April 1, 1999 Heavy Snowfall Event

From March 31st to April 1st, 1999 a vigorous storm system moved through northeast Wyoming and western South Dakota. A fairly wide swath of greater than 6" snows fell from northeast Wyoming into northwest South Dakota. The heaviest snow fell northwest of Gillette and from Devil's Tower to the Lead/Deadwood area. Another area of heavier snow was located near Buffalo, SD.

The contour map below could change if we receive late snowfall reports. The sharp edges you see is where our County Warning Area ends. The map only shows snowfall greater than 3". The contours have been smoothed.

Snowfall Map

Detailed Snowfall Reports (inches)

...SOUTH DAKOTA...
LOCATION         AMOUNT
DEADWOOD 13 INCHES
12SW HEREFORD 6-7
2N HEREFORD 6
9SE HEREFORD 4-5
HOOVER 6
3SE PIEDMONT 5
STURGIS 6
9S UNION CENTER 5
TILFORD 3-4
FAITH 3-4
DUPREE 2-3
4SSW PLAINVIEW 2-3
12S PLAINVIEW TRACE
3ESE ELM SPRINGS 1
15SSE DUPREE TRACE
2W GLAD VALLEY 6
RED OWL 5
10SW MAURINE 10
4E STURGIS 7
2S ST ONGE 11
SPEARFISH 10-11
4NW NEMO 8
1N TILFORD 3-4
2NE SILVER CITY 6-7
3N PACTOLA DAM 6
3SE DEERFIELD 7
4N CUSTER 6-8
23NNW EDGEMONT 1
FAIRBURN 3
HOT SPRINGS 1-2
EDGEMONT 2-3
10SSW ZEONA 3
BELLE FOURCHE 8-9
22NW B. FOURCHE 3
LEAD FIRE DEPT 10-12
8WNW USTA 7
BISON 6-8
LEMMON 6-7
7N MEADOW 5-6
7SW SHADEHILL 8-10
CAMP CROOK 4
1N RALPH 8-10
BUFFALO 8-10
ANTELOPE STN 6-8
15N BUFFALO 4
1SE LADNER 8
3SE HARDING 8
28E REDIG 8
11NE REDIG 5-6
CASTLE ROCK 4-5
...NORTHEASTERN WYOMING...
RECLUSE          12
2NW ECHETA 10-12
1E WESTON 6-8
WRIGHT 6-8
3S MOORCROFT 6-8
DILLINGER 6-7
HULETT 6
12 S GILLETTE 4-6
13SW UPTON 4
3E ROCHELLE 3
COLONY 3-4
20 SE WRIGHT 3
FOUR CORNERS 3
3N NEWCASTLE 1-2
DEVIL'S TOWER 5
SUNDANCE 8
3SE ALADDIN 8-10
5NE ALADDIN 8
14NW ALADDIN 7
11E GILLETTE 6-8

Weather Maps

The storm spun-up over the southwest United States on Wednesday (March 31st, 1999) and a piece of energy ejected into the plains. This is the energy that forced the band of heavy snow across the area.

A look at the upper-air analysis for 12z (all of the upper-air charts seen here is for 12z) April 1st, 1999 reveals some features of note. At 850mb a closed low was over central Nebraska. The thermal gradient, or the change of temperature across a distance, was fairly tight over South Dakota. You'll notice on the map there is 30-35kt 850mb wind speeds crossing the isotherms (dashed lines) over our area. This implies lift that is need to produce precipitation. At 700mb the closed low was over extreme southwest South Dakota. The heaviest snow in a storm frequently falls just to the north of the 700mb low. This thinking is validated by the snowfall map depicted near the top of this page.

Ratcheting our discussion up into the atmosphere reveals a closed low in east central Nevada on the 500mb analysis. Ahead of the low a shortwave is noted across southern Wyoming, northern Colorado and the Nebraska panhandle. You can see some darkening in the water vapor loop. The water vapor imagery is sensitive to moisture in the middle layers of the atmosphere. When we seen darkening or spinning in the loop, we can infer there is a shortwave in the vicinity. Finally, at 300mb there is a jet streak poking into southeast Wyoming. On the nose of a jet streak, and especially in the left front (exit region) portion of the jet, upper level divergence occurs. If air is diverging way up in the way, the air below it must fill the void which results in air moving from the air below the jet streak to the jet streak. We call this upward vertical motion (upsidence).

The snow and rain started Wednesday evening and quickly changed over to all snow in the higher elevations of Hills. This certainly helped snow totals there. The rest of the area gradually changed over to snow.

Between 3:00 AM and 5:00 AM Thursday convective snow developed. Several flashes of lightning and claps of thunder were heard across the area. Snowfall rates of an inch an hour were reported. We have made an infrared satellite loop for you to see the enhancement of the clouds during this time over western South Dakota.

Take a look at the surface maps we have compiled for you. The surface low moved from northeast Colorado to northeast Nebraska from 11:00 PM MST Wednesday to 11:00 AM MST Thursday.

Sequence of Forecast Events

The National Weather Service in Rapid City, SD is responsible for issuing advisories and warnings for these types of winter storms. Here are the products we issued on Tuesday and Wednesday.

  • Tuesday, March 30th
  • 3-4 PM - issued a Special Weather Statement for the potential of hazardous winter weather
  • Wednesday, March 31st
  • 3-4 AM - issued a Winter Storm Watch for the potential of heavy snow amounts in excess of 6 inches
  • 3-4 PM - issued a Winter Storm warning for heavy snow amounts averaging 6 inches or more
  • Thursday, April 1st
  • 3-4 PM - let the Winter Weather headlines expire as the storm wound down

The best way to hear about hazardous winter weather conditions in the Black Hills is NOAA Weather Radio. Our transmitter operates on a frequency of 162.55 MHz on station WXM-63. Our broadcasts can be heard on a scanner or via dedicated weather radios. These radios are available for purchase at your local electronics store. The information you receive will assist you in planning your day and will help you cope with winter storms.

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