Mesoscale Precipitation Discussion 0612
NWS Weather Prediction Center College Park MD
415 AM EDT Wed Aug 08 2018

Areas affected...Northwest to South Central OK...South Central
KS....

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

Valid 080814Z - 081400Z

SUMMARY...Convective Enhancement along NW-SE boundary that will
support training/repeat cells.  Two to Four inch totals pose
possible flash flooding, though dry soil conditions may limit
overall threat.

DISCUSSION...Rap/VWP analysis depict a shallow/narrow band of rich
moisture crossing Central to NW OK to the Arkansas River Valley in
SE CO.  Currently 925-850mb flow is coincident is fluxing within
the narrow band, but is expected to begin veering south and west
of the boundary enhancing 850mb FGEN forcing over the next few
hours. VWP suggests current convection is driven from convergence
on the north side of this plume with northerly/northeasterly low
level flow. 

Goes-16 WV suite also depicts 50kt 3H jet streak crossing KS with
some cyclonic curvature providing upper level evacuation, this
will further angle more eastward with time providing
further/stronger right entrance region forcing to maintain
convection along the sharpening boundary.

Still, in the short-term multiple clusters have already developed
along the boundary, with increased lightning and tops cooling to
-70C from Clark/Harper counties to the OKC/OUN metro zone.   While
upper level moisture is limited, the deeper moisture along the
boundary is already reaching total PWAT values of 1.5" as far NW,
allowing for some rainfall efficiency and instantaneous rates to
support 1-1.5" totals in less than 1 hr. Given multiple bouts and
increased moisture flux/convergence with the veering low level
profiles, totals of 2-4" are expected in points along the line
from SW KS to South Central OK over the late overnight into early
morning.  This is supported by a bulk of reliable Hi-Res CAMs,
including the NAM-Conest, NMMB, ARW2 which feed a strong signal in
the HREF mean to have some high confidence. 

A limiting factor is the persistent dry conditions across the area
supporting 1hr FFG values over 2.5" and as high as 4" in NW OK...
and 3hr values over 3".  These 3hr values may be exceeded but
scattered to isolated, limiting overall coverage.  Still, hard
pack soils may be initially hydrophobic for more run-off than
expected, especially in very strong downdraft bursts over 2"/hr. 
All considered, flash flooding is possible through 14z

Gallina

ATTN...WFO...DDC...OUN...

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

LAT...LON   37469924 36639820 35549686 35219643 34579660
            34899771 35699878 36749983 37439994