231
AWUS01 KWNH 221159
FFGMPD
OKZ000-KSZ000-221600-

Mesoscale Precipitation Discussion 0301
NWS Weather Prediction Center College Park MD
759 AM EDT Wed May 22 2024

Areas affected...Oklahoma

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

Valid 221158Z - 221600Z

Summary...Expanding showers and thunderstorms will train to the
northeast across Oklahoma this morning. Rainfall rates in excess
of 1"/hr are likely, which could result in 1-3" of rainfall. Flash
flooding is possible.

Discussion...The regional radar mosaic this morning shows an area
of rapidly expanding convection across central and northeast
Oklahoma. These thunderstorms are blossoming north of a surface
cold front, but appear to be forming along a remnant outflow
boundary (OFB) noted in the GOES-E nighttime micro-physics RGB
curve and within surface observations. This OFB is providing
sufficient low-level convergence to enhance ascent which is
already impressive on the synoptic scale due to an approaching
shortwave from the TX panhandle and at least weakly coupled jet
streaks: one exiting Kansas and another approaching from the
Desert Southwest. This large scale lift is working across
favorable thermodynamics noted by PWs of 1.2 to 1.4 inches,
nearing the 90th climatological percentile, and a gradient of
MUCAPE from 1000-3000 J/kg, both of which are being drawn
northward by the ascending LLJ. Recent radar estimated rain rates
have eclipsed 1"/hr to the NW of Oklahoma City.

The high-res CAMs are struggling with this morning development,
although the ARW and recent HRRR runs are at least capturing the
evolution, albeit displaced to the south of current activity. This
is resulting in lower confidence than typical for evolution, but
large scale ascent persisting for the next few hours should allow
convection to persist, and possibly intensify before the
combination of the veering LLJ and eastward translation of the
shortwave kicks convection to the southeast. Until this occurs,
rainfall rates of 1+"/hr are likely as reflected by HREF
neighborhood probabilities and the 15-min HRRR accumulated precip
fields. With 850-300mb mean flow aligned to the slowly advancing
OFB, this could result in training from SW to NE, producing
multiple rounds of this rainfall which could accumulate to 1-3" of
rainfall.

Much of OK has been dry the past 7 days, but some areas,
especially north of I-44 have experienced 150-300% of normal
rainfall leading to 40cm soil moisture that around the 90th
percentile according to NASA SPoRT. Training across these more
sensitive soils would have the greatest potential for runoff and
any associated impacts, but these intense rain rates could also
become problematic across less-permeable urban areas, leading to
the potential for at least isolated instances of flash flooding.

Weiss

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

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

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

LAT...LON   37039503 36899468 36369460 35859462 35409519
            35059635 34849787 34769858 34819898 35089933
            35839909 36589764 36909648 36989573