Weather Prediction Center issues Mesoscale Precipitation Discussion #543 concerning HEAVY RAINFALL...FLASH FLOODING POSSIBLE316
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Mesoscale Precipitation Discussion 0543
NWS Weather Prediction Center College Park MD
341 PM EDT Sat Jun 28 2025
Areas affected...Ohio Valley
Concerning...Heavy rainfall...Flash flooding possible
Valid 281940Z - 290130Z
Summary...Showers and thunderstorms blossoming ahead of a cold
front will expand and train through the afternoon and into the
evening. Rainfall rates of 1-2"/hr are expected, which through
training could produce 2-3" of rain. Flash flooding is possible.
Discussion...The regional radar mosaic this afternoon shows a
rapid uptick of convective coverage aligned SW to NE from eastern
Indiana through southwest Pennsylvania. These storms are
continuing to expand and intensify as reflected by the GOES-E
day-cloud phase RGB, suggesting more numerous storms will develop
during the next few hours. This convection is blossoming in
response to convergence along an approaching cold front, which is
impinging into robust thermodynamics characterized by PWs around
1.7 inches (above the 90th percentile at KILN according to the SPC
sounding climatology) and SBCAPE over 3000 J/kg.
Through the afternoon and into this evening, the cold front is
likely to sag slowly south and east as modest 500mb height falls
occur downstream of a shortwave moving into the Upper Midwest.
This evolution combined with modest upper diffluence will help
drive synoptic ascent atop the pronounced low-level convergence
ahead of the front. This lift will move into an increasingly
favorable environment as the 850mb inflow, while modest in speed
(10-15 kts and veering) maintains a resupply of favorable
thermodynamics as it originates from a pool of high PWs over 2
inches. The HRRR is under-forecasting the current activity, but
the ARWs, NAMnest, and even the RRFS have a better handle on the
ongoing coverage and are favored through the evening. This
suggests that storms will continue to expand and build into the
greater instability to the SW, and then train steadily to the east
as weak Corfidi vectors and 0-6km mean winds become aligned to
each other and the sagging front.
Rain rates will likely reach 1-2"/hr (50-60% chance from the REFS)
leading to short duration rainfall as much as 0.5-1.5 inches in 30
minutes, and this could quickly overwhelm soils leading to runoff.
However, the greater concern is where training occurs, which
should be prevalent along the front, as this could produce 2-3" of
rain in some areas over a short period of time. If this training
falls atop any urban areas, or across more sensitive soils due to
terrain or FFG that is as low as 1.5"/3hrs from recent rainfall,
instances of flash flooding would become more likely.
Weiss
...Please see www.wpc.ncep.noaa.gov for graphic product...
ATTN...WFO...CLE...CTP...ILN...IND...JKL...LMK...LWX...PBZ...
RLX...
ATTN...RFC...RHA...TIR...NWC...
LAT...LON 41017956 40737902 40127875 39187921 38577999
38298060 38228211 38548386 38868527 39188601
39458625 39778621 40138576 40198405 40418201
40738094 40918023
Source:
Weather Prediction Center issues Mesoscale Precipitation Discussion #543 concerning HEAVY RAINFALL...FLASH FLOODING POSSIBLE---------------
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