A Pacific low pressure system and moist upslope flow produced a prolonged period of moderate to heavy snowfall over the Snowy and Sierra Madre mountains. Snow total accumulations ranged from one to three feet.
Every event with a place to put it; 12 filed by county or forecast zone are drawn at its center, in a lighter ring. Tap one for its entry below.
Deaths and injuries are direct and indirect together, as the offices filed them. Damage is property and crops in the dollars of the year, not adjusted for inflation, and only where an office estimated it.
The episode as NWS CYS wrote it up.
A Pacific low pressure system and moist upslope flow produced a prolonged period of moderate to heavy snowfall over the Snowy and Sierra Madre mountains. Snow total accumulations ranged from one to three feet. Gusty west winds created blowing and drifting snow.
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 4, 1:10 PM MST, 1 hour 50 minutes earlier.
Area Forecast Discussion National Weather Service Cheyenne WY 210 PM MDT Sat Nov 4 2017 .SHORT TERM...(This evening through Sunday) Issued at 206 PM MDT Sat Nov 4 2017 Complex weather scenario will unfold over the next few days. Upper trough seen on GOES-16 WV imagery this afternoon over the Great Basin area will dampen as it ejects eastward over the Rockies and onto the plains by Sunday evening. A surface front currently is stretching across the northern one third of our CWA and this front will slowly sag south and west over the plains tonight before retreating north and eastward Sunday through Monday. Ahead of the front, gusty W to SW winds have developed with the strongest winds found between Laramie and Rawlins. Gusts have been less than high wind criteria through most of the morning but we have seen a few gusts around 55 mph. Will go ahead an cancel the high wind warning as we are near peak mixing now. Next concern will be precip type and amounts through Tuesday. Prevailing moist WSW flow against the Snowy and Sierra Madre ranges will be ideal for continued orographic ascent through Monday. Ascent will be augmented by frontal lift and some jet dynamics so think these areas will see around 2 ft of snow at the higher elevations and western facing slopes. Current WSW looks good here. To the east, upstream soundings at Great Falls and Rapid City show this front to be extremely shallow but quite cool. Current visible imagery and surface obs show an area of low clouds and fog associated with the front stretching from western Converse County into the Chadron area. Areas of fog are favored behind the front in prime upslope locations with temperatures cooling into the 20s and low 30s over the plains through early morning. Moisture looks shallow and there is even the hint of a warm nose aloft near 700 mb on forecast soundings. Think a mixed bag of light rain and drizzle, changing to light snow and freezing drizzle will take place over the plains tonight. May even see a period of freezing rain near Chadron but not confident enough to include at this time. Shallow cold air will be slow to erode on Sunday and with weak forcing driven mainly by low level warm advection think it will be a cloudy, raw day especially over the Panhandle where temps will struggle to get out of the 30s. Light rain and snow showers will be possible over the southern areas closer to the better jet dynamics. Models differ on how to handle the next shortwave in the northern stream diving into the northern Rockies on Monday. EC and to some extend the NAM split this system and leave some elongated troughing hanging back over NW Wyoming through Tuesday. 12Z GFS also trended this direction. This would favor the reinforcing front hanging up just to our south through much of Tuesday. Forecast soundings show cold air becoming much deeper over the plains Monday night with SW'ly overrunning developing. Thus a period of snow is likely especially over southern WY and the NE Panhandle Monday night through much of Tuesday. Bumped up snow totals into the 2-4 inch range and later shifts will need to monitor the potential for winter headlines in these areas. .LONG TERM...(Sunday night through Saturday) Issued at 206 PM MDT Sat Nov 4 2017 Shortwave ridging will build in the wake of the departing upper trough on Tuesday night and continue through Thursday. This will impart a warming and drying trend through mid week. A more significant upper trough will once again dig into the Pacific NW Thursday night and Friday and models differ on how to handle how this system progresses into the Rockies for Friday through Saturday. Potential for more unsettled weather as we head into next weekend. && .AVIATION...(For the 18Z TAFS through 18Z Sunday afternoon) Issued at 1126 AM MDT Sat Nov 4 2017 Wyoming TAFS...VFR at Rawlins until 01Z, then MVFR until 05Z, then IFR until 15Z, then VFR. VFR at Laramie until 12Z, then IFR until 15Z, then VFR. VFR at Cheyenne until 07Z, then IFR until 15Z, then VFR. At all sites, wind gusts of 35 to 45 knots until 01Z. Nebraska TAFS...IFR at Chadron until 15Z, then MVFR. VFR at Alliance until 21Z, then IFR until 15Z, then MVFR. VFR at Scottsbluff until 00Z, then IFR until 15Z, then VFR. VFR at Sidney until 05Z, then MVFR until 10Z, then IFR until 15Z, then MVFR. && .FIRE WEATHER... Issued at 206 PM MDT Sat Nov 4 2017 No Fire Weather concerns through early next week. Unsettled weather is expected over the area resulting in several chances for precipitation, cool temperatures, and high relative humidities. && .CYS WATCHES/WARNINGS/ADVISORIES... WY...Winter Storm Warning until 5 PM MST Monday for WYZ112-114. NE...None. && SHORT TERM...DEL LONG TERM...DEL AVIATION...RUBIN FIRE WEATHER...DEL
Hazardous Weather Outlook National Weather Service Cheyenne WY 556 AM MDT Sat Nov 4 2017 WYZ101-103>107-109>119-051200- Converse County Lower Elevations-North Laramie Range- Ferris/Seminoe/Shirley Mountains-Shirley Basin- Central Laramie Range and Southwest Platte County- East Platte 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- 556 AM MDT Sat Nov 4 2017 This hazardous weather outlook is for portions of southeast Wyoming .DAY ONE...TODAY AND TONIGHT Periods of gusty winds up to 55 mph are possible through this afternoon, especially in the wind prone areas along Interstate 25 and Interstate 80. .DAYS TWO THROUGH SEVEN...SUNDAY THROUGH FRIDAY Heavy snow is expected in the mountains through Monday afternoon where a Winter Storm Warning is in effect. Snow accumulations and some travel impacts are possible in the high valleys and adjacent plains along Interstate 25 Sunday morning and Monday night. .Spotter information statement... Spotter activation will not be required at this time. NEZ002-003-019>021-054-055-095-096-WYZ102-108-051200- Dawes-Box Butte-Scotts Bluff-Banner-Morrill-Kimball-Cheyenne- North Sioux-South Sioux-Niobrara County-Goshen County- 556 AM MDT Sat Nov 4 2017 This hazardous weather outlook is for western Nebraska and extreme southeast Wyoming. .DAY ONE...TODAY AND TONIGHT Patchy dense fog will lift and dissipate by late this morning. Travelers can expect visibilities below one half mile along the North Platte River valley before noon. .DAYS TWO THROUGH SEVEN...SUNDAY THROUGH FRIDAY The probability for widespread hazardous weather is low. .Spotter information statement... Spotter activation will not be required at this time.
PRELIMINARY LOCAL STORM REPORT
NATIONAL WEATHER SERVICE CHEYENNE WY
329 PM MDT SAT NOV 04 2017
..TIME... ...EVENT... ...CITY LOCATION... ...LAT.LON...
..DATE... ....MAG.... ..COUNTY LOCATION..ST.. ...SOURCE....
..REMARKS..
0105 PM NON-TSTM WND GST 3 NW I-80 EXIT 255 41.75N 106.51W
11/04/2017 M60 MPH CARBON WY DEPT OF HIGHWAYS
HALLECK RIDGE WYDOT SITE ON I-80. SUSTAINED 41 MPH FOR
OVER ONE HOUR.
0100 PM NON-TSTM WND GST 3 ESE ELK MOUNTAIN 41.67N 106.37W
11/04/2017 M57 MPH CARBON WY DEPT OF HIGHWAYS
COUNTY ROAD 402 WYDOT SITE ON I-80. SUSTAINED AT 40 MPH
FOR ONE HOUR.
1245 PM NON-TSTM WND GST 10 SSW HANNA 41.73N 106.65W
11/04/2017 M57 MPH CARBON WY DEPT OF HIGHWAYS
DANA RIDGE WYDOT SITE ON I-80.
1255 PM NON-TSTM WND GST 5 NW ARLINGTON 41.64N 106.29W
11/04/2017 M57 MPH CARBON WY DEPT OF HIGHWAYS
WAGONHOUND WYDOT SITE ON I-80. SUSTAINED NEAR 40 MPH FOR
ONE HOUR.
&&
GCLAYCOMThe national radar mosaic for the moment the first event began.
12 winter storm. Local standard time, as filed.
The Old Battle SNOTEL site (elevation 10000 ft) estimated two feet of snow.
The Divide Peak SNOTEL site (elevation 8880 ft) estimated 13 inches of snow.
The Webber Springs SNOTEL site (elevation 9250 ft) estimated 16 inches of snow.
The Little Snake River SNOTEL site (elevation 8915 ft) estimated 19 inches of snow.
The Whiskey Park SNOTEL site (elevation 8950 ft) estimated 14 inches of snow.
The Blackhall Mountain SNOTEL site (elevation 9820 ft) estimated 16 inches of snow.
The South Brush Creek SNOTEL site (elevation 8440 ft) estimated 17 inches of snow.
The North French Creek SNOTEL site (elevation 10130 ft) estimated 34 inches of snow.
The Sand Lake SNOTEL site (elevation 10050 ft) estimated 26 inches of snow.
The Brooklyn Lake SNOTEL site (elevation 10240 ft) estimated 20 inches of snow.
The Cinnabar Park SNOTEL site (elevation 9574 ft) estimated 25 inches of snow.
The Medicine Bow SNOTEL site (elevation 10500 ft) estimated 32 inches of snow.
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: 726947, 726948, 726950, 726951, 726952, 726953, 726955, 726956, 726957, 726959, 726960, 726961.