Flash Flood Guidance
Issued by NWS

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000
AWUS01 KWNH 302305
FFGMPD
OHZ000-MIZ000-INZ000-310203-

MESOSCALE PRECIPITATION DISCUSSION 0160
NWS WEATHER PREDICTION CENTER COLLEGE PARK MD
704 PM EDT SAT MAY 30 2015

AREAS AFFECTED...NORTHERN INDIANA...SOUTHERN MICHIGAN...NORTHWEST
OHIO

CONCERNING...HEAVY RAINFALL...FLASH FLOODING POSSIBLE

VALID 302303Z - 310203Z

SUMMARY...NORTHEASTWARD EXPANSION OF MPD #159 WHERE INCREASED WARM
SECTOR CONVECTION BECOMING CONFLUENT WITH FRONTAL ZONE INCREASING
ISOLATED FLASH FLOOD THREAT.

DISCUSSION...WV/VIS/RADAR SHOWS MCV CONTINUING TO PROGRESS
NORTHEAST ACROSS SOUTHERN ILLINOIS... WITH GOOD INSTABILITIES OF
1000-1500 J/KG IN THE WARM SECTOR CONVECTION BEGAN DEVELOPING
ALONG SURFACE MOISTURE CONVERGENCE BOUNDARIES...IN
PARTICULAR...THE DROPPING COLD FRONT ACROSS NORTHWEST INDIANA INTO
SOUTHERN MICHIGAN AS WELL AS SFC CONVERGENCE TROF ANALYZED FROM
TOL TO HUF. THIS INITIAL SURFACE BASED INITIATION ALLOWED FOR
EXPANSION NORTH AND SOUTH ALONG AN OLD SPOKE/OUTER BAND OF THE MCV
ACROSS NORTH CENTRAL INDIANA.  WITH THIS SURFACE AND MIDLEVEL
BOUNDARY CONFIGURATION...SLIGHT INCREASE IN 850MB SOUTHWESTERLY
MOISTURE TRANSPORT CONTINUES TO POOL MOISTURE BETWEEN THE TWO
SURFACE BOUNDARIES INCREASING THE POTENTIAL FOR RAINFALL
EFFICIENCY WITH RATES OF 1.0-1.5"/HR WITH POSSIBLE 2"/HR RATES
SEEN ALONG THE PRE-FRONTAL SURFACE BOUNDARY WHERE INSTABILITIES
ARE HIGHER DUE TO SOLAR INSOLATION AND CLEARER AIR ARE TAPPED.

ADDITIONAL ISENTROPIC LIFT ACROSS THIS BOUNDARIES AS THE MERGE
ALONG WITH RIGHT ENTRANCE JET DYNAMICS FOR UPPER-LEVEL OUTFLOW
SUPPORT SHOULD CONTINUE TO EXPAND THE MODERATE SHIELD
PRECIPITATION ACROSS SOUTHERN MICHIGAN AS WELL.

THE EVOLUTION IS SUPPORTED BY HI-RES MODELS SUCH AS THE 21Z HRRR
GEM-REG AND ENSEMBLE GUIDANCE - SSEO AND NCASE MEAN. A WIDE SWATH
OF 1.5-2.5" TOTALS OVER THE NEXT 3-4 HOURS IS LIKELY...FLASH FLOOD
THREAT IS MARGINAL GIVEN THE TOTALS OVER RELATIVELY HIGHER
GUIDANCE VALUE ACROSS INDIANA BUT AS THE THREAT INCREASES WITH THE
CONVERGENCE OF BOUNDARIES...SO THE FFG VALUES DECREASE ACROSS
NORTHWEST OHIO.

GALLINA

...PLEASE SEE WWW.WPC.NCEP.NOAA.GOV FOR GRAPHIC PRODUCT...

ATTN...WFO...CLE...DTX...GRR...ILN...IND...IWX...LOT...

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

LAT...LON   42378298 42038318 41698324 41348253 40648395
            40098567 40088604 40858613 41618703 42148529
            42298382


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