Black Hills Winter Storm: Updated snow total forecast as details become clearer

With the winter storm approaching quickly, we have a little more clarity on what we can expect for snow accumulation.

UPDATE: 3:20 PM – The Rapid City NWS has posted a new snowfall total map:

Nws Total 1212

With more certainty in the forecast as the winter storm approaches, snowfall total expectations have been updated.

Notice the dotted outline, which indicates the area of greatest uncertainty in terms of snow accumulation.

Areas within this outline can expect higher snow amounts if wind maintain an easterly component for a longer period of time.

When winds turn to the west, snow rates will diminish quickly.

regardless of accumulation, high winds will significantly reduce visibility and are still a big concern for areas that won’t see a lot of snow.


UPDATE- 9:30 AM MONDAY, DEC. 12 – Forecasted snow totals have not changed much over the last 12 hours. However, impacts could start as early as this afternoon. Freezing fog is expected to make its way into the area late this morning and afternoon with heavy cloud cover, which could cause icing on roadways long before snow moves in.

So far, here’s a look at watches, warnings, and advisories, along with what they mean. Keep in mind that these will change throughout the storm!

RED: Blizzard Warning, 2 a.m. Tuesday – 5 a.m. Thursday
PINK: Winter Storm Warning, 2 a.m. Tuesday – 5 a.m. Thursday
PURPLE: Winter Weather Advisory, 12 p.m. Monday – 12 p.m. Tuesday
BLUE: Winter Storm Watch, Monday night – Tuesday night
Keep in mind that Lawrence, Pennington, and Custer counties could see blizzard-like conditions too, especially if downslope winds in the Black Hills weaken and the dry pocket areas get a little added moisture.
Winter Warnings 12 12
One of the main concerns for Tuesday and Wednesday will be winds gusting from 40 to 50 mph, which will decrease visibility and will make travel difficult or impossible on Tuesday and Wednesday. This can also create blizzard conditions and add to icing and snow accumulation on roadways. Here’s an example of wind and snow on Tuesday afternoon and evening.

Tuesday 2 Pm SnowTuesday 2 Pm Wind

Tuesday 8 Pm SnowTuesday 8 Pm Wind

Finally, snow totals haven’t changed much since last night’s forecast. One thing to remember is that strong winds and blizzard conditions mean that the snow won’t cover the ground in perfect, uniform piles where there’s a consistent depth on every surface. Snow drifts are likely to build across western SD, so accumulation will vary greatly based on (1) location within a county, especially in the Black Hills and (2) location on your street, as snow can pile up in some places more than others. Nonetheless, here are some expected snowfall totals.

Forecasted Snow Totals 12 12

We expect that the snow will taper off on Thursday morning, but strong, stubborn winds remain in the area through Friday, so we could see poor road/driving conditions through the end of the week.


 

UPDATE – 4:00 PM – We are now 36 hours out from the anticipated start of the storm and, and we have a little more clarity on what snowfall total might look like.

Snow Map 1211

I’ve increased the expected snow total for most areas. There is still a decent amount of uncertainty though, which is why the ranges are fairly big.

The most uncertainty is for the southern Black Hills because it is still to early to tell just how much the downslope winds will affect the snow totals.

There are blizzard conditions that will be possible east of the Black Hills and freezing rain possible for the central plains.

Blizzard warnings have already been posted for the northern Nebraska panhandle and winter storm watches have been upgraded to winter storm warnings for the Bighorns.

The next 24 hours will be crucial, both for individual preparation and for forecasting.


UPDATE – 4:15 PM – Since the last update, the system that will be bringing us some significant winter weather is making landfall in the Pacific Northwest, here’s what that means:

  • With the system moving over land, we’ll be able to get weather balloons into it.
  • This means that we’ll actual be able to get a picture of the properties within the storm.
  • Having a more concrete picture of the system, will give our weather models better data to work with, and produce more accurate forecasts.

GOES 16

So, what do we know about the system right now?

  • We are fairly confident that the earliest effects of the storm will begin late Monday night into Tuesday morning.
  • Weather models are still producing vastly different snow totals. But…
  • The areas that will be seeing the most accumulation has been fairly consistent.
  • Those areas are the northern Black Hills and foothills and the central plains.
  • There is a good chance for freezing rain in the central plains, before transitioning to snow.
  • Model confidence is increasing for a dry pocket in the southern hills to set up, resulting in significantly less snow accumulation.

Here’s what you should be prepared for:

  • The northern hills should be ready for 6-12″ of accumulation
  • Portions of the central plains COULD receive a foot or more of snow, but his is heavily dependent on when and where the rain transitions to snow.
  • Blizzard conditions aren’t out of the question for areas east of the Black Hills.

As I’ve said before, there is still a lot of uncertainty with the exact snow totals, but this will still likely be the most significant winter event that we’ve seen this season.

Given that, Here’s what snow accumulations totals are looking like at the moment:

Snowmap 1210


UPDATE -3:50 PM – The NWS for Rapid City has issued winter storm watches for portions of western SD, ND, NE WY, SE MT, and north central NE.

Winter Watch 1209

  • The winter storm watches are for the potential for snow accumulations over 6 inches and high wind.
  • There is also the possibility for freezing rain ahead of the snow in the eastern watch areas.
  • The NWS rarely issues watches this early, so it is a sign that there is confidence for a big storm
  • The graphic below indicates that there is still a lot of uncertainty with this system

Winter Total 1209

  • The areas with the greatest uncertainty continue to be the southern Black Hills and the eastern foothills.
  • Model guidance will continue to improve over the next 48 hours.
  • There will be a winter storm next week, but exactly which areas see the greatest impacts is still up in the air.
  • The fact the the watches have been issued this early just means that everyone in the potential path of this storm needs to be prepared for its potential impacts, especially if you’re in the norther hills and central plains.

  • A Large winter storm is expected to impact large sections of South Dakota starting late Monday evening through  Thursday of next week.
  • Heavy snow, high winds and bitterly cold temperatures are likely in the areas of highest impact.
  • Confidence is high that the central portion of South Dakota is in the bullseye for these high impacts.
  • Heavy snow is also likely for the higher elevations of the Northern Black Hills
  • There is less confidence in the overall impacts for places like Northeastern Wyoming, Northwest South Dakota, the central and southern Black Hills, and the I-90 corridor including Spearfish, Sturgis and Rapid City.

Let’s break down the timeline

Futurecast 1

  • A Mix of rain, sleet, snow and freezing rain will be possible starting Monday evening.

Futurecast 2

  • As low pressure deepens and moves Northeast, more moisture is pulled in and is converted to snow in large section of South Dakota Tuesday morning.
  • Winds begin picking up out of the northwest.

Futurecast 3

  • Arguably the peak of our winter storm Tuesday evening as heavy snow, high winds and near impossible travel conditions settle in for large sections of the state.

Futurecast 4

  • Snow begins to lighten up, but still remain persistent through Wednesday, with high winds cropping visibility and continuing to make roads hazardous.
  • Heavy snow could still be falling in the higher elevations of the Northern Black Hills through Wednesday.

Futurecast 5

  • A reinforcing clipper system may bring an extra shot of cold air, wind and several inches of powdery snow by Thursday
  • Friday should see an end to most accumulating snowfall and the full exit of our system.

Snow Total

  • Long range snow maps depict heavy areas of snow East of the Black Hills, with the Northern Black Hills looking at upslope enhancement.
  • 6+” of snow with high winds out of the northwest will be likely in Ziebach, Haakon, Jackson, Bennett, Oglala Lakota and eastern portions of Meade and Pennington County.
  • There are still big questions marks for Northeastern Wyoming, The Central and Southern Hills and Rapid City. Dry Pockets may form in these areas and limit overall snow totals
  • Travel may be difficult if not impossible within a few miles of these dry pockets.
  • There will likely be more certainty with the complex Black Hills snow forecast by Saturday.
  • To make sure you’re up to date on all of the most current weather information, download the NewsCenter1 weather app for iOS and Android.

We understand the amount of preparation and travel alteration that is based on these forecasts. Thank you for trusting us. We will be providing updates as frequently as they become available.

-NC1 Weather team

 

Categories: Local News, Weather Daily