231
FXUS63 KIWX 300547
AFDIWX
AREA FORECAST DISCUSSION
NATIONAL WEATHER SERVICE NORTHERN INDIANA
147 AM EDT SUN MAR 30 2025
KEY MESSAGES
- OFF AND ON LIGHT SHOWERS CONTINUE INTO THE OVERNIGHT AND MAY
BECOME DRIZZLE OR SHUT OFF BY SUNDAY MORNING.
- STRONG TO SEVERE THUNDERSTORMS REMAIN ON THE TABLE FOR SUNDAY
WITH THE MAIN THREATS BEING DAMAGING WINDS AND A TORNADO OR
TWO. THE THREAT LOOKS TO OCCUR BETWEEN 2PM AND 11PM.
- BRIEF SHOT OF COOLER TEMPERATURES MONDAY INTO TUESDAY.
- ANOTHER CHANCE FOR STRONG TO SEVERE THUNDERSTORMS EXISTS ON
WEDNESDAY OF NEXT WEEK.
DISCUSSION
ISSUED AT 259 PM EDT SAT MAR 29 2025
A STRONG CONNECTION TO THE GULF FEEDS OUR CHANCES FOR RAIN TONIGHT
INTO EARLY SUNDAY, BUT WEAKER VORT MAXES MOVING THROUGH IN THE FLOW
LIMIT LIFT TO SOME EXTENT. THERE IS SOME UPPER DIVERGENCE NOTED
OVERHEAD THAT SHOULD HELP TO AUGMENT RAINFALL AND AN INCREASE IN 850
MB DEW POINTS TO AROUND 10C AFTER MIDNIGHT TONIGHT INDICATES THE
MOISTURE DEPTH TO WORK WITH. MODELS HOLD OFF THE ARRIVAL OF
INSTABILITY TO SUNDAY MORNING AT THE EARLIEST. MOISTURE DEPTHS TO
NEAR THE SURFACE IS THE CULPRIT HERE AND THOSE MODELS HOLD ON TO
THOSE MOISTURE DEPTHS INTO THE MORNING. AS LONG AS THAT CONTINUES,
INSTABILITY WILL CONTINUE TO BE A QUESTION FOR SUNDAY. THE NAM
LIMITS LOW LEVEL RATES TO LESS THAN 7 C/KM UNTIL MIDDAY INTO THE
AFTERNOON AT THE EARLIEST INDICATING LIMITED TIME FOR SB INSTABILITY
DEVELOPMENT MEANING IT'S STILL THIS EVENT'S LIMITING FACTOR. THE NAM
IS ONE MODEL THAT INCREASES THE LOW LEVEL JET MID SUNDAY MORNING
INTO MIDDAY AND THAT BRINGS IN INSTABILITY (ELEVATED TO START)
AROUND 17Z. THE ECMWF ALSO HAS SOME LARGE ASCENT TO WORK WITH THAT
IS EXPECTED TO PUSH THROUGH DURING THE AFTERNOON. THE BEST SHEAR
WORKS INTO THE AREA AFTER 19Z AND IT IS MAINLY BOUNDARY-PARALLEL
INDICATING MAINLY A LINEAR STORM MODE. HOWEVER, GIVEN HELICITY
VALUES BETWEEN 100 AND 200 MS/2S, CANNOT RULE OUT SOME EMBEDDED
AREAS OF ROTATION WITHIN OWING TO A QLCS STORM MODE IN A HSLC
ENVIRONMENT. THERE ARE SIGNS THAT AN EML MAY BE ABLE TO WORK THROUGH
WITH RATES BETWEEN 7.5 AND 8 C/KM NOTICEABLE. HOWEVER, THE QUESTION
REMAINS ABOUT IF IT IS MIXED OUT OR NOT. IF THE SURFACE LEVEL
IS SO MOIST (WITH LCLS BELOW 1000M), MAINTAINING LARGE HAIL TO
THE SURFACE COULD BE DIFFICULT IF MELTING OCCURS. STILL, IT
APPEARS DAMAGING WINDS AND A TORNADO OR TWO ARE THE MAIN THREAT
WITH LOCALLY HEAVY RAIN AND SOME HAIL POSSIBLE.
GIVEN AN AREA OF RAINFALL FROM NOBLE COUNTY INTO DEKALB COUNTY ON
FRIDAY THAT RECEIVED 1 TO 3 INCHES AND MORE RAIN FALLING TODAY AND
TONIGHT, RIVERS IN THIS AREA ARE FORECAST TO MOVE INTO ACTION STAGE
OR HIGHER AS A RESULT. STORM MOTIONS ARE EXPECTED TO BE RELATIVELY
QUICK WITH THE POTENTIALLY INSTABILITY ENHANCED SUNDAY EVENING
STORMS REACHING 30 TO 50 KTS, HOWEVER GIVEN ANTECEDENT CONDITIONS,
CANNOT RULE OUT SOME LOCALIZED PONDING/STANDING WATER, ESPECIALLY IN
MORE URBAN AREAS.
THE SYSTEM AND ITS FORCING ARE OUT OF HERE BY MONDAY MORNING, BUT
THE MILD AIR WE'VE HAD WILL BE REPLACED BY COOLER AIR. TEMPS IN THE
70S OVER THE WEEKEND WILL BE MORE LIKE 30S AND 40S ON MONDAY WITH NW
OH AREAS SEEING AROUND 50 DEGREES IN THE MORNING BEFORE FALLING
THROUGH THE DAY.
WARM ADVECTION RETURNS TUESDAY NIGHT INTO WEDNESDAY OUT AHEAD OF OUR
NEXT SYSTEM BRINGING TUESDAY'S HIGH, WHICH WAS IN THE 40S ON
MONDAY, BACK INTO THE 60S TO AROUND 70 DEGREES ALONG WITH DEW
POINTS SURPASSING 60 DEGREES AS WELL. GIVEN THIS WARMER AND MORE
MOIST AIRMASS AHEAD OF A COLD FRONT, THE CHANCE RETURNS FOR
SHOWERS AND THUNDERSTORMS. STRONG EFFECTIVE SHEAR VALUES WELL
SURPASSING 30 KTS AND HIGH HELICITY VALUES WELL SURPASSING 200
M2/S2 ARE CURRENTLY BEING MODELED TO BE IN PLACE. ONE QUESTION
WILL BE HOW QUICKLY A WARM FRONT CAN MAKE IT THROUGH OUR AREA
WEDNESDAY MORNING AS THERE ARE DIFFERENCES IN THE MID RANGE
MODELS ON INSTABILITY'S MAGNITUDE. SPC HAS THE AREA COVERED BY
ITS 15 PERCENT CHANCE WITH THE 30 PERCENT CHANCE RIGHT ON OUR
SOUTHERN BORDER. GUSTY SYNOPTIC WINDS WILL ALSO BE POSSIBLE AS A
55 TO 60 KT LOW LEVEL JET SWINGS THROUGH.
BEHIND THIS STORM CHANCE, THE BAROCLINIC BOUNDARY GETS HUNG UP TO
OUR SOUTHEAST. THE BOUNDARY IS ABLE TO ADVANCE BACK INTO THE AREA TO
END THE WEEK AS WEAK LOWS DEVELOP ALONG IT AND RIDE NORTHWARD
BRINGING RENEWED CHANCES FOR SHOWERS AND STORMS THROUGH
SATURDAY.
AVIATION /06Z TAFS THROUGH 06Z MONDAY/
ISSUED AT 146 AM EDT SUN MAR 30 2025
STRONG LOW LEVEL ADVECTION OF MOISTURE CONTINUES AT BOTH SITES
WITH STRATUS AND MAYBE SOME PATCHY DRIZZLE OR LIGHT SHOWERS
EXPECTED TO DOMINATE THROUGH 15 TO 17Z BEFORE STRONG MIXING
ARRIVES AHEAD OF A PRE-FRONTAL TROUGH. ANTICIPATE IFR CONDITIONS
AT KSBN (SOME POTENTIAL FOR BRIEF PERIODS OF LIFR) AND KFWA ON
THE MVFR/IFR LINE.
FOCUS THEM SHIFTS TO SHOWER/STORM CHANCES ALONG EITHER THE PRE-
FRONTAL TROUGH OR THE MAIN COLD FRONT. MODEL CAMPS REMAIN SPLIT
AND EACH RUN OF THE HI-RES MODELS SEEMS TO BRING A NEW SCENARIO
LEADING TO OVERALL LOW CONFIDENCE. STORMS (STRONG-SEVERE) COULD
DEVELOP AT KSBN AS EARLY AS 19Z OR AS LATE AS 23Z SO HAVE OPTED
TO KEEP THE PREVIOUS TIMING IN PLACE FOR NOW. INTRODUCED THUNDER
AT KFWA CLOSER TO 00Z MON. TOYED WITH THE IDEA OF A TEMPO, BUT
GIVEN THE LOW CONFIDENCE FELT A MORE BROADBRUSHED 3 HOUR WINDOW
SEEMED THE BEST WAY TO HANDLE. WHILE NOT REFLECTED IN THE
FORECAST, WIND GUSTS OVER 50 KTS AND HAIL AS WELL AS LOWER
CIGS/VSBY ARE ALL ON THE TABLE. LATER FORECASTS WILL NEED TO
FINE TUNE THINGS FURTHER.
IWX WATCHES/WARNINGS/ADVISORIES
IN...NONE.
OH...NONE.
MI...NONE.
MARINE...NONE.
DISCUSSION...ROLLER
AVIATION...FISHER
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