Mesoscale Precipitation Discussion 0009
NWS Weather Prediction Center College Park MD
502 PM EST Thu Jan 30 2025

Areas affected...mid-MS Valley into lower/middle OH Valley

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

Valid 302200Z - 310200Z

SUMMARY...Areas of moderate to heavy rain will maintain a flash
flood threat from northeastern AR/southeastern MO into the lower
and middle OH Valleys and much of western and central KY through
at least 02Z. Hourly rainfall of 0.5 to 1.0 inches will be
possible along with 3 hourly rainfall up to 2 inches.

DISCUSSION...A broad area of moderate to heavy rainfall extended
from near the MO Bootheel into the lower OH Valley as of 2130Z.
This area of rainfall has been translating northeastward during
the day and has been responsible for peak hourly rainfall up to
about 1 inch from the eastern AR/MO border into western KY and
northwestern TN since ~18Z. While hourly rainfall totals have not
been too high given MUCAPE has largely remained below 500 J/kg,
3-hour rainfall totals of 2 to 3+ inches have resulted in numerous
reports of flooding and flash flooding from southwestern to
northeastern AR.

The heaviest rainfall has been occurring at the nose of a 50-60 kt
low level jet measured between 925-850 mb, which has been
overrunning a surface warm front lifting north across AR and
northern MS. The axis of greatest low level moisture transport is
likely to continue to slowly shift east into KY/TN over the next
few hours with an elevated convergence axis aloft focusing from
near the MO Bootheel into the lower OH Valley. The orientation of
this low level convergence axis will be parallel to the mean
steering flow, allowing for repeating rounds of moderate to heavy
rain.

While instability is likely to remain limited into the late
evening/early overnight hours, forcing will remain strong in the
form of low level warm air advection and convergence beneath a
strengthening area of upper level divergence located within the
right-entrance region of a 150-160 kt upper level jet max centered
over OH/PA/NY. Peak hourly rainfall of 0.5 to 1.0 inches and
3-hourly rainfall of 1-2 inches may result in additional flash
flood concerns across downstream locations along the OH Valley as
these rains fall on top of locations that have already picked up 2
to 3+ inches of rain since this morning. Embedded within this
threat could be an isolated spot or two with higher end
runoff/flooding depending on local hydrologic conditions.

Otto

ATTN...WFO...ILN...ILX...IND...JKL...LMK...LSX...LZK...MEG...
OHX...PAH...

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

LAT...LON   38848597 38598485 38008385 37228401 36768481
            36528671 36118840 35438943 35109024 35369091
            36259103 37329028 38618767