High impact storm to bring heavy rain and snow to the area

RAPID CITY, S.D. (KEVN) - A strong storm system in the northern Rockies will bring heavy rain and snow to the area through Wednesday. Heavy snow will start to fall tonight near the Big Horns and into the morning/midday hours Tuesday for the rest of northeast Wyoming and the Black Hills. This will continue through Wednesday morning, before the storm starts to move out of the area Wednesday afternoon.

Winter Storm Warnings are in effect for the Big Horns, Sheridan, Campbell and Crook Counties, and the central, northern and Wyoming Black Hills. The heaviest snow is expected to fall in these locations with some spots getting more than a foot of snow! A Winter Weather Advisory is in place for Weston County and the northern foothills. These spots will pick up impactful snow, but less than those in the warnings.

The timing of these warnings vary significantly by location. The warnings for the Big Horns and rest of Sheridan County are in effect right now and will continue through 6 p.m. Wednesday. The warning for Campbell County will go into effect at midnight tonight (Monday night/Tuesday morning) and expire at 6 p.m. on Wednesday. The warnings for the central, northern and Wyoming Black Hills will go into effect at 6 p.m. Tuesday until 6 p.m. Wednesday. The warning for Crook County and advisory for Weston County will go into effect at midnight Tuesday night/Wednesday morning and expire at 6 p.m. Wednesday afternoon. Last, but not least, the advisory for the northern foothills, which includes Spearfish and Whitewood, will go into effect at 3 a.m. Wednesday morning and expire at 6 p.m. Wednesday afternoon.

Snow will fall near the Big Horns and into Sheridan tonight through Wednesday morning. Rain will transition to snow in Campbell County and the Black hills during the morning/midday hours Tuesday and fall through Wednesday. Rain will become snow for Crook and Weston Counties in Wyoming Wednesday late afternoon and evening and continue into Wednesday and the rain to snow changeover will take place in the Spearfish area Tuesday evening through Wednesday. The snow will get lighter through the day Wednesday as the storm system pushes north and east and takes the moisture with it. It will likely be all rain for the South Dakota plains with no changeover expected.

There is going to be a sharp cutoff from heavy wet snow, to heavy rain. That line looks to be just barely into western South Dakota. If that line shifts east or west, some of the totals on the plains could change. We will try to stay on top of that and update you if we see any changes occurring. The heaviest snow will be in the Black Hills and northeast Wyoming. More than a foot of snow is expected for Sheridan, with up to a foot or more possible in Gillette, Lead and Deadwood. The Wyoming Black Hills could see a half foot to possibly a foot of snow once this is all said and done. Spearfish looks to pick up nearly a half foot of snow and potentially more, depending on if the freezing line arrives sooner than later. While the chances of a foot for Spearfish are on the lower side of things, it is not impossible to see that happen. Northwest South Dakota will have rain change over to snow Wednesday morning through the afternoon. This could lead to some accumulations up near Buffalo, where a few inches are possible.

Rapid City is a tough forecast. The joy of early season storms that have a sharp rain/snow line. I believe downtown Rapid City will stay rain for much of this storm. If we do see snow fall, it will likely be after midnight Tuesday night and into the morning hours Wednesday. I could see the grassy surfaces getting a dusting of snow, but if temperatures get colder faster than expected, we could see a couple inches of snow, potentially. I’m not expecting the roads to become a mess in town, but if it does cool off faster, we might get a little slush here or there. It could be a different story for those who live south of Rapid City, where Mount Rushmore Road goes up the hill closer to Catron Blvd. Those spots could see some accumulations, but nothing significant is expected there. Around a few inches at best, if that.

Road conditions in the Black Hills, northern foothills, northeast Wyoming and near the Big Horns will likely become slippery and snow covered through the overnight hours Tuesday and into Wednesday. If you live or work in those locations, plan accordingly. Leave early for work, school, or anything else you have going on. Allow for extra time driving as you will likely not be going as fast as you normally would during dry conditions. Allow for plenty of space between you and the car ahead of you, so you can have time to brake suddenly, if needed.

Along with the heavy snow and rain, strong winds will be present from Tuesday through Wednesday. The strongest gusts are expected Wednesday. Strong winds will gust up to 40 mph through the day Tuesday and increase going into Wednesday, where gusts of 40 to 50 mph are likely for much of the area. Some spots from Rapid City and east toward Wall could have gusts up to 60 mph at times. Visibility will be reduced by the wind as rain and snow will be blowing for much of the area. This will create difficult driving conditions, even for those who will not see snow.

Now to the good news about this storm system - MOISTURE! While some may not be thrilled with the prospect of snow, the moisture we receive from this storm system will be beneficial for nearly everyone! Warmer temperatures hold more moisture compared to cooler temperatures, that is why you see western South Dakota with higher numbers, compared to northeast Wyoming, where it will be cooler with more snow. Anywhere from 1″ to 3″ of rain will be likely for the area. Some spots could pick up more than that! Given the latest drought outlook and all of the recent fires from the dry weather, this will help give the soil some much needed moisture as we head into the fall and winter months.

The drought monitor is released every Thursday, but this moisture we will pick up will not be accounted for until next Thursday, October 21. This is because the Climate Prediction Center gathers data from Tuesday to Monday, then uses a couple of days to put together the latest outlook. So, since this will be falling Tuesday/Wednesday, we will not see the results on the drought monitor for another week. Just a heads up in case you follow the drought monitor closely.

If you have not already done so, download the KEVN mobile weather app. It is available on both Android and iOS stores and it is FREE! Our team of meteorologists publish videos to the app multiple times a day as the forecast changes. You can get push alerts sent to your specific location whenever watches, advisories or warnings are issued by the National Weather Service. There is an interactive radar that you can use to stay up to date with where the precipitation is falling.

Since this is an early season storm with still some uncertainties, some changes will be likely into tomorrow. Stay tuned if further updates are needed. Stay safe!

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