Rapid City, South Dakota

• Mild and mostly dry this weekend
• Rain and potentially strong northwest wind gusts Monday into Monday night; some light snow possible over the higher Black Hills.

Latest nighttime microphysics RGB loop showed extensive stratus over the CWA, but nothing too low at this point. T/Td spreads are starting to converge with southeasterly upslope flow on the western SD plains. Areas of fog, potentially dense, will develop overnight and persist into Saturday morning before quickly burning off to a nice Fall day for most folks. Where stratus hangs on (like today), temperatures may be 5-10F than current forecast suggests.

Then Sunday night and Monday, upper trough/low eject from the southern Rockies in the northern Plains spreading well-defined synoptic lift over the CWA. Gulf moisture will be entrained into the system, especially east of the Black Hills. Looks like a good setup for high PoPs with some folks seeing 1"+ of QPF per several ensemble guidance depictions (northern Black Hills and toward south-central SD. ECMWF EFI gives 70-90th percentile QPF with shift of tails (SoT) of 1 to 2. System looks to have strong gusty northwest winds behind it with 60-80th percentile wind gusts with a bit of SoT. Bufkit momentum transfer forecasts also robust. Wind headlines seem likely as areal coverage and strength become more apparent this weekend.

A slow-moving deep upper trough is sitting just offshore the Pac NW. Southwesterly flow is stretching across most of the western CONUS into the northern Plains. WV imagery shows a strong shortwave crossing the Great Basin into WY. Surface obs show S/SE winds continuing with temps in the 40s to lower 50s at this time. Temps are struggling to warm across NW SD where low clouds/fog has lingered. Webcams show visibility has improved quite a bit but some fog is lingering especially across higher ridges and buttes. Low clouds will persist tonight with fog/drizzle expected to redevelop and expand across large portions of the western SD plains up to the foothills of the Black Hills...and even stretch back into portions of the NE WY plains. The fog will likely be dense again over some areas through Saturday morning. Dense Fog Advisories may be needed again. Weak ridging ahead of the incoming shortwave will bring some warm air advection in tonight into Saturday. Highs in the 60s to near 70 are expected, but if low clouds/fog end up lingering longer than expected across the western SD plains, this could keep temps cooler than forecast. Generally dry weather is expected Saturday, though could see isolated showers across south central SD late Sat as the shortwave crosses the region. The Pacific trough/low will finally make its way across the western CONUS through Sunday. Surface low pressure will develop across eastern WY through the CO Front Range. Southerly return flow will increase ahead of the low across the Neb/SD plains. Highs on Sunday will be in the 60s, but then cooler weather is expected Monday as colder air is ushered in on the backside of the low as it crosses the northern/central Plains. Strong forcing with this system will bring extensive rainfall to the region, but models at this time show most of that rain falling across East River SD. However, rain is still expected across the CWA...though lower amounts. The exception may be the northern Black Hills where upslope enhancement could bring higher totals. There still remains much uncertainty as to how much QPF the area might see. Gusty NW winds are also expected Monday into Monday night, but again, there is disagreement as to how strong these winds might be. Another variable to consider is how much snow the higher Black Hills might see. This system is quite warm, but light accumulations are possible across the highest terrain, depending on how much precip remains as colder air arrives. It`s another aspect of the storm we`ll be watching through the weekend.

Issued At 1111 AM MDT Sat Oct 31 2026

Scattered fog and low stratus continue to diminish over parts of western South Dakota and northeast Wyoming today, however, MVFR/IFR with transient LIFR conditions may stick around parts of northwestern South Dakota through the end of the TAF period. MVFR/IFR conditions look likely for both KRAP and KGCC as fog redevelops across the region during the overnight hours tonight. Conditions will gradually improve starting around 01/16-18z.

SD

None.

WY

None.