546
FXUS63 KIWX 141808
AFDIWX
AREA FORECAST DISCUSSION
NATIONAL WEATHER SERVICE NORTHERN INDIANA
208 PM EDT WED MAY 14 2025
KEY MESSAGES
- SCATTERED SHOWERS AND ISOLATED THUNDERSTORMS THIS AFTERNOON INTO
EARLY THIS EVENING.
- WARM ON THURSDAY WITH A CHANCE FOR SEVERE THUNDERSTORMS THURSDAY
EVENING. CONFIDENCE IS LOW.
- WARM AGAIN ON FRIDAY WITH A ROUND OF SHOWERS AND THUNDERSTORMS
POSSIBLY LATE FRIDAY AFTERNOON INTO FRIDAY NIGHT.
- COOLER, DRY AND BREEZY THIS WEEKEND.
DISCUSSION
ISSUED AT 207 PM EDT WED MAY 14 2025
COVERAGE OF SCATTERED SHOWERS AND ISOLATED THUNDER HAS BEEN GIVEN A
DIURNAL BOOST AS EXPECTED THIS AFTERNOON NEAR A LINGERING NARROW
CONVERGENCE AXIS LIFTING SLOWLY NORTHEAST THROUGH THE AREA. LOCALLY
HEAVY RAINFALL, ISOLATED LIGHTNING, COLD AIR FUNNELS AND PERHAPS A
30-40 MPH GUST POSSIBLE WITH MORE ROBUST SHOWERS/STORMS. THIS
ACTIVITY THEN QUICKLY DIMINISHES THIS EVENING AS THE TROUGH AXIS
BEGINS TO LIFT OUT OF THE AREA AND THE BOUNDARY LAYER STABILIZES.
A STRONG LOW PRESSURE SYSTEM EMERGES OVER THE EASTERN DAKOTAS
TONIGHT-THURSDAY, SENDING A WARM FRONT NORTHEAST THROUGH THE
LOCAL AREA DURING THE MIDDAY HOURS ON THURSDAY. STEEPENING MID
LEVEL LAPSE RATES OVER ONGOING WARM/MOIST ADVECTION SUGGEST NON-
ZERO CHANCES FOR ELEVATED CONVECTION IN ADVANCE OF THE WARM
FRONT LATE TONIGHT THROUGH EARLY THURSDAY AFTERNOON. HOWEVER,
CAPPING AND SOMEWHAT WEAK CONVERGENCE THIS FAR EAST SUPPORT
HOLDING WITH A DRY FORECAST DURING THIS TIME.
A WARM AND MODERATELY HUMID AIRMASS (SFC DEWPOINTS SURGE INTO THE
UPPER 60S) OVERSPREADS THURSDAY AFTERNOON IN WAKE OF THE WARM
FRONTAL PASSAGE WITH MLCAPE VALUES LIKELY APPROACHING ~3000 J/KG
THANKS TO THE HIGH DEWPOINT AIR AND STEEP MID LEVEL LAPSE RATES
(8C/KM). HIGHS MAY NEAR DAILY RECORDS IF THERE IS ENOUGH CLEARING
WITHIN THE CAPPED WARM SECTOR.
THE MAIN FOCUS REMAINS ON A CONDITIONAL SEVERE THREAT (CONDITIONAL
ON IF STORMS ACTUALLY DEVELOP) THURSDAY EVENING AS A PRE-FRONTAL
TROUGH OR DRYLINE TRACKS IN UNDER 40-50 KNOTS OF EFFECTIVE DEEP
LAYER SHEAR AND AMPLE INSTABILITY FOR SUPERCELLS (ALL HAZARDS
POSSIBLE). COVERAGE/CHANCES FOR CONVECTION REMAIN UNCERTAIN AMID
THIS VOLATILE AIR MASS AS MORE PRONOUNCED UPPER FORCING AND
CONVERGENCE WITH AN OCCLUDED FRONT BYPASS THROUGH WI/FAR NRN IL/NRN
MI DURING THIS TIME. WHETHER THERE WILL BE ENOUGH COOLING ALOFT AND
SUFFICIENT CONVERGENCE ALONG THE INCOMING DRYLINE TO BREAK THROUGH A
CAPPING INVERSION AT THE BASE OF THE EML REMAINS THE POINT OF
CONTENTION THIS FAR SOUTH. IT IS WORTH NOTING THAT THE BULK OF THE
12Z CAMS SOLUTIONS HINT AT THIS ACTIVITY BEING MORE ISOLATED TO
SCATTERED GIVEN THE FORCING LIMITATIONS. WILL CONTINUE TO MONITOR
TRENDS AS ANY DEEP CONVECTION SHOULD HAVE A LOT TO WORK WITH.
DRIER AIR DOES FILTER IN FOR A TIME INTO FRIDAY WITH WARM TEMPS AND
SOMEWHAT BREEZY SOUTHWEST WINDS POTENTIALLY LEADING TO AN ELEVATED
FIRE RISK IN AREAS THAT HAVE MISSED OUT ON PREVIOUS RAINS. MOISTURE
AND INSTABILITY DO TRY TO ADVECT BACK INTO AT LEAST SOUTHERN PORTIONS
OF THE IWX AREA LATE FRIDAY AFTERNOON INTO FRIDAY EVENING IN
RESPONSE TO A SHORTWAVE AND COLD FRONT TRACKING EAST THROUGH THE
REGION. RETAINED SHOWER/STORM CHANCES AS A RESULT WITH SOME POTENTIAL
FOR SEVERE STORMS (MAINLY SOUTH) IF ENOUGH RECOVERY IS ACHIEVED
PRE-FRONTAL.
COOLER, DRY AND SOMEWHAT BREEZY CONDITIONS STILL LOOK TO FOLLOW IN
FOR THE UPCOMING WEEKEND, WITH BETTER RAIN CHANCES NOT RETURNING
UNTIL THE MIDDLE OF NEXT WEEK.
AVIATION /18Z TAFS THROUGH 18Z THURSDAY/
ISSUED AT 155 PM EDT WED MAY 14 2025
REMNANT UPPER LEVEL CIRCULATION WILL ALLOW SOME DIURNALLY
ENHANCED SHOWERS AND ISOLATED THUNDERSTORMS TO DEVELOP AGAIN
THIS AFTERNOON. THE GREATEST POTENTIAL OF THESE SHOWERS AT
TERMINALS IS IN THE 19Z-23Z TIMEFRAME. INSTABILITY PROFILES ARE
RATHER LIMITED, BUT DAYTIME HEATING COMBINED WITH LOW-MID 60S
DEW POINTS MAY YIELD 750-1250 J/KG OF SURFACE BASED CAPE.
CONFIDENCE IN THUNDER AT TERMINALS IS TOO LOW TO MENTION AT THIS
TIME GIVEN THE LIMITED INSTABILITY MAGNITUDES. THESE SHOWERS
SHOULD DIMINISH WITH LOSS OF DIURNAL INSTABILITY AFTER 23Z OR
00Z. SOME PATCHY FOG DEVELOPMENT IS POSSIBLE AGAIN LATE
TONIGHT/EARLY THURSDAY, BUT WILL HOLD OFF ON MENTION AT THIS
TIME WITH SUSPICION THIS MAY BE A SHALLOW FOG SITUATION WITH
MORE LIMITED COVERAGE THAN THIS MORNING.
IWX WATCHES/WARNINGS/ADVISORIES
IN...NONE.
OH...NONE.
MI...NONE.
MARINE...DENSE FOG ADVISORY UNTIL 8 PM EDT THIS EVENING FOR LMZ043-046.
DISCUSSION...STEINWEDEL
AVIATION...MARSILI
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