Marine Weather and Tide Forecast for Rapid City, SD

DISCUSSION
(This Evening Through Friday)
Issued at 1230 PM MDT Fri May 15 2026

A pattern change is still expected this weekend. For now, we are still holding on to near-critical fire weather through Saturday.
Saturday night into early next week, the rain chances return to the area with cooler temps sliding in from the north.

To start the forecast, zonal flow in the upper levels will give very little change to our weather. So highs in the 70s and 80s are expected Saturday, overnight lows tonight through Saturday night will be in the 30s to 40s. Skies will be clear to mostly clear with clouds increasing from the west Saturday. And with not much moisture in the area, afternoon relative humidities will be low, at around 10 to 20%. Sustained winds will top out around 10 to 25 mph and gusts will reach near 20 to 40 mph, strongest winds in the SD plains northeast of the Black Hills. Decided to hold off on issuing a Red Flag Warning because the strongest wind speeds look to happen where relative humidity will be near 20%. And where the RH values bottom out near 10 to 15%, winds are forecast to be on the lighter side. These forecast conditions will be monitored closely and if needed, warning products will be issued.

Sunday and early next week, a passing upper level trough and surface cold front will bring some very different weather to NE WY and W SD. For starters, Saturday night into Sunday, showers and thunderstorms are likely. Some of those thunderstorms have the possibility to be strong to severe in south-central SD. The SPC has highlighted this area with a Marginal risk.

Sunday could play out to be an interesting weather day. It's looking like a surface low will develop near the NE-WY-to-Black- Hills area Sunday morning and track eastward. As it does, it will develop a cold front that will swing to the southside of the low.
As the cold front slides east, thunderstorm development is possible. The timing of the cold front will highly influence where the strongest storms will be. A slower moving front will lead to more storms in western SD while a quicker moving front will lead to most of the thunderstorm action happening to the east of the CWA For now, it's looking like a quicker moving front is the most likely scenario but uncertainty is high at this time.

As the cooler air slides into the area behind the cold front, most of the area has a decent chance of seeing rain but higher elevations of the Black Hills have a good chance of seeing accumulating snow Sunday night into Monday. At this times, upwards of 3 to 6 inches is possible. Stay tuned for updates.

For the rest of next week, PoPS diminish and temps warm back to the 60s and 70s for highs.

AVIATION
(For the 18Z TAFS Through 18Z Saturday)
Issued At 1150 AM MDT Fri May 15 2026

VFR conditions are expected through the forecast period.

FIRE WEATHER
Issued At 1230 PM MDT Fri May 15 2026

Warm, dry, and windy conditions with receptive fuels will continue to support near-critical conditions to most of western SD through Saturday.

The gusty winds from today will weaken this evening but RH values will see poor overnight recovery. Dry and breezy weather will stick around through Saturday. That being said, as of now, it's looking like the winds will be below thresholds where RH is low enough, so decided to hold off on issuing red flag warning for now.

Cooler with shower chances early next week, leading to a break in fire weather concerns although the best chance for wetting rains will be east of the area.

UNR WATCHES/WARNINGS/ADVISORIES
SD...None.
WY...None.