059
FXUS63 KIND 282306
AFDIND
AREA FORECAST DISCUSSION
NATIONAL WEATHER SERVICE INDIANAPOLIS IN
606 PM EST SUN DEC 28 2025
KEY MESSAGES
- NARROW CONVECTIVE LINE WITH THE POTENTIAL FOR BRIEF WIND GUSTS IN
EXCESS OF 50MPH AND PERHAPS A TORNADO WILL MOVE ACROSS CENTRAL
INDIANA EARLY THIS EVENING
- PEAK WIND GUSTS AT 45 TO 50MPH ACROSS THE NORTHERN HALF OF CENTRAL
INDIANA AT TIMES TONIGHT AND MONDAY
- RAPIDLY FALLING TEMPERATURES INTO THE TEENS AND 20S TONIGHT AND
MONDAY WITH WIND CHILL VALUES NEAR ZERO AT TIMES
- MUCH COLDER WEATHER THROUGH THE UPCOMING WEEK WITH CHANCES FOR
LIGHT SNOW WEDNESDAY NIGHT/NEW YEAR'S EVE
MESOSCALE UPDATE
ISSUED AT 606 PM EST SUN DEC 28 2025
LATEST DISCUSSION:
FURTHER ANALYSIS OF SOME OF THE UNDERLYING
FEATURES OF THIS ENVIRONMENT SET UP SHOWS GREATER SYNOPTIC LEVEL
THERMODYNAMICS ALONG AND SOUTH OF THE I-74 CORRIDOR DUE TO LESS
CONVECTIVE INHIBITION IN THE 800-700MB LAYER, BUT N OF I-74 DOES
HAVE GREATER 3CAPE AND THEREFOR COULD BE MORE LIKELY TO PRODUCING
A BRIEF SPIN-UP OVER THE NEXT HOUR. THAT SAID, THIS SHOULD EVOLVE
INTO A GREATER THREAT SOUTH OF THIS AREA WITH TIME (1 TO 3 HOUR
TEMPORAL RANGE).
PREVIOUS DISCUSSION AS FOLLOWS:
A VOLATILE FRONTAL BOUNDARY WILL ENTER CENTRAL INDIANA OVER THE NEXT
HOUR, OF WHICH WILL HAVE THE POTENTIAL TO PRODUCE SEVERE WIND GUSTS
AND A FEW TORNADOES.
LATEST ANALYSIS SHOWS A STRONG SHEAR IN THE LOWEST 3KM, MAINLY
ATTRIBUTED TO A 45-55KT LLJ. THIS IS AIDING IN THE INVIGORATION OF
ONGOING CONVECTION OVER CENTRAL IL AND NORTHWEST IN. THAT SAID,
NORTHERN PORTIONS OF THE LINE ARE APPROACHING AN AREA OF MID LEVEL
SUBSIDENCE OF WHICH WILL LIMIT CONVECTIVE INSTABILITY AND EFFECTIVE
SHEAR. THIS SHOULD WEAKEN THE OVERALL LINE WITH TIME AS IT PUSHES
INTO NORTHERN PORTIONS OF INDIANA, INCLUDING FAR N PORTIONS OF
CENTRAL INDIANA. FOR NOW, 50-60MPH WINDS WILL BE THE MAIN THREAT,
BUT GIVEN 150-200 M2/S2 OF 0-1KM SRH, A BRIEF SPIN-UP CANNOT BE
RULED OUT.
FURTHER SOUTH, GREATER LOW LEVEL INSTABILITY AND EFFECTIVE SHEAR
SHOULD RESULT IN THE CONTINUATION OF A STRONG LEWP CONVECTIVE LINE.
UPSTREAM, SOME OF THE HIGHEST REFLECTIVITY HAS BEEN PROGRESSING
ORTHOGONAL TO THE MEAN FLOW, LIKELY DUE TO A MID LEVEL GRAVITY WAVE.
THIS COULD LEAD TO A MORE EASTWARD PROPAGATION IN THE STRONGEST
THUNDERSTORM COMPONENTS. DUE TO THE LEWP FEATURES, BREAKS IN THE
FLOW COULD ALLOW FOR NARROW CORRIDORS OF ROTATION AND THEREFOR THE
TORNADO THREAT IS EXPECTED TO CONTINUE FOR THE NEXT FEW HOURS FROM
VERMILLION TO BOONE COUNTIES AND POINTS SOUTHWARD ALONG THE LINE.
SHORT TERM (THIS EVENING THROUGH MONDAY)
ISSUED AT 1244 PM EST SUN DEC 28 2025
THE PRIMARY FOCUS FOR THE SHORT TERM PERIOD WILL BE TRACKING A
POTENT SYSTEM THIS EVENING INTO TONIGHT WHICH WILL BRING A LINE OF
STRONG TO SEVERE STORMS, STRONG GRADIENT WINDS, AND A 40+ DEGREE
TEMPERATURE DROP OVER 6 TO 9 HOURS. AS OF EARLY THIS AFTERNOON,
SKIES REMAIN MOSTLY CLOUDY ACROSS THE STATE WITH WINDS GRADUALLY
RAMPING UP AS THE LLJ STRENGTHENS. THE SURFACE LOW ASSOCIATED WITH
THE SYSTEM CONTINUES TO DEEPEN AS IT MOVES ACROSS NORTHERN ILLINOIS
WITH SHOWERS AND STORMS WERE MOVING ACROSS NORTHERN ILLINOIS. THESE
ARE EXPECTED TO REMAIN NORTHWEST OF THE FORECAST AREA THROUGH THE
REMAINDER OF THE AFTERNOON WITH THE MAIN TIMEFRAME FOR CONCERN FROM
AROUND 5PM TO 10PM AS THE AFOREMENTIONED LINE MOVES IN.
SEVERE THREAT.
DEW POINTS ACROSS BOTH CENTRAL INDIANA HAVE RISEN INTO THE LOW 60S
WITH MOST AREAS NOW SEEING TEMPERATURES IN THE LOW TO MID 60S WITH
INCREASING CONFIDENCE IN A NARROW AXIS OF EVEN HIGHER DEWPOINTS JUST
AHEAD OF THE FRONT. HIGH RESOLUTION MODELS CONTINUE TO PICK UP ON A
NARROW AXIS OF HIGHER DEWPOINTS JUST AHEAD OF THE FRONT WHICH WILL
ALLOW FOR ML CAPE VALUES OF 500-800 J/KG ACROSS ILLINOIS WHERE
CONVECTIVE INITIATION IS EXPECTED. DYNAMIC INDICES ARE ALL FAVORABLE
FOR CONVECTION WITH 0-1KM SHEAR UPWARDS OF 20KTS AND SRH VALUES
UPWARDS OF 300/400 M2/S2. THE MAIN QUESTION WILL BE HOW FAR EAST THE
BETTER INSTABILITY STRETCHES WITH THE LOSS OF DIURNAL HEATING
TOWARDS THE TIME THE LINE CROSSES INTO WESTERN INDIANA. THE TORNADO
THREAT WILL MAINLY BE ACROSS THE WESTERN AND NORTHWESTERN PORTIONS
OF THE FORECAST AREA BEFORE THE LOSS OF INSTABILITY BEGINS TO
TRANSITION THE THREAT TO JUST DAMAGING WINDS. WITH THE LINE EXPECTED
TO BECOME ORGANIZED, THE SEVERE THREAT WILL PERSIST THROUGH ALL OF
CENTRAL INDIANA EVEN AS INSTABILITY DROPS. WHILE THE GREATER THREAT
WILL BE ACROSS ILLINOIS, DO HAVE CONCERNS IN WIDESPREAD 40-55 MPH
WINDS ALONG THE LINE WITH SPORADIC 60-65 MPH WINDS AND AT LEAST A
FEW KINKS IN THE LINE WHICH COULD PRODUCE TORNADOES.
GRADIENT WIND THREAT.
OUTSIDE OF STORMS, GRADIENT WINDS WILL GUST 40-50 MPH ALONG AND JUST
BEHIND THE LINE OF STORMS WITH THE STRONGER GUSTS WITH OCCASIONAL
GUSTS OF 35-50 MPH CONTINUING THROUGH THE NIGHT. MODEL SOUNDINGS
SHOW THAT AS THE CAA STRENGTHENS, THE BOUNDARY LAYER NEVER FULLY
DECOUPLES WITH MIXING UP TO AROUND 3000FT THROUGH THE NIGHT. THE
BOUNDARY LAYER WINDS WILL BE STRONGEST TOWARDS DAYBREAK TOMORROW
WHICH IS WHEN THE CONFIDENCE IS HIGHEST IN THE HIGHER-END GUSTS.
WINDS ALOFT WILL GRADUALLY WEAKEN THROUGH THE DAY AS THE SYSTEM
EXITS WHICH WILL BRING AN END TO THE STRONGER GUSTS BY THE EVENING.
FLASH FREEZE AND SNOW THREAT.
THE OTHER FOCUS FOR TONIGHT WILL BE THE TEMPERATURE CRASH IN THE
AFTERMATH OF THE FRONTAL PASSAGE WITH A DROP FROM THE 60S INTO THE
20S IN AROUND SIX HOURS. THIS PRESENTS A RISK FOR A FLASH FREEZE.
WHILE STRONG POST-FRONTAL WINDS WILL HELP EVAPORATE SOME SURFACE
MOISTURE, ANY RESIDUAL STANDING WATER ON UNTREATED SURFACES,
PARTICULARLY BRIDGES AND OVERPASSES, WILL LIKELY FREEZE RAPIDLY
BEFORE IT CAN DRY ALONG WITH AREAS WHERE WATER HAD PONDED EARLIER IN
THE NIGHT. THE SNOW THREAT LOOKS INCREASINGLY MINIMAL TONIGHT AS
THERE WILL BE LITTLE TO NO FORCING BY THE TIME THE TEMPERATURES DROP
BELOW FREEZING. SOME SNOW SHOWERS WILL BE POSSIBLE ACROSS THE
NORTHERN COUNTIES TOMORROW ALONG WITH FLURRIES TO THE SOUTH
ASSOCIATED WITH THE BACKEND OF THE SYSTEM BUT ANY LAKE EFFECT SNOW
WILL REMAIN NORTH OF THE FORECAST AREA BASED ON EXPECTED WIND FIELDS.
LONG TERM (MONDAY NIGHT THROUGH SUNDAY)
ISSUED AT 231 PM EST SUN DEC 28 2025
A LARGE SCALE CLOSED LOW OVER THE GREAT LAKES TO JAMES BAY WILL
DOMINATE THE AREA FOR MOST IF NOT ALL OF THE LONG TERM PERIOD,
PRODUCING DRAMATICALLY COOLER CONDITIONS AND A COUPLE OF
OPPORTUNITIES FOR PRECIPITATION AMIDST A MOSTLY DRY STRETCH FOR THE
WEEK.
THE COOLEST TEMPERATURES WILL BE EARLY IN THE PERIOD IN THE WAKE OF
THE SHARP COLD FRONT EXPECTED THIS EVENING, WITH LOWS MONDAY NIGHT
IN THE TEENS AND HIGHS TUESDAY STRUGGLING BACK INTO THE MID 20S TO
AROUND 30.
A WEAK, QUICK-HITTING CLIPPER ON THE PERIPHERY OF THE LARGER SCALE
CLOSED LOW WILL BRING LOW CHANCES FOR SNOW SHOWERS TO PORTIONS OF
THE AREA MAINLY WEDNESDAY NIGHT.
EVEN LOWER CHANCES FOR PRECIP COME FRIDAY NIGHT INTO EARLY SATURDAY,
MAINLY ACROSS SOUTHERN PORTIONS OF THE AREA. LATEST DETERMINISTIC
RUNS ARE KEEPING THIS PRECIPITATION WELL TO OUR SOUTH, SO WOULD NOT
BE SURPRISED TO SEE THE BLEND CATCH UP IN THE NEXT DAY OR TWO AND
RETURN A DRY FORECAST HERE.
IN GENERAL, EXPECT TEMPERATURES TO BE MUCH MORE SEASONABLE FOR THE
FINAL WEEK OF 2025 INTO THE START OF 2026, WITH AT LEAST ONE,
PERHAPS TWO CHANCES FOR LIGHT PRECIPITATION AS WE GO THROUGH THE
WEEK. KEEP AN EYE ON SNOW CHANCES FOR NEW YEAR'S EVE, PARTICULARLY
THOSE PLANNING TO BE ON THE ROADS THAT NIGHT.
AVIATION (18Z TAF ISSUANCE)
ISSUED AT 1244 PM EST SUN DEC 28 2025
IMPACTS:
- MVFR CIGS EXPECTED THROUGH THE TAF PERIOD WITH BRIEF IFR AT TIMES
- LINE OF SHOWERS AND STORMS THIS EVENING, MAINLY FROM 23Z TO
01Z
- SOUTHWEST WINDS GUSTS PEAKING AT 25-30KTS THIS AFTERNOON, VEERING
TO WESTERLY TONIGHT AND INCREASING TO 40KTS
- FLURRIES AND LIGHT SNOW TOMORROW, HIGHEST CHANCES AT LAF
DISCUSSION:
MVFR CONDITIONS EXPECTED THROUGH THE TAF PERIOD WITH CIGS
OCCASIONALLY DROPPING TO IFR AT TIMES THROUGH 04Z. A LINE OF SHOWERS
AND STORMS IS EXPECTED TO MOVE FROM WEST TO EAST THIS EVENING FROM
AROUND 23Z TO 01Z WITH A WIND SHIFT FROM THE SOUTH TO WEST IN THE
AFTERMATH OF THE STORMS. WINDS WILL BEGIN TO GUST TO AROUND 25KTS
AFTER 20Z WITH GUSTS OF 30-40KTS IN THE AFTERMATH OF THE STORMS
THROUGH THE NIGHT. THE STRONGER WINDS WILL BEGIN TO RELAX TOWARDS
THE AFTERNOON TOMORROW WITH THE POTENTIAL OF SEEING FLURRIES AND
LIGHT SNOW AT TIMES. CONFIDENCE IN ACCUMULATING SNOW IS LOW WITH
BEST CHANCES TOWARDS LAF.
IND WATCHES/WARNINGS/ADVISORIES
WIND ADVISORY UNTIL 5 PM EST MONDAY FOR INZ021-028>031-035>049-
051>057-060>065-067>072.
MESOSCALE...UPDIKE
SHORT TERM...WHITE
LONG TERM...NIELD
AVIATION...WHITE
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