501  
FXUS63 KIWX 192342  
AFDIWX  
 
AREA FORECAST DISCUSSION  
NATIONAL WEATHER SERVICE NORTHERN INDIANA  
742 PM EDT MON APR 19 2021  
   
SYNOPSIS
 
 
ISSUED AT 422 PM EDT MON APR 19 2021  
 
RAIN CHANCES WILL SLOWLY DIMINISH WITH LOWS DROPPING INTO THE 30S.  
RAIN WILL REDEVELOP TUESDAY ACROSS THE AREA, WITH A TRANSITION TO  
ALL SNOW LATE AFTERNOON INTO TUESDAY EVENING. SNOWFALL TOTALS OF  
2 TO 4 INCHES ARE POSSIBLE ALONG AND SOUTH OF US 24 AND EAST OF  
INTERSTATE 69 WITH LESSER AMOUNTS NORTHWEST. THE WEDNESDAY MORNING  
COMMUTE MAY BE SLICK, SO PLAN FOR EXTRA TIME TO REACH YOUR  
DESTINATION. A FREEZE WARNING IS IN EFFECT FOR TUESDAY NIGHT AND  
WEDNESDAY NIGHT, WITH LOW TEMPERATURES FALLING INTO THE 20S.  
 

 
   
UPDATE
 
 
ISSUED AT 730 PM EDT MON APR 19 2021  
 
CHANGES MADE TO SLOW DOWN SOUTHEAST PROGRESS OF RAINFALL AS BAND  
CONTINUES TO REDEVELOP. QUESTIONS STILL REMAIN HOW FAR SOUTHEAST  
THE RAIN WILL MAKE IT BEFORE SLOWLY DIMINISHING. HAVE BLENDED AS  
BEST AS POSSIBLE TO KEEP SOME POPS OVERNIGHT BEFORE RAMP UP IN  
POPS ON TUESDAY. OTHERWISE NO OTHER CHANGES.  
 

 
   
SHORT TERM
 
(THIS EVENING THROUGH WEDNESDAY NIGHT)  
ISSUED AT 422 PM EDT MON APR 19 2021  
 
BOTTOM LINE UP FRONT: UPGRADED TO A FREEZE WARNING FOR THE CWA GIVEN  
HIGH CONFIDENCE IN TEMPERATURES TUESDAY NIGHT AND WEDNESDAY NIGHT  
FALLING BELOW 32 DEGREES. EVEN IF WE DO GET CLOUD COVER, THE AIRMASS  
IS COLD ENOUGH THAT WE'LL SEE AT LEAST UPPER 20S IN MOST AREAS, IF  
NOT MID 20S. IT IS A LITTLE BIT EARLIER THAN WE USUALLY ISSUE  
WARNINGS BUT GIVEN THE SIGNIFICANT IMPACTS UPPER 20S WILL HAVE ON  
THE FRUIT CROPS AND OTHER VULNERABLE VEGETATION, FIGURED WE MIGHT AS  
WELL ENSURE THE WORD IS OUT. CURRENT FORECAST HAS LOWS OF 23F TO  
AROUND 30F, WITH LOCATIONS CLOSE TO LAKE MI CLOSER TO 32F.  
 
AS FOR OUR POTENTIAL SNOW EVENT, THE UPPER LEVEL JET STILL LOOKS TO  
PROVIDE THE BEST FORCING BETWEEN 00-6Z TUESDAY NIGHT, WITH THE MID  
LEVEL TROUGH TO THE WEST OF OUR CWA PROVIDING A BROAD REGION OF DVA-  
STRONGEST IN THE SOUTHEAST. INSTABILITY STILL LOOKS FAVORABLE IN  
THAT AREA FOR HIGHER RATES, WITH NEGATIVE EPV ABOVE THE FRONTAL  
ZONE.REGARDING ANY WINTER WEATHER ADVISORIES AND WARNINGS, STILL NOT  
THE GREATEST CONFIDENCE IN SNOW TOTALS AND THE IMPACTS FOR SO WILL  
HOLD OFF FOR NOW ON ISSUING ANYTHING. THE SOUTHEASTWARD SURFACE LOW  
PRESSURE TRACK TREND CONTINUES, AND MODELS ARE COMING MORE IN LINE  
WITH ONE ANOTHER IN REGARDS TO THE TIMING. HOWEVER, THEY DIFFER  
QUITE A BIT AS FAR AS THE MAGNITUDE AND LOCATION OF THE HIGHEST QPF,  
WITH THE NAM THE FARTHEST NORTHWEST DETERMINISTICALLY SPEAKING.  
THERE IS ALSO STILL QUITE A BIT OF SPREAD IN ENSEMBLE DATA. THE  
ECMWF, GEM, AND OF COURSE, THE GFS-HAVE ALL TRENDED SOUTHEAST. USED  
AROUND A 10:1 RATIO, WITH MOSTLY A RAIN/SNOW MIX TUESDAY AFTERNOON  
TRANSITIONING TO ALL SNOW FROM WEST TO EAST TUESDAY EVENING.  
 
AS FAR AS ACCUMULATIONS GO, I HAVE AROUND 2 TO 4 INCHES SOUTH OF US  
24 AND UP TO 2 INCHES NORTH OF US 24, WITH THE HIGHEST TOTALS EAST  
OF I-69. THE TEMPERATURES TUESDAY AFTERNOON ARE A LITTLE HIGHER THAN  
PREVIOUSLY FORECASTED IN ALIGNMENT WITH THE LATEST MODEL GUIDANCE,  
BUT IT'S POSSIBLE THE TEMPS END UP BEING A LITTLE LOWER AFTER 18Z IN  
THE NORTHWEST. IF THIS HAPPENS, WE'LL TRANSITION TO ALL SNOW A  
LITTLE EARLIER THAN I CURRENTLY HAVE IN THE FORECAST (AFTER 00Z). I  
DID LOWER THEM A LITTLE BIT FROM WHAT THE MODELS SUGGESTED TO  
ACCOUNT FOR THE POTENTIALLY FASTER COOLING, BUT DIDN'T HAVE THE  
CONFIDENCE TO LOWER MUCH MORE THAN MID-UPPER 30S. IF WE DO  
TRANSITION EARLIER TUESDAY AFTERNOON WE COULD ADD UP TO ANOTHER INCH  
OF SNOW TO THE FORECAST IN THE NORTHWEST (HENCE THE WORDING "UP TO  
2").  
 
ON WEDNESDAY, THE UPPER TROUGH (OR CLOSED LOW AT THIS POINT) DRIFTS  
SLOWLY OVER LOWER MICHIGAN, TAKING THE BEST FORCING QUICKLY TO THE  
EAST. HOWEVER, A SHORTWAVE PIVOTS AROUND THE BASE, WHICH WILL BRING  
US CHANCES FOR SHOWERS IN THE SOUTH AND WESTERN FORECAST AREA IN THE  
AFTERNOON. HAVE HIGHS REACHING UP TO ABOUT 40-48 DEGREES (WARMEST  
SOUTHWEST), SO WE WILL HAVE CHANCES FOR RAIN/SNOW SHOWERS.  
 

 
   
LONG TERM
 
(THURSDAY THROUGH MONDAY)  
ISSUED AT 422 PM EDT MON APR 19 2021  
 
TEMPS MODERATE FOR THE END OF THE WEEK THOUGH STILL SLIGHTLY ON THE  
COOL SIDE OF NORMAL. CUT INITIAL BLENDED HIGHS OVER THE WEEKEND WITH  
POTENTIAL FOR PRECIP SAT AND GENERAL NW FLOW. LATEST GUIDANCE  
SUGGESTS FRIDAY WILL REMAIN DRY WITH NEXT HIGH AMPLITUDE TROUGH  
ARRIVING ON SAT WITH NEXT CHANCE OF RAIN. 12Z GUIDANCE IN DECENT  
AGREEMENT ON LONGWAVE RIDGE DEVELOPMENT EARLY NEXT WEEK YIELDING  
MUCH WARMER TEMPS.  
 

 
   
AVIATION
 
(FOR THE 00Z TAFS THROUGH 00Z TUESDAY EVENING)  
ISSUED AT 730 PM EDT MON APR 19 2021  
 
PERIOD OF FUEL ALTERNATE CONDITIONS (CIGS) AS ARRIVED AT KSBN, BUT  
IT WILL LIKELY BE SHORT LIVED, ENDING AS THE RAIN SINKS SOUTH AWAY  
FROM THE SITE. TAF TRENDS HAVE BEEN ADJUSTED TO REFLECT THIS WITH  
TRANSITION BACK TO VFR AFTER 2Z. AT KFWA FORECAST MORE PROBLEMATIC  
WITH EXPECTED DECREASE IN PRECIP WITH TIME. FUEL ALTERNATE  
CONDITIONS MAY STAY AWAY FROM THE SITE, BUT MVFR CIGS WILL LIKELY  
DOMINATE AS THE FRONT STALLS OUT.  
 
FOCUS THEN SHIFTS TO RETURN OF RAIN BETWEEN 15 AND 19Z AT BOTH  
SITES (KSBN FIRST). STILL CHALLENGES AS TO HOW FAST THE PRECIP  
WILL SHIFT SOUTH AND COLD AIR ARRIVE TO CAUSE A SWITCH TO A MIX OF  
RA/SN AS WELL EVENTUAL CHANGE TO ALL SNOW. HAVE LEFT ALL RAIN WITH  
MVFR CIGS MOVING BACK IN AT BOTH LOCATIONS WITH THE ARRIVAL OF THE  
RAIN, THEN POTENTIAL TRANSITION TO IFR CONDITIONS MAINLY AT KFWA  
AS BOTH CIGS DROP AND TRANSITION TO SNOW OCCURS (THE TRANSITION  
LIKELY MORE AFTER 00Z). EXPECTED FURTHER CHANGES TO BOTH TAFS AS  
WE GET CLOSER TO THE EVENT.  
 

 
   
IWX WATCHES/WARNINGS/ADVISORIES
 
 
IN...FREEZE WARNING FROM 10 PM EDT /9 PM CDT/ TUESDAY TO 8 AM EDT /7  
AM CDT/ THURSDAY FOR INZ003>009-012>018-020-022>027-032>034.  
 
MI...FREEZE WARNING FROM 10 PM TUESDAY TO 8 AM EDT THURSDAY FOR  
MIZ077>081.  
 
OH...FREEZE WARNING FROM 10 PM TUESDAY TO 8 AM EDT THURSDAY FOR  
OHZ001-002-004-005-015-016-024-025.  
 
LM...NONE.  

 
 

 
 
UPDATE...FISHER  
SYNOPSIS...MCD  
SHORT TERM...MCD  
LONG TERM...AGD  
AVIATION...FISHER  
 
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