The Snowy and Sierra Madre mountain ranges in south-central Wyoming received 5 to 10 inches of snow accumulation starting early in the morning on the 18th. Strong winds in the area also resulted in blowing snow and reductions to visibility.
Every event with a place to put it; 2 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.
The Snowy and Sierra Madre mountain ranges in south-central Wyoming received 5 to 10 inches of snow accumulation starting early in the morning on the 18th. Strong winds in the area also resulted in blowing snow and reductions to visibility.
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 Feb 18, 10:50 PM MST, 1 hour 10 minutes earlier.
Area Forecast Discussion
National Weather Service Cheyenne WY
1050 PM MST Sat Feb 18 2023
.SHORT TERM...(This evening through Monday night)
Issued at 400 PM MST Sat Feb 18 2023
Main concern in the short term will deal with two separate strong
wind events. One ongoing right now...followed by a more widespread
event taking shape Sunday through Tuesday morning. Mountain snow
will be the other issue that will be discussed in the long term
section of this discussion.
Currently...Strong winds are ongoing this afternoon at Arlington
and Bordeaux with Craig to Casper 850/700mb height gradients
peaking across the area through 00Z this afternoon. Have yet to
get going over the Summit. Surface trough has shifted ever so
slightly east through the late morning and afternoon and has
allowed the winds to increase at Bordeaux. Further northwest
across Washington and Oregon...our next shortwave is moving
onshore.
Will see a brief decrease in gradients around 00-03Z this
evening...before they begin to increase once again up to 55/50mtrs
after 03Z. GFS 700/750mb winds remain strong this evening at
55-60kts through Sunday morning. Latest high wind guidance showing
gradients easing after 09Z tonight...that could lead to current
wind warnings being cancelled earlier than expected.
Confidence is high on a big wind event beginning Sunday afternoon
as the trough currently over the PACNW tracks across northern
Wyoming. Craig to Casper height gradients rapidly increase up to
51/60mtrs by 21Z and then 68/72mtrs by 00Z Monday. GFS 700mb winds
up to 60kts by 00Z across much of the I-80 Corridor in southeast
Wyoming with 750/800mb winds of 55-60kts at that time as well. By
03Z Monday...we are looking at widespread 700/750mb winds over
70-75kts across much of southeast Wyoming. Craig/Casper gradients
up near 90/83mtrs Sunday evening. This will not be a typical high
wind event with surface winds forecast to be in excess of 75-80
mph for many locations. Random Forest guidance showing 90 percent
probability of warning level winds at Arlington...80 percent for
Bordeaux and Summit. Gradients this high usually indicate that
locations outside the wind prone areas are going to get warning
level winds as well.
Other aspect with this transiting shortwave will be snow for the
Sierra Madre and Snowy Range. Looks like these two zones are going
to hit solidly for advisory level snow for 6-10 inches tonight
through Sunday. Current winter weather advisory looks good with no
changes planned.
Strong winds continue through at least Tuesday with all in house
wind guidance showing strong winds through Tuesday. Craig to
Casper gradients remain in the upper 60s to low 70s through 18Z
Tuesday. After that time...winds may ease and be confined to the
wind prone areas through Tuesday evening.
.LONG TERM...(Tuesday through Saturday)
Issued at 400 PM MST Sat Feb 18 2023
Very active weather will continue into the extended forecast period.
The main concerns at this time are:
* A prolonged heavy mountain snowfall event is expected to begin
Monday and continue through Wednesday night. After a lull
Thursday, additional mountain snowfall is possible Thursday night
through Saturday. Expect dangerous conditions in the mountains
beginning Monday and continuing through at least Thursday morning.
* Confidence is increasing in a widespread accumulating snow event
for much of the forecast area Tuesday night through Wednesday
night.
* Another round of arctic cold will come with this system. Bitterly
cold temperatures are likely Wednesday and Thursday.
MOUNTAIN SNOW: Drier air will bring an end to the initial advisory
level snowfall event Sunday night. However, the break is expected to
be short lived. The nose of a potent Pacific jet will creep closer
to the area on Monday and bring significant positive theta-e
advection into our area from the WNW. Orographic lift is expected to
cause snow to resume in the mountains Monday morning, with half-inch
or greater per hour snowfall rates possible during the afternoon.
Very strong winds will be ongoing even before the snow starts
falling, which may cause significant blowing snow concerns from
Sunday's fresh snowfall. Wind gusts up to 60 MPH are possible Sunday
night and Monday in the Sierra Madre range, and up to 80 MPH in the
Snowy range. Whiteout conditions will be possible. Winds will be
strongest Sunday night and Monday, but high winds will remain
possible Tuesday. Expect lighter winds Tuesday night through
Thursday, but some areas of blowing snow are still possible. Those
recreating in the mountains over the next week should be prepared
for very dangerous travel conditions for several consecutive days.
Since impactful heavy snow is expected to begin Monday, and there
doesn't appear to be a clear break between the initial atmospheric
river induced snowfall Monday through early Tuesday, and the snow
associated with the main trough swinging through Tuesday night
through early Thursday, so decided to issue one long Winter Storm
Watch beginning Monday morning and continuing to Thursday morning.
There are likely to be lulls or periods of temporarily lighter
snowfall, but this isn't clear enough to break up the events.
Total accumulations between Monday and Thursday are likely to be
in the 2 to 4 feet range in the Sierra Madre, and 18-36 inch range
in the Snowy range. However, would not be surprised to see
reports of some higher peaks approaching 5 feet of new snow.
WIDESPREAD SNOW: Moist northwest flow will become more westerly on
Tuesday as a vigorous upper level low plunges into the Pacific
northwest before swinging across the Rockies by Thursday morning.
Models have trended slower with the frontal passage, but still did
go faster than NBM which appeared to slow down too much. The surface
front looks likely to come through overnight Tuesday night, clearing
through most of the area by daybreak Wednesday. Initially, this will
be fairly shallow arctic air mostly just in the surface layer. As
the upper level low approaches Tuesday night, 700-mb winds will
start to turn southerly. This will initiate significant warm air and
positive theta-e advection aloft. Winds on the isentropic surface
look nearly perpendicular to the isobars, indicating strong
isentropic lift along with solid mid-level frontogenesis. The best
estimate on timing is between midnight Tuesday night and mid
afternoon Wednesday for the heaviest snowfall, though this certainly
could change as the lead time decreases. Models have trended
slightly further south with the main trough, stalled mid-level
frontal boundary, and lee cyclogenesis over Colorado. This is
pushing the area of heavier snow further south too, with ensemble
mean liquid precipitation around 0.35 to 0.6" CWA wide. The ECE mean
is still slightly further south than the GEFS mean, and also
slightly slower. Thus uncertainty remains considerable, but
confidence is increasing in an event reaching advisory criteria for
the entire forecast area, with potential for widespread warnings,
though the exact location of the highest totals are still uncertain.
Lastly, significant cold is expected. Temperatures are likely to
drop through the day Wednesday, bottom out at some impressive cold
Thursday morning. Ensembles are in fairly strong agreement for
-10 to -15F temperatures for much of the area. Wind chill
headlines will likely be needed. Forecast uncertainty increases
considerably beyond Thursday, but most models continue to trend in
the direction of hanging a piece of the upper level low over
California and resuming moist WSW flow aloft that may keep
mountain snow going Friday. The extreme cold should moderate, but
remain below average.
&&
.AVIATION...(For the 06Z TAFS through late Sunday evening)
Issued at 1050 PM MST Sat Feb 18 2023
A broad upper level trough is currently moving southeast across
Wyoming/northern Front Range through Sunday morning. Some snow
showers are possible around KRWL early Sunday morning, with breezy
conditions for all southeast Wyoming terminals through tonight and
early Sunday morning as winds gust up to 35 knots at times.
HAZARDS/WEATHER TRENDS: VFR conditions expected to prevail for all
terminals, with some MVFR CIGS and VIS possible at KRWL between 06z
and 14z due to snow shower activity. Added a TEMPO group for now
based on the current radar loop. Otherwise, gusty winds around 25 to
35 knots expected to continue for KRWL, KLAR, and maybe KCYS at
times. There may be a brief lull in the gusty winds when surface
winds decouple, so kept LLWS around 45 knots mainly along the I-80
corridor terminals.
&&
.FIRE WEATHER...
Issued at 315 AM MST Fri Feb 17 2023
No fire weather concerns will be present as continued cool and dry
conditions are expected for most locations. Recent snowfall has
assisted with keeping fuels out of elevated concerns. However,
minimum relative humidity values will be in the 20-30 percent range
across portions of southeast Wyoming and strong, gusty winds will be
present this weekend as well.
&&
.CYS WATCHES/WARNINGS/ADVISORIES...
WY...High Wind Watch from Sunday afternoon through Tuesday morning
for WYZ104-105-107>109-115-118-119.
High Wind Warning until 8 AM MST Sunday for WYZ106-110-116.
High Wind Watch from Sunday morning through Tuesday afternoon
for WYZ106-110-116-117.
Winter Weather Advisory from 11 PM this evening to 5 PM MST
Sunday for WYZ112-114.
Winter Storm Watch from late Sunday night through late Wednesday
night for WYZ112-114.
NE...None.
&&
SHORT TERM...GCC/MN
LONG TERM...MN
AVIATION...TJT
FIRE WEATHER...BWHazardous Weather Outlook National Weather Service Cheyenne WY 601 AM MST Sat Feb 18 2023 WYZ104-106>110-116>119-191315- Ferris/Seminoe/Shirley Mountains- Central Laramie Range and Southwest Platte County- East Platte County-Goshen County-Central Carbon County- North Snowy Range Foothills-South Laramie Range- South Laramie Range Foothills-Central Laramie County- East Laramie County- 601 AM MST Sat Feb 18 2023 This hazardous weather outlook is for portions of south central Wyoming and southeast Wyoming. .DAY ONE...TODAY AND TONIGHT Breezy winds develop this afternoon. Winds could gust as high as 35 mph. .DAYS TWO THROUGH SEVEN...SUNDAY THROUGH FRIDAY Prolonged period of strong winds begin on Sunday and continue into Tuesday. High Wind Watches and Warnings have been issued. See active highlights for more details. Widespread snowfall accumulation to start Tuesday night and continue for the rest of the week. Strong cold front will bring very cold temperatures and even colder wind chill values. .Spotter information statement... Spotter activation will not be required. WYZ101>103-105-111-113-115-191315- Converse County Lower Elevations-Niobrara County- North Laramie Range-Shirley Basin-Southwest Carbon County- Upper North Platte River Basin-Laramie Valley- 601 AM MST Sat Feb 18 2023 This hazardous weather outlook is for portions of east central Wyoming...south central Wyoming and southeast Wyoming. .DAY ONE...TODAY AND TONIGHT Breezy winds develop this afternoon. Winds could gust as high as 35 mph. .DAYS TWO THROUGH SEVEN...SUNDAY THROUGH FRIDAY Widespread snowfall accumulation to start Tuesday night and continue for the rest of the week. Strong cold front will bring very cold temperatures and even colder wind chill values. .Spotter information statement... Spotter activation will not be required. WYZ112-114-191315- Sierra Madre Range-Snowy Range- 601 AM MST Sat Feb 18 2023 This hazardous weather outlook is for portions of south central Wyoming. .DAY ONE...TODAY AND TONIGHT Snow will begin to fall later this afternoon. Falling snow will be accompanied by strong, gusty winds. Winter Weather Advisories have been issued. .DAYS TWO THROUGH SEVEN...SUNDAY THROUGH FRIDAY Prolonged period of heavy snow, and strong winds may create instances of blizzard conditions in the highest elevations. Snowfall accumulation could range from 3-4 feet of snow. .Spotter information statement... Spotter activation will not be required. NEZ002-003-019>021-054-055-095-096-191315- Dawes County-Box Butte County-Scotts Bluff County-Banner County- Morrill County-Kimball County-Cheyenne County- Northern Sioux County-Southern Sioux County- 601 AM MST Sat Feb 18 2023 This hazardous weather outlook is for portions of panhandle Nebraska. .DAY ONE...TODAY AND TONIGHT No hazardous weather is expected. .DAYS TWO THROUGH SEVEN...SUNDAY THROUGH FRIDAY Prolonged period of strong winds begin on Sunday and continue into Tuesday. Widespread snowfall accumulation to start Tuesday night and continue for the rest of the week. Strong cold front will bring very cold temperatures and even colder wind chill values. .Spotter information statement... Spotter activation will not be required.
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</html>PRELIMINARY LOCAL STORM REPORT
NATIONAL WEATHER SERVICE CHEYENNE WY
839 PM MST SAT FEB 18 2023
..TIME... ...EVENT... ...CITY LOCATION... ...LAT.LON...
..DATE... ....MAG.... ..COUNTY LOCATION..ST.. ...SOURCE....
..REMARKS..
0826 PM NON-TSTM WND GST 1 SSE BORDEAUX 41.93N 104.94W
02/18/2023 M63 MPH PLATTE WY DEPT OF HIGHWAYS
MESONET STATION KBRX 1.4 S BORDEAUX (WYDOT).
0826 PM NON-TSTM WND GST 7 ESE ARLINGTON 41.55N 106.09W
02/18/2023 M62 MPH CARBON WY DEPT OF HIGHWAYS
MESONET STATION WY24 6.9 E ARLINGTON
(WYDOT).
0726 PM NON-TSTM WND GST 7 ESE ARLINGTON 41.55N 106.09W
02/18/2023 M66 MPH CARBON WY DEPT OF HIGHWAYS
MESONET STATION WY24 6.9 E ARLINGTON
(WYDOT).
&&
MBPRELIMINARY LOCAL STORM REPORT
NATIONAL WEATHER SERVICE CHEYENNE WY
951 PM MST SAT FEB 18 2023
..TIME... ...EVENT... ...CITY LOCATION... ...LAT.LON...
..DATE... ....MAG.... ..COUNTY LOCATION..ST.. ...SOURCE....
..REMARKS..
0944 PM NON-TSTM WND GST 1 SSE BORDEAUX 41.93N 104.94W
02/18/2023 M76 MPH PLATTE WY DEPT OF HIGHWAYS
MESONET STATION KBRX 1.4 S BORDEAUX (WYDOT).
0938 PM NON-TSTM WND GST 1 SSE BORDEAUX 41.93N 104.94W
02/18/2023 M65 MPH PLATTE WY DEPT OF HIGHWAYS
MESONET STATION KBRX 1.4 S BORDEAUX (WYDOT).
0926 PM NON-TSTM WND GST 1 SSE BORDEAUX 41.93N 104.94W
02/18/2023 M58 MPH PLATTE WY DEPT OF HIGHWAYS
MESONET STATION KBRX 1.4 S BORDEAUX (WYDOT).
&&
MBThe national radar mosaic for the moment the first event began.
2 winter weather. Local standard time, as filed.
Multiple SNOTELs estimated 5 to 9 inches of snow accumulation, especially at elevations above 9000 feet.
Multiple SNOTELs near 10000 feet elevation estimated 8 to 10 inches of snow accumulation, including the Med Bow SNOTEL.
After NWS Directive 10-1605, the rules offices file Storm Data by.
Every storm in Wyoming in 2023Every state in 2023This day in weather historyWarnings in Wyoming, February 2023
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 2026-10-01. Each event’s entry at NCEI: 1070543, 1070545.