Excessive Rainfall Discussion
NWS Weather Prediction Center College Park MD
328 AM EST Wed Dec 07 2022
Valid 12Z Wed Dec 07 2022 - 12Z Thu Dec 08 2022
...THERE IS A MARGINAL RISK OF EXCESSIVE RAINFALL FROM PORTIONS OF
THE SOUTHERN PLAINS EAST TO THE TENNESSEE VALLEY AND SOUTHERN
...North Texas and Eastern Oklahoma eastward into the western
Models still suggest the potential for locally heavy to excessive
rainfall from parts of North TX into central-eastern Oklahoma and
across portions of the Lower MS Valley and TN Valley, though the
signal for anything other than an isolated (marginal) threat has
diminished considerably over the past couple of model cycles.
Aloft, a southern stream trough pivots across the Southwest U.S.
on Wednesday and across the High Plains Wednesday night. This
initial shortwave will be moving rather swiftly, given the
increased confluence (de-amplification of the shortwave with time)
by late Wednesday night. Given the flattening wave and more
west-east oriented front, the the degree and depth of
south-southwest low-mid layer flow will be somewhat restricted
(warm conveyor belt or WCB more compact). Moreover, limited
deep-layer instability (MUCAPEs 500-1000 J/Kg early dropping below
500 J/Kg later this afternoon and overnight) will also limit the
short-term rainfall rates. So despite a relatively quick bout of
robust low-mid layer moisture transport, with PW values topping
out between 1.5-1.7", the lack of instability along with
progressive nature of the favorable forcing (forward-propagating
Corfidi or MBE vectors) will lead to a more limited (isolated)
flash flood threat. In addition, per the latest NASA SPoRT
analysis, 0-100cm soil moisture percentiles are running between
10-30% of normal across much of the outlook area. As a result, the
Slight Risk area that was present in yesterday's Day 2 ERO has
been dropped to a Marginal.
Valid 12Z Thu Dec 08 2022 - 12Z Fri Dec 09 2022
The probability of rainfall exceeding flash flood guidance is less
than 5 percent.
The Day 3 outlook will be updated by 0830Z.
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