MESOSCALE PRECIPITATION DISCUSSION 0161
NWS WEATHER PREDICTION CENTER COLLEGE PARK MD
927 PM EDT SAT MAY 30 2015
 
AREAS AFFECTED...INDIANA...NORTHERN OHIO...FAR NORTHWEST
PENNSYLVANIA...FAR WESTERN NEW YORK 
 
CONCERNING...HEAVY RAINFALL...FLASH FLOODING POSSIBLE 
 
VALID 310130Z - 310630Z
 
SUMMARY...ISOLATED POTENTIAL FOR FLASH FLOODING FROM DEEP
CONVECTIVE CORES BEFORE TRANSITIONING OVER TO ISENTROPICALLY
FORCED MODERATE SHIELD PRECIPITATION LATE THIS EVENING INTO EARLY
SUNDAY MORNING. 

DISCUSSION...A MESSY SURFACE ANALYSIS SHOWS A WELL DEFINED COLD
FRONT ACROSS LAKE ERIE BACK INTO NORTHWEST INDIANA BEFORE DROPPING
SOUTH TOWARD SOUTHERN ILLINOIS.  SOUTHEAST...IN THE WARM
SECTOR...A SURFACE INFLECTION OF THE APPROACHING MCV FROM SOUTHERN
ILLINOIS CAN BE SEEN JUST NORTHWEST OF IND PER METARS AND KIND
RADAR LOOP.  EXTENDING FROM THIS WEAK SURFACE INFLECTION IS A
SURFACE TROF THAT CROSSES NORTHERN OHIO INTO FAR WESTERN NEW YORK.
 THIS TROF HAS BEEN ACTING AS A FOCUSING MECHANISM FOR VERY DEEP
CONVECTION WITH MUCH HIGHER UP TO 1.5"/HR RATES AS INSTABILITY HAS
BEEN POOLED ALONG AND SOUTH OF IT THROUGHOUT THE EVENING.  WITH
SOUTHWESTERLY 850MB MOISTURE TRANSPORT OUT AHEAD OF THE MCV ACROSS
SOUTHERN INDIANA... ISENTROPIC LIFT ALLOWS FOR SIMILARLY EFFICIENT
CONVECTION NORTH OF THE TROF BUT SOUTH OF THE COLD FRONT BEFORE
BECOMING FULLY STRATIFORM WITH RATES LESS THAN .75"/HR ACROSS
SOUTHERN MICHIGAN. 

AS MENTIONED IN MPD 160...THE CONVECTIVE ELEMENTS HAVE BEEN
ORIENTING PERPENDICULAR (NORTH-SOUTH) TO THE BOUNDARIES AS THEY
APPEAR TO BE FORMER SPOKES OR OUTER BANDS OF THE ADVANCING MCV...
THIS HAS ALLOWED FOR MULTIPLE ROUNDS OF STRONG CONVECTION TO TRACE
ACROSS NORTHEAST INDIANA AND NORTHERN OHIO THIS EVENING.  AS ONE
GETS FURTHER EAST...THE 850MB MOISTURE TRANSPORT BECOMES MORE
WEST-SOUTHWESTERLY NEARLY PARALLEL TO THE FORCING
BOUNDARIES...THIS HAS ALLOWED FOR SOME ADDITIONAL CONFLUENCE OF
THE CONVECTION INTO A MORE NARROWLY FOCUSED AXIS ALONG THE OHIO
LAKE ERIE SHORELINE.  THIS TREND HAS CONTINUED ALLOWING FOR
TRAINING ACROSS A MORE FOCUSED LINE IN NORTHEAST OHIO MOVING INTO
FAR NORTHWEST PA/WESTERN NY. 

IN THE NEXT 3-5 HOURS...INSTABILITY RAPIDLY DECLINES ALLOWING FOR
A TRANSITION FROM DEEP CONVECTION INTO MODERATE
ISENTROPIC/DEFORMATION ZONE SHOWER DEVELOPMENT...EFFECTIVELY ALONG
THE SAME AXIS AS THE MCV MOVES EAST INTO OHIO...THIS IS IN LINE
WITH MUCH OF THE GLOBAL MODEL AND RECENT HI-RES RUNS. 

GALLINA

ATTN...WFO...BUF...CLE...CTP...ILN...IND...IWX...LOT...PBZ...

ATTN...RFC...NCRFC...OHRFC...

LAT...LON   42587926 42077875 41278001 40258381 39858523 
            39818582 40078623 40558716 41098706 41658482 
            41708343 41508284 41478238 41568158 41968065 
            42257982