513  
FXUS63 KIWX 282342  
AFDIWX  
 
AREA FORECAST DISCUSSION  
NATIONAL WEATHER SERVICE NORTHERN INDIANA  
742 PM EDT FRI APR 28 2017  
   
SYNOPSIS
 
 
ISSUED AT 124 PM EDT FRI APR 28 2017  
 
A WARM FRONT OVER THE SOUTHERN U.S. CONTINUES TO LIFT NORTH INTO  
THE OHIO VALLEY THIS EVENING, CAUSING SHOWERS AND A FEW  
THUNDERSTORMS. THE WARM FRONT WILL MOVE SLOWLY NORTH ACROSS OUR  
AREA OVER THE WEEKEND AS A STRONG LOW PRESSURE SYSTEM MOVES SLOWLY  
NORTHEAST FROM THE SOUTHERN PLAINS RESULTING IN SHOWERS AND  
SCATTERED THUNDERSTORMS WITH LOCALLY HEAVY RAINFALL ACROSS OUR  
AREA. THE LOW WILL MOVE SLOWLY NORTHEAST ACROSS THE GREAT LAKES  
EARLY NEXT WEEK RESULTING IN WINDY AND COOL CONDITIONS ACROSS OUR  
AREA WITH A CHANCE OF SHOWERS.  
 

 
   
SHORT TERM
 
(THIS EVENING THROUGH SUNDAY NIGHT)  
ISSUED AT 339 PM EDT FRI APR 28 2017  
 
PERIODS OF RAIN/EMBEDDED THUNDER AND POSSIBLE FLOODING THIS  
WEEKEND...  
 
INITIAL SHOT OF ELEVATED THETA-E ADV/ISENTROPIC ASCENT WITH  
LEAD/SHEARED SHORTWAVE WILL BRING A PERIOD OF RAIN TO PORTIONS OF  
OUR IN/OH COUNTIES LATE THIS AFTERNOON AND EVENING. THE RAINFALL  
WILL BE LIGHT IN MOST LOCATIONS, THOUGH A PERIOD OF MORE MODERATE  
RAIN AND PERHAPS SOME THUNDER POSSIBLE FOR AREAS SOUTHEAST OF US 24  
CLOSER TO DEVELOPING LOW LEVEL FRONTAL BOUNDARY/INSTABILITY AXIS  
NEAR A DEVELOPING LOW LEVEL JET.  
 
SOME DRIER AIR FILTERS INTO AT LEAST OUR NW IN/LOWER MI ZONES LATER  
TONIGHT INTO EARLY SATURDAY MORNING AS SFC HIGH PRESSURE NUDGES EAST  
INTO THE NORTHERN/WESTERN GREAT LAKES. MAY EVEN SEE A LULL IN THE  
SHOWER/ISO STORM COVERAGE SOUTHEAST OF US 24 DURING THIS TIME WITH  
THE SURFACE PORTION (CONVECTIVE OUTFLOW) OF THE AFOREMENTIONED FRONT  
SETTLING TOWARD THE OHIO RIVER.  
 
RAIN CHANCES/INTENSITY WILL QUICKLY RATCHET BACK UP FROM SOUTH TO  
NORTH DURING THE DAY ON SATURDAY AS STRENGTHENING LOW LEVEL  
SOUTHERLY FLOW TRANSPORTS DEEP GULF OF MEXICO MOISTURE INTO A  
NORTHWARD RETURNING WARM FRONT. THIS WARM FRONT WILL GET A SLOW KICK  
NNW INTO OUR AREA AS LOW PRESSURE ORGANIZES ACROSS THE SOUTHERN  
PLAINS/MISSOURI VALLEY. THE MORE ORGANIZED RAIN/THUNDER ACTIVITY  
THEN LIKELY PIVOTS INTO OUR NW IN/SW LOWER MI COUNTIES BY LATER  
SATURDAY NIGHT-SUNDAY MORNING AS DEEPENING LOW LIFTS NORTH AND  
CONVERGENT/DEEP MOISTURE CHANNEL SETS UP MORE SW TO NE ON LEADING  
EDGE OF STRONGER HEIGHT FALLS. EXPECTED CONVECTIVE ELEMENTS COMBINED  
WITH 850 MB DEWPOINTS OF 12-14C (PRECIPITABLE WATER VALUES IN EXCESS  
OF 1.50 INCHES) COULD ALLOW FOR SOME IMPRESSIVE RAINFALL  
TOTALS/RATES...ESPECIALLY SATURDAY AFTERNOON SOUTH OF US 30, ACROSS  
THE ENTIRE AREA SATURDAY EVENING, AND THEN SHIFTING MAINLY INTO NW  
IN/SW LOWER MI LATE SATURDAY NIGHT INTO SUNDAY MORNING. PER  
COLLABORATION DID PULL THE TRIGGER ON A FLASH FLOOD WATCH ACROSS  
FAR NW IN/SW LOWER MI WHERE PIVOT POINT OF FRONT AFFORDS LONGER  
DURATION OF HEAVIER RAINFALL. LOWER CONFIDENCE ELSEWHERE FOR  
ANYTHING MORE THAN AN INCH OR TWO, SO HELD WITH EST/HWO MENTION  
HERE.  
 
SYSTEM WARM SECTOR WILL LIKELY BUILD IN FOR A TIME ON SUNDAY/SUNDAY  
EVENING AS FRONTAL ZONE STALLS NORTH NEAR THE LAKE MI  
SHORELINE/LOWER MI. THE RESULT WILL BE WARMER TEMPS AND CHANCES FOR  
SCATTERED SHOWERS/STORMS AS ENVIRONMENT BECOMES AT LEAST WEAKLY  
UNSTABLE WITH CONVECTIVELY INDUCED/SMALLER SCALE PERTURBATIONS  
LIFTING THROUGH IN STRONG SOUTHWEST FLOW. A MORE ORGANIZED LINE OF  
RAIN/EMBEDDED THUNDER THEN ROLLS THROUGH THE AREA SUNDAY NIGHT/EARLY  
MONDAY ALONG COLD FRONT/OCCLUSION. THE MAIN THREAT WILL CONTINUE TO  
BE LOCALLY HEAVY RAIN AS MARGINAL INSTABILITY AND LATE ARRIVAL OF  
COLD FRONT LIKELY LIMITS THE SEVERE THREAT.  
 

 
   
LONG TERM
 
(MONDAY THROUGH FRIDAY)  
ISSUED AT 339 PM EDT FRI APR 28 2017  
 
MONDAY INTO TUESDAY WILL FEATURE A TREND TOWARD COOLER/WINDY  
CONDITIONS UNDER FILLING/DEEP LOW TRACKING ENE THROUGH THE UPPER  
MIDWEST/NORTHERN GREAT LAKES. CYCLONIC FLOW/WRAP AROUND MOISTURE AND  
SECONDARY FRONT MAY GENERATE A FEW LIGHT RAIN SHOWERS EACH DAY.  
DRY/COOL THEN FOR THE MIDDLE OF THE WEEK AS WEAK RIDGING BRIEFLY  
MOVES IN.  
 

 
   
AVIATION
 
(FOR THE 00Z TAFS THROUGH 00Z SATURDAY EVENING)  
ISSUED AT 740 PM EDT FRI APR 28 2017  
 
VFR SHOWERS THIS EVENING IMPACTING MAINLY KFWA. HIRES GUIDANCE  
SUGGEST ACTIVITY WILL SHIFT SOUTH OF TERMINALS LATER THIS EVENING.  
NEXT WAVE RIDES NORTH TOWARD DAYBREAK AND SHOULD SEE ANOTHER AREA  
OF SHOWERS MOVE NORTH FOR SATURDAY. TRENDED TOWARD MVFR OVERNIGHT  
AND CONTINUED THROUGH END OF PACKAGE. MAY SEE LOWER CONDITIONS  
DEVELOP LATE TONIGHT AND AGAIN SAT AFTERNOON BUT CONFIDENCE LOW SO  
KEPT OUT OF TERMINALS AT THIS TIME.  
 

 
   
IWX WATCHES/WARNINGS/ADVISORIES
 
 
IN...FLASH FLOOD WATCH FROM SATURDAY AFTERNOON THROUGH MONDAY MORNING  
FOR INZ003-004-012.  
 
MI...FLASH FLOOD WATCH FROM SATURDAY AFTERNOON THROUGH MONDAY MORNING  
FOR MIZ077-078.  
 
OH...NONE.  
LM...SMALL CRAFT ADVISORY FROM 1 PM SATURDAY TO 5 AM EDT SUNDAY FOR  
LMZ043-046.  
 

 
 

 
 
SYNOPSIS...ROLLER  
SHORT TERM...STEINWEDEL  
LONG TERM...STEINWEDEL  
AVIATION...LASHLEY  
 
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