Marine Weather and Tide Forecast for Rapid City, SD

DISCUSSION
(Today Through Thursday)
Issued at 144 AM MDT Fri Oct 3 2025

Digging western CONUS trough will push east and phase with a deep northern stream trough. This will allow for very warm temperatures today. However, a strong cold front will bring rain, breezy winds, and much colder temps later this weekend. Thermal ridge is pushing into the region this morning with mostly clear skies other than a few cirrus. Expect highs today into the 90s on the Plains, with a few areas east of the BH into the upper 90s, well above seasonal norms for early October. Breezy southerly winds can also be expected today. Upper trough will shift east and phase with a deep southern Canadian upper trough as a plume of Pac moisture shifts northeast into the region, forcing a cold front into the area Sat. Highs will range from the 60s across northeast WY to around 90 ahead of the front. Given phasing and overall slowing of eastward progression, the sfc front will take its time progressing across the region allowing for another warm day toward central SD. Precip chances will ensue during the day Sat with a convective component at first, supporting chances for showers and isolated TS, esp in the late afternoon as a jet streak moves into the region from the southwest. The best chances for precip will be Sat night when the best overlapped of lift, moisture, and convergence shifts over the region, with most if not all of the precip expected to be post frontal. Ongoing CAA may allow for rain to mix with or change over to snow in the higher elevations of the BH. Not expecting any accums given warm ground temps and limited window for snowfall. Given strong forcing and slow system progression per phasing, expecting many locations across the western 2/3 to see a half to one inch of rain, with the higher amounts across far NW SD under the deformation zone. The other impact of this system will be gusty NW winds which will develop late Sat night into Sunday with gusts over 50 mph likely on the NW SD Plains and in the lee of the BH. Showers will linger into Sunday per cyclonic flow and unstable profiles. Any lingering precip may mix with snow on portions of northeast WY and the BH Sunday night. Much cooler weather will arrive for the first part of next week with highs in the 50s on the Plains and 40s in the BH. Upper trough will shift east out of the area by Tues with upper ridging expected mid week. This will allow for a warming trend and dry weather then. Another cool front and associated upper trough looks to move through the area by the end of the week. However, the degree of height falls and local effects remains at low confidence per large model spreads.

AVIATION
(For the 18Z TAFS Through 18Z Saturday)
Issued At 1116 AM MDT Fri Oct 3 2025

VFR conditions will continue through the forecast period. South- southwesterly winds will remain gusty this afternoon, with gusts 20 to 30 knots expected across northeast WY and the western SD plains. Winds are expected to subside by 00Z this evening before becoming gusty from the northwest Saturday morning.

FIRE WEATHER
Issued At 144 AM MDT Fri Oct 3 2025

Warm temperatures, deep mixing, and breezy southwest winds will support elevated to critical fire weather conditions across most of the area today. RH's will fall to around 10 to 15 percent across northeast WY and much of southwest SD in the afternoon with breezy southwest winds developing. Winds across northeast WY and portions of the SD Plains will gust over 25 mph with a few gusts over 30 mph. When combined with dry fuels, much of northeast WY and southwest SD will see critical fire weather conditions this afternoon.

UNR WATCHES/WARNINGS/ADVISORIES
SD...Red Flag Warning until 7 PM MDT this evening for SDZ321-322- 324>326-329-332.
WY...Red Flag Warning until 7 PM MDT this evening for WYZ314>317.