Excessive Rainfall Discussion
NWS Weather Prediction Center College Park MD
815 PM EDT Tue Apr 23 2024

Day 1
Valid 01Z Wed Apr 24 2024 - 12Z Wed Apr 24 2024

The probability of rainfall exceeding flash flood guidance is less
than 5 percent.

Bann

Day 2
Valid 12Z Wed Apr 24 2024 - 12Z Thu Apr 25 2024

The probability of rainfall exceeding flash flood guidance is less
than 5 percent.

...OK/AR...
OK/AR will remain just east of a migrating mid-level ridge axis
translating east from the Four Corners region. At the surface, a
stationary front will initially extend from northwestern TX into
southern OK/AR, but the boundary is likely to lift north as a warm
front after 06Z Thursday in advance of the approaching upper level
trough from the Southwest. Standardized precipitable water
anomalies of +1 to +2 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. W to WNW steering flow could
allow for training and 1 to 2 inches per hour with stronger cores
and locally 2-4 inch totals. However, the 12Z hires model suite
does not show a strong signal for sufficient magnitude and coverage
of 2+ inch rainfall totals for the 24 hour period ending 12Z
Thursday. Given no Marginal Risk was inherited for this 21Z update,
we will continue to consider the region from central/eastern OK
into portions of western AR as an area with a "less than 5
percent" chance of flash flooding.

Otto

Day 3
Valid 12Z Thu Apr 25 2024 - 12Z Fri Apr 26 2024

...A MARGINAL RISK OF EXCESSIVE RAINFALL EXISTS FROM PORTIONS OF THE
RED RIVER VALLEY...NORTHWARD INTO THE MIDDLE MISSOURI RIVER
VALLEY...

A mid-level trough over the southwestern U.S. on Thursday morning
is forecast by the model consensus to eject out across the central
and southern High Plains by Friday morning with increasing upper
level divergence and diffluence tied to a 110 kt jet max aloft at
250 mb. 850 mb winds will remain southerly across the Great Plains
for much of the day on Thursday into Friday but with an increasing
magnitude approaching 50-60 kt through Thursday night. Moisture
transport will allow precipitable water values to exceed 1.5 inches
for some locations from east-central TX into eastern OK and
possibly into southeastern KS/southwestern MO. While cloud cover
and subsequent surface heating is uncertain, the 12Z model
consensus supports a broad area of instability east of a forming
central High Plains surface low and attendant cold front/dryline,
with values of 1000 to 3000 J/kg from northern TX/southern OK into
KS and NE.

Some degree of convection may be ongoing at the start of the period
over OK/AR but additional development is anticipated to occur
during Thursday afternoon ahead of the cold front/dryline in KS/OK
with thunderstorm development expanding through the evening and
early overnight across TX and northern locations including NE and
IA. Wind profiles are supportive of repeating and training of
cells with rainfall rate potential of at least 1-2 in/hr and storm
totals of 3-5 inches. The QPF guidance from the recent 12Z
deterministic and ensemble guidance is fairly broad with location
of highest rainfall but with the best agreement from OK/KS into
MO/AR.

Otto


Day 1 threat area: www.wpc.ncep.noaa.gov/qpf/94epoints.txt
Day 2 threat area: www.wpc.ncep.noaa.gov/qpf/98epoints.txt
Day 3 threat area: www.wpc.ncep.noaa.gov/qpf/99epoints.txt