On the evening of October 31, 1999 a strong cold front plowed through northeast Wyoming and western South Dakota. The cold front raced across the region in less than 6 hours. At 5 PM the cold front was noted on the surface map below.
By 10 PM, the cold front had raced through most of the area as seen below.
Strong pressure rises on the order of 4-8mb in 3 hours were noted across much of northeast Wyoming and western South Dakota. Our in-house rule-of-thumb is that for every millibar of pressure rise in 3 hours, you can expect a 10 knot (11 MPH) wind to occur. This has worked fairly well, and did work fairly well for this case.
The cold front was observed on 3.9u satellite imagery. A still picture of the imagery with cold front at 0415Z on the evening of Halloween is seen below.
The black spots you see on the imagery is where the satellite picked up much warmer readings than normal. These "hot spots" showed us where fires were occurring. The black spot south of Gillette was the remnants of a fire that burned several tens of thousands of acres of mainly grassland. On the animations we have put together a few lines down, you can see the fires going ahead of the cold front and then as the cold front passes, they flare up dramatically as strong, gusty wind fans the flames.
A lot of dust was also experienced with this cold front as well as much colder temperatures. This can been seen very well on a set of satellite animations that we have put together for you.
The recorded wind gusts from this system are provided for you perusal.
PRELIMINARY LOCAL STORM REPORT
NATIONAL WEATHER SERVICE RAPID CITY SD
705 AM MST MON NOV 01 1999
TIME(MST) .....CITY LOCATION..... STATE ...EVENT/REMARKS...
0800 PM CAMP CROOK SD NON TSTM WINDS
10/31/99 HARDING 63 MPH NON TSTM WINDS.
0828 PM RAPID CITY SD NON TSTM WINDS
10/31/99 PENNINGTON 71 MPH NON TSTM WINDS.
REPORTED AT THE RAPID
CITY NWS OFFICE.
0840 PM ELLSWORTH AFB SD NON TSTM WINDS
10/31/99 MEADE 62 MPH NON TSTM WINDS.
0900 PM NEMO SD NON TSTM WINDS
10/31/99 LAWRENCE 52 MPH WIND GUST.
0922 PM (PHP)PHILIP ARPT SD NON TSTM WINDS
10/31/99 HAAKON 55 MPH WIND GUST.
1105 PM BUFFALO ARPT SD NON TSTM WINDS
10/31/99 HARDING 71 MPH NON TSTM WINDS.
1231 AM (RAP)RAPID CITY ARPT SD NON TSTM WINDS
11/01/99 PENNINGTON 64 MPH NON TSTM WINDS.
1245 AM FAITH MUNI ARPT SD NON TSTM WINDS
11/01/99 MEADE 60 MPH NON TSTM WINDS.
0200 AM DEVILS TOWER WY NON TSTM WINDS
11/01/99 CROOK 55 MPH WIND GUST.
0400 AM 10 S WALL SD NON TSTM WINDS
11/01/99 PENNINGTON 63 MPH NON TSTM WINDS.
REPORTED AT PINNACLES