341  
FXUS63 KIWX 181124  
AFDIWX  
 
AREA FORECAST DISCUSSION  
NATIONAL WEATHER SERVICE NORTHERN INDIANA  
624 AM EST FRI JAN 18 2019  
   
SYNOPSIS
 
 
ISSUED AT 354 AM EST FRI JAN 18 2019  
 
MODERATE SNOW WILL BEGIN ALONG AND NORTH OF THE TOLL ROAD LATE THIS  
EVENING AND WILL SPREAD ACROSS THE ENTIRE AREA DURING THE DAY  
SATURDAY. SNOWFALL TOTALS OF 4 TO 7 INCHES ARE EXPECTED FOR MOST OF  
THE AREA. NORTHEAST WINDS GUSTING TO 25 TO 35 MPH WILL ALSO LEAD TO  
CONSIDERABLE BLOWING AND DRIFTING SNOW. ARCTIC AIR WILL ALSO RETURN  
WITH WIND CHILLS STEADILY DROPPING THROUGH THE WEEKEND...TO AROUND  
15 BELOW ZERO BY MONDAY MORNING.  
 

 
   
SHORT TERM
 
(TODAY THROUGH SATURDAY)  
ISSUED AT 354 AM EST FRI JAN 18 2019  
 
APART FROM SOME BR AND PERHAPS SOME LINGERING FLURRIES/DRIZZLE EARLY  
THIS MORNING...NO SENSIBLE WEATHER CONCERNS THROUGH TODAY AND WILL  
SKIP STRAIGHT TO FEATURE OF INTEREST ON SO MANY MINDS THIS WEEK.  
BOTTOMLINE UP FRONT...ONLY MINOR CHANGES TO THE GOING FORECAST WITH  
GENERALLY 4-7" FOR MOST OF THE CWA. DID LOWER SNOW AMOUNTS SLIGHTLY  
FOR AREAS SOUTH OF THE TOLL ROAD GIVEN SLIGHTLY FASTER/WEAKER 00Z  
SOLUTIONS BUT RAISED SNOW AMOUNTS SLIGHTLY IN THE NORTH BASED ON  
STRONGER FGEN BAND EXPECTED TONIGHT. SEVERAL LINGERING DOUBTS ON  
FINAL SNOWFALL AMOUNTS THAT WARRANT HOLDING ONTO JUST A WATCH FOR  
NOW. HEART OF THE EVENT IS STILL OVER 24 HOURS AWAY AND GIVEN  
MARGINAL CRITERIA...WOULD RATHER SACRIFICE A BIT OF LEAD TIME THAN  
ZIGZAG ON HEADLINES. EVENING WATER VAPOR AND UPPER AIR ANALYSIS SHOW  
PACIFIC JET STREAK AND ATTENDANT SHEAR VORT MAX WERE ONLY PARTIALLY  
SAMPLED AT 00Z. WILL GET A MUCH BETTER SAMPLE AT 12Z THAT SHOULD  
PROVIDE MORE CLARITY AND CONFIDENCE IN FORECAST DETAILS.  
 
FIRST PHASE OF THE EVENT WILL BE CLASSIC RIGHT-ENTRANCE REGION FGEN  
BAND TO IMPACT OUR NORTHERN ZONES TONIGHT. 400-300MB JET STREAK IS  
DECENT (120+ KTS) BUT PULLS AWAY BY SAT MORNING WITH INCREASINGLY  
MUDDLED UPPER LEVEL PATTERN AS SOUTHERN STREAM TROUGH/JET STREAK  
APPROACH. NEVER DO GET A TRULY COUPLED UPPER LEVEL JET AND THIS IS  
BORNE OUT IN FGEN FIELDS WHICH ARE SIMILARLY DISJOINTED AND OVERALL  
UNIMPRESSIVE. AS PREVIOUSLY NOTED...THERE IS SOME REDUCED STATIC  
STABILITY ALOFT (ABOVE 500MB) BUT THIS IS WELL ABOVE PRIMARY FGEN  
CENTER (GENERALLY FOCUSED AROUND 700MB). CERTAINLY ENOUGH SUPPORT  
FOR SOME LIGHT/MODERATE SNOW (ESPECIALLY GIVEN 850-700MB MIXING  
RATIOS NEAR 3 G/KG) BUT MORE AGGRESSIVE QPF TOTALS (PARTICULARLY IN  
THE NAM12) SEEM SUSPECT. DID UP SNOW AMOUNTS FOR THE TONIGHT PERIOD  
BUT STILL GENERALLY IN THE 2-5" RANGE AND FOCUSED IN A MORE NARROW  
CORRIDOR ALONG AND NORTH OF THE TOLL ROAD AS SUGGESTED BY HIGHER  
RESOLUTION GUIDANCE.  
 
PRECIP THEN TRANSITIONS TO A MORE WIDESPREAD, DEFORMATION DRIVEN  
EVENT DURING THE DAY SAT AS LEFT EXIT REGION OF SOUTHERN STREAM JET  
MOVES OVERHEAD. ASSOCIATED PV ANOMALY PASSES JUST SOUTH OF OUR AREA  
AND DOES EVENTUALLY PHASE WITH NORTHERN STREAM SHORTWAVE BUT THIS  
PROCESS HAPPENS A BIT TOO LATE/DOWNSTREAM FOR ANY NOTICEABLE IMPACTS  
IN OUR AREA. AGAIN, FGEN FIELDS ARE DECENT BUT NOT SPECTACULAR WITH  
A MUDDLED LOOK AND ONLY MODEST/ELEVATED REDUCTION IN STABILITY.  
PLENTY OF AVAILABLE MOISTURE IN DEFORMATION ZONE NORTH OF 850MB LOW  
TO SUPPORT A QUICK 0.3" OR SO OF QPF BUT FOR ALL BUT OUR FAR SE  
ZONES...THIS PRECIP WILL BE IN AND OUT QUICKLY. CENTER PARTS OF OUR  
CWA MAY ONLY SEE ABOUT A 9-HOUR WINDOW OF PRECIP THAT WILL LIMIT  
SNOWFALL TOTALS. DEFORMATION LINGERS A BIT LONGER IN OUR FAR SE  
WHERE AROUND 0.5" QPF IS LIKELY. SNOW RATIOS WILL PROBABLY VARY  
QUITE A BIT ACROSS THE CWA WITH A SLIGHTLY WARMER PROFILE IN THE SE  
FAVORING MORE RIMING AND LIMITED STELLAR DENDRITES WHERE A SLIGHTLY  
COLDER PROFILE IN THE NW (ISOTHERMAL AROUND -10C) COULD FAVOR HIGHER  
RATIOS. EXPECT TO AVERAGE AROUND 16:1 IN OUR NW AND CLOSER TO 10:1  
IN OUR SE. NET RESULT IS A NEAR-UNIFORM 4-7" SNOWFALL FOR MUCH OF  
THE AREA WITH THE LOWEST AMOUNTS IN OUR SOUTHWEST WHERE DURATION IS  
MOST LIMITED.  
 
OF COURSE, WIND IS STILL EXPECTED TO BE A MAJOR FACTOR IN WHAT WOULD  
OTHERWISE LIKELY BE JUST AN ADVISORY-LEVEL EVENT. SUSTAINED WINDS  
WILL BE FROM THE NORTHEAST AROUND 20 MPH DURING THE DAY SAT WITH  
GUSTS UP TO 35 MPH POSSIBLE IN OUR SE BASED ON LATEST FORECAST  
SOUNDINGS AND TIME/HEIGHT CROSS-SECTIONS OF MIXING HEIGHTS AND  
WINDS. THIS WILL LEAD TO CONSIDERABLE BLOWING AND DRIFTING. WIND  
CHILLS WILL ALSO DROP INTO THE SINGLE DIGITS DURING THE DAY SAT.  
 
PUTTING EVERYTHING TOGETHER AND AFTER COLLABORATING WITH  
NEIGHBORS...FEEL BEST APPROACH IS TO HOLD WITH WATCH FOR ONE MORE  
CYCLE. CONFIDENCE IN SNOW AMOUNTS REMAINS ON THE LOWER SIDE AND  
COULD EASILY SEE ADJUSTMENTS IN EITHER DIRECTION. THOUGH SNOW WILL  
BEGIN IN OUR NORTH LATE THIS EVENING...BULK OF THE IMPACTFUL EVENT  
WILL BE SAT WHICH IS STILL A BIT FAR OUT TO UPGRADE WITH SUCH  
MARGINAL SNOW AMOUNTS.  
 

 
   
LONG TERM
 
(SATURDAY NIGHT THROUGH THURSDAY)  
ISSUED AT 354 AM EST FRI JAN 18 2019  
 
COLD TEMPS STILL THE STORY FOR THE EARLY PART OF NEXT WEEK. HIGHS  
WILL BE IN THE LOWER TEENS WITH LOWS WELL BELOW ZERO SUN NIGHT. WIND  
CHILL ADVISORY WILL LIKELY BE NEEDED FOR MON MORNING WITH WIND CHILL  
VALUES AROUND -15F. SOME LAKE EFFECT SNOW POSSIBLE IN OUR FAR NW  
ZONES ON SUN BUT LATEST GUIDANCE KEEPS DOMINANT BAND PRIMARILY WEST  
OF OUR AREA.  
 
WITH MAIN FOCUS ON SHORT-TERM CONCERNS...DID NOT MAKE MANY  
ADJUSTMENTS TO CONCENSUS INITIALIZATION IN LONG-TERM. ANOTHER SYSTEM  
EXPECTED MIDWEEK THOUGH CURRENT TRACK SUGGESTS MORE RAIN  
POTENTIAL AS HIGHS QUICKLY REBOUND INTO THE MID/UPPER 30S ON TUE.  
 

 
   
AVIATION
 
(FOR THE 12Z TAFS THROUGH 12Z SATURDAY MORNING)  
ISSUED AT 549 AM EST FRI JAN 18 2019  
 
NOT MUCH CHANGE IN FORECAST OF THE 12Z TAF CYCLE. MVFR CEILINGS TO  
PREVAIL THROUGHOUT THE DAY WHILE WINDS SLOWLY SHIFT OUT OF THE  
WEST TO OUT OF THE EAST. INFLUENCES OF APPROACHING UPPER LOW WILL  
START TO BE NOTICED AT KSBN AFTER 02Z AS A BAND OF SNOW STRETCHES  
ACROSS LAKE MICHIGAN. THIS SNOW IS NOT EXPECTED TO IMPACT KFWA  
UNTIL THE FINAL HOURS OF THIS TAF CYCLE. WHILE SNOW AFFECTS THE  
TERMINALS EXPECTED IFR TO LIFR CEILINGS/VISBY.  
 

 
   
IWX WATCHES/WARNINGS/ADVISORIES
 
 
IN...WINTER STORM WATCH FROM LATE TONIGHT THROUGH LATE SATURDAY NIGHT  
FOR INZ008-009-013-015>018-020-022>027-032>034.  
 
WINTER STORM WATCH FROM THIS EVENING THROUGH SATURDAY EVENING  
FOR INZ003>007-012-014.  
 
MI...WINTER STORM WATCH FROM THIS EVENING THROUGH SATURDAY EVENING  
FOR MIZ077>081.  
 
OH...WINTER STORM WATCH FROM LATE TONIGHT THROUGH LATE SATURDAY NIGHT  
FOR OHZ001-002-004-005-015-016-024-025.  
 
LM...SMALL CRAFT ADVISORY FROM 10 PM THIS EVENING TO 4 PM EST SUNDAY  
FOR LMZ043-046.  
 

 
 

 
 
SYNOPSIS...AGD  
SHORT TERM...AGD  
LONG TERM...AGD  
AVIATION...CM  
 
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