Mesoscale Precipitation Discussion 0676...Corrected
NWS Weather Prediction Center College Park MD
422 PM EDT Thu Aug 16 2018

Corrected for discussion of model guidance

Areas affected...North-central/Northeast OK...Southwest
MO...Northwest AR

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

Valid 162015Z - 170000Z

Summary...Showers and thunderstorms are becoming a bit better
organized and may a flash flood threat this afternoon.

Discussion...The latest radar and satellite imagery is showing
shower and thunderstorm activity becoming much better organized
and with expansion in coverage across north-central OK in
association with a well-defined MCV that is advancing off to the
east. The MCV is interacting with a substantial amount of
diurnally enhanced instability pooled out ahead of it, with MLCAPE
values already of 2000 to 3000 j/kg in place.

Further destabilization of the boundary layer is expected
downstream across northeast OK, southwest MO and into northwest AR
over the next few hours given additional solar insolation, and
this coupled with proximity of a weak surface boundary/trough and
approaching mid level dynamics of the vort should support a
sustainable and more expansive axis of convection downstream with
very heavy rainfall rates.

PWATS as per the latest GPS-derived data are on the order of 1.8
to 2.0 inches and this will support highly efficient rainfall
processes for enhanced rainfall rates that could approach 2.5
inches/hr. This will especially be the case within the already
very cold convective cloud tops that are currently evolving.

The HRRR guidance is not capturing this convective system well at
all, and the 12Z ARW/NMMB solutions are not much better. Only the
12Z ARW2 seems to have some idea of the heavy rainfall potential
that appears to be evolving currently.

Based on this and the latest satellite and radar trends, there
will be some risk of cell-training across areas of northeast AR,
and areas of southwest MO and northwest AR will need to be closely
monitored by late afternoon. Expect as much as 3 to 5+ inches of
rain to be possible, and these amounts will likely cause flash
flooding, and especially for some areas that have seen heavy
rainfal recently.

Orrison

ATTN...WFO...LZK...OUN...SGF...TSA...

ATTN...RFC...ABRFC...LMRFC...

LAT...LON   36989711 36989542 36889390 36779263 36509216
            36099207 35719247 35559335 35559396 35609482
            35639584 35739698 36089777 36699800