903
AWUS01 KWNH 191903
FFGMPD
MOZ000-ARZ000-OKZ000-200100-

Mesoscale Precipitation Discussion 0962
NWS Weather Prediction Center College Park MD
302 PM EDT Tue Aug 19 2025

Areas affected...The Ozarks

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

Valid 191902Z - 200100Z

Summary...Showers and thunderstorms developing ahead of an MCV
will expand in coverage through the aftn. Rainfall rates of
1-2"/hr are expected, which could result in 2-3" of rainfall with
locally higher amounts. Flash flooding is possible.

Discussion...The regional radar mosaic this aftn depicts rapid
expansion of increasing reflectivity associated with developing
convection from southeast Missouri through far eastern Oklahoma.
These thunderstorms are developing in response to ascent produced
through weak upper level directional divergence atop subtle height
falls as a convectively enhanced shortwave and remnant MCV tracks
southward from Missouri. An outflow boundary (OFB) ahead of this
MCV noted in satellite imagery is producing additional lift
through convergence, while general N/NW flow is producing modest
upslope ascent into the Ozarks as well. This ascent is acting upon
favorable thermodynamics characterized by PWs measured by GPS of
1.7 to 1.8 inches, around the 90th percentile for the date,
collocated with MUCAPE around 3000 J/kg south of the OFB.

Cells that have developed so far have been generally small with
narrow updrafts, which within the pulse environment (limited bulk
shear) is keeping rainfall intensity to around 0.5-1"/hr with
short temporal lifespans. However, the CAMs suggest that
thunderstorms will become more widespread and intense as the MCV
and OFB drop southward into the evening, and as coverage
increases, storm mergers and collisions will lead to regenerating
cells with longer lifetimes. During this time, PWs are likely to
increase to above 2", suggesting the thermodynamic environment
will become even more favorable as the forcing intensifies, with
the result being HREF neighborhood probabilities for 2"/hr rain
rates peaking above 30%. Although cells should steadily move
southward on mean 0-6km winds of 5-10 kts, propagation vectors may
veer sufficiently to allow redevelopment upstream suggesting that
in addition to storm mergers, some areas could receive repeating
rounds of thunderstorms. Where this occurs, total rainfall of
2-3", with locally 3-4", is possible as reflected by HREF
exceedance probabilities for 3"/6hrs of 40%.

Soils across this area are generally dry according to NASA SPoRT
due to minimal recent rainfall noted via AHPS. This has allowed
FFG to reach 3-4"/3hrs. While this should limit the magnitude and
coverage of any flash flooding, isolated impacts are possible
where any repeating cells can occur, especially within urban areas
or any more sensitive terrain.


Weiss

...Please see www.wpc.ncep.noaa.gov for graphic product...

ATTN...WFO...LSX...LZK...MEG...PAH...SGF...TSA...

ATTN...RFC...KRF...MSR...ORN...TUA...NWC...

LAT...LON   37639064 37638986 37418952 36988951 36248997
            35739069 35389151 35249225 35029322 34849408
            34769465 34749508 35019555 35339540 35749483
            36279363 36969266 37259231 37569160