785
FXUS63 KIND 182302
AFDIND
AREA FORECAST DISCUSSION
NATIONAL WEATHER SERVICE INDIANAPOLIS IN
602 PM EST THU DEC 18 2025
KEY MESSAGES
- MODERATE TO HEAVY RAIN SHOWERS AND WIND GUSTS UP TO 50 MPH
POSSIBLE THROUGH THIS EVENING.
- SLICK/ICY SPOTS POSSIBLE FRIDAY MORNING AS TEMPERATURES DROP
QUICKLY TO WELL BELOW FREEZING.
- SNOW SHOWERS AT TIMES LATE TONIGHT INTO THE EARLY MORNING HOURS ON
FRIDAY WITH ACCUMULATIONS UP TO 1 INCH POSSIBLE.
- WIND CHILLS INTO THE SINGLE DIGITS POSSIBLE FRIDAY MORNING.
- WARMER THAN NORMAL TEMPERATURES IN THE 50S TO LOWER 60S LIKELY
SECOND HALF OF CHRISTMAS WEEK.
SHORT TERM (THIS EVENING THROUGH FRIDAY)
ISSUED AT 255 PM EST THU DEC 18 2025
A STRONG STORM SYSTEM MOVING THROUGH THE REGION WILL CONTINUE TO
SUPPORT MULTIPLE WEATHER HAZARDS THROUGH THE OVERNIGHT. A STRONGLY
FORCED HEAVY RAIN SQUALL LINE ALONG A COLD FRONT HAS HAD A HISTORY
OF PRODUCING WIND GUSTS OVER 50 MPH IN CENTRAL AND SOUTHERN ILLINOIS
THE LAST FEW HOURS. IN ADDITION, GRADIENT WIND GUSTS FROM 30-40 MPH
HAVE BEEN PREVALENT ACROSS THE FORECAST AREA THE LAST FEW HOURS.
BOTH THE GRADIENT WIND GUSTS AND THE PRECIP ENHANCED WIND GUSTS WILL
SUPPORT THE NEED FOR A WIND ADVISORY UNTIL THE EARLY EVENING HOURS
(01Z) BEFORE THE COLD FRONT MOVES EAST OF THE AREA. THE THREAT FOR
THUNDERSTORMS REMAIN VERY ISOLATED GIVEN POOR LAPSE RATES AND
NEGLIGIBLE MUCAPE IN THE SUB -20C LAYER. SPC HAS THE FAR SW PART OF
THE FORECAST AREA IN A MARGINAL RISK FOR SEVERE WIND GUSTS.
THE FORECAST THEN TURNS TO THE SHARPLY COLDER TEMPERATURES MOVING
INTO THE REGION FROM THE NW OVERNIGHT. 2M TEMP CONSENSUS SHOWS
READINGS REACHING 32F BY 04Z IN THE FAR NW PART OF THE FORECAST AREA
TO 08Z IN THE FAR SE. LOW TEMPERATURES BY 12Z FRIDAY RANGING FROM 15-
20 F NORTH TO 20-25 F IN THE SOUTH FROM THE BLENDED GUIDANCE LOOK
REASONABLE. THE QUICK FALL IN TEMPERATURES WITH RECENT QPE (0.25 TO
0.75 INCH PER MRMS) AND ADDITIONAL QPF OF 0.30 TO 0.6 INCH, SHOULD
SUPPORT SOME PONDING AND RESIDUAL WATER ON AREA ROADS WELL INTO THE
NIGHT. THEREFORE THE THREAT FOR A FLASH FREEZE LATER REMAINS A
CONCERN FOR LATER TONIGHT. IN ADDITION, THE THERMODYNAMIC AND LARGE
SCALE FORCING SUPPORT A CLASSIC "GROUND EFFECT" SNOW SHOWER EVENT
FOR CENTRAL INDIANA OVERNIGHT. THE TRANSITION TO SNOW WILL OCCUR
ROUGHLY THE SAME TIME AS MENTIONED FOR THE 32 F LINE. STEEP LOW
LEVEL LAPSE RATES UP TO 850MB, SUBTLE LOW LEVEL VERTICAL MOTION,
(OROGRAPHIC LIFT FROM THE MS VALLEY) AND THE PRESENCE OF MID
LEVEL PVA ALL SUPPORT THESE SNOW SHOWERS. ACCUMS UP TO 1 INCH LOOK
POSSIBLE AND MOST LIKELY THESE SNOW SHOWERS WILL BE IN SEVERAL
PARALLEL BANDS ORIENTED ALONG THE MEAN SHEAR VECTOR IN THE BL.
SNOW SHOWERS SHOULD DIMINISH FROM WEST TO EAST BETWEEN 09-13Z FRIDAY
AS MID LEVEL HEIGHT RISES AND A STRENGTHENING LOW LEVEL INVERSION
BUILD IN TO THE REGION IN THE WAKE OF THE SHORTWAVE TROUGH AXIS.
SKIES WILL GRADUALLY CLEAR BY AFTERNOON FROM WEST TO EAST AS DRIER
AIR/GREATER SUBSIDENCE MOVE INTO THE REGION. HAVE BUMPED UP WIND
GUSTS THROUGH THE NIGHT TO NEAR 30-35 MPH LASTING INTO THE MID
MORNING HOURS FOLLOWING A BLEND OF THE HRRR AND OTHER CAMS THANKS TO
THE STEEP LAPSE RATES AND STRONG CAA. THESE WIND GUSTS WILL ABATE TO
LESS THAN 20 MPH BY LATE AFTERNOON AS SURFACE HIGH PRESSURE RIDGE
BUILDS INTO INDIANA FROM THE MS VALLEY.
LONG TERM (FRIDAY NIGHT THROUGH THURSDAY)
ISSUED AT 255 PM EST THU DEC 18 2025
FRIDAY NIGHT THROUGH SUNDAY...
MOSTLY QUIET WEATHER IS EXPECTED EARLY IN THE PERIOD WITH SURFACE
HIGH PRESSURE REMAINING IN CONTROL. A LOW PRESSURE SYSTEM AND PARENT
TROUGH WILL MOVE THROUGH THE GREAT LAKES REGION LATE SATURDAY
PUSHING A COLD FRONT ACROSS CENTRAL INDIANA. PRECIPITATION IS
UNLIKELY DUE TO FORCING REMAINING NORTH OF INDIANA, BUT INCREASING
WARM ADVECTION SHOULD MODERATE TEMPERATURES CONSIDERABLY. THE COLDER
AIRMASS SETTLING IN EARLY FRIDAY SHOULD GENERALLY KEEP HIGHS IN THE
MID 20S TO LOW 30S WITH WARMER HIGHS IN THE MID 40S TO LOW 50S BY
SATURDAY.
A TIGHTENING MSLP GRADIENT AND DIURNAL MIXING MAY PROMOTE WIND GUSTS
BETWEEN 25-35 MPH ON SATURDAY. COOLER AIR THEN SETTLES BACK IN
SATURDAY NIGHT INTO SUNDAY. EXPECT LOWS IN THE 20S OVERNIGHT WHILE
HIGHS SUNDAY ONLY REACH THE 30S UNDER PERSISTENT CAA.
MONDAY ONWARD...
MODEL GUIDANCE DEPICTS AMPLIFYING RIDGING ALOFT NEXT WEEK WITH
SUBTLE WAVES MOVING ACROSS THE NORTHERN PERIPHERY OF THE RIDGING.
THESE SUBTLE WAVES ALONG WITH INCREASING WARM AIR ADVECTION SUPPORTS
LOW CHANCES FOR PRECIPITATION AT TIMES. LOOK FOR HIGHS IN THE 40S TO
WARM INTO THE 50S TUESDAY AND EVENTUALLY WIDESPREAD 60S BY
CHRISTMAS. PREDOMINATELY RAIN IS EXPECTED DUE TO THE SIGNIFICANT
WARM UP.
THERE ARE SLIGHT HINTS A WEAK WAVE COULD MOVE IN DURING THE
DAY MONDAY WITH THE POTENTIAL FOR LIGHT SNOW BEFORE TEMPERATURES
WARM UP ENOUGH. THIS SOLUTION IS AN OUTLIER AND APPEARS UNLIKELY AS
MOST GUIDANCE SHOWS THE WEAK IMPULSE MOVING IN LATER WHEN
TEMPERATURES ARE ABOVE FREEZING, BUT WILL CONTINUE TO MONITOR
TRENDS FOR ANY CHANGES.
AVIATION (00Z TAF ISSUANCE)
ISSUED AT 601 PM EST THU DEC 18 2025
IMPACTS:
- RAIN DIMINISHING, THEN LIGHT SNOW SHOWERS AFTER 03Z
- GUSTS UP TO AROUND 30KT AT TIMES THROUGH THE PERIOD
- MVFR/VFR CEILINGS BECOMING MVFR OVERNIGHT
DISCUSSION:
CEILINGS WILL BOUNCE BETWEEN MVFR AND VFR THROUGH THE FIRST QUARTER
OR SO OF THE PERIOD, THEN CEILINGS SHOULD SETTLE INTO MVFR THROUGH
FRIDAY MORNING. IMPROVEMENT IS EXPECTED FRIDAY AFTERNOON.
RAIN WILL DIMINISH THROUGH MID-EVENING, THEN SCATTERED TO NUMEROUS
SNOW SHOWERS WILL MOVE IN AS THE HEART OF THE COLDER AIR MOVES IN
LATE THIS EVENING INTO THE OVERNIGHT. MVFR VISIBILITY IS EXPECTED IN
SNOW SHOWERS. SNOW SHOULD EXIT THE SITES BY AROUND 12Z FRIDAY.
IND WATCHES/WARNINGS/ADVISORIES
WIND ADVISORY UNTIL 8 PM EST THIS EVENING FOR INZ021-028>031-
035>049-051>057-060>065-067>072.
SHORT TERM...CROSBIE
LONG TERM...MELO
AVIATION...50
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