AWUS01 KWNH 030000
FFGMPD
OHZ000-KYZ000-MIZ000-INZ000-ILZ000-030555-

Mesoscale Precipitation Discussion 0107
NWS Weather Prediction Center College Park MD
759 PM EDT Wed Apr 02 2025

Areas affected...Lower OH Valley into IN, western OH into
southeastern MI

Concerning...Heavy rainfall...Flash flooding possible

Valid 022358Z - 030555Z

SUMMARY...Areas of training are expected to shift into much of IN
and portions of southeastern MI/western OH through 06Z. Rainfall
rates of 1-2 in/hr will be possible within areas of training and
flash flooding will be possible. However, by 06Z or so, rainfall
intensity is expected to decrease as instability lowers,
especially for northern locations.

DISCUSSION...2330Z radar imagery showed that a pre-frontal axis of
convection extended from far southwestern MI into southeastern MO,
with embedded mesoscale vortices/bowing segments, but with an
overall movement toward the east. The environment along and ahead
of the elongated line of thunderstorms contained 500 to 1500+ J/kg
MLCAPE and anomalous PWATs at or above the climatological max for
early April via SPC sounding climatology. In addition to
increasing upper jet induced divergence aloft, continued low level
moisture advection within 50-60 kt of 850 mb flow has allowed
instability to increase over the past few hours, and as a result,
convective organization has increased over eastern IL into
northwestern IN since 21Z/22Z. There have been occasional
instances of training where line orientation has matched the mean
steering flow, supporting hourly rainfall of 1.0 to 1.5 inches
over IL into northwestern IN.

Recent runs of the RAP suggest that CAPE values over IL/IN are
near their peak for the evening/night and over the next several
hours, a general downward trend in CAPE is expected with the onset
of nocturnal cooling, not including minor increases in instability
over southeastern MI and western OH due to low level moisture
advection. As the cold front/outflow boundary continues to advance
east, the ongoing axis of thunderstorms will follow with a general
progressive movement but there will be embedded areas of training
as different embedded speeds within the line setup short term
areas of training. The threat for short term training will
translate into much of IN and portions of southeastern MI and
western OH over the next few hours, but with an expectation for
weakening rainfall intensity toward 06Z as instability fades.

Otto

ATTN...WFO...CLE...DTX...GRR...ILN...ILX...IND...IWX...LMK...
LOT...PAH...

ATTN...RFC...LMRFC...NCRFC...OHRFC...NWC...

LAT...LON 42838266 42458251 41798282 41458233 39988349=20
38758468 38008569 37288720 37308865 38198878=20
40268733 41768595 4271841

$$
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