Excessive Rainfall Discussion
NWS Weather Prediction Center College Park MD
323 AM EST Wed Feb 08 2023
 
Day 1
Valid 12Z Wed Feb 08 2023 - 12Z Thu Feb 09 2023 

...THERE IS A SLIGHT RISK OF EXCESSIVE RAINFALL FOR MUCH OF 
ARKANSAS AND SOUTHEASTERN MISSOURI...

A Slight Risk area has been maintained for the new Day 1 outlook, 
primarily encompassing north-central Arkansas and southeastern 
Missouri (along with some small portions of adjoining states). 
Showers and thunderstorms are ongoing early this morning in the 
ArkLaTex region, and the relatively slow forward speed of the main 
upper trough as it lifts northeastward (and gradually takes on a 
negative-tilt) is expected to lead towards a distinct QPF maxima 
(per WPC) of 2-4 inches (centered over northern AR). Deep layer 
southerly flow ahead of the trough will facilitate these 
precipitation totals, as tropospheric moisture levels are in the 
process of broadly increasing across the MS/OH Valleys, which 
should result in precipitable water values peaking as high as 
1.3-1.7 inches (from 1.0-1.4 inches early this morning) across the 
outlook area. This increased tropospheric moisture, along with 
strong lift and sufficient instability (MUCAPE of 500-1500 J/kg), 
will result in multiple rounds of heavy rainfall across the Slight 
Risk area (with only one distinct round of more progressive 
convection farther south in LA/MS). NASA SPoRT data shows elevated 
0-40 cm relative soil moisture values across portions of the Lower 
MS Valley (as high as the 80-90th percentile across southern AR), 
while soil moisture values in the Middle MS and OH Valleys are 
well below normal (as low as the 10th percentile across portions 
of southern MO/IL/IN and western KY). These drier soils (along 
with a lack of instability) will likely preclude meaningful 
coverage of any flash flooding well north of the AR/MO border, but 
strong frontogenetic forcing may still allow for an isolated 
occurrence or two of meaningful runoff into portions of central MO 
and southern IL. Farther south across LA/MS, any instances of 
flash flooding should remain rather isolated given the progressive 
nature of the convection (with 0-6 km shear on the order of 40-60 
kts). 

Churchill
 
Day 1 threat area: www.wpc.ncep.noaa.gov/qpf/94epoints.txt