074  
FXUS63 KIWX 251023  
AFDIWX  
 
AREA FORECAST DISCUSSION  
NATIONAL WEATHER SERVICE NORTHERN INDIANA  
623 AM EDT SUN JUN 25 2017  
   
SYNOPSIS
 
 
ISSUED AT 345 AM EDT SUN JUN 25 2017  
 
A FEW LIGHT SHOWERS OR SPRINKLES WILL CONTINUE EARLY THIS MORNING  
ACROSS SOUTHERN LOWER MICHIGAN, BUT MAINLY DRY CONDITIONS ARE  
EXPECTED ACROSS THE REGION FOR MOST OF THE DAY ALONG WITH  
CONTINUED BELOW NORMAL TEMPERATURES. THERE IS A SLIGHT CHANCE OF A  
SHOWER OR THUNDERSTORM ACROSS FAR NORTHERN INDIANA AND SOUTHERN  
LOWER MICHIGAN LATER THIS AFTERNOON, BUT MOST LOCATIONS WILL  
REMAIN DRY. A FEW SHOWERS MAY PERSIST INTO THIS EVENING, WITH  
ANOTHER DISTURBANCE BRINGING A CHANCE OF SHOWERS AND THUNDERSTORMS  
AGAIN FOR MONDAY. DRY WEATHER IS THEN EXPECTED TO RETURN LATER  
MONDAY EVENING INTO TUESDAY. HIGH TEMPERATURES TODAY WILL RANGE  
FROM 70 TO 75 WITH LOW TEMPERATURES TONIGHT DROPPING INTO THE LOW  
TO MID 50S. HIGH TEMPERATURES ON MONDAY WILL BE LIMITED TO THE  
UPPER 60S TO AROUND 70.  
 

 
   
SHORT TERM
 
(TODAY THROUGH MONDAY NIGHT)  
ISSUED AT 345 AM EDT SUN JUN 25 2017  
 
PREVIOUS FORECAST REMAINS IN GOOD SHAPE WITH FOCUS OF THE REMAINDER  
OF THE WEEKEND INTO MONDAY ON THE BELOW NORMAL TEMPERATURES AND  
ISOLATED SHOWER/STORM POTENTIAL.  
 
A STRONG BUT MOISTURE-STARVED UPPER VORT MAX ACROSS THE WESTERN  
GREAT LAKES WILL BE ACCOMPANIED BY A FEW SHOWERS ACROSS EXTREME  
NORTHERN INDIANA/SOUTHERN LOWER MICHIGAN OVER THE NEXT FEW HOURS.  
FORCING WITH THIS WAVE WILL EVENTUALLY SHIFT EASTWARD AFTER  
DAYBREAK. LOOKING UPSTREAM, NO IMMEDIATE SIGNIFICANT SHORT WAVE IS  
EVIDENT THIS MORNING THAT WILL IMPACT THE LOCAL AREA TODAY, WITH  
JUST A SHEARED VORTICITY MAXIMUM SHIFTING EASTWARD ACROSS THE  
SOUTHERN GREAT LAKES THIS AFTERNOON. WITH A DRY AIR LOW LEVEL AIR  
MASS IN PLACE AND RELATIVELY WEAK MID LEVEL LAPSE RATES, SHOWER  
POTENTIAL STILL LOOKS QUITE LIMITED GIVEN LACK OF SUBSTANTIAL  
UPPER FORCING. HAVE OPTED TO HOLD ONTO THE 15 TO 20 POPS ACROSS  
NORTHERN THIRD OF THE AREA LATER THIS AFTERNOON DURING PEAK  
HEATING/WEAK SURFACE BASED INSTABILITY. AS WAS THE CASE LAST  
EVENING, STRONGER UPPER FORCING WITH NEXT UPSTREAM WAVE DROPPING  
OUT OF SOUTHERN MANITOBA SHOULD REACH THE SOUTHERN GREAT LAKES  
LATER TONIGHT WITH A FEW SHOWERS POSSIBLE. PASSAGE OF SECONDARY  
COLD FRONT THIS MORNING WILL TAKE ANOTHER FEW DEGREES OFF HIGH  
TEMPERATURES TODAY, GENERALLY IN THE LOWER 70S. STEEP LOW LEVEL  
LAPSE RATES WILL ALLOW FOR GUSTY WEST WINDS AGAIN TODAY INTO THE  
20 TO 25 MPH RANGE.  
 
MID/UPPER LEVELS WILL CONTINUE TO COOL FOR MONDAY WITH NEXT UPPER  
LEVEL SHORT WAVE OF INTEREST DROPPING SOUTHEAST OUT OF THE  
NORTHERN/CENTRAL PLAINS MONDAY AFTERNOON. STRONGEST UPPER LEVEL  
Q-VECTOR CONVG SIGNAL WITH THIS WAVE STARTING TO LOOK MORE  
FAVORABLE ACROSS SOUTHWEST/SOUTHERN PORTIONS OF THE FORECAST AREA  
LATE MONDAY AFTERNOON INTO EARLY MONDAY EVENING WHERE BROAD LOW  
LEVEL CONFLUENCE ZONE SHOULD ALSO SET UP. STEEPER MID LEVEL LAPSE  
RATES MONDAY SHOULD COMPENSATE FOR STILL MEAGER MOISTURE TO  
PROVIDE SOME UPTICK IN SFC BASED INSTABILITY, AND HAVE NOT MADE  
MUCH CHANGE TO LOW CHANCE RAIN/SLIGHT CHANCE THUNDER POPS MONDAY  
AFTERNOON. GIVEN RECENT GUIDANCE TRENDS IN TIMING THIS WAVE, DID  
ACCEPT MODEL CONSENSUS IDEA OF PROLONGING LOW POPS INTO THE EARLY  
EVENING MONDAY. COOLEST TEMPS OF THE PERIOD EXPECTED MONDAY WHEN  
HIGHS ACROSS THE NORTH WILL LIKELY BE LIMITED TO THE MID-UPPER 60S  
TO AROUND 70 SOUTH. RECORD LOW MAXIMUM TEMPERATURES FOR MONDAY  
WILL LIKELY NOT BE THREATENED HOWEVER (65 AT KSBN IN 1970, AND 61  
AT KFWA IN 1928).  
 

 
   
LONG TERM
 
(TUESDAY THROUGH SATURDAY)  
ISSUED AT 345 AM EDT SUN JUN 25 2017  
 
TUESDAY/TUESDAY NIGHT WILL BE DRY AS MID/UPPER HEIGHT RISES  
SPREAD EASTWARD. LOW LEVEL THERMAL TROUGHING WILL LINGER ACROSS  
THE REGION HOWEVER AS ANOTHER HUDSON BAY VORT SHOULD ALLOW FOR  
ONLY SLOW LOW LEVEL THERMAL MODERATION TUESDAY. THERMAL/MOISTURE  
ADVECTION BECOMES STRONGER FOR THE WED/WED NIGHT PERIOD WITH  
EVENTUAL DEAMPLIFICATION OF CENTRAL CONUS UPPER RIDGE IN RESPONSE  
TO A SERIES OF PACIFIC SHORT WAVES. WHILE DETAILS WILL NEED TO BE  
SORTED OUT/REFINED IN TERMS OF TIMING AND STRENGTH OF INDIVIDUAL  
SHORT WAVES, THE WED NIGHT-FRI PERIOD IS STILL SHAPING UP AS AN  
ACTIVE ONE WITH INCREASING DEEP MOISTURE AND A COUPLE OF FRONTAL  
WAVES LIKELY IMPACTING THE REGION DUE TO ACTIVE PACIFIC SHORT WAVE  
PATTERN. WHILE TIMING IS STILL OF LOW CONFIDENCE, MAY NEED TO  
WATCH A FEW PERIODS OF STRONG STORM AND HEAVY RAIN POTENTIAL THU-  
FRI. CONTINUED TEMPERATURE MODERATION IS EXPECTED FOR WED-THU WITH  
HIGHS BACK INTO THE LOWER TO MID 80S BY THURSDAY. SOME  
INDICATIONS IN MEDIUM RANGE MODEL CONSENSUS THAT FRONTAL BOUNDARY  
MAY BE DRIVEN FAR ENOUGH SOUTH BY NEXT WEEKEND TO LESSEN PRECIP  
COVERAGE FOR THE HOLIDAY WEEKEND, WITH TEMPS NEAR OR SLIGHTLY  
BELOW NORMAL BEFORE HEAT BUILDS BACK IN CLOSER TO THE 4TH OF JULY.  
 

 
   
AVIATION
 
(FOR THE 12Z TAFS THROUGH 12Z MONDAY MORNING)  
ISSUED AT 614 AM EDT SUN JUN 25 2017  
 
GUSTY WINDS WILL DOMINATE THROUGH MUCH OF THE DAYLIGHT HOURS WITH  
JUST AN OUTSIDE CHANCE FOR A SHOWER MAINLY NORTH OF THE TAF SITES.  
VFR CIGS/VSBYS EXPECTED.  
 

 
   
IWX WATCHES/WARNINGS/ADVISORIES
 
 
IN...BEACH HAZARDS STATEMENT THROUGH MONDAY EVENING FOR INZ003.  
 
MI...BEACH HAZARDS STATEMENT THROUGH MONDAY EVENING FOR MIZ077.  
 
OH...NONE.  
LM...SMALL CRAFT ADVISORY UNTIL 8 PM EDT MONDAY FOR LMZ043-046.  
 

 
 

 
 
SYNOPSIS...MARSILI  
SHORT TERM...MARSILI  
LONG TERM...MARSILI  
AVIATION...FISHER  
 
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