839
FXUS63 KIWX 271004
AFDIWX
AREA FORECAST DISCUSSION
NATIONAL WEATHER SERVICE NORTHERN INDIANA
604 AM EDT SUN SEP 27 2026
KEY MESSAGES
- COOL AND DRY CONDITIONS PERSIST THROUGH TUESDAY.
- RAIN CHANCES RETURN WEDNESDAY THROUGH THE WEEKEND.
- THE MOST LIKELY CHANCE FOR THUNDERSTORMS CAPABLE OF HEAVY RAIN
IS FRIDAY INTO THE WEEKEND. HOWEVER, CONFIDENCE IS LOW AT THIS
TIME.
DISCUSSION
ISSUED AT 128 AM EDT SUN SEP 27 2026
A DIFFUSE AREA OF VORTICITY RUNS INTO THE VIGOROUS SHORTWAVE
ASSOCIATED WITH THE NOR'EASTER ALONG THE EAST COAST AND THIS ALLOWS
FOR MINIMAL IMPACTS ON OUR DRY WEATHER AT HAND AS SURFACE HIGH
PRESSURE AND MID LEVEL RIDGING CONTINUE TO REMAIN IN CONTROL OF THE
WEATHER. 850 MB TEMPERATURES REMAIN BETWEEN 10 AND 13C, WARMEST WEST
OF IN-15, UNTIL TUESDAY NIGHT AND REALLY THE KEY TO TEMPERATURES
INCREASING WILL BE LOW LEVEL LAPSE RATES WHICH ARE THE BEST ON
MONDAY EAST OF I-69, BUT ALSO REACH 7+C/KM TODAY AND TUESDAY. THIS
HELPS TO KEEP HIGH TEMPERATURES IN THE 70 TO 75F RANGE THROUGH
MONDAY. FINALLY, WARMER MID TEENS 850 MB TEMPS WORK INTO THE AREA
TUESDAY THROUGH THURSDAY WITH MID 70S MORE COMMON ACROSS OUR
SOUTHWEST COUNTIES AND SOUTHERN 1 ROW OF COUNTIES. THIS IS AS A
HIGHER THETA-E PLUME SWINGS THROUGH THE AREA DURING THIS TIME FRAME.
THE AFOREMENTIONED THETA-E PLUME ALSO BRINGS IN ENOUGH MOISTURE TO
RETURN TALK ABOUT RAIN IN THE FORECAST AGAIN. BY THE TIME WE GET TO
WEDNESDAY, THE STRONG NOR'EASTER ALONG THE EAST COAST HAS PUSHED
EASTWARD INTO THE ATLANTIC AND A DIFFUSE AREA OF VORTICITY
ASSOCIATED WITH A POSITIVELY TILTED TROUGH ALOFT AND A SURFACE WARM
WARM FRONT ENTERS THE AREA. THESE WARM FRONTS ARE SYNONYMOUS WITH
HAVING ISSUES WITH DRY AIR WHEN IT COMES TO CAUSING PRECIPITATION,
ESPECIALLY WHEN DRY SURFACE ANTICYCLONES HAVE BEEN IN PLACE OVERHEAD
LIKE WE'VE HAD. MODELS CONTINUE TO STRUGGLE WITH TIMING THE
PRECIPITATION INTO THE AREA WITH THE ECMWF BEING THE ONLY MED RANGE
MODEL CAUSING PRECIP ACROSS THE AREA LATE TUE NIGHT INTO EARLY THU,
AND IT APPEARS TO BE QUITE DRY IN ITS OWN RIGHT. FINALLY, BOTH THE
GFS/AIGFS/CMC ALL BEGIN TO PUSH MORE RAIN INTO THE AREA THU AND THIS
IS WHEN THE ECMWF FINALLY BRINGS ITS BETTER MOISTURE (65F DEW
POINTS, 10+C 850 MB DEW POINTS) THROUGH THE AREA. DURING THIS WHOLE
TIME, TUE THROUGH LATE WORK WEEK, MUCAPE STAYS BELOW 100 J/KG WHICH
MEANS THE CONVECTIVE ELEMENT REMAINS MISSING THROUGH THIS WHOLE TIME
PERIOD WHERE RAIN CHANCES ARE HEIGHTENED. THE ECMWF HAS A PERIOD OF
WEAK LARGE SCALE ASCENT MOVING INTO THE AREA WEDNESDAY MORNING AS
WELL AS AT TIMES BETWEEN THURSDAY AND THE WEEKEND. MODELS NOW APPEAR
TO BE MUCH SLOWER BRINGING THE CUTOFF LOW IN THE SOUTH NORTHWARD
TOWARD THE AREA, WAITING UNTIL THE WEEKEND TO DO SO AND THAT'S WHY
THE ECMWF HAS SO MUCH MORE LARGE SCALE ASCENT TO WORK WITH DURING
THE WEEKEND. AS WE HEAD INTO THE LATE WEEK PERIOD, WE'LL ALSO HAVE
TO SEE WHERE A COLD FRONT SETS UP BECAUSE IF IT IS JUST TO OUR
SOUTH, WE LIKELY AVOID THE BETTER MOISTURE ADVECTION INTO THE AREA
AND SURFACE HIGH PRESSURE IS OUR MAIN WEATHER MAKER. IN SUMMARY, FOR
THIS WEDNESDAY INTO THE WEEKEND PERIOD, RAIN APPEARS POSSIBLE AT
TIMES, BUT HEAVY RAIN AND STRONGER STORMS APPEARS HARDER TO COME BY.
THE GREATEST CHANCE FOR HEAVY RAIN WOULD BE THE LATER FRIDAY THROUGH
SUNDAY PERIOD AS LONG AS A STALLED FRONT SETS UP JUST RIGHT ACROSS
THE AREA. IN LINE WITH THE LATE WEEK/WEEKEND CHANCE FOR RAIN, OUR
HIGHS IN THE 70S FORECAST LEADING UP TO THIS PERIOD ARE EXPECTED TO
BE COOLER, MORE LIKE IN THE MID TO UPPER 60S. AT LEAST OUR LOWS IN
THE 40S WARM INTO THE 50S AND, AT TIMES, 60S WITH THE RAIN AROUND.
THESE RAIN CHANCES LOOK TO BE OUT OF THE AREA BY THE TIME WE GET TO
EARLY NEXT WEEK.
AVIATION /12Z TAFS THROUGH 12Z MONDAY/
ISSUED AT 602 AM EDT SUN SEP 27 2026
DRY WEATHER REMAINS WITH THE SURFACE HIGH PRESSURE SYSTEM NEARBY AND
MID LEVEL RIDGING EXERTING ITS INFLUENCE OVER THE AREA. PATCHY FOG
IS AROUND THIS MORNING, ESPECIALLY IN AGRICULTURAL AREAS, BUT
WOULD EXPECT THAT TO EVAPORATE BY AROUND 13Z. THIS DOES LOOK TO
STAY AWAY FROM THE TERMINALS THOUGH. WINDS BACK NORTHERLY FROM
NORTHEASTERLY EARLY IN THE PERIOD AND STAY BELOW 10 KTS
SUSTAINED.
IWX WATCHES/WARNINGS/ADVISORIES
IN...NONE.
OH...NONE.
MI...NONE.
MARINE...NONE.
DISCUSSION...ROLLER
AVIATION...ROLLER
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