN YESTERDAY AND THIS MAY BE
BECAUSE OF THE CHANCE FOR CLOUDS TO COME INTO NORTHWESTERN AREAS.
GIVEN THE DRY AIR ARRIVING FROM THE NORTHWEST, IT MAY BE THAT A
SUDDEN DROP THROUGH THE 30S TOWARDS FREEZING OCCURS, BUT CLOUDS
ARRIVING FROM THE NORTHWEST MAY PROVIDE A BIT OF A BLANKET TO
KEEP US AT OR POTENTIALLY SLIGHTLY ABOVE FREEZING, THUS ADDING
SOME UNCERTAINTY. STILL THE GREATEST CHANCE TO SEE BELOW
FREEZING TEMPERATURES IS ACROSS THE HEART OF OUR FORECAST AREA. AS
WE HEAD INTO THE DAYTIME SATURDAY, SURFACE HIGH PRESSURE MOVING
IN DRIES THINGS OUT AND WE ACHIEVE THE LOW 50S FOR HIGHS.
WE'VE GOT ANOTHER OPPORTUNITY FOR FREEZING/FROST SUNDAY MORNING,
WHICH CAN STILL HAPPEN EVEN AS WARM ADVECTION BEGINS MOVING IN LATE
DURING THE OVERNIGHT (AS HAPPENS THIS TIME). IT DOES APPEAR THAT THE
BETTER CHANCE FOR FROST/FREEZE WILL BE SHIFTED EASTWARD, EAST OF
IN-15, COMPARED TO WHAT IS FORECAST FOR TONIGHT. IT MAY BE MORE
OF A WIDESPREAD FROST WITH OUTLYING AREAS RECEIVING A FREEZE,
THOUGH. CLOUDS LOOK TO ARRIVE AGAIN TOWARDS MORNING, SUNDAY,
WITH A THETA-E PLUME AND WEAK LOW/WEAK VORT MAX ARRIVING DURING
THE AFTERNOON. SO, EVEN THOUGH THE NAM AND GFS WANT TO BRING THE
RAIN IN HERE DURING THE MORNING, AM A LITTLE BIT MORE INCLINED
TO KEEP OUR FORECAST OF AFTERNOON ARRIVAL RUNNING.
SUNDAY NIGHT LOWS ARE WARMER AS THE WARM ADVECTION HELPS TO CAUSE A
WARMING TREND WITH LOW 70S FOR HIGHS ON MONDAY. A DEEPENING LOW
PRESSURE SYSTEM DIVES SOUTHWARD FROM CANADA AND ENDS UP IN THE
NORTHERN GREAT LAKES. THIS PUSHES A FRONTAL BOUNDARY SOUTHWARD WHICH
DRAWS GULF MOISTURE TOWARDS THE AREA. IT STILL LOOKS LIKE SFC DEW
POINTS STAY BELOW 60F WHILE 850 MB DEW POINTS STAY BELOW 10C AND
PWATS ARE ONLY AROUND 1", WHICH LEANS AROUND NORMAL AND TENDS TO PUT
A CEILING ON HEAVIER RAIN CHANCES. ADDITIONALLY, IT APPEARS THAT AN
EML MOVES THROUGH DURING SUNDAY NIGHT, BUT MIXES OUT MONDAY MORNING.
WE'LL HAVE SOME EFFECTIVE SHEAR TO WORK WITH AS WELL AS SOME LOW
LEVEL TURNING, BUT BOTH INSTABILITY AND SHEAR APPEAR TO DROP OFF
AFTER SUNSET, WHICH POINTS TO THIS SCENARIO BEING LIMITED BY
INSTABILITY SINCE WE DON'T HAVE MOISTURE OR MID LEVEL LAPSE RATES TO
HELP SUSTAIN AFTER SUNSET. THE ONE THING TO WATCH WILL BE THE SERIES
OF FRONTS/BOUNDARIES COMING DOWN AND SERVING AS PLACES FOR STORMS TO
BECOME ROOTED FOR SPINUPS DURING THE AFTERNOON/EVENING OR A HYDRO
ISSUE INTO THE OVERNIGHT. DEPENDING ON WHERE THE FRONT STALLS, RAIN
CHANCES WILL BE POSSIBLE, ESPECIALLY FOR AREAS SOUTH OF US-24
TUESDAY AND WEDNESDAY (PERHAPS WITH A SFC LOW DEVELOPING ON THE
SERIES OF FRONTS IN THE AREA), BUT SEVERE CHANCES APPEAR LOW WITH
THE FRONT HAVING MOVED THROUGH.
THE VORTICITY-FILLED TROUGH SWINGS THROUGH THE AREA WEDNESDAY NIGHT
INTO THE WEEKEND AND BRINGS OPPORTUNITIES FOR SCATTERED INSTABILITY
SHOWERS CAUSED BY THE COOLER UPPER AIR AS OPPOSED TO WARMER SFC AIR
THAT WE'VE BEEN HAVING. HIGHS IN THE 50S AND 60S APPEAR COMMON AND
FROST MAY BE POSSIBLE WEDNESDAY OR THURSDAY NIGHT NEXT WEEK AS TEMPS
THREATEN THE 30S AT NIGHT THEN.
AVIATION /18Z TAFS THROUGH 18Z SATURDAY/
ISSUED AT 131 PM EDT FRI MAY 1 2026
MAINLY VFR CATEGORY DIURNAL CLOUDS CURRENTLY OVER THE AREA IN
THE WAKE OF THE DISTURBANCE THAT BROUGHT THE RAINFALL OVERNIGHT
WILL SEE INCOMING RIDGING BRING LIGHTER WINDS AND CLEARING
SKIES. VFR CONDITIONS EXPECTED THROUGH THE REMAINDER OF THE TAF
FORECAST WITH DIURNAL CUMULUS AGAIN DEVELOPING MAINLY FOR KFWA
AFTER 16Z SAT. A FEW REMAINING DIURNALLY DRIVEN NORTHWESTERLY
GUSTS AROUND 20 KTS POSSIBLE FOR KSBN THIS AFTERNOON BUT WILL
SEE WINDS AT BOTH SITES TREND LIGHTER INTO THE OVERNIGHT PERIOD
BEFORE A SLIGHT INCREASE RETURNS FOR TOMORROW AFTERNOON.
IWX WATCHES/WARNINGS/ADVISORIES
IN...FREEZE WARNING FROM 2 AM EDT /1 AM CDT/ TO 9 AM EDT /8 AM CDT/
SATURDAY FOR INZ005>009-014-017-018-024>027-103-104-116-
203-204-216.
FROST ADVISORY FROM 2 AM EDT /1 AM CDT/ TO 9 AM EDT /8 AM CDT/
SATURDAY FOR INZ012-013-015-020-022-023-032>034.
OH...FREEZE WARNING FROM 2 AM TO 9 AM EDT SATURDAY FOR OHZ001-004-
015-024.
FROST ADVISORY FROM 2 AM TO 9 AM EDT SATURDAY FOR OHZ002-005-
016-025.
MI...FREEZE WARNING FROM 2 AM TO 9 AM EDT SATURDAY FOR MIZ078>081-
177-277.
MARINE...NONE.
DISCUSSION...ROLLER
AVIATION...ANDERSEN
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