Excessive Rainfall Discussion
NWS Weather Prediction Center College Park MD
348 PM EDT Wed Apr 24 2024
Day 1
Valid 16Z Wed Apr 24 2024 - 12Z Thu Apr 25 2024

...A MARGINAL RISK OF EXCESSIVE RAINFALL EXISTS IN AND NEAR EASTERN
OKLAHOMA AND WESTERN ARKANSAS...

16 UTC update...
Signals for heavy rainfall this afternoon are pretty weak from the
latest 12z guidance, and HREF exceedance probabilities are very
low to nothing across the eastern OK/western AR. Still though, the
ingredients are there and models have not been depicting the
ongoing convection into OK this morning well, so opted to keep the
marginal given potential for any developing storms to tap the
anomalous moisture/instability. No major changes to the marginal
risk area put in place overnight. See previous discussion below for
additional details.

Santorelli

Previous discussion issued at 0700 UTC...
...OK/AR...
OK/AR will remain an area of diffluent 1000-500 hPa thickness just
east of a migrating mid- level ridge axis translating east from
the Four Corners region. At the surface, a front will lift north
Wednesday night into early Thursday in advance of the approaching
upper level trough from the Southwest. Mid-level capping should be
minimal based on the forecasted 700 hPa temperatures, under 9C.
Precipitable water values 1-2 sigmas above average for late April
-- 1.5-1.75" -- are forecast by the model consensus to be in place
near and just north of the surface front with elevated CAPE of
1000 to 2000 J/kg (higher to the south) may allow for stronger
cells capable of high rainfall rates. Effective bulk shear/low-
level inflow should increase to 35-40 kts. Non- traditional cell
training within a WNW steering flow near and poleward of the front
could allow for hourly totals to 2" and local 4" amounts. While
the 00Z HREF isn't sold on 3"+ amounts in the area, precipitable
water values in the area have trended upwards each day, and now
the 00z Canadian Regional, though at a smaller scale, supports the
wetter ECMWF solution. Went ahead and introduced a Marginal Risk
in this update.

Roth