774
FXUS63 KIWX 250522
AFDIWX
AREA FORECAST DISCUSSION
NATIONAL WEATHER SERVICE NORTHERN INDIANA
122 AM EDT FRI APR 25 2025
KEY MESSAGES
- INCREASING CHANCES (20-30%) FOR SHOWERS AND THUNDERSTORMS
LATER TONIGHT THROUGH FRIDAY MORNING.
- SHOWERS AND THUNDERSTORMS WILL BE MOST WIDESPREAD FRIDAY
AFTERNOON AND EVENING (70% CHANCE).
- COOL ON SATURDAY WITH HIGHS NEAR 60 BUT BECOMING VERY WARM
THEREAFTER.
DISCUSSION
ISSUED AT 215 PM EDT THU APR 24 2025
HIGH PRESSURE OVERHEAD SUPPRESSES RAIN CHANCES FOR THIS AFTERNOON AND
EARLY THIS EVENING. LARGE DEW POINT DEPRESSIONS OF 30 DEGREES ARE
NOTED AT MANY STATIONS. MOISTURE ADVECTION IS UNDERWAY, HOWEVER,
ALONG THE OHIO RIVER VALLEY WHERE DEW POINTS ARE IN THE 60S. THIS
AIRMASS LIFTS NORTH THROUGH THE REMAINDER OF THE DAY ON THE WESTWARD
EDGE OF A SOUTHEAST US RIDGE. RH VALUES IMPROVE THROUGH THE COLUMN
OVERNIGHT, PRIMARILY AFTER 2AM EDT WHICH IS WHEN THE CHANCE FOR
ISOLATED AND SHOWERS AND THUNDERSTORMS ENTERS THE FORECAST. CAMS ARE
INCREDIBLY VARIED IN THEIR COVERAGE OF SHOWERS AND STORMS, LIKELY
OWING TO WEAK FORCING BEYOND THE IMPLIED WARM FRONT. UPPER-LEVEL
FORCING IMPROVES AFTER DAYBREAK FRIDAY AS THE CANADIAN TROUGH NEARS
AND SURFACE LOW PRESSURE OVER THE PLAINS ARRIVES. FORECAST SOUNDINGS
ARE GENERALLY UNIMPRESSIVE, MAINLY DUE TO A LACK OF SHEAR. THUS,
SEVERE WEATHER IS NOT ANTICIPATED FRIDAY. REMAINING MILD WITH HIGHS
WELL INTO THE 70S.
A COLD FRONT MOVES THROUGH OVERNIGHT FRIDAY AND ANY LINGERING
SHOWERS AND STORMS WILL DEPART AFTER DAYBREAK SATURDAY. RELATIVELY
COOL WITH HIGHS ONLY NEAR 60 (COOLER LAKESIDE) FOLLOWED BY LOWS
SATURDAY NIGHT IN THE UPPER-30S. DEW POINT DEPRESSIONS MAY BE LARGE
ENOUGH TO FEND OFF FROST.
THE NEXT ITEM OF INTEREST IS THE CHANCE OF THUNDERSTORMS TUESDAY.
CLUSTER ANALYSIS REVEALS DIFFERING SPEEDS AND STRENGTH OF A POSITIVE-
TILT 500MB TROUGH MOVING ACROSS THE NORTHERN STATES. WHILE THE
TROUGH IS SOMEWHAT BROAD, THE 500-MB WIND FIELD IS FAVORABLE LOCALLY
WITH OUR AREA RESIDING NEAR THE RIGHT ENTRANCE REGION. PRE-FRONTAL,
EARLY-DAY CONVECTION COULD MUDDY THE WATERS HERE; SOMETHING THAT
WON'T BE RESOLVED UNTIL 24-HOURS IN ADVANCE. INITIAL MESOSCALE
INGREDIENTS APPEAR FAVORABLE FOR SEVERE THUNDERSTORMS, BUT WITH 16-
20+ MODEL CYCLES TO GO UNTIL TUESDAY EVENING, PLENTY OF TIME TO
MONITOR THE TRENDS IN GUIDANCE.
AVIATION /06Z TAFS THROUGH 06Z SATURDAY/
ISSUED AT 122 AM EDT FRI APR 25 2025
VFR CONDITIONS WILL PERSIST THROUGH THE MORNING WITH ABUNDANT
MID/UPPER LEVEL CLOUDS THANKS TO APPROACHING SHORTWAVE. MARGINAL
INSTABILITY IN A MOIST ENVIRONMENT WILL SUPPORT NUMEROUS SHOWERS
AND STORMS BY THE AFTERNOON. THERE REMAINS A LOT OF UNCERTAINTY
IN THE TIMING WITH STORMS POSSIBLE AS EARLY AS 16Z AND AS LATE
AS 01Z. KEPT TEMPO TSRA MENTION IN THE MIDDLE WHICH HAS THE BEST
SUPPORT AMONG HI-RES GUIDANCE (19-23Z). MVFR (POSSIBLY IFR)
STRATUS WILL THEN BUILD SOUTH FRIDAY NIGHT GIVEN INCREASING
POSTFRONTAL CAA AND PLENTY OF RESIDUAL BOUNDARY LAYER MOISTURE.
IWX WATCHES/WARNINGS/ADVISORIES
IN...NONE.
OH...NONE.
MI...NONE.
MARINE...SMALL CRAFT ADVISORY FROM 5 PM THIS AFTERNOON TO 8 PM EDT
SATURDAY FOR LMZ043-046.
DISCUSSION...BROWN
AVIATION...AGD
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