690
AWUS01 KWNH 121816
FFGMPD
OKZ000-KSZ000-130015-

Mesoscale Precipitation Discussion 0658
NWS Weather Prediction Center College Park MD
215 PM EDT Sat Jul 12 2025

Areas affected...OK and southern KS

Concerning...Heavy rainfall...Flash flooding likely

Valid 121815Z - 130015Z

Summary...Expanding convection ahead of an MCV will result in
areas of heavy rainfall and an isolated to scattered flash flood
risk over portions of central and eastern Oklahoma and far
southern KS. A more concentrated area of flash flooding is
possible near a lingering outflow boundary over central OK.

Discussion...A well defined MCV moving across OK will likely
trigger additional convective development as we head through the
afternoon hours. A pretty messy convective pattern at the current
time with several convective clusters ongoing ahead of the MCV.
High res model guidance has been inconsistent in the handling of
convection...but a combination of recent HRRR and RRFS runs, along
with observational trends, has resulted in an increase in
confidence on how things should evolve. Despite the ongoing
convection and cloud cover, instability is on the uptick ahead of
the MCV...with MLCAPE around 2000 J/KG. PWs average around 1.8",
and should continue to tick up slightly, likely approaching 2" in
spots by later this afternoon. Deep layer shear remains weak, but
the combination of the MCV and decent upper level divergence
centered over the state should help sustain convection. Deep layer
mean flow is relatively weak (about 10-15 kts) out of the
southwest. Given this is similar to the MCV track, would generally
expect a slow northeast movement to convection. Upwind propagation
vectors are divergent over the region...typically an indicator of
potential backbuilding and/or stationary cluster motions. We have
already seen some of this during the morning hours over portions
of eastern OK.

The overall expectation is that convection will expand in coverage
over the next few hours ahead of the MCV as destabilization
continues. The aforementioned slow deep layer mean flow and
backbuilding potential alone would point to some flash flood risk.
However this risk may be exacerbated by the presence of the long
lived outflow boundary that resulted in the earlier flash flooding
near Tulsa. This boundary has persisted longer than earlier
guidance had expected...and now should play a role in the flash
flood risk going forward as well. The general expectation is that
convection will build into this boundary...with some continued
south southwest propagation possible. This should allow for a
pronounced training convective risk and the likelihood of at least
some additional flash flooding, some of which could be locally
significant.

The 15z run of the experimental RRFS does indeed show an evolution
such as this...resulting in additional rainfall of 3-5". Given
that the RRFS seems to have a decent handle on the current
outflow, its evolution seems plausible. The 16z HRRR is a bit less
aggressive...but still shows 2-3" totals...despite not having a
great handle on the aforementioned outflow boundary. Thus tend to
think amounts will likely exceed the HRRR output, and would expect
hourly rainfall locally exceeding 2", and additional rainfall
totals approaching or even exceeding 5" on an isolated basis
through 00z.

Chenard

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

ATTN...WFO...ICT...OUN...TSA...

ATTN...RFC...TUA...NWC...

LAT...LON   37609721 37469658 36719598 36399578 35829521
            35159477 34349554 34009674 34389765 35109806
            35899855 36909841 37389790