Areas affected…Central /Eastern SD
Concerning…Heavy rainfall…Flash flooding likely
Valid 021610Z – 022130Z
SUMMARY…Very heavy showers and thunderstorms across areas of
central and eastern SD will be slow-moving over the next few
hours. Areas of flooding and flash flooding will be likely, and
especially with extremely heavy rainfall rates in place.
DISCUSSION…The latest GOES-16 WV imagery shows a subtle
mid-level shortwave impulse drifting east-southeast across central
SD which is interacting with an inverted surface trough and wave
of low pressure across the region. Locally focused surface
convergence coupled with moist and persist low-level southeast
flow and proximity of an instability axis has been helping to
generate plenty of shower and thunderstorm activity this morning.
However, over the last couple of hours there has been some
additional cooling of the convective tops and an expansion of the
convective coverage which suggests some stronger large scale
ascent over the region courtesy of the aforementioned shortwave
energy.
The moisture environment across the region along and to the right
of the surface trough is rather conducive to enhanced rainfall
rates, with the latest CIRA-LPW data sets showing a concentrated
channel of moisture advected up across central and southern SD in
the 850/500 mb layer. This is aiding in some highly efficient
rainfall processes for enhanced rain rates that have already been
as high as 2.5 inches in 30 minutes within some of the stronger
convective cores.
The latest hires model guidance led by recent runs of the HRRR
favor very slow-moving and efficient convection going through at
least 18Z, and locally as long as 21Z across areas of especially
central SD. Additional rainfall amounts of 3 to 6 inches will be
possible locally as indicated by the HRRR, which appears
reasonable considering such high rainfall rates that are already
ongoing, and with cloud tops generally still cooling.
Areas of flooding and flash flooding appear likely given the
set-up, and especially considering the heavy rains that have
already occurred this morning across portions of the MPD threat
area. Will continue to closely monitor.
Orrison
…Please see www.wpc.ncep.noaa.gov for graphic product…
ATTN…WFO…ABR…FSD…UNR…
ATTN…RFC…MBRFC…
LAT…LON 45429801 45159743 44629743 43689805 43089883
43019998 43110051 43660068 44140044 44859977
45289923 45379874