Winter Storm Watch issued for the Black Hills: Timeline and forecast discussion

SUNDAY UPDATE: Advisories have been issued for winter weather in the higher elevations of the Black Hills – lets break down what we know.

• To start, Sunday will be warm, breezy and overall uneventful
• We still have Red Flag Warnings for areas of Northeastern Wyoming, so keep vigilant through Sunday.

• Temperatures will generally be in the 80s, with a few exceptions in the 90s – The Black Hills could see a few 70s

• A steady wind will be clocking from the North and Northwest around 10-20, with some gusts up to 35 MPH through Sunday evening.

• The National Weather Service in Rapid City has issued a Winter Storm Watch for the higher elevations of Pennington, Lawrence and Meade County.
• Local areas, particularly above 5000 feet, could see 6″ or more of snow – this will come through Monday evening through Tuesday morning.
• Periods of heavy snow could lead to snow covered roads in some cases, with full foliage trees being weighed down by heavy, wet accumulations.

• Sunday night into Monday morning, a cold front will slowly meander southwards through our region, bringing breezy conditions and rain – first to areas of Carter, Harding, and Perkins County before pushing South.

• Winds will start to clock Easterly and Southeasterly with the passage of the cold front. This will lead to abundant moisture and quickly cooling temperatures.

• Precipitation may struggle to stretch southwards through Monday morning, but as easterly winds fill in the moisture gaps rain will quickly push South through the lunch hour.

• Temperatures will drop into the 40s from North to South, with higher elevations seeing 30s by the late afternoon. a transition to a mix of rain/snow wont be far behind.

• By Monday afternoon, steady – in some cases heavy rain with breezy conditions will move through large portions of our area.
• Snow will begin in the higher elevations and slowly work their way lower in elevation – eventually hanging around the 5000 feet level.
• The Bighorn Mountains will see periods of heavy snow develop early in the afternoon.

• Winds will begin to shift Monday afternoon to the North and Northeast, some gusts up to 30-35 MPH.

• By late Monday afternoon and evening, our system will be in full throttle – with areas of heavy rain, breezy conditions, and in some cases areas of heavy snow.
• Cool and breezy conditions will continue to filter in from the North and Northeast.

• Chilly, blustery conditions will be prevent across the area by Monday evening, temperatures will drop into the 40s and 30s, with the I-90 corridor seeing temperatures drop into the mid 30s overnight.

• By Early Tuesday morning, most of the rain is pushing out of the region, with Northeasterly winds pushing local areas of upslope enhancement along the Northern Black Hills.
• The Bighorns will also see residual snowfall stick around through Tuesday morning.
• Most precipitation will be ending by daylight hours Tuesday morning.

• Accumulations are going to be a tough call – a slight shift in temperatures could drastically decrease… or increase snowfall amounts for local areas of the Black Hills.
• A good bet could be made that anywhere in the Northern Hills above 5000 feet could see over 6″ of snow, with areas like Lead, Deadwood, Cheyenne Crossing and Deerfield seeing somewhere around 3″-6″ of snow. Most of these heavier accumulations will gather on light, grassy surfaces.
• Snow accumulations could push as far South as Custer, but it’s going to be tough as most snow will be kicked off by Northeasterly upslope enhancement along the I-90 corridor, so anywhere South of Pennington County may have trouble seeing the larger snow amounts.
• Periods of large, wet, pancake snowflakes will be likely Monday evening in the higher elevations of Lawrence and Pennington County. This could lead to quick accumulations – even on road surfaces along with low visibility.
• A distinct concern will be trees that still have their leaves, as heavy wet snow could bring branches down – perhaps a few power outages as a result. Not expecting this to be a widespread issue, but something we will be keeping an eye on as a possibility.
• I could easily see portions of the I-90 corridor from Sundance through Western Rapid City receiving a burst or two of snowfall. Should downtown Rapid City receive any measurable snowfall before midnight Monday, it’ll be the first time in recorded history.

• The Eastern foothills could even see a few bursts of snow – if things come together just right – but overall the forecast calls for mostly rain everywhere outside the Hills.
• Much needed moisture will move through large swaths of our area – with most seeing anywhere between half an inch to perhaps one and a half inches of rain. 0.5″-1.5″

• One of the distinct concerns with this system won’t be the snow, but the widespread frost that is likely Tuesday night through Wednesday.
• Areas of the South Dakota plains could plunge into the upper 20s – which could cut the growing season short.

• We will continue to monitor temperature trends through Wednesday morning – but frost as this point is looking likely.
• Temperatures rebound later next week with 60s and 70s back in the forecast.

FORECAST DISCUSSION

Full disclosure – this forecast is a tough call. A slight shift in wind direction could rob huge swaths of the Black Hills of surface moisture – leading to much lower snowfall amounts. The same can be said of extra moisture being pumped into local areas. Precipitable water is expected to be high, so if the snow machine gets going – we could see some VERY impressive snow rates of 1″-2″ per hour in  the higher elevations. That would put places like Terry peak well above the 6″ mark.

We’re monitoring trends closely – if there’s any shift in the forecast we’ll get that information out as soon as possible. We’re not here to save face – we’re here to send out wholesome, complete forecasts. We know ranchers and people who live off the land make financial choices based on these forecasts – and we’re here to give you the best information we have available at the given time.

So far, this looks like a chilly, blustery, rainy event for most. A highly curious, high moisture, relatively low impact event. We’ve already made history for heat records on Saturday, we’ll more than likely set cold records for Monday – perhaps even an early snowfall record for Rapid City. That’s the Black Hills though – we’re good at setting the bar for the outrageous and the unusual.

Thanks for tuning in – we appreciate you trusting us with these forecasts. Be safe out there! updates to follow

-Brant