192  
FXUS63 KIWX 190004  
AFDIWX  
 
AREA FORECAST DISCUSSION  
NATIONAL WEATHER SERVICE NORTHERN INDIANA  
704 PM EST FRI JAN 18 2019  
   
SYNOPSIS
 
 
ISSUED AT 657 PM EST FRI JAN 18 2019  
 
A WINTER STORM WILL AFFECT THE REGION TONIGHT THROUGH SATURDAY  
EVENING. SNOW IS EXPECTED TO OVERSPREAD MAINLY EXTREME NORTHERN  
INDIANA AND SOUTHERN LOWER MICHIGAN LATER THIS EVENING, AND ACROSS  
THE REMAINDER OF THE AREA OVERNIGHT. SNOW WILL GRADUALLY TAPER OFF  
FROM NORTHWEST TO SOUTHEAST SATURDAY AFTERNOON. STORM TOTAL SNOW  
ACCUMULATIONS OF 4 TO 8 INCHES ARE POSSIBLE. GUSTY NORTHEAST  
WINDS WILL ALSO CREATE BLOWING AND DRIFTING SNOW SATURDAY AND  
SATURDAY EVENING. BITTERLY COLD CONDITIONS WILL BUILD ACROSS THE  
REGION SATURDAY NIGHT THROUGH MONDAY MORNING. WIND CHILLS TO 15  
BELOW ZERO ARE POSSIBLE MONDAY MORNING.  
 

 
   
SHORT TERM
 
(THIS EVENING THROUGH SATURDAY)  
ISSUED AT 335 PM EST FRI JAN 18 2019  
 
THE WINTER STORM WATCH HAS BEEN UPGRADED TO A WINTER STORM  
WARNING.  
 
COMPLICATED FORECAST SCENARIO WILL BEGIN TO UNFOLD THIS EVENING  
AS NARROW ELEVATED WARM ADVECTION WING/MID-UPPER LEVEL FGEN  
FORCING SHIFTS ACROSS THE SOUTHERN GREAT LAKES. WELL DEFINED RIGHT  
ENTRANCE REGION OF GREAT LAKES JET STREAK WILL ALSO SUPPORT  
EASTWARD PROGRESSION OF BETTER BANDING CURRENTLY TAKING SHAPE  
ACROSS IOWA/MINNESOTA THIS AFTERNOON. STILL SOME UNCERTAINTY AS  
TO EXACTLY WHERE THIS BANDING WILL SET UP, BUT CURRENTLY EXPECTING  
AREAS ROUGHLY NORTH OF ROUTE 6 TO BE BEST INLINE FOR THE INITIAL  
ACCUMULATIONS LATER THIS EVENING INTO THE EARLY OVERNIGHT. THERE  
WILL LIKELY BE SHARP SOUTH TO NORTH CUT-OFF WITH THIS INITIAL  
BAND. MOST OF NORTHERN INDIANA AND NORTHWEST OHIO WILL HAVE TO  
WAIT UNTIL LATE OVERNIGHT OR EARLY SATURDAY MORNING AS STRONGER  
LOW/MID LEVEL ADVECTIVE FORCING BEGINS TO SHIFT EAST. IN ADDITION  
TO MID/UPPER LEVEL F-GEN BAND TONIGHT, OTHER ITEM OF UNCERTAINTY  
WILL BE DETAILS REGARDING EVOLUTION OF PRIMARY SOUTHERN STREAM  
UPPER TROUGH. SUBTLE DIFFERENCES IN AMPLITUDE/WAVELENGTH OF THIS  
FEATURE AS IT LIFTS EAST/NORTHEAST APPEAR TO BE PLAY A MAJOR ROLE  
IN AFFECTING STRENGTH/DURATION OF DEFORMATION FORCING LATER  
SATURDAY AFTERNOON INTO EARLY SATURDAY EVENING. CONVECTION ACROSS  
THE LOWER/MID MS VALLEY MAY ALSO BE PLAYING SOME ROLE IN  
AFFECTING UPPER LEVEL HEIGHT FIELDS IN MODEL GUIDANCE WITH THIS  
TROUGH.  
 
IT STILL APPEARS AS THOUGH HEAVIEST SNOWFALL POTENTIAL WILL BE  
SOUTH OF US 24 ACROSS NORTHEAST INDIANA AND NORTHWEST OHIO DEPENDING  
ON HOW DEFORMATION FORCING EVOLVES. MID/LEVEL FRONTOGENESIS WILL  
INCREASE ACROSS THE AREA AGAIN DURING THE DAY SATURDAY AS  
DIRECTIONAL CONVERGENCE ASSOCIATED WITH LOW LEVEL JET INCREASES.  
MODEL TIME/HEIGHT SECTIONS DO INDICATE GOOD DEAL OF INSTABILITY  
ABOVE THIS FORCING WHICH COULD YIELD DECENT RESPONSE. GREATEST  
CONFIDENCE FOR 6+ INCH SNOW TOTALS IS ACROSS THE FAR SOUTHEAST  
WHERE MORE PROLONGED DEFORMATION FORCING IS EXPECTED INTO SATURDAY  
EVENING. SNOW RATIOS WILL VARY QUITE A BIT ACROSS THE AREA WITH  
HIGHEST RATIOS ACROSS THE NORTHWEST AND LOWEST RATIOS ACROSS THE  
SOUTHEAST WHERE LARGE PORTION OF LOW LEVEL SOUNDING IS IN THE 0 TO  
-6 DEG CELSIUS RANGE SATURDAY MORNING WITH INCREASED POTENTIAL OF  
RIMING.  
 
OPTED TO GO WITH A WARNING WITH THIS EVENT GIVEN COMBINATION  
SNOW/WIND THREAT, BUT AS MENTIONED ABOVE CONFIDENCE IS ON THE LOW  
SIDE IN ACCUMULATIONS GIVEN MULTI-FACETED ASPECT OF THIS STORM AND  
POTENTIAL THAT DEFORMATION BAND MAY END UP JUST SOUTH OF THE  
LOCAL AREA. IMPACTS WILL BE LIKELY EVEN IF LOWER END AMOUNTS  
VERIFY WITH GUSTS TO 25 TO 35 MPH, WITH BLOWING/DRIFTING CONCERNS  
GREATEST SATURDAY AFTERNOON/SATURDAY EVENING.  
 
BITTERLY COLD TEMPERATURES WILL BE THE OTHER CONCERN WITH SINGLE  
DIGIT LOWS ABOVE ZERO FOR SATURDAY NIGHT AND WIND CHILLS OF 5  
BELOW TO 10 BELOW ZERO.  
 

 
   
LONG TERM
 
(SATURDAY NIGHT THROUGH FRIDAY)  
ISSUED AT 335 PM EST FRI JAN 18 2019  
 
NOT MUCH CHANGE TO THE EXTENDED FORECAST WITH LOW CONFIDENCE IN  
LAKE EFFECT FOR SUNDAY. CONTINUED INDICATIONS THAT TRAJECTORIES  
AND LAKE AGGREGATE TROUGHING MAY FAVOR NE ILLINOIS/EXTREME NW  
INDIANA FOR BETTER LAKE EFFECT BANDING. GIVEN THIS UNCERTAINTY,  
WILL LIMIT POPS TO LOW TO MID CHANCE ACROSS NW INDIANA. BITTERLY  
COLD TEMPERATURES FOR SUNDAY-MONDAY WITH HIGHS ONLY REACHING 10  
TO 15 SUNDAY, AND LOWS SUNDAY NIGHT BELOW ZERO AWAY FROM LAKE  
EFFECT CLOUDS. WIND CHILLS MAY FLIRT WITH ADVISORY CRITERIA SUNDAY  
NIGHT/MONDAY MORNING, ALTHOUGH WINDS WILL BE DIMINISHING IN THE  
EVENING.  
 
ACTIVE PATTERN CONTINUES NEXT WEEK WITH RETREAT OF ARCTIC AIR AND  
ADDITIONAL EASTERN PACIFIC WAVES. ON TUESDAY INDICATIONS STILL  
POINT TO STRONG LOW LEVEL JET AHEAD OF ONE OF THESE WAVES AND  
STRONG THERMAL ADVECTION LEADING TO A BRIEF PERIOD OF SNOW LIKELY  
CHANGING TO RAIN. ADDITIONAL CHANCES OF SNOW WERE MAINTAINED FOR  
MID-LATE NEXT WORK WEEK.  
 

 
   
AVIATION
 
(FOR THE 00Z TAFS THROUGH 00Z SATURDAY EVENING)  
ISSUED AT 656 PM EST FRI JAN 18 2019  
 
DIFFICULT AVIATION FORECAST WITH TIMING OF LOWERING CIGS AND VIS  
WITH SNOW MAIN ISSUES. A NARROW AREA OF LIGHT SNOW WAS OVER KSBN  
AND OVER PERFORMING EARLY THIS EVENING. HAVE INCLUDED A TEMPO  
GROUP FOR EARLY EVENING BUT EXPECT THIS TO LIFT NORTH. BETTER  
FORCING ARRIVES LATE EVENING AND CONTINUES THROUGH SATURDAY  
AFTERNOON. SNOW WILL SPREAD INTO KFWA AFTER 10Z AND CONTINUE  
SATURDAY. IFR EXPECTED WITH LIFR POSSIBLE BRIEFLY AT TIMES WITH  
HEAVIER SNOW SHOWERS. CONDITIONS IMPROVE MID AFTERNOON KSBN AND  
LATE AFTERNOON OR EARLY EVENING KFWA.  
 

 
   
IWX WATCHES/WARNINGS/ADVISORIES
 
 
IN...WINTER STORM WARNING FROM 4 AM TO 10 PM EST SATURDAY FOR INZ026-  
027-032>034.  
 
WINTER STORM WARNING FROM 4 AM EST /3 AM CST/ TO 7 PM EST /6 PM  
CST/ SATURDAY FOR INZ008-009-012>018-020-022>025.  
 
WINTER STORM WARNING UNTIL 2 PM EST /1 PM CST/ SATURDAY FOR  
INZ003>007.  
 
MI...WINTER STORM WARNING UNTIL 2 PM EST SATURDAY FOR MIZ077>081.  
 
OH...WINTER STORM WARNING FROM 4 AM TO 10 PM EST SATURDAY FOR OHZ016-  
024-025.  
 
WINTER STORM WARNING FROM 4 AM TO 7 PM EST SATURDAY FOR OHZ001-  
002-004-005-015.  
 
LM...SMALL CRAFT ADVISORY FROM 10 PM THIS EVENING TO 4 PM EST SUNDAY  
FOR LMZ043-046.  
 

 
 

 
 
SYNOPSIS...LASHLEY  
SHORT TERM...MARSILI  
LONG TERM...MARSILI  
AVIATION...LASHLEY  
 
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