Excessive Rainfall Discussion
NWS Weather Prediction Center College Park MD
336 PM EDT Wed May 21 2025
Day 3
Valid 12Z Fri May 23 2025 - 12Z Sat May 24 2025

...THERE IS A MARGINAL RISK OF EXCESSIVE RAINFALL FROM EASTERN
KANSAS AND OKLAHOMA THROUGH THE OZARKS...

Broad closed low over the Northeast and an expanding mid-level
ridge blossoming across the Southern Plains will sandwich the
Central Plains and Mid-Mississippi Valley between them. This will
result in pronounced W/NW flow across the region on D3, within
which embedded shortwaves will track quickly, leading to periods of
enhanced ascent. At the same time, a jet streak digging around the
trough to the northeast will at least peripherally place its RRQ
across the region, especially late Friday/Friday night, leading to
enhanced deep layer lift over the area.

This deep layer ascent will impinge upon improving thermodynamics
as return flow from the Gulf surges PWs to above 1.5" Friday night
as the 850mb LLJ reaches as high as 40 kts. This will additionally
transport elevated instability northward, and the overlap of this
CAPE with the moisture and lift will lead to increasing
thunderstorm coverage, especially Friday night. With Corfidi
vectors aligned perpendicular to the mean 850mb flow, and 0-6km
bulk shear forecast to exceed 45 kts, convection should rapidly
grow upscale into an MCS with training of echoes from WNW to ESE
through the night. This will likely result in axes of at least 2-3"
of rain, with locally higher amounts possible.

At this time, there remains enough spread, both temporally and
spatially, to preclude any upgrades to a SLGT risk. However, the
MRGL risk was pulled a bit SW from inherited to best match the
latest guidance, and to overlap regions of higher instability where
convection may develop first the latter half of D3. It is possible
a SLGT risk will be needed eventually, as this setup (continuing
into D4) appears favorable for flash flooding.


Weiss

Day 3 threat area: www.wpc.ncep.noaa.gov/qpf/99epoints.txt