875 

AWUS01 KWNH 230605

FFGMPD

SDZ000-WYZ000-231003-



Mesoscale Precipitation Discussion 1116

NWS Weather Prediction Center College Park MD

204 AM EDT Sun Aug 23 2026



Areas affected...southwestern South Dakota and vicinity



Concerning...Heavy rainfall...Flash flooding possible



Valid 230603Z - 231003Z



Summary...A conditional risk of flash flooding exists with

scattered storms near the Rapid City area.



Discussion...Deep convection has materialized over the Black Hills

vicinity over the past couple hours - very near the WY/SD border

region.  The storms are persistent despite larger-scale ridging

aloft, and are primarily tied to mid-level shortwave troughs

traversing the region, focused convergence on the nose of 20-25 kt

850mb flow across the High Plains, steep (7+ C/km) lapse rates

aloft, and 1.5 inch PW in the vicinity of the storms.  While these

storms were fairly localized, spots of 1-3 inch/hr rain rates were

estimated per MRMS recently with the activity.  Furthermore, the

meso- and synoptic-scale features forcing the convection (mainly

the 850mb convergence into the region) should change little over

the next 2-4 hours.  These factors suggests a continued risk of

heavy rainfall from Newcastle WY to Rapid City and across the

Black Hills, with flash flooding becoming possible should rainfall

develop in locally sensitive areas through 10Z/5a central.  FFG

thresholds are as low as 1-1.5 inch/hr in spots across the

discussion area, which should also be threatened at times beneath

the most persistent heavy rainfall axes.



Cook



...Please see www.wpc.ncep.noaa.gov for graphic product...



ATTN...WFO...CYS...UNR...



ATTN...RFC...KRF...NWC...



LAT...LON   44660340 44340196 43590160 43090231 43260464 

            44400487