Black Hills Winter Storm: Complete forecast breakdown with Brant Beckman

The National Weather Service in Rapid City has issued Winter Storm Warnings and Advisories for portions the Black Hills Region.

• Areas south of I-90 are expected to receive the heaviest impacts, including heavy snow, gusty winds and low visibility.
• This winter storm features two prominent actors – dry air and rain – both of which could throw a monkey wrench into overall forecast snow totals.
• Areas South of the Black Hills will be close to the bullseye of this system – blizzard conditions will be possible the further south you travel.
• Impacts are expected to being tonight and go all the way through Monday morning.
• These impacts will be vastly different and start at different times depending on location – let’s do a complete breakdown of this timeline.

• Northeast Wyoming will be at constant battle with dry air from the north and northwest – this will stunt snow accumulations.. particularly North of I-90
• There is still expected to be gusty winds from the Northeast – so even with low snow accumulations impacts could still be felt through Monday morning

• The Black Hills are covered with Winter Storm Warnings, save for the I-90 corridor from Sturgis to Beulah Wyoming which features a Winter Weather Advisory.
• Spearfish, Whitewood, and Belle Fourche can expect dry air to cut down on overall totals.
• Notice the Timeline begins early Saturday evening for the Central and southern Black Hills.

• Areas South and East of the Black Hills also feature a mix of Winter Storm Warnings and Advisories.
• Blizzard Warnings on the Nebraska border should be a warning to residents to Fall river and Oglala Lakota County that higher impacts will be just a stones throw away to the South. Stay Alert.

• Kicking off the timeline later on this afternoon, most of the area will feature rain showers moving south to North in a large shield.
• Dry air coming in from the north could delay this band of moisture all the way through Sunday morning… but most models advancing rain/snow showers moving in by Saturday evening.

• By 10 PM, travel impacts will begin to be felt for areas of the Central and Southern hills, including Fall River county plains.
• Rapid City and the I-90 corridor is expected to be battling dry, warm air in the late evening – so impacts aren’t expected until early Sunday.

• Notice a nose of warm temperatures North and East of the Black Hills around the 10 PM to 12 AM hour.
• The longer this warmer drier air stays in place, the less overall snow totals will be for the I-90 corridor and areas East of the Hills.

• By 5-7 AM Sunday, a transition to snow is expected for the I-90 corridor and Northeastern Wyoming.
• Rain is expected to continue mixing with snow North and East of the Black hills – so impacts may hold off until the noon hour Sunday for these areas.

• Easterly and northeasterly Winds are expected to start picking up Early Sunday morning and go through the afternoon.
• sustained winds of 15-25 MPH… with gusts up to 35-40 MPH will be possible South and East of the Black Hills.
• Once again, even if snow totals are relatively low – blowing snow could impacts travel in these areas.

• By 2 PM Sunday, most areas indicated in Winter Storm Warnings and Winter Weather Advisories will be a mess of rain, snow, wind, and pockets of dry air.
• consistency would be the worst way to describe Sunday – as conditions are going to be flipping around like a shuffling deck of cards every 15 minutes in some cases.
• Areas close to the rain/snow line will feature snow rates at 1″-2″ per hour… so even if you transition to snow late in the game you could quickly add accumulations and travel impacts.

• Easterly winds will still be steady, but losing vigor by Sunday evening.
• Areas of blowing snow will be likely – particularly in the plains.

• By late Sunday, dry air from Montana will be handily winning the battle as it advances to the Southwest
• This will cut off surface moisture and halt accumulations for northeastern Wyoming and areas North of the Black Hills as soon as Sunday night.
• Large improvements to travel conditions are expected through Monday morning, though crews will need time to clear the roads – particularly in areas harder hit with high accumulations and blowing snow.

SNOW TOTALS:

• Starting with Northeastern Wyoming, you can see the distinct cut-off of moisture North of I-90.
• Winter Storm Warnings for Johnson, Southern Campbell and Weston County will specifically be for the Southern portions of those counties and areas close to the bighorn Mountains.
• Notice the dry slot crossing the Western Black Hills – this will significantly cut into snow totals from SE Montana through Crook and Weston County to the Southeast.

• The potential for very heavy snow will be pressed on two fronts by opposing factors: dry air and warm rain.
• Confidence is growing that dry air to the north will play a large role in cutting into snow totals for the Northern and Western Black Hills.
• Exactly how far this dry air pushes Southeast will be critical in determining travel impacts for Lawrence County, and possibly even portions of Pennington County.
• On the Eastern flank, warm rain will be fighting to remain in the I-90 corridor…. and still has the potential to punt snow totals from the 8″-12″ range to several inches of wet mushy snow on grassy areas.
• Having that said – I believe upslope potential and easterly winds will cool the air just enough to bring heavy, wet accumulations to Rapid City, Nemo, and potentially Black Hawk and Summerset.
• Tilford, Sturgis and Western Meade county will not only be battling dry air to the Northwest, but warm rain to the East. I’ve brought down overall totals in this are for that reason.

• The Central and Southern hills could comfortably see a foot or more of snow, with the Hermosa foothills expecting to be in the splash zone of 6″-10″
• An area of high interest will by Western Custer County and NW Fall River County – this is where dry air is expected to infiltrate surface moisture and potentially slash overall snow totals by several inches… if not all accumulation completely.
• Even places like Custer could see this dry air push into the area temporarily and give a break in overall snow.
• Places like Hot Springs and Oelrichs along SD-79 could see high snow totals, thanks to upslope potential and closer proximity to the Low pressure system crossing the panhandle of Nebraska. Pine Ridge can be included in this zone of high impacts. THIS AREA SHOULD PREPARE FOR HIGH IMPACTS FROM THIS WINTER STORM.

• Areas East of the Black Hills will see a WILD mixed bag of rain, snow, wind and pockets of high snow totals that defy this forecast.
• Overall though, rain should cut snow snow totals in huge swaths across Eastern Pennington, Jackson, Bennett and Northeastern Oglala Lakota County.
  However, winds are expected to be a larger impact in this region, so even a few inches of snow combined with these gusty Easterly winds could cause significant travel impacts. stay alert.

• Areas north of the Black Hills will struggle to see many impacts from this storm.
• With dry air squeezing from the northwest and warm rain from the East – snow totals should be considered on the light to moderate range at best.
• If you see more than 3″ of snow anywhere north of Belle Fourche… go get a lottery ticket.

DISCUSSION

It would have been a much safer bet to put Rapid City, among other towns, in the 2″-20″ range. that’s the truth. But that’s not helpful to anyone – particularly those who have to make a call – who have to prepare for a specific outcome. We are wholly aware that these preparations take time, energy, resources and finances. These snow total numbers have been scrupulously thought out, rehashed, edited, and thrown around like a rag doll over the last 24 hours.

There are several forecast guidance models that keep rain/snow out of Rapid City until 6 PM Sunday! but… we have to make the reasonable assumption given the timing and trending of the forecast that 15% of the models shouldn’t make us scared to post what 85% of our experience tells us.

We stand by our numbers – and if dry air and warm rain cut in to it – there are no regrets. We want to properly prepare everyone for the reasonable potential for widespread impacts. If Impacts are cuts down dramatically, consider it a win. Many are happy to receive the moisture.

We will be *constantly* updating these numbers and this forecast up to the 11th hour. If you have questions – feel free to reach out and we will do the best we can to answer those questions with detail and in a timely manner.

Be safe out there – thank you for trusting us with your forecast.

-Brant and the NC1 team