015
FXUS63 KIWX 031603
AFDIWX
AREA FORECAST DISCUSSION
NATIONAL WEATHER SERVICE NORTHERN INDIANA
1203 PM EDT FRI OCT 3 2025
KEY MESSAGES
- WARM AND DRY FOR THE WEEKEND THROUGH EARLY NEXT WEEK. HIGH
TEMPERATURES WELL ABOVE NORMAL IN THE MID TO UPPER 80S.
- MINIMUM RELATIVE HUMIDITIES AS LOW AS 25% TO 40% OVER THE
WEEKEND MAY BE CONDUCIVE FOR ELEVATED FIRE DANGER, ESPECIALLY
SUNDAY WHEN BREEZES PICK UP.
- CHANCES FOR RAIN ARRIVE LATE MONDAY NIGHT THROUGH TUESDAY. IN
TOTAL, 0.25" TO 0.75" OF RAIN WILL BE POSSIBLE, WHICH WILL
NOT BE ENOUGH TO OFFSET ONGOING DROUGHT.
- NOTICEABLY COOLER BY MIDWEEK WITH TEMPERATURES CLOSER TO
SEASONABLE LEVELS. HIGHS IN THE LOW TO MID 60S WITH LOWS IN
THE 40S TO UPPER 30S POSSIBLE.
UPDATE
ISSUED AT 1008 AM EDT FRI OCT 3 2025
THE REMNANTS OF AN OLD CUT-OFF UPPER LEVEL SHORT WAVE TROUGH
ARE BEING SHEARED AS THIS VORT FILAMENT HAS LIFTED INTO
CENTRAL/NORTHERN ILLINOIS THIS MORNING. THIS FEATURE IS ALSO
ASSOCIATED WITH SOME HIGHER LOW LEVEL THETA-E AIR WHICH HAS BEEN
CONDUCIVE FOR ENOUGH INSTABILITY FOR A FEW ISOLATED SHOWERS
ACROSS CENTRAL ILLINOIS/NORTHEAST ILLINOIS. THIS LOCAL THETA-E
MAXIMUM SHOULD ATTEMPT TO ADVECT INTO NORTHWEST INDIANA THIS
AFTERNOON, BUT IN A WEAKER STATE. RAP SHORT TERM PROGS DO
INDICATE ~ 500 J/KG OF SFC BASED CAPE ACROSS THE FAR WEST THIS
AFTERNOON WITH THE INCREASED LOW LEVEL MOISTURE POSSIBLY
HELPING TO OVERCOME SOME WEAK LOW LEVEL CIN. GIVEN WEAKENING
NATURE TO MID/UPPER LEVEL FORCING AND VERY WEAK INSTABILITY,
WILL CONTINUE TO KEEP POPS BELOW MENTIONABLE LEVELS AROUND 10%,
GENERALLY TO THE WEST OF US-31 ACROSS NORTHERN INDIANA. NO MAJOR
CHANGES TO THE GOING FORECAST WILL BE MADE AT THIS TIME, WITH
LOWEST MIN AFTERNOON RELATIVE HUMIDITIES ACROSS FAR NE IN/NW OH.
DISCUSSION
ISSUED AT 258 AM EDT FRI OCT 3 2025
SURFACE HIGH PRESSURE RESIDES IN THE NORTHEASTERN US AND SLIDES
SOUTHWARD SLOWLY THROUGH TODAY. AT THE MID LEVELS, RIDGING IS IN
PLACE AND ACTS TO SUPPRESS LARGE SCALE DISTURBANCES. AT THE SAME
TIME, MID LEVEL SHORTWAVES STILL ROTATE AROUND THE HIGH PRESSURE
SYSTEM AS WELL AS AN AREA OF BETTER MOISTURE IN THE FORM OF 60
DEGREE DEW POINTS AS WARM AIR ADVECTION ENSUES. WITH THIS WARM AIR
ADVECTION TODAY, WE'LL HAVE SCATTERED CLOUD COVER THAT SHOWS ITSELF
IN TIME-SECTIONS AND SOUNDINGS JUST ABOVE 850 MB. IT WILL ALSO HELP
THE AREA RETURN SECURELY BACK INTO 80 DEGREE HIGH TEMPERATURES. IN
FACT, MID 80S OR HIGHER SEEM POSSIBLE FOR MOST PLACES AS MIXING GETS
UP TO AROUND 800 MB WHERE 10C RESIDES. THERE HAVE BEEN VARIOUS FIELD
AND GRASS FIRES OBSERVED ACROSS THE AREA IN RECENT DAYS AND THESE
HAVE BEEN HELPED ALONG BY OUR DRY DROUGHT CONDITIONS. THE LIMITING
FACTOR FOR THESE CONDITIONS HAS BEEN THE RELATIVELY WEAK WINDS SO
THAT ANY FIRES THAT START HAVE TROUBLE GETTING OUT OF CONTROL.
GRASSES AND CROP FIELDS HAVE BEEN DRYING OUT AND BROWNING THE LAST
COUPLE OF DAYS AND THIS LIKELY ALSO SERVES AS A FACTOR IN FIRE
CONDITIONS. FOR SATURDAY, SIMILAR HIGH TEMPERATURES AND SIMILAR DEW
POINTS TO FRIDAY PAINT A SIMILAR FIRE CONDITION PICTURE, BUT
SLIGHTLY HIGHER WINDS AND MIXING TO REDUCE DEW POINTS WILL MAKE 30
PERCENT MINRH VALUES LIKELY AND PERHAPS A FEW 20 PERCENT VALUES
COULD BE OBSERVED. ONE INTERESTING WRINKLE ON SATURDAY IS THAT THE
NAM WANTS TO BRING THE 60 DEGREE SFC DEW POINTS FARTHER EAST AND
PRODUCE SOME LIGHT PRECIPITATION AS A RESULT. AM NOT ENTIRELY
CONVINCED BASED ON FORECAST SOUNDINGS THAT RAIN IS PRODUCED, THOUGH.
SUNDAY'S FIRE WEATHER POTENTIAL IS ONE OF THE HIGHEST IN THIS
FORECAST WITH INCREASED WIND GUSTS UP TO 20 TO 25 MPH (THE COLD
FRONT EDGES CLOSER AND THE GRADIENT INCREASES CAUSING THE LOW LEVEL
JET TO PUSH INTO THE AREA), AND DRIER TRENDS IN DEW POINTS THROUGH
THE 50S TO THE 40S BY DAY'S END, ALL THE WHILE TEMPERATURES RISE
INTO THE MID 80S. MINRH PERCENTAGES IN THE 30S ARE LIKELY AND 20
PERCENT IS ALSO POSSIBLE.
BY THE TIME WE GET TO MONDAY, THE TROUGH IN THE WESTERN US SHEARS
OUT AND THE ENERGY PUSHES NORTHEAST INTO CANADA AS HELPED ALONG BY
THE UPPER LOW THERE. PAST MODEL RUNS HAVE BEEN INSISTENT ON BRINGING
MOISTURE INTO THE AREA OUT AHEAD OF THE SLOW MOVING COLD FRONT AND
CAUSING SHOWERS. AM SKEPTICAL OF PRE-FRONTAL INITIATION GIVEN OUR
ANTECEDENT DRY AIR AND THE FACT THAT THE MOISTURE PLUME REALLY
STRUGGLES TO ADVANCE THIS FAR NORTH. EVEN THE GFS, WHICH BRINGS RAIN
INTO THE AREA ON MONDAY, IS QUITE DRY BELOW 700 MB, WHICH POINTS TO
SPRINKLES AND LIGHT RAIN OR VIRGA IF IT HAPPENS AT ALL. HAVE MORE
CONFIDENCE ON RAIN ALONG THE MAIN FRONT, WHICH MOVES THROUGH BETWEEN
MONDAY NIGHT AND TUESDAY. THERE IS SOME INSTABILITY TO WORK WITH
DURING THIS TIME (~500 J/KG OF MUCAPE EARLY MONDAY NIGHT AND THEN UP
TO 1000 J/KG OF MUCAPE TUESDAY AFTERNOON) SO THERE COULD BE SOME
THUNDERSTORMS WITH LOCALLY HEAVY RAIN.
IT'LL TAKE A SHORTWAVE TRAVERSING THE BOTTOM OF THE TROUGH TO PUSH
THE COLD FRONT THROUGH THE AREA. EXPECT DRY AND COOLER CONDITIONS
BEHIND THE COLD FRONT WITH DEW POINTS BACK IN THE 40S, BUT HIGHS IN
THE 60S AS OPPOSED TO THE 80S FROM MONDAY. WITH THE ARRIVAL OF COLD
AIR, WE'LL NEED TO WATCH FOR FROST WEDNESDAY NIGHT SINCE UPPER 30
DEGREE LOW TEMPS DRAIN SOUTHWARD FROM MICHIGAN.
AVIATION /18Z TAFS THROUGH 18Z SATURDAY/
ISSUED AT 1203 PM EDT FRI OCT 3 2025
VFR CONDITIONS, LIGHT WINDS, AND MAINLY CLEAR SKIES WILL PERSIST
AGAIN THIS PERIOD ON THE BACKSIDE OF HIGH PRESSURE.
IWX WATCHES/WARNINGS/ADVISORIES
IN...NONE.
OH...NONE.
MI...NONE.
MARINE...NONE.
UPDATE...MARSILI
DISCUSSION...ROLLER
AVIATION...STEINWEDEL
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