An upper low that moved across Wyoming brought rain to the lower elevations and heavy snow to the northeast Bighorn Mountains.
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The episode as NWS BYZ wrote it up.
An upper low that moved across Wyoming brought rain to the lower elevations and heavy snow to the northeast Bighorn Mountains.
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 Billings, MT wrote its last area forecast discussion before the first event at May 7, 2:20 AM MST, 3 hours 10 minutes earlier. Its key messages:
Area Forecast Discussion
National Weather Service Billings MT
320 AM MDT Tue May 7 2024
.DISCUSSION...
Today through Wednesday...
Dynamic upper low continues to spin over northwestern South
Dakota at this time. Spokes of precipitation were continuously
rotating into eastern counties with some isolated lightning while
a large band of precipitation was located from the Snowies
southeast to the SE corner of Big Horn County. In the
meantime...areas of wind continued with the highest gust overnight
at Alzada (59 mph). Snow has let up in the Big Horns and the
Winter Weather Advisory there was allowed to expire.
Ensemble means from the GFS and EC both now generally show the
500 mb low wobbling/spinning over the western Dakotas into
tonight. Analysis indicated 700 mb frontogenesis was generating
the larger precipitation band across our central zones...a little
further west than model proggs had placed it. We have adjusted
POPs and QPF for this for the rest of tonight into Tuesday.
Generally, more of the same today with considerable precipitation
mainly east of Yellowstone county where some areas could see an
additional 0.50 or more of liquid today (probability 40-70% in
parts of Custer and Rosebud counties) where large scale ascent and
trowal effects are strongest. The western areas will see
primarily wind again today with gusts 50-65 mph common as a
powerful 700 mb wind corridor stretches from Wheatland county to
SE MT. Strong winds could also impact areas in the east with local
gusts over 50 mph due to the strong pressure gradient associated
with the surface low.
The 700 mb jet gradually weakens tonight as the upper low slowly
fills and begins to drift south. So look for those strong winds
to continue into this evening before gradually weakening tonight.
No changes to the High Wind Warning thats in place for much of
the CWA.
As the upper low drifts south tonight into Wednesday the better
ascent and frontogenesis will sink south and be aided by low to
mid level flow turning more northerly (upslope). Thus, the more
efficient precipitation production will shift to areas over and
near the north facing slopes of the mountains. Models are
suggesting heavy snow along the north/northwest facing slopes with
snow levels near 5000 ft tonight as it starts...and climbing
Wednesday to around 6500 ft. The snow will continue into Wednesday
night and early Thursday. Totals may range well over a foot of
snow above 6500 feet by Thu morning in both the northern Big
Horns/Beartooths (chance of over a foot of snow as high as
70-90%). Thus we have issued a Winter Storm Watch for the
mountains from midnight tonight through Thursday morning. Please
see extended discussion below.
Highs will be in the mid 40s to lower 50s the next couple of days.
Overnight lows in the mid to upper 30s. BT
Wednesday night through Tuesday...
.KEY MESSAGES...
- Precipitation comes to an end Thursday afternoon into evening
- Heavy snowfall for the Bighorn and Beartooth mountains. Winter
storm watch has been issued
- Friday through early next week will be pleasant with
temperatures in the 70s with dry conditions
Wednesday night into Thursday will see continued precipitation
across the region, though with decreasing intensity. WPC clusters
show a secondary low spinning of to the west of the main low. The
stronger this low is and the farther to the west is stretches, the
higher precipitation totals we will see Thursday. This higher
precipitation scenario would bring 0.25-0.5 inches of
precipitation across much of our west, especially the higher
terrain, though this is only favored by 10% of members. The
majority of members (90%) have less than 0.25 for this time frame.
There is good model agreement that precipitation will come to an
end Thursday afternoon into evening.
As the low pressure system wraps around and brings moisture, the
Bighorn and Beartooth mountains will see heavy snow. 700mb winds
will be out of the north leading to north facing slopes being
favored for the heaviest snowfall. Currently, these north facing
slopes have a 70-90% chance of getting over 1 foot of snow. Snow
will start this evening and continue until Thursday afternoon.
Breezy to windy conditions may continue Wednesday evening,
decreasing throughout the night which will bring calm winds by
Thursday morning for the first time in a while. This is reflected
in the ECMWF EFI tables which have no significant wind signal for
Thursday. Thursday will see a decent pressure gradient set up over
the eastern portion of the CWA. This combined with low level
lapse rates conducive to mix down, will lead to the return of
gusty conditions to locations such as Miles City and Baker where
winds could gust into the 20s kts. Friday, there will be a wave
moving down from the north which ensemble clusters are agreeing
could once again bring breezy conditions to our eastern areas. The
farther west this wave is the farther west the strong winds will
move impacting more of the region. 30% of models have winds
gusting into the 30s as far west as Forsyth. Currently, only areas
along the Dakotas border have a chance (20%) of getting a wind
gust over 40mph Friday.
Friday through the weekend will see ridging return to the region
with westerly downsloping on Monday. This will bring the return
of temperatures in the 70s with dry conditions. Torgerson
&&
.AVIATION...
Showers and thunderstorms will continue to impact the region over
the next 24 hours. Before 21Z today the precipitation will mainly
be from Billings and locations to the east. After that the
precipitation will pivot and start to impact western areas as
well. Winds will remain strong across the region today with
widespread gusts in the 40s kts with locations in the western gap
areas (K6SO, KLVM, K1KM) seeing gusts into the 50s kts. Tonight
around 06Z winds will begin to decrease mainly in our northeast
(KMLS, KBHK) while still remaining breezy with gusts in the 20s
kts. Torgerson
&&
.PRELIMINARY POINT TEMP/POPS...
Tdy Wed Thu Fri Sat Sun Mon
-------------------------------------------------------
BIL 050 039/051 043/060 042/069 045/076 048/079 050/078
4/R 99/R 97/R 11/U 00/U 01/U 12/T
LVM 049 036/046 039/056 036/066 040/072 044/075 046/075
3/R 89/O 94/R 10/U 00/U 01/U 12/T
HDN 049 037/053 042/062 040/069 040/076 045/080 047/078
9/R 99/R +8/R 21/B 00/U 11/U 12/T
MLS 045 039/055 042/062 043/067 044/075 047/078 049/077
9/T 85/R 65/R 11/U 00/U 01/U 11/U
4BQ 044 037/051 040/059 043/064 041/074 046/077 049/077
9/R 76/R 86/R 21/B 00/U 01/U 11/U
BHK 047 036/054 037/063 040/065 040/073 044/075 046/075
9/T 75/R 43/R 11/B 01/U 01/U 11/U
SHR 052 036/047 038/057 036/064 037/072 042/076 045/075
2/R 58/R +7/R 21/U 01/U 01/U 22/T
&&
.BYZ WATCHES/WARNINGS/ADVISORIES...
MT...High Wind Warning remains in effect until midnight MDT
tonight FOR ZONES 29>32-34-42-57-138-170-173-235.
High Wind Warning remains in effect until 6 PM MDT this
evening FOR ZONES 36-37-58.
High Wind Warning remains in effect until 6 AM MDT Wednesday
FOR ZONES 63-65-66-141-172-228.
Winter Storm Watch in effect from late tonight through
Thursday morning FOR ZONES 67-68-171.
WY...High Wind Warning remains in effect until midnight MDT
tonight FOR ZONE 199.
Winter Storm Watch in effect from late tonight through
Thursday morning FOR ZONE 198.
&&
weather.gov/billingsThe national radar mosaic for the moment the first event began.
1 winter storm. Local standard time, as filed.
Snowfall of 12+ inches was reported in the mountains.
After NWS Directive 10-1605, the rules offices file Storm Data by.
Every storm in Wyoming in 2024Every state in 2024This day in weather historyWarnings in Wyoming, May 2024
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: 1173333.