MESOSCALE PRECIPITATION DISCUSSION 0198
NWS WEATHER PREDICTION CENTER COLLEGE PARK MD
135 PM EDT FRI JUN 12 2015
 
AREAS AFFECTED...BORDERLANDS OF THE SOUTHERN GREAT LAKES 
 
CONCERNING...HEAVY RAINFALL...FLASH FLOODING POSSIBLE 
 
VALID 121734Z - 122334Z
 
SUMMARY...INCREASING INSTABILITY COMBINED WITH STRONG WESTERLY
LOW-LEVEL INFLOW AND INCREASING THUNDERSTORM ACTIVITY WITH HOURLY
RAIN RATES UP TO 2" COULD LEAD TO FLASH FLOODING.

DISCUSSION...RADAR IMAGERY HAS SHOWN A SLOW INCREASE IN CONVECTIVE
ACTIVITY ACROSS IN, IL, AND WESTERN OH SINCE 16Z, ALONG THE
TRAILING EDGE OF A MID-LEVEL VORTICITY MAXIMUM MOVING INTO THE
LOWER PENINSULA OF MI.  THUNDERSTORMS HAVE BEEN MOVING
EAST-NORTHEAST AT ROUGHLY 35 KTS, CLOSE TO THE MAGNITUDE OF THE
FORWARD PROPAGATING CORFIDI VECTORS.  A WAVY BAROCLINIC ZONE IS
HELPING TO ACT AS THE FOCUS OF ACTIVITY.  DAYTIME HEATING HAS
CAUSED SBCAPE VALUES TO REACH 3500 J/KG ACROSS CENTRAL IL AND
APPROACH 3000 J/KG ACROSS NORTHEAST OH/NORTHWEST PA PER SPC
MESOANALYSIS.  PRECIPITABLE WATER VALUES OF 1.75-2" ARE MOVING
INTO THE REGION, WHICH IS 2.5 SIGMAS ABOVE THE MEAN FOR MID-JUNE. 
INFLOW AT 850 HPA IS 30-45 KTS, ABOVE THE MAGNITUDE OF THE 850-400
HPA MEAN WIND, WHICH HAS BEEN ALLOWING FOR PRECIPITATION
EFFICIENCY.  A REPORT OF 1" OF RAIN IN 30 MINUTES WAS RECENTLY
RECEIVED FROM VAN WERT OH/THE IWX/NORTHERN INDIANA FORECAST OFFICE.

SURFACE OBSERVATIONS INDICATE THE FORMATION OF A LAKE BREEZE
BOUNDARY JUST EAST OF LAKE ERIE, WHICH SHOULD JOIN IN AS A FOCUS
FOR CONVECTION THIS AFTERNOON.  THE SIGNAL IN THE MESOSCALE QPF
GUIDANCE IS WEAK TO MODERATE, WITH LOCAL AMOUNTS OF 2-3" GENERALLY
INDICATED WITHIN THIS REGION. AREAS OF NORTHEAST IL, NORTHWEST OH,
NORTHWEST PA, AND WESTERN NY WOULD BE THE MOST THREATENED BY HEAVY
RAINFALL/FLASH FLOODING, WITH POCKETS OF 1.5-2" IN THREE HOURS
INDICATED AS THE THRESHOLD BY THE FLASH FLOOD GUIDANCE.  THE 12Z
SPCWRF WAS ESPECIALLY BULLISH ON ACTIVITY ALONG THE LAKE ERIE SEA
BREEZE BOUNDARY.  THE AVAILABLE MOISTURE INDICATES THAT HOURLY
RAIN RATES UP TO 2" ARE POSSIBLE.  WITH CELL MOTION THIS QUICK,
CELL TRAINING IS THE MAIN CONCERN.

ROTH

ATTN...WFO...BGM...BUF...CLE...CTP...DTX...DVN...ILN...ILX...
LOT...PBZ...

ATTN...RFC...MARFC...NCRFC...NERFC...OHRFC...

LAT...LON   43297756 43277744 43277674 42007765 40847978 
            40098274 39818522 39898753 39878766 40358879 
            41058970 41808795 41808654 41708481 41718308 
            41568197 42218002 42507951 42767893 43267818