266
FXUS63 KIWX 311028
AFDIWX
AREA FORECAST DISCUSSION
NATIONAL WEATHER SERVICE NORTHERN INDIANA
628 AM EDT MON MAR 31 2025
KEY MESSAGES
- MUCH COLDER TODAY WITH SOME MODERATION IN TEMPERATURES FOR
TUESDAY.
- DRY WEATHER TODAY THROUGH TUESDAY AFTERNOON, BUT SHOWER
CHANCES INCREASE LATE TUESDAY NIGHT (50-70% NW IN/SW LOWER MI
TO 20% NW OHIO)
- ANOTHER CHANCE FOR STRONG TO SEVERE THUNDERSTORMS EXISTS ON
WEDNESDAY, MAINLY FROM MID AFTERNOON THROUGH THE EVENING
HOURS. ALL SEVERE WEATHER HAZARDS ARE POSSIBLE INCLUDING
DAMAGING WIND GUSTS, LARGE HAIL, AND ISOLATED TORNADOES. IN
ADDITION, SOME HEAVY RAINFALL IS POSSIBLE WEDNESDAY NIGHT THAT
MAY LEAD TO SOME FLOODING.
DISCUSSION
ISSUED AT 400 AM EDT MON MAR 31 2025
THE POTENTIAL OF SEVERE THUNDERSTORMS WEDNESDAY AFTERNOON INTO
WEDNESDAY NIGHT REMAINS THE PRIMARY FORECAST ISSUE TO RESOLVE FOR
THIS CYCLE.
FOR TODAY, DEFORMATION FORCING AND PASSAGE OF MID/UPPER LEVEL TROUGH
AXIS IS ALLOWING FOR SOME POCKETS OF DRIZZLE, LIGHT RAIN, AND
LIGHT SNOW TO CONTINUE ACROSS SOUTHEAST WI/NORTHEAST
IL/NORTHWEST IN EARLY THIS MORNING. THE MID LEVEL WAVE SHOULD
CONTINUE TO DAMPEN EARLY THIS MORNING AS IT LIFTS ACROSS
SOUTHEAST ONTARIO WHICH WILL RESULT IN SHARP DECLINE IN LIGHT
PRECIP ACROSS THE WESTERN GREAT LAKES HEADING TO DAYBREAK. SFC
COLD FRONT IS JUST ABOUT TO EXIT FAR SOUTHEAST PORTIONS OF THE
FORECAST AREA AS OF 07Z, WITH LOW LEVEL COLD ADVECTION TODAY
ALLOWING FOR NORTHWEST WIND GUSTS INTO THE 20 TO 25 MPH RANGE.
AFTER FALLING TEMPERATURES THIS MORNING, TEMPS MAY HOLD STEADY
IN THE AFTERNOON IN THE MID 30S/LOWER 40S. CLOUDS WILL KEEP A
STUBBORN HOLD AS FRONTAL INVERSION KEEPS SOME RESIDUAL LOW
LEVEL MOISTURE LOCKED IN PLACE WITH LOW/MID LEVEL SUBSIDENCE
ACTING TO STRENGTHEN THE INVERSION.
WINDS WILL DIMINISH TOWARD EVENING AS A LOW LEVEL RIDGE AXIS PUSHES
IN FROM THE WEST. SOME MUCH DRIER LOW LEVEL AIR ASSOCIATED WITH THIS
RIDGE SHOULD HELP TO ERODE LOW CLOUDS FROM WEST TO EAST LATE IN THE
AFTERNOON INTO EARLY EVENING. TIMING OF THIS LOW LEVEL RIDGE AXIS
SHOULD OPTIMIZE RADIATIONAL COOLING TONIGHT WITH MINS BACK BELOW
NORMAL FROM MID 20S TO AROUND 30.
LOW LEVEL WARM ADVECTION WILL RAMP UP AGAIN EARLY TUESDAY AS LOW
LEVEL RIDGE DEPARTS TO THE EAST WHILE NEXT STRONG EASTERN PACIFIC
JET STREAK CARVES OUT A BROAD SOUTHWEST CONUS NEGATIVE UPPER
HEIGHT ANOMALY. STRONGER LOW/MID LEVEL MOISTURE TRANSPORT WILL
BE DISPLACED ACROSS THE PLAINS ON TUESDAY WITH LEADING EDGE OF
BETTER ELEVATED WARM/MOIST ADVECTION REACHING THE WESTERN GREAT
LAKES BY LATE TUESDAY NIGHT. SPC HAS PLACED FAR WESTERN PORTIONS
OF THE FORECAST AREA IN A MARGINAL RISK OF SEVERE STORMS FOR
TUESDAY, MAINLY FOR VERY LATE IN THE PERIOD TOWARD DAYBREAK
WEDNESDAY IN RESPONSE TO SOME INCREASE IN HAIL THREAT FROM
HIGHLY ELEVATED INSTABILITY MOVING IN.
SEVERE WEATHER POTENTIAL FOR WEDNESDAY AFTERNOON/WEDNESDAY
NIGHT...
GUIDANCE TRENDS CONTINUE TO SUPPORT A POTENTIALLY CONCERNING SEVERE
WEATHER SETUP FOR WEDNESDAY. THE EASTERN PACIFIC JET WILL BEGIN TO
PROGRESS THROUGH DOWNSTREAM PORTION OF THE UPPER TROUGH ACROSS THE
ROCKIES TUESDAY NIGHT HELPING TO TAKE STRONG SFC LOW PRESSURE INTO
THE UPPER MIDWEST/UPPER MS VALLEY REGION WEDNESDAY AFTERNOON.
SHOWERS AND EMBEDDED STORMS WILL LIKELY BE ONGOING WEDNESDAY MORNING
ACROSS THE SOUTHERN GREAT LAKES DUE TO VERY STRONG ADVECTIVE WING
FORCING AND INCREASING ELEVATED INSTABILITY. OUTSIDE OF A LOW
CONFIDENCE HAIL THREAT WITH THE ELEVATED INSTABILITY, STORMS SHOULD
LARGELY BE SUB-SEVERE THROUGH EARLY AFTERNOON WEDNESDAY.
DECENT AGREEMENT NOTED IN GUIDANCE THAT WEAK TO MODERATE MUCAPE AXIS
SHOULD BEGIN TO APPROACH WESTERN GREAT LAKES REGION LATER IN THE
AFTERNOON WITH EXPECTATION THAT LOW LEVEL WARM FRONT WILL RETREAT
ACROSS CENTRAL LOWER MICHIGAN BY EARLY WEDNESDAY EVENING. DEEP,
STRONG FLOW PROFILES WILL RAPIDLY DEVELOP WEDNESDAY AFTERNOON WITH
A 50-60 KNOT LOW LEVEL JET IN WAKE OF THE WARM FRONT PASSAGE.
COMBINATION OF STRONG KINEMATICS WITH THIS SYSTEM AND EVENTUAL
EASTWARD PROGRESSION OF MLCAPE AXIS INTO THE LOCAL AREA (500-1200
J/KG), COULD SUPPORT SOME INITIAL DISCRETE DEVELOPMENT ACROSS
NORTHEAST IL EASTWARD ACROSS SOUTHERN GREAT LAKES. WHILE INSTABILITY
OF THIS MAGNITUDE WOULD NOT NORMALLY SUPPORT A SUBSTANTIAL SEVERE
RISK, THE POTENTIALLY UNIQUE COMBINATION OF STRONG WIND
PROFILES/SHEAR AND INSTABILITY RAISES CONCERN FOR SUPERCELL STORM
MODE AND THE WHOLE SPECTRUM OF SEVERE HAZARDS INCLUDING
DAMAGING WINDS, LARGE HAIL, AND TORNADOES.
WHILE WE ARE STILL 3 DAYS OUT FROM THIS POTENTIAL EVENT, LARGE
SCALE SIGNALS HAVE BEEN CONSISTENT AND MAIN MODULATING FACTOR TO
THE EXTENT OF THE SEVERE THREAT WILL BE INSTABILITY MAGNITUDES
AS IS USUALLY THE CASE FOR THESE COLD SEASON SETUPS. CURRENTLY
EXPECTING PERIOD OF GREATEST CONCERN TO BE ROUGHLY IN THE
21Z-03Z TIMEFRAME WEDNESDAY AFTERNOON INTO WEDNESDAY NIGHT WHEN
PRIMARY INSTABILITY AXIS IS EXPECTED TO SAG SOUTHEAST INTO THE
AREA. THIS TIMEFRAME ALSO CORRESPONDS TO SOME HIGHLY ANOMALOUS
LOW/MID LEVEL MOISTURE TRANSPORT (IVT 4-6 STANDARD DEVIATION
ANOMALIES FOR EARLY APRIL PER NAEFS). WHILE SEVERE THREAT SHOULD
GRADUALLY WIND DOWN LATE EVENING INTO THE EARLY OVERNIGHT AS
INSTABILITY WANES, THE POTENTIAL OF SOME LOCALLY HEAVY RAINFALL
COULD PERSIST ACROSS NE IN/NW OH AS FRONT SLOWS AND SOME UPWIND
DEVELOPMENT BECOMES MORE LIKELY GIVEN STRONG UNIDIRECTIONAL WIND
PROFILES. STAY TUNED FOR LATER UPDATES ON THIS POTENTIAL SEVERE
WEATHER EVENT AS DETAILS BECOME MORE CLEAR OVER THE NEXT FEW
DAYS.
NOT MANY CHANGES MADE TO THE FORECAST POST-WED NIGHT WITH MAIN FOCUS
FOR ADDITIONAL SHOWERS AND STORMS THURSDAY AND FRIDAY TO THE SOUTH
OF THE LOCAL AREA IN PROXIMITY TO THE MAIN FRONTAL ZONE. BROADBRUSH
POPS HAD TO BE MAINTAINED INTO NEXT WEEKEND (HIGHEST ACROSS THE
SOUTH) FOR THE POTENTIAL OF ADDITIONAL FRONTAL WAVES
INTERACTING WITH THIS FRONT FOR MORE RAIN CHANCES.
AVIATION /12Z TAFS THROUGH 12Z TUESDAY/
ISSUED AT 608 AM EDT MON MAR 31 2025
A SECONDARY SFC TROUGH DROPPING ACROSS THE SOUTHERN GREAT LAKES
THIS MORNING HAS PRODUCED SOME LIGHT RAIN, DRIZZLE, AND PATCHY
LIGHT SNOW ACROSS NORTHEAST ILLINOIS AND NORTHWEST INDIANA.
THIS TROUGH WILL SINK SOUTHWARD THROUGH MID MORNING AND COULD
BRING A LITTLE BIT OF BRIEF DRIZZLE TO KFWA. STEEP LOW LEVEL
LAPSE RATES TODAY COUPLED WITH SHARPENING FRONTAL INVERSION
SHOULD ALLOW MVFR CLOUDS TO BE LOCKED IN PLACE THROUGH MUCH OF
THE DAY. LATER THIS AFTERNOON INTO EARLY EVENING SHOULD START TO
SEE LOW CLOUDS ERODE FROM NORTHWEST TO SOUTHEAST IN RESPONSE TO
MUCH DRIER LOW LEVEL AIR SINKING INTO THE REGION IN ASSOCIATION
WITH A LOW LEVEL RIDGE. GUSTY NORTHWEST TO AROUND 20 KNOTS WILL
CONTINUE TODAY, BUT GUSTS WILL DIMINISH EARLY THIS EVENING.
IWX WATCHES/WARNINGS/ADVISORIES
IN...NONE.
OH...NONE.
MI...NONE.
MARINE...SMALL CRAFT ADVISORY UNTIL 5 AM EDT TUESDAY FOR LMZ043-046.
DISCUSSION...MARSILI
AVIATION...MARSILI
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