Mesoscale Precipitation Discussion 0164
NWS Weather Prediction Center College Park MD
958 PM EDT Thu Apr 18 2024

Areas affected...sern MO/nern AR into lower OH Valley and nwrn TN

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

Valid 190157Z - 190700Z

SUMMARY...Short term training of thunderstorms from west to east
may result in localized flash flooding from 2-3 inches of rain.
The threat will extend through 07Z for portions of southeastern MO
into northeastern AR, and eastward into the lower OH Valley and
northwestern TN.

DISCUSSION...Infrared imagery and 01Z surface observations helped
identify a cold front extending from a surface low in west-central
IL, southwestward into northwestern AR. A line of thunderstorms
was located in southeastern IL, well out ahead of the cold front,
arcing southwestward into southeastern MO (with gaps in intensity)
where the line was more coincident with the frontal boundary.
While the presence of hail may be over-inflating MRMS rainfall
estimates, peak rainfall rates were averaging between 1-2 in/hr
over the past few hours according to MRMS data.

The cold front is forecast by the model consensus to continue a
steady movement toward the southeast through at least the first
half of the night, limiting flash flood concerns just considering
movement of the boundary. However, given radar trends and short
term extrapolation of the leading line of thunderstorms in IL,
moving out ahead faster than the portion of the line in MO, there
could be some portions of the convective line that orient parallel
to mean steering flow, supporting at least a short period of
training. Where/if this occurs, rainfall rates of 1-2 in/hr could
result in 2-3 inches of rain in roughly a 2 hour window. 925-850
mb winds from the SSW at 01Z were focusing the best low level
moisture transport up the MS River Valley and this axis is
expected to edge eastward over the next few hours while gradually
veering through 06Z. The flash flood threat is expected to
decrease beyond 06Z with reducing instability and veering low
level flow, in line with the hires model consensus, but trends
will be monitored for changes to the forecast evolution.

Otto

ATTN...WFO...LMK...LSX...LZK...MEG...OHX...PAH...SGF...

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

LAT...LON   38238735 38058667 37598622 36728621 36268650
            36078727 35988819 35858968 36099170 36619216
            36699211 37039149 37349083 37748961