840  
FXUS63 KIWX 210924  
AFDIWX  
 
AREA FORECAST DISCUSSION  
NATIONAL WEATHER SERVICE NORTHERN INDIANA  
424 AM EST TUE FEB 21 2017  
   
SYNOPSIS
 
 
ISSUED AT 323 AM EST TUE FEB 21 2017  
 
A WEAKENING COLD FRONT WILL MOVE INTO OUR AREA TODAY, LIKELY  
CAUSING SOME SHOWERS, MAINLY NORTHWEST PORTIONS AND MAINLY THIS  
MORNING. TEMPERATURES WILL REMAIN UNSEASONABLY WARM TODAY. LIGHT  
WINDS AND CLEARING SKIES SHOULD ALLOW PATCHY FOG TO DEVELOP OVER  
THE AREA TONIGHT. DRY CONDITIONS AND VERY WARM TEMPERATURES ARE  
EXPECTED WEDNESDAY AS SOUTHWEST WINDS STRENGTHEN AHEAD OF AN  
APPROACHING WEAK COLD FRONT. THIS FRONT WILL DROP INTO OUR AREA  
WEDNESDAY NIGHT AND REMAIN STATIONARY THURSDAY. A STRONG LOW  
PRESSURE SYSTEM MOVING NORTHEAST FROM THE CENTRAL PLAINS ACROSS  
THE GREAT LAKES WILL BRING INCREASING CHANCES OF SHOWERS AND  
THUNDERSTORMS TO OUR AREA THURSDAY NIGHT AND FRIDAY. SEVERE STORMS  
WITH DAMAGING WINDS ARE POSSIBLE FRIDAY AS THE COLD FRONT  
ASSOCIATED WITH THIS SYSTEM MOVES THROUGH THE AREA. TEMPERATURES  
WILL REMAIN UNSEASONABLY WARM THROUGH FRIDAY BUT RETURN CLOSER TO  
LATE FEBRUARY NORMALS SATURDAY THROUGH MONDAY. THE NORTHWEST FLOW  
SHOULD RESULT IN SOME SNOW SHOWERS OVER THE WEEKEND, MAINLY  
ACROSS NORTHWEST PORTIONS OF OUR AREA.  
 

 
   
SHORT TERM
 
(TODAY AND TONIGHT)  
ISSUED AT 323 AM EST TUE FEB 21 2017  
 
WKNG SHRTWV MOVG ACROSS THE UPR GRTLKS TODAY SHOULD RESULT IN BAND  
OF SHOWERS OVER IL/WI REACHING OUR NW THIS MORNING, BUT WK  
FORCING/LIMITED MOISTURE SUGGESTS SHOWERS PRBLY WON'T SURVIVE  
INTO THE SE. CAA BEHIND THIS SYSTEM NEGLIGIBLE WITH H85 TEMPS  
REMAINING NEAR 10C TODAY, BUT CONSIDERABLE CLOUDINESS SHOULD  
RESULT IN HIGH TEMPS A BIT LOWER THAN YDAY. TONIGHT, DRYING IN THE  
MID-UPR LEVELS COMBINED WITH A WK LOW LEVEL GRADIENT MAY RESULT  
IN SOME FOG/STRATUS DEVELOPMENT. TEMPS WILL REMAIN VERY MILD WITH  
LOWS ONLY IN THE 40S.  
 

 
   
LONG TERM
 
(WEDNESDAY THROUGH MONDAY)  
ISSUED AT 323 AM EST TUE FEB 21 2017  
 
ANOTHER SHRTWV EXPECTED TO MOVE EAST ACROSS THE UPR GRTLKS WED.  
LOW LEVEL WAA AND INCREASING SWLY GRADIENT WINDS/MIXING HEIGHTS  
SHOULD RESULT IN WARMER TEMPS WITH HIGHS EXPECTED IN THE UPR 60S  
TO LOWER 70S. CDFNT ASSOCIATED WITH THIS SHRTWV WILL MOVE INTO OUR  
AREA WED NIGHT. WK FORCING AND LIMITED MOISTURE SHOULD RESULT IN  
LITTLE OR NO RAIN ALONG THE FRONTAL BOUNDARY. THIS FRONT WILL  
STALL OVER OUR AREA WED NGT AS FLOW ALOFT BACKS IN RESPONSE TO  
STRONG SHRTWV DIGGING INTO THE CENTRAL ROCKIES. AS THIS SYSTEM  
MOVES INTO THE CENTRAL PLAINS AND STRENGTHENS THU SOME SHOWERS MAY  
DEVELOP ALONG THE STRENGTHENING STNRY FRONTAL BOUNDARY. SFC LOW  
STILL EXPECTED TO LIFT NE THU NGT TRANSITIONING STNRY FRONT TO A  
WARM FRONT WHICH WILL LIFT NORTH INTO MI. SHOWERS AND A PSBLY  
TSTMS EXPECTED ALONG THIS FRONTAL BOUNDARY WITH GREATEST IMPACT  
ACROSS NRN PORTION OF THE CWA. AS THE STRONG LOW LIFTS NE ACROSS  
THE UPR GRTLKS FRI, A STRONG CDFNT WILL SWEEP EAST ACROSS OUR  
AREA. WK INSTABILITY, BUT STRONG WIND FIELDS AND DEEP LAYER SHEAR  
SHOULD RESULT IN A LINE OF SHOWERS AND PSBLY TSTMS ALONG THE  
FRONT, SOME OF WHICH COULD BE ACCOMPANIED BY DAMAGING WINDS. TEMPS  
WILL AGAIN BE VERY MILD AHEAD OF THIS FRONT WITH HIGHS EXPECTED  
IN THE MID TO UPR 60S DESPITE CONSIDERABLE CLOUDINESS. STRONG CAA  
OVERSPREAD OUR AREA FRI NGT WILL RESULT IN TEMPS BACK TO LATE FEB  
NORMALS ON SAT. WRAP AROUND MOISTURE AND UPR TROF MOVG THROUGH  
WILL LIKELY RESULT IN SOME SNOW SHOWERS SAT, ESPECIALLY ACROSS THE  
NW WHERE SOME LAKE INDUCED INSTABILITY WILL BE PRESENT AS H85  
TEMPS FALL BELOW -10C. GENERALLY DRY WX WITH SEASONABLE TEMPS  
EXPECTED SUN-MON, THOUGH WITH CONTD NW FLOW STILL SOME POTENTIAL  
FOR SNOW SHOWERS, MAINLY NW INTO SUNDAY.  
 

 
   
AVIATION
 
(FOR THE 06Z TAFS THROUGH 06Z TUESDAY NIGHT)  
ISSUED AT 1245 AM EST TUE FEB 21 2017  
 
WEAKENING COLD FRONT STILL EXPECTED TO WASH ACROSS THE AREA LATER  
TODAY. MAIN CHANGE TO TAF'S WAS TO SLIGHTLY IMPROVE EXPECTED  
CONDITIONS. SYSTEM LACKS GOOD UPPER SUPPORT WHILE LOW LEVEL  
MOISTURE AND CONVERGENCE ARE SIMILARLY LACKING. LATEST FORECAST  
SOUNDINGS INDICATE FUEL ALTERNATE CONDITIONS MAY PROVE DIFFICULT  
AND KFWA COULD EVEN REMAIN VFR WITH FRONTAL PASSAGE. THIS IS  
SUPPORTED BY UPSTREAM OBSERVATIONS. WEAK POSTFRONTAL CAA COULD  
SUPPORT SOME AFTERNOON MVFR STRATOCU BUT EVEN THAT IS SOMEWHAT  
QUESTIONABLE. BIGGEST AVIATION CONCERN MAY BE FOG DEVELOPMENT AT  
THE VERY END OF THIS TAF PERIOD GIVEN LIGHT WINDS, NOCTURNAL  
COOLING, AND SUFFICIENT NEAR-SURFACE MOISTURE.  
 

 
   
IWX WATCHES/WARNINGS/ADVISORIES
 
 
IN...NONE.  
MI...NONE.  
OH...NONE.  
LM...SMALL CRAFT ADVISORY UNTIL 4 AM EST EARLY THIS MORNING FOR  
LMZ043-046.  
 

 
 

 
 
SYNOPSIS...JT  
SHORT TERM...JT  
LONG TERM...JT  
AVIATION...AGD  
 
VISIT US AT WWW.WEATHER.GOV/IWX  
 
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WWW.FACEBOOK.COM/NWSNORTHERNINDIANA  
WWW.TWITTER.COM/NWSIWX  
WWW.YOUTUBE.COM/NWSNORTHERNINDIANA  
 
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