A period of high gap winds developed across the northern Snowy Range foothills and Laramie Valley. Frequent gusts of 65 to 75 mph were observed.
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The episode as NWS CYS wrote it up.
A period of high gap winds developed across the northern Snowy Range foothills and Laramie Valley. Frequent gusts of 65 to 75 mph were observed.
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 Cheyenne, WY wrote its last area forecast discussion before the first event at Nov 29, 3:20 AM MST, 5 minutes earlier.
Area Forecast Discussion National Weather Service Cheyenne WY 320 AM MST Wed Nov 29 2017 .SHORT TERM...(Today through Thursday Night) Issued at 205 AM MST Wed Nov 29 2017 Latest water vapor loop was showing a fairly distinct shortwave moving towards northwest Wyoming. Ahead of this shortwave, latest surface analysis have been showing pressure falls taking place along the Big Horn mountains and down the spine of the Laramie Range. As a result, we have noticed the gradients tightening within a corridor between Casper and Craig Colorado. In response to this tightening gradient wind speeds have increased considerably during the last couple of hours at Casper, Deer Creek, and our gap wind corridor near Arlington where some gusts of 50 to 60 mph have been occurring. This trend should continue through the morning hours with the potential for strong winds around Arlington and western Converse county. We were tempted on issuing a high wind warning for Converse county, but since the lee side trof is mostly setup along the Laramie range it will most likely be a small portion of the county with some potential gusts of 50 to 55 mph. Truckers traveling along I-25 west of Douglas should use extra caution in this area. Later this afternoon, we will see better mixing as the upper level trof moves through northern Wyoming and provides better subsidence to Converse and Niobrara counties. Day shift may need to keep an eye on how this evolves on any potential highlights in that region. For now, we just bumped up wind speeds to reflect this potential. The rest of the forecast area should also see pretty decent mixing through the afternoon with some gusts up to 40 mph mainly in the Wyoming. High pressure is expected to move into the area tonight and allow for good radiational cooling. The next subtle shortwave is expected to push through the area Thursday night. As a result, temperatures should begin to moderate a bit on Thursday with afternoon highs climbing into the 50s especially east of the Laramie Range. We did bump wind speeds again on Thursday night mainly over the Arlington region again since the surface trof will be setting up along the Laramie Range again which will tighten the gradients and gap wind potential to the west. .LONG TERM...(Friday through next Tuesday night) Issued at 250 AM MST Wed Nov 29 2017 Medium to Long Range models continue to show a more unsettled weather pattern beginning late in the weekend and continuing into early next week. Much colder temperatures appear likely during this time frame after the zonal flow earlier in the weekend becomes much more amplified over time. For Friday, another marginal gap wind event is possible across the wind prone areas early Friday, and to a lesser extent, early Saturday morning. A series of upper level shortwaves embedded in the westerly flow aloft will push eastward well north of southern Wyoming, llvl gradients may strengthen just enough to see gusts between 50 to 60 mph across the Wind Prone areas of southeast Wyoming. The main upper level trough axis will move into Wyoming on Sunday, ending the marginal High Wind threat. Although much colder temperatures are highly likely by early next week, precipitation chances are much less certain because of timing differences between ensemble forecasts and operational models as well as the effects of split flow aloft. Thus, low confidence with this portion of the forecast through early Wednesday morning next week. The Canadian and ECMWF are much more amplified compared to the GFS and most of the ensemble forecasts, showing an upper level trough digging southeast across the area. The Canadian is the furthest south and shows the formation of an upper level low at the base of the trough for Monday around the four corners region. The ECMWF is more progressive and further north, but shows strong frontogenesis and lift along the I-80 corridor Sunday night resulting in accumulating snow. The GFS is much weaker with this system and shows hardly any precipitation at all until late Monday. With all this disagreement, had a hard time justifying POP above 30 percent outside the mountains. So kept a slight chance of snow and/or low end chance of snow in the forecast. High temperatures will likely struggle to reach the low to mid 30's by early next week, but will have to monitor the arctic airmass to the north as well as a potential upper level low near the four corners region in this time frame. && .AVIATION...(For the 12Z TAFS through 12Z Thursday morning) Issued at 305 AM MST Wed Nov 29 2017 VFR conditions expected today and tonight with windy conditions across southeast Wyoming and western Nebraska. A dry cold front will move across the area late this afternoon and this evening. Other than some cloudiness and winds shifting into the northwest, not much impact is expected from this front. && .FIRE WEATHER... Issued at 205 AM MST Wed Nov 29 2017 Dry and windy conditions will persist during the next several days as a couple of upper level disturbances move through the area. The strongest disturbance will move through today and create some gusty wind speeds. The strongest wind speeds will be between Laramie and Rawlins and Fire Weather Zone 301 where some gusts of 50 to 55 mph will be possible. Elsewhere, afternoon wind gusts today will range from 25 to 35 mph with humidity values ranging from 20 to 25 percent. Another disturbance is expected to move through Thursday night and Friday morning and create more gusty wind speeds between 20 to 30 mph. Afternoon humidities through the remainder of the week will generally range from 25 to 35 percent. && .CYS WATCHES/WARNINGS/ADVISORIES... WY...High Wind Warning until noon MST today for WYZ110. NE...None. && SHORT TERM...REC LONG TERM...TJT AVIATION...TJT FIRE WEATHER...REC
Hazardous Weather Outlook National Weather Service Cheyenne WY 144 PM MST Tue Nov 28 2017 WYZ101>119-292045- Converse County Lower Elevations-Niobrara County- North Laramie Range-Ferris/Seminoe/Shirley Mountains- Shirley Basin-Central Laramie Range and Southwest Platte County- East Platte County-Goshen County-Central Carbon County- North Snowy Range Foothills-Southwest Carbon County- Sierra Madre Range-Upper North Platte River Basin-Snowy Range- Laramie Valley-South Laramie Range-South Laramie Range Foothills- Central Laramie County-East Laramie County- 144 PM MST Tue Nov 28 2017 This hazardous weather outlook is for portions of east central Wyoming...south central Wyoming and southeast Wyoming. .DAY ONE...THIS AFTERNOON AND TONIGHT Strong west to southwest winds will develop after midnight tonight across the North Snowy Range Foothills including Interstate 80 between Laramie and Rawlins. Refer to the High Wind Warning for further details. .DAYS TWO THROUGH SEVEN...WEDNESDAY THROUGH MONDAY Strong and gusty winds will continue through midday Wednesday between Rawlins and Laramie before subsiding in the afternoon. A low pressure system is forecast to impact the area early next week and bring chances for snow along with colder temperatures Monday through Tuesday. .Spotter information statement... Spotter activation will not be required at this time. NEZ002-003-019>021-054-055-095-096-292045- Dawes-Box Butte-Scotts Bluff-Banner-Morrill-Kimball-Cheyenne- North Sioux-South Sioux- 144 PM MST Tue Nov 28 2017 This hazardous weather outlook is for portions of western Nebraska. .DAY ONE...THIS AFTERNOON AND TONIGHT No hazardous weather is expected at this time. .DAYS TWO THROUGH SEVEN...WEDNESDAY THROUGH MONDAY A low pressure system is forecast to impact the area early next week and bring chances for snow along with colder temperatures Monday night and Tuesday. .Spotter information statement... Spotter activation will not be required at this time.
The national radar mosaic for the moment the first event began.
14 high wind. Local standard time, as filed.
The WYDOT sensor at Halleck Ridge measured wind gusts of 58 mph or higher, with a peak gust of 72 mph at 29/0600 MST.
The WYDOT sensor at Interstate 80 mile post 249 measured sustained winds of 40 mph or higher, with a peak gust of 60 mph at 29/0455 MST.
The WYDOT sensor at Arlington measured sustained winds of 40 mph or higher, with a peak gust of 67 mph at 29/0655 MST.
The WYDOT sensor at Foote Creek measured sustained winds of 40 mph or higher, with a peak gust of 68 mph at 29/0625 MST.
The WYDOT sensor at Wagonhound measured sustained winds of 40 mph or higher, with a peak gust of 65 mph at 29/0615 MST.
The WYDOT sensor at Elk Mountain measured sustained winds of 40 mph or higher, with a peak gust of 63 mph at 29/0615 MST.
The wind sensor at the Elk Mountain Airport measured sustained winds of 40 mph or higher, with a peak gust of 63 mph at 29/0555 MST.
The WYDOT sensor at Arlington East measured sustained winds of 40 mph or higher, with a peak gust of 68 mph at 29/0635 MST.
The WYDOT sensor at Cooper Cove measured wind gusts of 58 mph or higher, with a peak gust of 68 mph at 29/0815 MST.
The WYDOT sensor at County Road 402 measured sustained winds of 40 mph or higher, with a peak gust of 59 mph at 29/0730 MST.
The WYDOT sensor at Strouss Hill measured wind gusts of 58 mph or higher, with a peak gust of 70 mph at 29/1025 MST.
The UPR sensor at Rock River measured wind gusts of 58 mph or higher, with a peak gust of 82 mph at 29/1030 MST.
The WYDOT sensor at Quealy Dome measured wind gusts of 58 mph or higher, with a peak gust of 74 mph at 29/1020 MST.
The WYDOT sensor at Herrick Lane measured sustained winds of 40 mph or higher, with a peak gust of 63 mph at 29/1040 MST.
After NWS Directive 10-1605, the rules offices file Storm Data by.
Every storm in Wyoming in 2017Every state in 2017This day in weather historyWarnings in Wyoming, November 2017
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: 728612, 728613, 728606, 728611, 728615, 728609, 728610, 728605, 728607, 728608, 728614, 728618, 728617, 728616.