Winter Storm Bulletins Posted for the Black Hills: Heavy snow rates possible

This article is being constantly updated, so check back frequently for any last minute changes!

The National Weather Service in Rapid City has issued a Winter Storm Warning for the Northern Black Hills, and a Winter weather Advisory for areas along and south of I-90.

• The overall timeline has been pushed slightly back to early Saturday afternoon, with snow bands expected to move in during that time frame.
• This is a system that will bring hyper local impacts, where most will see very little to moderate snow accumulations, and a few could see some hefty totals and difficult travel conditions.
• Quickly accumulating snow will be one of the the biggest impacts, where snowfall rates of 1″ per hour of heavy, wet snow will surprise travelers who are unprepared.

Lets break it down

• Satellite from GOES-16 shows a deepening low pressure system in Central Wyoming, tracking due East at this time.
• The small, compact nature of this system makes it difficult to forecast – but so far consistency in models are giving higher confidence that impacts are likely for the Black Hills Region

• To start, clouds will slowly increase through the late morning and early afternoon.
• Sheridan and Johnson County in Wyoming are already seeing impacts, and thus will have their Winter Weather Advisories expire earlier than everyone else around 5-6 PM.

• Current guidance suggests snow bands creeping into the Black Hills by about 2 PM, coming in from the southwest and hovering over specific regions for long periods of time.
• Accumulations, thus, will be sporadic and diverse. Your neighbor across the street could see snow bands as early as 2 PM, and your lawn doesn’t see a snowflake until 5-6 PM.
• Deformation bands in compact low pressure systems are complicated, but essential to high moisture/heavy snow events.
• We need to be on our toes from 2 PM onwards in the Black Hills and I-90 corridor.

• By 5-7 PM, pockets of heavy accumulations are well developed in the Bear Lodge Mountains and Northern Black Hills.
• Pockets of heavy accumulations are appearing along and South of I-90 in South Dakota at this point as well.
• The hours of 6 PM to 10 PM will feature some of the stronger impacts we’ll see out of this system

• Once the sun goes down, travel could be difficult, and even treacherous in the higher elevations of Lawrence County specifically.
• The I-90 corridor will see heavy snow bands move down towards Rapid City in waves as Northeasterly surface winds bring upslope potential.
• Travel conditions along I-90 from Sundance, WY to Wall, SD could quickly deteriorate during this time.
• Gusty winds could lead to areas of blowing and drifting snow, although this parameter will be dampened by the heavy, wet nature of the snowflakes in most cases.

• Snow bands will quickly lose steam in Northeastern Wyoming as the core of low pressure pushes into Central Nebraska.
• Winter Weather advisories will be kept for areas East of the Black Hills through 5 AM Sunday for this reason, as snow bands could still be hunting through the area even  in the overnight hours.

• Conditions will quickly improve through Sunday morning, where plentiful sunshine and warming temperatures into the 30s and 40s are expected.

• Here’s a look at potential accumulations through Tomorrow morning. Keep in mind that many of these accumulations will be of the heavy, wet snow variety.
• Notice the thin band of heavy snow that is expected for this system, moving through the I-90 corridor from Gillette, through Spearfish and potentially through Kadoka.
• 6″-8″ of snow are likely for the higher elevations of the Black Hills, but this number may be on the lower side – particularly for spots like Terry Peak, Cheyenne Crossing, and Central City. Numbers closer to 7″-10″ or even a foot aren’t out of the question.
• A period of upslope snow is likely for the I-90 corridor in the late afternoon and evening, stretching from Beulah, WY through Spearfish, Sturgis, Piedmont, Black Hawk, Nemo, Summerset, and potentially Rapid City. If this is the case, snowfall rates of 1″ per hour are possible and estimations of 3″-6″ of snow may be on the lower side.
• Western Pennington County, Custer County and Fall River County have been trending upwards in latest model trends. Custer and Hill City have seen the biggest boost to potential totals, where I think 2″-4″ or 3″-6″ of snow are reasonable estimates at this point. As you approach Hot Springs, and the Fall River Plains, there could be a sharp cutoff in totals. The exception would be the Hermosa foothills where easterly winds could enhance upslope potential, if even for a short period of time.
• The most volatile area of change is I-90 from Rapid City stretching East. There has been consistency in model runs of a skinny area of heavy snow potential, but the north/south component is bouncing around – badly. If you live along or South of I-90 in west river, most will see a 2″-5″ mark… but there remains a heavier pocket of snow that is likely to develop within this area… that could reach as high as 5″-8″. Right now, this pocket is shown to be in a triangle between Wasta, Philip and Pine Ridge. Use caution if you must travel this evening.

FORECAST DISCUSSION

In many ways, this is exactly what the doctor ordered. Heavy, wet snow with good moisture content, without the high winds or bitterly cold temperatures. Unfortunately, areas north of the Black Hills continue to be left out of the bonanza – and that’s not looking to change anytime soon.

Many of us will see little travel impacts from this – roads are generally warm thanks to last weeks warm-up – but we need to treat this like a boxing ring. Most of us will be spectators – but if you’re in the ring… keep your head on a swivel. This “ring” has been shifting around in models, but is starting to hone in on the Northern Black Hills and I-90 corridor from Sundance to Rapid City.

If you hate the snow, you wont have to wait long for temperatures to reach the 50s next week.

Send in those snow totals and pictures! If you haven’t gotten the NC1 weather App, you’re missing out – I post all my forecast blogs and discussions directly there… not to mention you get radar and winter weather bulletins sent directly to you. Pretty nifty.

Stay safe out there.

Brant