963
AWUS01 KWNH 161223
FFGMPD
TXZ000-OKZ000-161700-

Mesoscale Precipitation Discussion 0273
NWS Weather Prediction Center College Park MD
822 AM EDT Thu May 16 2024

Areas affected...Parts of Oklahoma

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

Valid 161221Z - 161700Z

Summary...Thunderstorms blossoming along an elevated convergence
boundary will expand and move slowly through the morning. Rainfall
rates of 1-2"/hr will be common, with brief 3"/hr rates also
possible. This could result in 2-3" of rain and instances of flash
flooding.

Discussion...The regional radar mosaic this morning indicates a
stripe of intensifying showers and thunderstorms draped NE to SW
across Oklahoma. This convection is developing along the nose of
the LLJ which is analyzed by the SPC RAP and measured via VWPs at
PSF and TUL to be 30-35 kts. This LLJ is resupplying favorable
thermodynamics northward noted by a ribbon of elevated PWs
reaching 1.3 inches as measured by GPS, and 500-1000 J/kg of
MUCAPE. These robust thermodynamics are aligning favorably along
the elevated convergence boundary/LLJ nose, which is leading to
the rapid growth of convection along the boundary itself. Radar
estimated rainfall rates from KTLX have reached 2-3"/hr, and this
has resulted in one ongoing FFW already this morning.

The high-res models are initializing with coverage that is much
too low, leading to lower than typical confidence of the evolution
in the next few hours. However, the continued LLJ, despite slow
veering, should maintain thermodynamic transport into the elevated
front, which will allow convection to persist. At the same time,
synoptic forcing through mid-level divergence and increasing upper
level diffluence should additionally contribute ascent, and it is
probable thunderstorms will expand and maintain for several hours
until the core of the LLJ shifts east by early this aftn. Until
this occurs, however, rainfall rates of 1-2"/hr, locally as high
as 3"/hr are possible, as forecast by HREF exceedance
probabilities despite the struggling CAMs. These rainfall rates
could produce 2-3" of rain in a short period of time as the
Corfidi vectors veer to the north/northeast and collapse to just 5
kts, indicating the potential for nearly stationary thunderstorms
at times. Bulk shear is modest, and the corridor of higher
moisture/instability is narrow, so residence times of any
individual cell should be modest, but this rainfall could still be
sufficient to produce rapid runoff.

FFG across the area is elevated at around 2-2.5"/3hrs thanks to
normal to below-normal 7-day rainfall noted in AHPS. However, the
nearly stationary movement of the intense rain rates could still
overcome this, even though HREF exceedance probabilities for 3-hr
FFG are only 10-20%. This suggests at least an isolated threat for
flash flooding through the morning hours.

Weiss

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

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

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

LAT...LON   36849605 36679527 36279512 36059568 35909621
            35529705 34909769 34479803 34269879 34159923
            34389972 34939990 35749913 36499749 36629707