955  
FXUS63 KIWX 140816  
AFDIWX  
 
AREA FORECAST DISCUSSION  
NATIONAL WEATHER SERVICE NORTHERN INDIANA  
416 AM EDT MON OCT 14 2019  
   
SYNOPSIS
 
 
ISSUED AT 405 AM EDT MON OCT 14 2019  
 
THE COOL WEATHER PATTERN WILL CONTINUE TODAY AS A RIDGE OF HIGH  
PRESSURE BUILDS IN FROM THE WEST. HIGH TEMPERATURES THIS AFTERNOON  
ARE EXPECTED TO BE IN THE 50S ACROSS THE AREA UNDER MOSTLY SUNNY  
SKIES. SOME PATCHY FROST IS POSSIBLE TONIGHT INTO EARLY TUESDAY  
ACROSS PORTIONS OF FAR NORTHEAST INDIANA, SOUTHERN LOWER MICHIGAN,  
AND NORTHWEST OHIO. ANOTHER SYSTEM WILL BRING A CHANCE OF SHOWERS  
ON TUESDAY, WITH THE BEST CHANCE OF SHOWERS FOR TUESDAY EVENING.  
HIGH TEMPERATURES WILL MODERATE INTO THE MID AND UPPER 60S  
TUESDAY, BUT WILL COOL BACK DOWN TO AROUND 50 ON WEDNESDAY AS THIS  
SYSTEM PASSES OFF TO THE EAST. WINDY CONDITIONS WILL ALSO DEVELOP  
TUESDAY NIGHT INTO WEDNESDAY AS THIS COLDER AIR MOVES BACK INTO  
THE REGION.  
 

 
   
SHORT TERM
 
(TODAY AND TONIGHT)  
ISSUED AT 405 AM EDT MON OCT 14 2019  
 
MAIN CONCERN FOR THE SHORT TERM WILL BE PATCHY FROST POTENTIAL THIS  
MORNING, AND THEN AGAIN FOR TONIGHT/EARLY TUESDAY MORNING.  
 
HIGHLY SHEARED UPPER LEVEL VORT MAX PROGRESSING THROUGH SOUTHERN  
PORTION OF DEPARTING ONTARIO UPPER LEVEL LOW HAS ENHANCED LOW  
LEVEL FRONTOGENESIS FORCING LAST EVENING INTO EARLY THIS MORNING.  
THIS FORCING WILL DIMINISH THIS MORNING AS THE SHEARED VORT MAX  
CONTINUES TO DEPART EASTWARD ACROSS THE EASTERN GREAT LAKES.  
CLOUDS SHOULD DIMINISH ACROSS THE NORTH THROUGH DAYBREAK, BUT  
LIKELY PERSIST DOWNWIND OF LAKE MICHIGAN FOR A TIME AS SECONDARY  
COLD FRONT PUSH ALLOWS SOME LAKE ENHANCED CLOUDINESS TO PERSIST  
THIS MORNING. FROST ADVISORY REMAINS IN EFFECT FOR MUCH OF  
NORTHWEST INTO PORTIONS OF NORTH CENTRAL INDIANA THIS MORNING.  
THESE LOW CLOUDS HAVE COMPLICATED FROST FORECAST A BIT ACROSS  
NORTHERN PORTIONS OF THE ADVISORY AREA, BUT WILL NOT MAKE ANY  
CHANGES TO CURRENT FROST ADVISORY GIVEN ANTICIPATED DIMINISHING  
CLOUD TRENDS OVER NEXT FEW HOURS ACROSS THE ADVISORY AREA WHICH  
SHOULD ALLOW TEMPERATURES TO DROP OFF INTO THE MID-UPPER 30S.  
OTHERWISE FOR TODAY, NOTABLY LESS WIND AS GRADIENT SLACKENS OFF  
WITH THE APPROACH OF SURFACE ANTICYCLONE. DESPITE A GOOD DEAL OF  
SUN THIS AFTERNOON, BELOW NORMAL TEMPERATURES WILL BE IN STORE  
WITH PASSAGE OF THE SECONDARY COOL FRONT. LOW LEVEL TEMPS BEGIN TO  
MODERATE SOME THIS AFTERNOON, BUT A BIT MORE SHALLOW MIXING TODAY  
MAY COMPENSATE FOR THAT TO LIMIT HIGH TEMPS FROM THE LOW-MID 50S  
NORTH TO THE MID-UPPER 50S SOUTH.  
 
LOW LEVEL WARM ADVECTION WILL BEGIN TO STRENGTHEN TONIGHT, BUT  
DEVELOPMENT OF LOW LEVEL INVERSION AND DECOUPLING SHOULD ALLOW FOR  
GOOD RADIATIONAL COOLING, PARTICULARLY ACROSS THE NORTH/NORTHEAST  
IN CLOSER PROXIMITY TO DEPARTING LOW LEVEL THERMAL TROUGH.  
CONSIDERED ISSUING ANOTHER FROST ADVISORY FOR FAR NORTHEAST  
INDIANA/SOUTHERN LOWER MICHIGAN/FAR NORTHWEST OHIO, BUT GIVEN  
ONGOING HEADLINES AND CONFIDENCE ON THE MODERATE SIDE, WILL DEFER  
THIS DECISION TO NEXT SHIFT.  
 

 
   
LONG TERM
 
(TUESDAY THROUGH SUNDAY)  
ISSUED AT 405 AM EDT MON OCT 14 2019  
 
FOR TUESDAY, FOCUS WILL TURN TO WELL ADVERTISED POSITIVELY TILTED  
PACIFIC WAVE AS IT DROPS EAST-SOUTHEAST ACROSS THE NORTHERN  
PLAINS. LOW LEVEL MOISTURE TRANSPORT WILL BE INITIALLY ON THE LESS  
THAN IMPRESSIVE SIDE FOR FIRST PART OF TUESDAY. A COMPACT UPPER  
JET STREAK PROGRESSING THROUGH BASE OF THIS SHORT WAVE SHOULD TEND  
TO GIVE THIS TROUGH MORE NEUTRAL TO SLIGHT NEGATIVE TILT AS IT  
DIGS ACROSS THE SOUTHERN GREAT LAKES LATER TUESDAY NIGHT. WITH  
INITIAL BETTER MOISTURE RETURN MORE HIGHLY ELEVATED FOR FIRST PART  
OF TUESDAY, HAVE CONTINUED THE TREND OF THE PREVIOUS FORECAST IN  
SLIGHTLY DELAYING ONSET OF POPS. WILL KEEP HIGHEST POPS FOR THE  
TUESDAY EVENING PERIOD AS BETTER LOW LEVEL MOISTURE TRANSPORT  
COMBINES WITH DECENT MID LEVEL LAPSE RATES FOR BETTER SHOWER  
POTENTIAL. BY LATER TUESDAY EVENING, FRONTAL CIRCULATION SHOULD  
ALSO MATURE AS THE UPPER TROUGH UNDERGOES THE TRANSITION TO  
NEUTRAL/SLIGHT NEGATIVE TILT. GREATEST RAINFALL AMOUNTS ARE  
EXPECTED EAST OF THE INTERSTATE 69 CORRIDOR WHERE ABOVE  
INGREDIENTS MAY COME TOGETHER FOR A BRIEF TIME. HOWEVER, OVERALL  
PROGRESSION OF THIS SYSTEM SHOULD LIMIT RAINFALL AMOUNTS.  
 
LOW LEVEL THERMAL TROUGH DIGS ACROSS THE REGION BEHIND TUESDAY  
NIGHT SYSTEM, SETTING UP A RAW AND POTENTIALLY DAMP WEDNESDAY.  
LAKE INDUCED INSTABILITY WILL BE ON THE INCREASE LATER TUESDAY  
NIGHT INTO WEDNESDAY WITH A POTENTIAL OF SOME SCATTERED LAKE  
EFFECT/ENHANCED RAIN SHOWERS. OUTSIDE OF LAKE EFFECT, SOME PATCHY  
LIGHT DRIZZLE NOT COMPLETELY OUT OF THE QUESTION AS WEAK SHORT  
WAVE DIGGING THROUGH UPSTREAM PORTION OF DEPARTING MAIN UPPER  
LEVEL HEIGHT MINIMUM INTERACTS WITH LINGERING SHALLOW MOISTURE.  
GIVEN ABOVE FACTORS OF EXPANSIVE LOW CLOUDS/LIGHT PRECIP  
POTENTIAL, HAVE COLLABORATED SLIGHT DROP IN HIGH TEMPS FOR  
WEDNESDAY TO AROUND 50 DEGREES WITH SURROUNDING OFFICES. WINDY  
CONDITIONS CAN ALSO BE EXPECTED LATE TUESDAY NIGHT INTO WEDNESDAY  
AS LOW LEVEL LAPSE RATES STEEPEN WITH THE COLD ADVECTION.  
 
NOT MUCH CHANGE MADE TO PREVIOUS FORECAST POST-WEDNESDAY AS THU-  
FRI STILL SETS UP TO BE A RELATIVE LULL IN MORE ACTIVE PATTERN  
WITH SLOW MODERATION IN TEMPERATURES. THERE COULD BE ANOTHER  
WINDOW OF FROST POTENTIAL THURSDAY NIGHT/FRIDAY MORNING AS LOW  
LEVEL THERMAL TROUGH BEGINS TO RETREAT. MEDIUM RANGE GUIDANCE  
CONTINUES TO INDICATE EVOLUTION OF MORE AMPLIFIED LONGWAVE TROUGH  
ACROSS WESTERN CONUS BY THE FIRST PART OF THE WEEKEND. WHILE  
GUIDANCE IS IN AGREEMENT ON GENERAL NATURE OF UPPER FLOW PATTERN  
THIS PERIOD, STILL SOME PHASING AND TIMING ISSUES WILL NEED TO BE  
RESOLVED TO GET A BETTER HANDLE ON PERIODS WITH HIGHER RAIN  
CHANCES. OF GREATER CONFIDENCE IS THE TRANSITION TO NEAR TO ABOVE  
NORMAL TEMPERATURES FOR NEXT WEEKEND IN ADVANCE OF THIS SYSTEM.  
 

 
   
AVIATION
 
(FOR THE 06Z TAFS THROUGH 06Z MONDAY NIGHT)  
ISSUED AT 120 AM EDT MON OCT 14 2019  
 
VFR EXPECTED TO PERSIST THROUGH THE PERIOD. CURRENT CANOPY OF  
CLOUDS WILL SLOWLY DISSIPATE LATER THIS MORNING AS PARENT TROUGH  
LIFTS NORTHEAST AND SUBSIDENCE/DRY AIR BUILD. WINDS WILL ALSO BE  
MUCH LIGHTER THIS PERIOD AS SURFACE HIGH PRESSURE BUILDS OVER THE  
REGION.  
 

 
   
IWX WATCHES/WARNINGS/ADVISORIES
 
 
IN...FROST ADVISORY UNTIL 9 AM EDT /8 AM CDT/ THIS MORNING FOR INZ003-  
004-012>017-020-022>025-032.  
 
MI...NONE.  
OH...NONE.  
LM...SMALL CRAFT ADVISORY UNTIL 10 AM EDT THIS MORNING FOR LMZ043-046.  
 

 
 

 
 
SYNOPSIS...MARSILI  
SHORT TERM...MARSILI  
LONG TERM...MARSILI  
AVIATION...AGD  
 
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