853  
FXUS63 KIWX 111114  
AFDIWX  
 
AREA FORECAST DISCUSSION  
NATIONAL WEATHER SERVICE NORTHERN INDIANA  
614 AM EST SUN DEC 11 2016  
   
SYNOPSIS
 
 
ISSUED AT 606 AM EST SUN DEC 11 2016  
 
LOW PRESSURE WILL LIFT RAPIDLY NORTHEAST FROM THE SOUTHERN PLAINS  
TODAY AND ACROSS THE WESTERN GREAT LAKES TONIGHT CAUSING SNOW IN  
OUR AREA, MIXING WITH OR CHANGING TO RAIN OVER SOUTHERN PORTIONS  
OF THE AREA THIS AFTERNOON AND EVENING. HIGH PRESSURE WILL MOVE  
INTO THE MIDWEST MONDAY PROVIDING DRY WEATHER. A COLD FRONT WILL  
MOVE ACROSS THE AREA TUESDAY FOLLOWED BY VERY COLD AIR WITH  
TEMPERATURES 15 TO 20 DEGREES BELOW NORMAL THE REMAINDER OF THE  
WORK WEEK.  
 

 
   
SHORT TERM
 
(TODAY AND TONIGHT)  
ISSUED AT 447 AM EST SUN DEC 11 2016  
   
..FIRST WIDESPREAD SNOW EVENT WELL UNDERWAY
 
 
WIDESPREAD LIGHT SNOW WAS PERSISTING ACROSS THE AREA WITH OCCASIONAL  
REPORTS INDICATING MANY SPOTS HAVE SEEN ANYWHERE FROM 2 TO 4 INCHES  
OF SNOW THUS FAR. RADAR TRENDS SUGGEST A QUICK CUT OFF IN  
PRECIPITATION TAKING PLACE ACROSS MUCH OF CENTRAL ILLINOIS. SOME  
CONCERNS THAT THIS COULD WORK INTO FAR S/SW AREAS THIS MORNING AND  
REDUCE SNOWFALL AMOUNTS SOMEWHAT. RENEWED FGEN BAND WAS INCREASING  
RETURNS ACROSS MUCH OF THE WESTERN THIRD TO HALF OF THE FORECAST  
AREA WITH VISIBILITIES GENERALLY 1 TO 2 MILES. EXPECTING ANOTHER  
INCH OR 2 OF SNOW THROUGH SUNRISE IN THESE AREAS WITH LESSER AMOUNTS  
EAST. AFTER 12Z INCREASING LOW LEVEL JET AND MUCH RICHER AIR MASS  
WILL COME SCREAMING NORTHEAST IN RESPONSE TO THE NEXT WAVE MOVING  
THROUGH THE PLAINS. WHILE NOT OVERLY STRONG, PLENTY OF LIFT WILL  
ACCOMPANY THIS FEATURE TO ALLOW FOR A RAPID EXPANSION AND  
INTENSIFICATION OF PRECIPITATION ACROSS THE AREA. CONFIDENCE IN THE  
WARNING AREA REMAINS HIGH THAT MOST IF NOT ALL PRECIPITATION WILL BE  
IN THE FORM OF SNOW, WHICH COULD BECOME LOCALLY HEAVY AT TIMES THIS  
AFTERNOON. AT PRESENT, SAVING GRACE FOR SIGNIFICANTLY HIGHER AMOUNTS  
WILL BE DECREASING SNOW RATIOS AS WARMER TEMPERATURES ARRIVE IN THE  
COLUMN ALSO DISPLACING THE DGZ FROM THE AREA OF BEST LIFT. EVEN SO,  
STILL SHOULD SEE SOME GOOD BURSTS OF SNOW WITH RATES OF AN INCH OR  
MORE PER HOUR POSSIBLE. HAVE TRENDED SLIGHTLY UPWARD WITH TOTALS AS  
QPF CONTINUE TO INCREASE ON ALL MODELS.  
 
NOW FOR THE EVEN TOUGHER PART, THE ADVISORY AREA. MAIN PUSH OF  
TEMPERATURES NEAR/ABOVE FREEZING STILL LOOKS TO REMAIN NEAR/SOUTH OF  
ROUTE 24 LATE AFTERNOON INTO THIS EVENING HELPING KEEP SNOW AMOUNTS  
IN CHECK. HOWEVER, WILL BE A CLOSE CALL ON POTENTIAL TO INCREASE  
HEADLINES TO A WARNING 1 TIER OF COUNTIES SOUTH DEPENDING ON HOW  
FAST THE MIX PRECIP ARRIVES AND FINAL TEMPERATURES. NORTH OF 24  
GRIDS REFLECT 4 TO 7 INCHES WITH LOCALLY HIGHER AMOUNTS BY THE TIME  
EVERYTHING IS DONE, WITH RAPID DROP IN SNOW AMOUNTS SOUTH AS SNOW  
RATIONS DROP BELOW 10:1. WILL DEFER TO DAY SHIFT FOR ANY HEADLINE  
MODIFICATIONS IN THE SOUTH AS ONLY A DIFFERENCE OF A DEGREE OR 2  
COULD HAVE A LARGE IMPACT.  
 
WITH REGARDS TO TONIGHT, DID KEEP CATEGORICAL POPS LINGERING THROUGH  
THE EVENING THEN A QUICK TAPER OVERNIGHT.  
 

 
   
LONG TERM
 
(MONDAY THROUGH SATURDAY)  
ISSUED AT 447 AM EST SUN DEC 11 2016  
 
TROUGH RESPONSIBLE FOR THE MESSY WEATHER IN THE SHORT TERM WILL EXIT  
TO THE EAST WITH ARCTIC LOW (AROUND 479 DM) CENTERED WEST OF HUDSON  
BAY SET TO PINWHEEL SOUTH AND THEN EAST ALONG THE SOUTHERN SHORES OF  
HUDSON BAY BY THURSDAY BEFORE EXITING INTO NORTHERN MAINE THURSDAY  
NIGHT. AS THIS TRANSITIONS SOUTH, THE WELL ADVERTISED BLAST OF  
ARCTIC AIR WILL SLAM INTO THE REGION STARTING MONDAY NIGHT AND  
PERSISTING INTO THURSDAY WITH COLDEST TEMPS BEING SEEN WEDS THROUGH  
THURS NGT AS HIGHS WILL STRUGGLE INTO THE TEENS (MAYBE STAYING IN  
SINGLE DIGITS IN SOME AREAS) AND LOWS SINGLE DIGITS (BELOW ZERO WITH  
SNOWPACK AND CLEARING??).  
 
SOME MODERATION IN TEMPERATURES WILL OCCUR FRIDAY INTO SATURDAY AS  
THE NEXT STRONG SYSTEM TAKES SHAPE IN THE SOUTHERN PLAINS AND HEADS  
INTO THE GREAT LAKES. LOTS OF VARIATIONS ON TRACK AND PRECIP TYPES  
WITH POTENTIAL FOR MIXED BAG OF WEATHER FOR ONSET FOLLOWED BY  
POSSIBLE PERIOD OF NEAR/ABOVE FREEZING TEMPS AND YET ANOTHER COLD  
BLAST RIGHT BEHIND IT. GFS/ECMWF IN ENOUGH AGREEMENT TO ALLOW  
SUPERBLEND POPS TO REMAIN IN THE HIGH CHC TO LIKELY RANGE FRIDAY  
NIGHT INTO SATURDAY.  
 

 
   
AVIATION
 
(FOR THE 12Z TAFS THROUGH 12Z MONDAY MORNING)  
ISSUED AT 606 AM EST SUN DEC 11 2016  
 
LARGE AREA OF LIGHT SNOW WITH EMBEDDED HEAVIER BANDS IN WAA REGIME  
AHEAD OF LOW PRESSURE OVER THE SRN/CENTRAL PLAINS CONTS TO IMPACT  
NRN IN ATTM. FORCING AND MOISTURE WILL INCREASE AS THIS SYSTEM  
APPROACHES SO SOME INCREASE IN PRECIP INTENSITY AND LOWERING OF  
AVIATION CONDITIONS EXPECTED TODAY. WAA MAY BE STRONG ENOUGH TO  
CAUSE A MIX OR CHANGEOVER TO RAIN ESPECIALLY AT FWA WHERE IT WAS  
INCLUDED IN THE TAF THIS EVE. PRECIP SHOULD COME TO AN END AROUND  
06Z BUT LOW CIGS WILL LIKELY PERSIST UNTIL THE END OF THE TAF  
PERIOD.  
 

 
   
IWX WATCHES/WARNINGS/ADVISORIES
 
 
IN...WINTER WEATHER ADVISORY UNTIL 4 AM EST /3 AM CST/ MONDAY FOR  
INZ013-015-017-018-020-022>027-032>034.  
 
WINTER STORM WARNING UNTIL 4 AM EST /3 AM CST/ MONDAY FOR  
INZ003>009-012-014-016.  
 
MI...WINTER STORM WARNING UNTIL 4 AM EST MONDAY FOR MIZ077>081.  
 
OH...WINTER WEATHER ADVISORY UNTIL 4 AM EST MONDAY FOR OHZ004-005-015-  
016-024-025.  
 
WINTER STORM WARNING UNTIL 4 AM EST MONDAY FOR OHZ001-002.  
 
LM...SMALL CRAFT ADVISORY UNTIL 4 PM EST MONDAY FOR LMZ043-046.  
 

 
 

 
 
SYNOPSIS...JT  
SHORT TERM...FISHER  
LONG TERM...FISHER  
AVIATION...JT  
 
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