After a very warm day, a strong cold front passed through during the evening hours. The strongest winds developed in the Rapid City area and adjacent plains, where a few gusts around 60 mph were recorded.
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The episode as NWS UNR wrote it up.
After a very warm day, a strong cold front passed through during the evening hours. The strongest winds developed in the Rapid City area and adjacent plains, where a few gusts around 60 mph were recorded.
The local office's own words before the first event, as it sent them, from the Iowa Environmental Mesonet's archive of National Weather Service text.
NWS Rapid City, SD wrote its last area forecast discussion before the first event at Sep 24, 5:58 PM MST, 3 hours 2 minutes earlier.
Area Forecast Discussion For Western SD and Northeastern WY
National Weather Service Rapid City SD
658 PM MDT Thu Sep 24 2020
.UPDATE...
Issued at 658 PM MDT Thu Sep 24 2020
Based on upstream obs and the expectation of enhanced pressure
rises behind an approaching cold front, confidence is increasing
in a strong wind event tonight for much of the wrn SD plains. Main
point of consideration this evening has been the potential for
nocturnal stabilization to limit ability for winds to make it to
the sfc, particularly given a lack of appreciable CAA behind the
front. Nevertheless, based on fcst soundings and observed post-
frontal pressure rise of 5 mb/2 hr at KMLS, think CAA will be
just enough to promote steep lapse rates in the lowest 1-2 kft
above ground layer, facilitating the transfer of some gusts 40+
kt to the sfc. Thus, have introduced a wind advisory for much of
the area through 10z, with the expectation that the winds will
develop from NW to SE across the advisory area beginning shortly.
Suspect highest gusts will be in the "squeeze" zone east of the
Black Hills, likely beginning closer to 04-06z.
Expiration time of 02z for Red Flag Warning over nern WY still
looks to be on track. Prefrontal SW winds are gradually
diminishing and should mostly give way to nocturnal stabilization
in the next hour or so. As the front crosses the area later this
evening, winds will increase out of the NW, but RH will also rise.
&&
.DISCUSSION...(This Evening Through Thursday)
Issued at 146 PM MDT Thu Sep 24 2020
Water vapor shows upper ridge extending from the Desert SW into
the Northern Plains, with upper trof over the Pac NW into the
Northern Rockies. At the surface, low is centered over
northeastern MT with dryline extending southward into northeastern
WY, and cold front through south central MT. Dry/Gusty southwest
winds across northeastern WY early this afternoon with expanding red
flag conditions.
Dry cold front associated with trof moving through the Northern
Rockies will create a period of gusty northwest winds this
evening and overnight, with winds decreasing on Friday. Highs
Friday will be a bit cooler than today.
Mean upper trof shifts through the Northern Rockies into the
Northern Plains late Friday into Saturday. Strong cold front moves
through early Saturday producing gusty northwest winds and cooler
temps. Not much moisture to work with, but there could be a few
showers. Given the strength of winds and cold advection, some
wind highlights may be necessary especially for northwest SD.
A strong jet streak will deepen the trof over the Northern Plains
on Sunday, driving another cold front through the area. Another
period of gusty northwest winds and potential wind highlights can
be expected with highs in the 50s/60s. Again, not much moisture
to work with but a few -showers expected, possibly mixing with
snow at times in the higher elevations.
Upper trof sets up over the Upper Midwest/Great Lakes through the
end of next week, with periodic dry cold fronts and bouts of gusty
northwest winds and elevated fire weather conditions. Temps likely
to be near and below climo for most of the period.
&&
.AVIATION...(For the 00Z TAFS Through 00Z Friday Evening)
Issued At 525 PM MDT Thu Sep 24 2020
Despite continued smoke/haze, VFR conds should persist through the
TAF period.
Main concern this period will be the potential for strong wind
gusts behind a front that will cross the area from NW to SE this
evening/overnight. Limiting factors will be any nocturnal
stabilization prior to the front's arrival and the lack of strong
cold air advection behind the front, which could limit potential
for higher-end gusts. However, think some 35-40 kt or higher gusts
will be possible across portions of the wrn SD plains thru approx
12z.
&&
.FIRE WEATHER...
Issued at 146 PM MDT Thu Sep 24 2020
Dry/gusty southwest winds behind a dry line have created red flag
conditions over northeast WY this afternoon. Red flag conditions
are expected to continue into the evening, before a cold front
brings slightly higher relative humidity back into the region
tonight. There will be a period of gusty northwest winds behind
the cold front.
Gusty northwest winds will develop both Saturday and Sunday across
the region as a series of cold front moves through. Although a few
showers will be possible, moisture will be limited and most areas
will remain dry. Minimum relative humidity of 20-35 percent both
days combined with the gusty winds will create elevated fire
weather conditions through the weekend.
Much of next will be near or a bit cooler than average. A series
of dry cold fronts will bring gusty northwest winds and low
relative humidity at times along with elevated fire weather
conditions.
&&
.UNR WATCHES/WARNINGS/ADVISORIES...
SD...Wind Advisory until 4 AM MDT Friday for SDZ001-002-012>014-026-
031-032-043-072-073.
WY...Red Flag Warning until 8 PM MDT this evening for WYZ314>317.
&&
Update...Sherburn
DISCUSSION...Johnson
AVIATION...Sherburn
FIRE WEATHER...JohnsonHazardous Weather Outlook National Weather Service Rapid City SD 443 AM MDT Thu Sep 24 2020 SDZ001-WYZ054>056-058-251045- Harding-Northern Campbell-Southern Campbell-Western Crook-Weston- 443 AM MDT Thu Sep 24 2020 This Hazardous Weather Outlook is for portions of northwestern South Dakota...and northeast Wyoming. .DAY ONE...Today and Tonight Hot, dry, and breezy weather today will result in critical fire weather conditions this afternoon and early evening. See the Red Flag Warning product for more details. A cold front will cross the area tonight, bringing a period of gusty northwest winds. .DAYS TWO THROUGH SEVEN...Friday through Wednesday Mild, dry, and windy weather will result in elevated fire weather concerns for the next several days. Saturday looks particularly gusty, with sustained winds of 25 to 35 mph, and gusts around 50 mph possible. .SPOTTER INFORMATION STATEMENT... Spotter activation will not be needed today. && Stay tuned to NOAA weather radio for further updates...or check our web site at weather.gov/rapidcity SDZ002-012>014-024>032-041>044-072>074-WYZ057-071-251045- Perkins-Butte-Northern Meade Co Plains-Ziebach- Northern Black Hills-Northern Foot Hills-Rapid City- Southern Foot Hills-Central Black Hills-Southern Black Hills- Custer Co Plains-Pennington Co Plains-Haakon-Fall River- Oglala Lakota-Jackson-Bennett-Sturgis/Piedmont Foot Hills- Southern Meade Co Plains-Hermosa Foot Hills-Wyoming Black Hills- Northeastern Crook- 443 AM MDT Thu Sep 24 2020 This Hazardous Weather Outlook is for portions of northwestern South Dakota...southwestern South Dakota...the Black Hills of South Dakota...northeast Wyoming...and the Black Hills of Wyoming. .DAY ONE...Today and Tonight Hot, dry, and breezy conditions will result in very high fire danger today. A cold front will cross the area tonight, bringing a period of gusty northwest winds. .DAYS TWO THROUGH SEVEN...Friday through Wednesday Mild, dry, and windy weather will result in elevated fire weather concerns for the next several days. Saturday looks particularly gusty, with sustained winds of 25 to 35 mph, and gusts around 50 mph possible. .SPOTTER INFORMATION STATEMENT... Spotter activation will not be needed today. && Stay tuned to NOAA weather radio for further updates...or check our web site at weather.gov/rapidcity SDZ046-047-049-251045- Mellette-Todd-Tripp- 543 AM CDT Thu Sep 24 2020 This Hazardous Weather Outlook is for portions of south central South Dakota. .DAY ONE...Today and Tonight A cold front will cross the area tonight, bringing a period of gusty northwest winds. .DAYS TWO THROUGH SEVEN...Friday through Wednesday Mild, dry, and windy weather will result in elevated fire weather concerns for the next several days. Saturday looks particularly gusty. .SPOTTER INFORMATION STATEMENT... Spotter activation will not be needed today. && Stay tuned to NOAA weather radio for further updates...or check our web site at weather.gov/rapidcity
PRELIMINARY LOCAL STORM REPORT
NATIONAL WEATHER SERVICE RAPID CITY SD
909 PM MDT THU SEP 24 2020
..TIME... ...EVENT... ...CITY LOCATION... ...LAT.LON...
..DATE... ....MAG.... ..COUNTY LOCATION..ST.. ...SOURCE....
..REMARKS..
0704 PM NON-TSTM WND GST 7 NW ROCKYPOINT 44.99N 105.19W
09/24/2020 M50 MPH CROOK WY MESONET
0824 PM NON-TSTM WND GST 1 N BUFFALO 45.60N 103.55W
09/24/2020 M54 MPH HARDING SD ASOS
&&
KDSThe national radar mosaic for the moment the first event began.
3 high wind. Local standard time, as filed.
After NWS Directive 10-1605, the rules offices file Storm Data by.
Every storm in South Dakota in 2020Every state in 2020This day in weather historyWarnings in South Dakota, September 2020
NOAA National Centers for Environmental Information, Storm Events Database, compiled from the National Weather Service’s monthly Storm Data. Complete through 2026-06; NCEI adds each month about 75 days after it ends and revises past years a few times a year. Rebuilt 2026-09-24. Each event’s entry at NCEI: 914518, 914519, 914520.