997
FXUS63 KIWX 011655
AFDIWX
AREA FORECAST DISCUSSION
NATIONAL WEATHER SERVICE NORTHERN INDIANA
1255 PM EDT TUE APR 1 2025
KEY MESSAGES
- SLIGHTLY BELOW NORMAL TEMPERATURES AND DRY CONDITIONS TODAY.
- SHOWERS INCREASE IN COVERAGE LATE TONIGHT INTO WEDNESDAY
MORNING WITH A FEW EMBEDDED STORMS POSSIBLE. SOME LOCALIZED
HEAVIER RAINFALL AMOUNTS POSSIBLE ACROSS FAR NORTHERN INDIANA
INTO SOUTHERN LOWER MICHIGAN. SOME SMALL HAIL IS ALSO POSSIBLE
WEDNESDAY MORNING.
- THERE IS AN ENHANCED RISK OF SEVERE THUNDERSTORMS WEDNESDAY AFTERNOON
THROUGH WEDNESDAY EVENING. ALL SEVERE HAZARDS ARE POSSIBLE
INCLUDING DAMAGING WINDS, LARGE HAIL, AND TORNADOES. SOME
THREAT OF LOCALLY HEAVY RAINFALL EXISTS WEDNESDAY NIGHT ACROSS
FAR NORTHEAST INDIANA INTO NORTHWEST OHIO.
- WINDY ON WEDNESDAY EVEN OUTSIDE OF ANY SHOWERS AND STORMS, WITH
GUSTS TO 30 TO 40 MPH AT TIMES.
DISCUSSION
ISSUED AT 345 AM EDT TUE APR 1 2025
THE MAIN WEATHER STORIES THIS MORNING INCLUDE THE SEVERE WEATHER
POTENTIAL FOR WED/WED NIGHT, FOLLOWED BY SOME HYDROLOGY CONCERNS
THROUGH THE WEEK.
SOME PATCHY STRATOCU IS NOTED IN SATELLITE THIS IMAGERY
DROPPING SOUTH ACROSS NORTHERN INDIANA IN ASSOCIATION WITH A
WEAK REINFORCING COLD FRONT/LOW LEVEL TROUGH. THE SHORT WAVE
RESPONSIBLE FOR THIS LAST PUSH OF COLDER AIR IS ALREADY
DEPARTING TO THE EASTERN GREAT LAKES. SHORT WAVE RIDGING WILL
BUILD ACROSS THE WESTERN GREAT LAKES BY MIDDAY WITH TRANSITION
BACK TO LOW LEVEL WARM ADVECTION. CYCLOGENESIS IN THE LEE OF
THE ROCKIES TODAY AND EASTWARD DEPARTURE OF LOW LEVEL RIDGE WILL
KEEP AN EASTERLY GRADIENT IN PLACE ACROSS THE REGION ALLOWING
FOR MAINTENANCE OF THE DRY LOW LEVEL AIRMASS TODAY.
FOR TONIGHT, A STRONG EASTERN PACIFIC JET WILL ALLOW UPPER TROUGH
ACROSS THE ROCKIES TO STRENGTHEN AND WILL INDUCE THE DEVELOPMENT OF
A STRONG LOW LEVEL JET FROM TEXAS INTO THE MID MS VALLEY. VERY
STRONG LOW/MID LEVEL THETA-E ADVECTION WILL CHARACTERIZE THIS
EVOLUTION WITH A POCKET OF 500-1000 J/KG MUCAPES WORKING ACROSS
THE SOUTHERN GREAT LAKES BY 12Z WEDNESDAY. THIS ADVECTIVE WING
FORCING WILL ALLOW AN EXTREMELY STRONG LOW LEVEL INVERSION TO
DEVELOP WITH DECENT ELEVATED INSTABILITY BASED ATOP THIS
INVERSION. THIS MORE VEERED SOUTH/SOUTHWEST LOW/MID LEVEL FLOW
WILL ALSO ADVECT SOME STEEPER MID LEVEL LAPSE RATES IN FROM THE
PLAINS POSSIBLY AIDING IN SOME INSTANCES OF SMALL HAIL INTO
EARLY WEDNESDAY MORNING.
THE THREAT OF SEVERE STORMS EXISTS FROM THE SOUTHERN GREAT
LAKES TO THE OHIO RIVER VALLEY WEDNESDAY/WEDNESDAY NIGHT...
THE UPPER LEVEL TROUGH ACROSS THE NORTHERN ROCKIES WILL LIFT INTO
THE NORTHERN PLAINS WEDNESDAY MORNING AS IT BEGINS TO ACQUIRE SOME
NEGATIVE TILT. DEEP LOW PRESSURE ACROSS NW IA/S MN WILL RESULT
IN VERY STRONG DOWNSTREAM SOUTHERLY LOW LEVEL FLOW FIELDS
(60-70 KNOTS AT 850 MB) THAT SHOULD ALLOW LOW LEVEL WARM FRONT
TO CLEAR THE AREA INTO CENTRAL LOWER MICHIGAN BY MIDDAY. SOME
UNCERTAINTY STILL EXISTS REGARDING THIS WARM FRONTAL POSITION
HOWEVER, WHICH COULD BE IMPACTED FROM EARLY MORNING CONVECTION.
ONE ITEM OF UNCERTAINTY REGARDING AFTERNOON SEVERE POTENTIAL
WEDNESDAY IS HOW QUICKLY PRIMARY INSTABILITY AXIS SHIFTS
EASTWARD, AND THE MAGNITUDE OF THE INSTABILITY WILL BE IN PART
DICTATED BY THE STRENGTH OF THE EML. THE NAM IS MOST PRONOUNCED
WITH THE EML LEADING TO MORE ROBUST 1000-1500 J/KG MLCAPE AXIS
SHIFTING ACROSS THE REGION IN THE AFTERNOON WHILE OTHER GUIDANCE
IS A BIT MORE TEMPERED WITH MUCAPES OF 500-1200 J/KG.
NONETHELESS, THE COMBINATION OF DEEP LAYER SHEAR OF 50-70 KNOTS
AND EVEN LOWER END INSTABILITY WOULD RAISE AT LEAST THE
POTENTIAL OF SUPERCELL MODE THUNDERSTORMS IN THE AFTERNOON/EARLY
EVENING IN THE PRE-FRONTAL ENVIRONMENT WITH ALL SEVERE HAZARDS
POSSIBLE. WHERE THIS INITIATION BECOMES PREFERRED BASED ON
INSTABILITY GRADIENT, WARM FRONTAL POSITION, AND EML STRENGTH IS
STILL UNCERTAIN.
VERY STRONG LOW/MID LEVEL PROFILES AND HIGHLY ANOMALOUS 0-1 AND 0-
3KM SRH VALUES YIELD A CONCERN FOR TORNADIC SUPERCELLS IF
ENOUGH INSTABILITY CAN BE REALIZED. TORNADIC SUPERCELLS IN THIS
ENVIRONMENT WOULD HAVE THE POTENTIAL TO BE LONGER TRACKED IF ALL
THE INGREDIENTS COME TOGETHER. CONVECTIVE MODE BECOMES A BIT
MORE UNCLEAR HEADING INTO THE EVENING, WHETHER STORMS REMAIN
DISCRETE A BIT LONGER, OR STORMS CONGEAL MORE QUICKLY, OR IF A
MIXED-MODE EVOLUTION DEVELOPS. GREATEST SEVERE THREAT STILL
APPEARS TO BE IN THE 21Z-06Z TIMEFRAME, DIMINISHING OVERNIGHT AS
FLOW BECOMES MORE VEERED WITH APPROACH OF COLD FRONT.
SLOWING FRONTAL BOUNDARY LATE WEDNESDAY NIGHT AND HIGHLY ANOMALOUS
MOISTURE TRANSPORT WILL LEAD TO SOME POTENTIAL OF HEAVY RAINFALL
WEDNESDAY NIGHT WITH PERHAPS AN ISOLATED FLASH FLOOD THREAT.
LOOKING AHEAD INTO THE WEEKEND, STALLING FRONT TO THE SOUTH WILL
BE SUSCEPTIBLE TO ADDITIONAL FRONTAL WAVES AS A LONG WAVE
TROUGH IS EXPECTED TO TAKE SHAPE ACROSS SOUTHWEST CONUS. THIS
COULD YIELD SOME AREAL FLOOD ISSUES FOR THE WEEKEND INTO MONDAY,
PARTICULARLY ALONG AND SOUTH OF US 24.
LONGWAVE PATTERN FINALLY SHOWS MORE PROGRESSION BY MONDAY WITH
AN END TO ANY ADDITIONAL ROUNDS OF HEAVIER RAINFALL. AFTER THE
MUCH ABOVE NORMAL TEMPERATURES WEDNESDAY, TEMPS SHOULD BECOME
MORE SEASONABLE FOR THE WEEKEND, AND TRENDING BELOW NORMAL FOR
MONDAY AS FRONTAL BOUNDARY SAGS SOUTHWARD.
AVIATION /18Z TAFS THROUGH 18Z WEDNESDAY/
ISSUED AT 1246 PM EDT TUE APR 1 2025
HIGH PRESSURE CENTERED OVER ONTARIO IS PROVIDING A DRY, SUNNY
DAY ACROSS OUR FORECAST AREA. VFR CONDITIONS ARE EXPECTED TO
PREVAIL THROUGH THIS EVENING, BEFORE CLOUDS MOVE IN AFTER
MIDNIGHT AHEAD OF OUR NEXT IMPACTFUL WEATHER SYSTEM. CEILINGS
WILL QUICKLY DROP TO MVFR BY 06-09Z AS SHOWERS AND STORMS
ADVANCE NORTHWARD AHEAD A WARM FRONT. THE BEST CHANCES FOR
SHOWERS AND SOME EMBEDDED THUNDERSTORMS WILL BE AT KSBN. WINDS
WILL SHIFT TO THE SOUTH AND BECOME SUSTAINED AROUND 15-20 KTS
WITH GUSTS AS HIGH AS 30-35 KTS IN THE EARLY MORNING HOURS OF
WEDNESDAY. AS WINDS BECOME INCREASINGLY GUSTY, EXPECT SOME LLWS
AFTER 09Z. A BREAK IN PRECIPITATION IS LIKELY LATE MORNING INTO
THE AFTERNOON BEFORE ANOTHER CHANCE FR STRONGER STORMS LATER IN
THE DAY WEDNESDAY. A LOW PRESSURE SYSTEM WILL LIFT NORTHEAST
THROUGH THE MIDWEST WITH THE ATTENDANT COLD FRONT SWEEPING
THROUGH THE AREA JUST BEYOND THIS FORECAST PERIOD, BRINGING A
LINE OF STRONG TO SEVERE STORMS WEDNESDAY EVENING. WIND GUSTS UP
TO 60KTS WILL BE POSSIBLE FROM 22Z TO 04Z THURSDAY.
IWX WATCHES/WARNINGS/ADVISORIES
IN...NONE.
OH...NONE.
MI...NONE.
MARINE...SMALL CRAFT ADVISORY FROM 10 PM THIS EVENING TO 5 AM EDT
WEDNESDAY FOR LMZ043-046.
GALE WATCH FROM LATE TONIGHT THROUGH WEDNESDAY AFTERNOON FOR
LMZ043-046.
DISCUSSION...MARSILI
AVIATION...JOHNSON
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