943  
FXUS63 KIND 151058  
AFDIND  
 
AREA FORECAST DISCUSSION  
NATIONAL WEATHER SERVICE INDIANAPOLIS IN  
558 AM EST SUN DEC 15 2024  
   
KEY MESSAGES
 
 
- RAIN AND DRIZZLE TODAY, DIMINISHING LATE  
 
- A SECOND ROUND OF RAIN WITH THE POTENTIAL FOR EMBEDDED  
THUNDERSTORMS ARRIVES EARLY MONDAY MORNING.  
 
- MILDER TEMPERATURES THROUGH MONDAY  
 
- COOLER TEMPERATURES ARRIVE FROM TUESDAY ONWARD  
 

 
   
SHORT TERM (TODAY AND TONIGHT)
 
 
ISSUED AT 254 AM EST SUN DEC 15 2024  
 
EARLY THIS MORNING THROUGH TODAY...  
 
EARLY THIS MORNING, AN UPPER LEVEL LOW WAS ACROSS CENTRAL ILLINOIS,  
WITH A SURFACE LOW ACROSS WESTERN ILLINOIS. AN 850MB JET WAS PUMPING  
MOISTURE INTO THE AREA. THESE WERE WORKING TOGETHER TO PRODUCE RAIN  
ACROSS MUCH OF THE FORECAST AREA.  
 
THE 850MB JET WILL MOVE OFF TO THE EAST DURING THE REMAINDER OF THE  
PRE-DAWN HOURS, TAKING THE SOLID AREA OF RAIN WITH IT. HOWEVER, AS  
THE UPPER LOW MOVES NORTHEAST, ADDITIONAL AREAS OF RAIN WILL DEVELOP  
AHEAD OF IT AND MOVE INTO THE AREA.  
 
THIS WILL CONTINUE PAST 12Z AS THE LOW MOVES INTO LOWER MICHIGAN.  
WILL GO AT LEAST LIKELY CATEGORY POPS ACROSS MUCH OF THE AREA  
THROUGH 12Z, THEN GRADUALLY PUSH THESE POPS EAST THROUGH THE MORNING  
AS THE UPPER LOW CONTINUES ITS JOURNEY NORTHEAST.  
 
UPPER MOISTURE WILL DIMINISH AS THE LOW MOVES NORTHEAST, BUT LOW  
LEVEL MOISTURE WILL LINGER. SOME WEAK FORCING MAY REMAIN IN THIS  
LAYER, WHICH WILL LIKELY LEAD TO SOME DRIZZLE. WILL CONTINUE WITH A  
DRIZZLE MENTION INTO THE AFTERNOON.  
 
IN ADDITION, WILL HAVE TO WATCH FOR SOME FOG IN THE NORTHERN  
FORECAST AREA THIS MORNING AS THE UPPER LOW MOVES BY, BASED ON WHAT  
IS ONGOING UPSTREAM.  
 
EVEN WITH THE CLOUDS AND RAIN/DRIZZLE, SOUTHERLY FLOW WILL ALLOW  
TEMPERATURES TO PEAK IN THE MIDDLE 40S TO MIDDLE 50S.  
 
TONIGHT...  
 
BRIEF UPPER RIDGING WILL MOVE IN FOR THIS EVENING AHEAD OF THE NEXT  
SYSTEM. THIS WILL KEEP THE AREA DRY DURING THE EVENING. HOWEVER,  
FORCING FROM THE NEXT UPPER TROUGH WILL MOVE IN OVERNIGHT. AN 850MB  
JET WILL RETURN AS WELL, BRINGING IN DEEPER MOISTURE ONCE AGAIN.  
 
THERE ARE SOME QUESTIONS THOUGH ABOUT HOW FAST FORCING AND MOISTURE  
RETURN, WHICH WILL IMPACT HOW FAR EAST THE RAIN WILL GET BY 12Z  
MONDAY. GIVEN THE UNCERTAINTY, WILL KEEP THE EASTERN PART OF THE  
AREA IN CHANCE POPS, WITH HIGHER POPS TO THE WEST.  
 
SOME WEAK INSTABILITY WILL MOVE INTO PORTIONS OF THE SOUTHERN  
FORECAST AREA, SO A RUMBLE OF THUNDER WILL BE POSSIBLE THERE  
LATE TONIGHT.  
 
LITTLE CHANGE IN AIRMASS PLUS CONTINUING CLOUD COVER WILL KEEP LOW  
TEMPERATURES IN THE 40S MOST AREAS.  
 

 
   
LONG TERM (MONDAY THROUGH SATURDAY)
 
 
ISSUED AT 254 AM EST SUN DEC 15 2024  
 
MONDAY/MONDAY NIGHT:  
 
BY MONDAY MORNING, A MOISTURE TONGUE ASSOCIATED  
WITH A MODEST WSW LLJ STREAK WILL BE BREACHING CENTRAL INDIANA,  
INITIATING A NEW ROUND OF PRECIPITATION. TRENDS CONTINUE TO SHIFT  
THIS INITIAL LLJ STREAK SOUTHWARD, NOW WITH HREF CLUSTERS GENERALLY  
JUST SOUTH OF THE OHIO RIVER. THIS HAS PLACED THE GREATEST  
PRECIPITATION AXIS (1.5-3") TO OVER THE OHIO RIVER, WITH GENERALLY  
0.5-1.0" OVER SOUTHERN INDIANA. WITHIN THE LLJ, STRONG DIFFERENTIAL  
WAA ALSO LOOKS TO CREATE STEEP 850-500MB LAPSE RATES, CREATING AN  
ELEVATED, EMBEDDED THUNDER THREAT THROUGH MONDAY MORNING. THIS  
THREAT WOULD LIKELY STAY CONFINED TO FAR SOUTHERN PORTIONS OF  
CENTRAL INDIANA.  
 
EVEN WITH SOME INCREASING HREF CONTINUITY, THERE ARE STILL SOME  
UNCERTAINTIES WITH MONDAY'S SYSTEM. THIS MOSTLY RESIDES WITH THE  
MAGNITUDE OF NORTHWARD THETA-E ADVECTION OUT AHEAD OF THE WAVE  
DURING THE DAY ON MONDAY. THE GREATER THE ADVECTION, THE GREATER THE  
BAROCLINICITY WILL BE AHEAD OF THE PRESSURE TROUGH, LEADING TO  
CHANCES FOR CONVECTIVE SHOWERS AND THUNDERSTORMS IN THE  
AFTERNOON/EVENING (CURRENTLY BEING MODELED BY THE HRRR/RAP).  
HOWEVER, LOOKING AT THE WHOLE HREF SUITE, ALONG WITH MODEL TRENDS,  
THERE LOOKS TO BE A GREATER THAN 50% CHANCE THE LOW LEVEL FLOW WILL  
REMAIN SW/WSW AHEAD OF THE PRESSURE TROUGH, MITIGATING NORTHWARD  
ADVECTION, AND THEREFORE LIMITING AFTERNOON CONVECTION CHANCES (MORE  
ALIGNED WITH THE NAM). WE WILL CONTINUE TO MONITOR THIS IN THE  
COMING ISSUANCES, AS THIS COULD ALSO IMPACT TOTAL QPF AND AFTERNOON  
HIGH TEMPERATURES, ALONG WITH POTENTIAL LOW END CONVECTIVE HAZARDS.  
 
TUESDAY ONWARD:  
 
AFTER THE PASSAGE OF THE WAVE ON MONDAY, LATEST MODEL GUIDANCE  
REMAINS STEADFAST WITH A MARGINAL COOLING TREND LATE MONDAY THROUGH  
TUESDAY. WITHOUT A LARGE UPPER LEVEL TROUGH, THIS CHANGE IN AIRMASS  
WILL BE MUCH MORE MARGINAL, WITH TEMPERATURES FALLING BACK TOWARDS  
SEASONAL (VS THE ARCTIC-LIKE AIRMASS WE HAD IN PREVIOUS WEEKS). THIS  
BEGINS TO CHANGE SOME MID-WEEK AS ANOTHER WAVE FURTHER TAPS INTO AIR  
OVER THE CANADIAN PLAINS. THIS WAVE WILL LIKELY STILL BE EARLY IN  
ITS LIFE CYCLE AS IT ARRIVES TUESDAY NIGHT INTO WEDNESDAY, WITHOUT A  
TRUE COLD CONVEYOR BELT FORMED. THEREFOR, P-TYPE ISSUES ARE NOT  
EXPECTED WITH THE MIDWEEK SYSTEM INITIALLY; THERE IS A LOW CHANCE OF  
SOME FROZEN PRECIP ON THE BACKSIDE OF THE WAVE WEDNESDAY EVENING.  
OUTSIDE OF GENERAL TEMPERATURE CONTINUITY, THERE IS LITTLE IN THE  
WAY OF MODEL CONSISTENCY REGARDING THIS SYSTEM'S TRACK AND  
MAGNITUDE, LEADING TO LOW CONFIDENCE ON SPECIFIC TIMING AND QPF  
AMOUNTS.  
 
DAYS 6-10: A SIGNAL FOR BROAD EAST COAST TROUGHING REMAINS WITHIN  
ENSEMBLE GUIDANCE BEGINNING LATE NEXT WEEK. SUCH A PATTERN TYPICALLY  
LEADS TO A COOLER AND DRIER PATTERN IN INDIANA UNDER NORTHWESTERLY  
FLOW. GUIDANCE DAMPENS THE TROUGHING SIGNATURE BY ABOUT CHRISTMAS  
WHICH IS LIKELY DUE TO UNCERTAINTY BETWEEN THE VARIOUS MEMBERS.  
 

 
   
AVIATION (12Z TAF ISSUANCE)
 
 
ISSUED AT 558 AM EST SUN DEC 15 2024  
 
IMPACTS:  
 
- IFR AND POTENTIALLY WORSE CONTINUING THROUGH MIDDAY, THEN  
RETURNING OVERNIGHT  
 
- GENERALLY MVFR FOR A PERIOD THIS AFTERNOON AND EVENING  
 
DISCUSSION:  
 
IFR AND POTENTIALLY LOWER CONDITIONS SHOULD BE PREDOMINANT THROUGH  
MIDDAY, THEN MVFR CEILINGS WILL LIKELY RETURN FROM THEN INTO THE  
EVENING. SOME VFR CONDITIONS ARE POSSIBLE LATE THIS AFTERNOON AT  
KHUF.  
 
AREAS OF RAIN AND DRIZZLE MAY REDUCE VISIBILITY AT TIMES THIS  
MORNING.  
 
OVERNIGHT, IFR CONDITIONS WILL RETURN ALONG WITH SOME RAIN.  
 

 
   
IND WATCHES/WARNINGS/ADVISORIES
 
 
NONE.  

 
 

 
 
SHORT TERM...50  
LONG TERM...UPDIKE  
AVIATION...50  
 
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