Mesoscale Precipitation Discussion 0560
NWS Weather Prediction Center College Park MD
215 AM EDT Mon Jul 30 2018

Areas affected...Central and Southern OK

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

Valid 300614Z - 301200Z

SUMMARY...An intensifying mesoscale convective system moving into
an increasingly moist and unstable environment could produce
hourly rainfall rates in excess of 2.00 inches during the
overnight hours over much of OK east from the TX pandhandle.
Separate development ahead of the line would add to the flash
flood threat despite dry antecedent conditions in southern
portions of OK.

DISCUSSION...As of 06Z regional radars and GOES-16 IR imagery
showed strengthening convection pushing south to southeast over OK
and eastern portions of the TX panhandle early this morning. Rain
rates have recently increased to 2 in/hr. This convective activity
is entering higher instability (2000 J/Kg MUCAPE per latest RAP on
the SPC mesoanalysis page) and moisture (precipitable water around
1.6 inches per GPS data). A stationary front persists near the Red
River. The low level jet is increasing (southerly 850mb flow
currently 10 to 15 kt per VWP north TX into OK increases to 20 kt
through 09Z per recent RAP runs.

Continued cold pool development and mean layer northwest winds
around 25 kt will keep the main convective line progressive to the
southeast. However, three main flash flood threats are seen. 2-3
in/hr rain rates would cause urban flooding concerns including for
OKC. Left bookends within or at the end of the developing line
could prolong heavy rain enough to cause flash flooding. Pre-MCS
development in the southerly low level flow north of the surface
front (depicted best in the 00Z ARW2 and recent HRRR runs) would
create a repeat heavy rain scenario. Antecedent conditions are
increasingly dry south across OK. Therefore, the flash flood
threat should remain localized and is considered possible.

Jackson

ATTN...WFO...OUN...SHV...TSA...

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

LAT...LON   36379661 34809465 33919512 34239910 34679993
            35849991