401
AWUS01 KWNH 221800
FFGMPD
LAZ000-ARZ000-TXZ000-OKZ000-230000-

Mesoscale Precipitation Discussion 0303
NWS Weather Prediction Center College Park MD
159 PM EDT Wed May 22 2024

Areas affected...North Texas through the ArkLaTex

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

Valid 221800Z - 230000Z

Summary...Showers and thunderstorms will expand in coverage
through the afternoon while organizing ahead of a cold front.
Rainfall rates will likely reach 2-3"/hr, with briefly higher
rates possible, producing 2-4" of rain with locally higher
amounts. Flash flooding is possible.

Discussion...The regional radar mosaic this afternoon indicates
rapid expansion of reflectivity associated with intensifying
convection from North Texas through the ArkLaTex and into southern
AR. This convection is blossoming in a region of extreme
thermodynamics characterized by PWs of 1.7 to 1.9 inches, and a
ribbon of MLCAPE exceeding 4000 J/kg. This MLCAPE is being
produced thanks to a robust EML noted in the 12Z FWD U/A sounding,
with LIs around -10 further evidence of the intensity of this
environment. Although the area appears to be in the less-favorable
RFQ of a jet streak to the north, strong low-level convergence
along the front, weak PVA ahead of an impulse rotating through the
flow, and at least modest 850mb convergence on the nose of an
intensifying surge out of the Gulf of Mexico will likely allow
showers and thunderstorms to continue to expand and strengthen.
Rainfall rates of 1-1.5"/hr have already been estimated via KFWS
WSR-88D.

During the next several hours, the cold front will waver near the
Red River Valley of the South as a wave of low pressure moves
along it to the east. This will produce enhanced lift through
convergence, which will act upon the extremely unstable
environment to expand convective coverage, and likely lead to more
intense rainfall rates. This is reflected by HREF neighborhood
probabilities for 2"/hr reaching as high as 60%, with the HRRR
15-min rainfall suggesting brief 4"/hr rates likely, especially
where storms become most organized in the presence of more than 50
kts of bulk shear. This will likely lead to supercells and
clusters, which could grown downstream into a complex over
southern AR as noted in recent ARW and HRRR runs. While rainfall
rates may be most intense in any supercells, the organization into
clusters could prolong the duration of these rainfall rates, and
this will likely produce more than 3" of rain in many areas as
noted by HREF probabilities exceeding 70%, with 5" or more
possible where multiple rounds of storms occur. Training and
backbuilding upstream into the higher instability across North
Texas is also expected.

Recent rainfall, using the 7-day AHPS as proxy, has been well
below normal across much of this region. This has allowed FFG to
recover to 3-4"/3hrs which has only a 10-20% chance of exceedance
according to the recent HREF. Still, the likelihood of intense
rain rates and storm organization, along with the potential for
multiple rounds or some upstream training, could still produce
instances of flash flooding into this evening.


Weiss

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

ATTN...WFO...FWD...LZK...OUN...SHV...TSA...

ATTN...RFC...ABRFC...LMRFC...WGRFC...NWC...

LAT...LON   35039405 34929329 34629266 33989227 33389233
            33129273 32669392 32239549 32069716 32079801
            32329833 32549843 33089835 33589810 34139737
            34459676 34869566