An atmospheric river brought an abundance of moisture to Eastern Utah. This, paired with the passage of an upper level trough across the Northern Rockies and associated cold front, resulted in moderate to heavy snow for the northern and southern mountains.
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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 GJT wrote it up.
An atmospheric river brought an abundance of moisture to Eastern Utah. This, paired with the passage of an upper level trough across the Northern Rockies and associated cold front, resulted in moderate to heavy snow for the northern and southern mountains. Mild air associated with the atmospheric river kept snow levels high with mostly all rain or a rain/snow mix in the valleys. Winds gusted up to 58 mph at times in the 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 Grand Junction, CO wrote its last area forecast discussion before the first event at Mar 9, 9:51 PM MST, 2 hours 9 minutes earlier.
Area Forecast Discussion
National Weather Service Grand Junction CO
951 PM MST Thu Mar 9 2023
.SHORT TERM...(Tonight through Friday night)
Issued at 245 PM MST Thu Mar 9 2023
GOES-16 satellite imagery reveals partly to mostly sunny skies
across the Western Slope this afternoon. This is the result of a
transient ridge that is in the process of building over the Four
Corners states. Despite the chilly air aloft that was brought in
behind last night's cold front, mid-March sunshine is helping to
boost temperatures to near seasonable levels for many. The
exceptions to that however are northeast Utah and northwest
Colorado where deep snow cover is keeping temperatures at or below
freezing. Other than the sun, the other thing you're probably
noticing today is how much less wind is blowing across eastern
Utah and western Colorado, particularly in the higher elevations.
The strong jet aloft that sat overhead and brought relentless
winds for almost an entire week has finally lifted out to the
north and east. Enjoy the reprieve while it lasts because it won't
last long.
The ridge axis moves east of the CWA tonight, setting up broad
southwest flow and the beginning of a stout warm advection regime.
Clouds will gradually increase, thicken and lower tonight as the
nose of another very strong upper jet punches into the region from
the west. This blast of Pacific air has tropical origins and will
help to deliver highly anomalous moisture... otherwise known as an
atmospheric river. While a good bit of moisture will be wrung out
across the Sierras and other mountain ranges to our west, we'll
still get our fair share here given PWAT values running 200 to
300% of normal. As has been mentioned previously, there's really
not a whole lot of dynamic lift with this system. Instead, we're
more or less dealing with brute force orographics... as in, fast
moving moisture-laden air being forced up the terrain. This of
course may lead to some shadowing in valleys downstream, but most
areas will at least get some precipitation out of this system.
Speaking of precipitation, it likely starts moving in over the
higher elevations and adjacent valleys across the north shortly
after daybreak Friday. Over the course of the day, precipitation
is then expected to fill in from north to south, first in the
mountains and then in the lower valleys. Southwest flow and the
Pacific origins of the air mass coming in mean that snow levels
will be fairly high and generally above 8000 feet or so.
Precipitation type below that level, which includes many higher
and lower valleys, will be either a mix of rain or snow... or more
likely just plain rain. Above 8000 feet... the snow show will be
on. The heaviest and most widespread period of precipitation comes
Friday evening into Friday night when a low amplitude shortwave
enhances precipitation rates and coverage. In fact, snowfall rates
in heavier bands in the mountains may exceed 1 or even 2 inches
per hour during this time frame. In addition to the precipitation
aspect of this storm, we'll also be dealing with another period of
very strong winds. Latest guidance continues to highlight the
higher elevations where gusts of 50 to 60 mph will be possible.
Winds of those speeds combined with heavy snow will lead to all
kinds of travel problems, particularly at pass level. If you have
to travel up high Friday night, make sure you are prepared for
difficult to borderline impossible driving conditions.
Towards the end of the night, a cold front will begin dropping in
from the north and west which should bring colder air across the
north and lower snow levels. That being said, drier air will
likely be moving in too, which may shut precipitation off early.
Something to keep an eye on going forward. Given all of the above
and the growing confidence for many if not all of our mountains
to have a significant high water content snowfall event, decided
to upgrade all of the Winter Storm Watches to Winter Storm
Warnings with this package. Also decided to issue a Winter Storm
Warning for the eastern Uinta mountains in collaboration with WFO
SLC, though the heaviest snowfall will be closer to or even across
our border. Finally, issued a Winter Weather Advisory for the
Road and Tavaputs Plateaus given potential for still solid, but
more minor snowfall.
The storm continues into Saturday and for more details on that,
see the long term discussion below.
.LONG TERM...(Saturday through Thursday)
Issued at 245 PM MST Thu Mar 9 2023
As discussed previously, the bulk of precipitation will fall
during the Friday night to Saturday morning period. More organized
banded precipitation associated with a cold front will linger
across the southern and central mountains through the morning
hours on Saturday, but should come to an end by noon. Behind this
front, flow aloft turns zonal, which is a favorable direction for
orographic snowfall across the northern mountains, especially when
there is moisture in the flow. And oh boy is there going to be
moisture. While PWAT values drop a bit behind the departing low
pressure, we're talking 150-200% of normal compared to the
200-300% of normal ahead of the system, which is still well above
normal. That's plenty to work with, and as a result mountain snow
shower activity shows little sign of stopping. Ridging starts to
build in on Saturday, which will mark the beginning of a slow
warming trend for areas mainly along and south of I-70. This ridge
will keep things on the quieter side for the lower elevations,
despite the amount of available moisture. The only exception comes
with a shortwave working through the flow on Sunday, which will
bring one last burst of valley rain and mountain snow. All told,
by Sunday night the highest elevations of the area will see snow
totals in the 2-4 feet range, with the northern valleys seeing a
couple inches as well. The lower valleys that will see
predominantly rain are looking at 0.50- 0.75 inches of QPF by
Sunday night. It's going to be a wet weekend no matter where you
are.
By Monday morning, the ridge is in full control across the Great
Basin. The ridge will be building through the Great Basin during
this period and will deflect that fire hose of Pacific moisture to
the north, away from eastern Utah and western Colorado. As such,
a bit of drying trend is in the cards for Monday into Tuesday,
with even the orographic showers tapering off in the drier
northwest flow. By Tuesday morning, the ridge axis will be passing
overhead and the next Pacific low will be dropping south around
the parent trough. This will dig a trough off the Pacific Coast
and redirect the AR moisture plume back to the south in a more
favorable configuration for moisture to reach the Great Basin.
Ahead of this, flow turns southwesterly, which will allow for
strengthening warm air advection. Along and south of I-70, current
guidance has temperatures running around 5 degrees above average,
with areas north of I-70 finally seeing a day of near-normal
temperatures.
Models have been in surprisingly good agreement up to this point,
with only minor differences here and there. There are some much
more significant discrepancies beginning Wednesday. The
deterministic ECMWF favors a solution that keeps the cutoff low
over the Pacific Northwest, with an open trough moving over the
Great Basin. The GFS favors a solution that develops a cutoff low
over southern California and an open trough to the north, with
both providing energy to power shower activity. Different
solutions, yes, but showing the same general pattern...lower
heights over the western CONUS and plenty of moisture available to
work with. Now, the Canadian solution is the outlier, indicating
only a dry trough moving through the Great Basin. The cluster
ensemble solutions bear this out as well, with 3 of the 4 clusters
indicating ensemble members favor some form of the troughy
pattern presented by the GFS and ECMWF. The last cluster, composed
of 50% Canadian ensemble members, favors that drier solution.
There is a signal there, stranger things have happened. But with
ensemble solutions overwhelming favoring another strong, wet
system for mid-next week, the current forecast is leaning more
heavily to that end. But stay tuned, this time of year forecasts
can change fast.
&&
.AVIATION...(For the 06Z TAFS through 06Z Friday night)
Issued at 948 PM MST Thu Mar 9 2023
Atmospheric river moisture will continue to move across the Great
Basin and hit the mountains...bringing widespread mountain
precipitation to the forecast by noon. Eventually this moisture
will work down into the valleys with widespread MVFR or lower
conditions expected by early evening...persisting well beyond this
forecast.
&&
.GJT WATCHES/WARNINGS/ADVISORIES...
CO...Winter Weather Advisory from 11 AM Friday to 8 PM MST Saturday
for COZ003.
Winter Storm Warning from 5 AM Friday to 8 PM MST Saturday for
COZ004-013.
Winter Storm Warning from 11 AM Friday to 8 PM MST Saturday for
COZ009-017.
Winter Storm Warning from 11 AM Friday to 11 PM MST Saturday for
COZ010-012.
Winter Storm Warning from 11 AM MST Friday to 6 AM MDT Sunday
for COZ018-019.
UT...Winter Storm Warning from 11 AM Friday to 8 PM MST Saturday for
UTZ028.
Winter Storm Warning from 5 AM Friday to 5 AM MST Saturday for
UTZ023.
&&
SHORT TERM...MDM
LONG TERM...BGB
AVIATION...TGJTHazardous Weather Outlook National Weather Service Grand Junction CO 304 AM MST Thu Mar 9 2023 COZ001>014-017>023-UTZ022>025-027>029-101015- Lower Yampa River Basin-Central Yampa River Basin- Roan and Tavaputs Plateaus-Elkhead and Park Mountains- Upper Yampa River Basin-Grand Valley-Debeque to Silt Corridor- Central Colorado River Basin-Grand and Battlement Mesas- Gore and Elk Mountains/Central Mountain Valleys- Central Gunnison and Uncompahgre River Basin- West Elk and Sawatch Mountains-Flat Tops- Upper Gunnison River Valley-Uncompahgre Plateau and Dallas Divide- Northwest San Juan Mountains-Southwest San Juan Mountains- Paradox Valley/Lower Dolores River- Four Corners/Upper Dolores River-Animas River Basin- San Juan River Basin-Southeast Utah-Eastern Uinta Mountains- Eastern Uinta Basin-Tavaputs Plateau-Arches/Grand Flat- La Sal and Abajo Mountains-Canyonlands/Natural Bridges- 304 AM MST Thu Mar 9 2023 This hazardous weather outlook is for eastern Utah and western Colorado. .DAY ONE...Today and Tonight A system will moderate to heavy snow Friday and Saturday to most of the mountain ranges mainly above 8000 feet. Generally 10 to 20 inches are possible with locally higher amounts upwards of 30 inches. Winds in excess of 50 mph may cause blowing and drifting snow to the pass elevations. Light mountain snow showers may continue on Sunday and Monday. .DAYS TWO THROUGH SEVEN...Friday through Wednesday Another storm is possible mid next week but there is still some uncertainty with regards to strength and timing. Stay tuned to the latest forecasts for updates. .SPOTTER INFORMATION STATEMENT... Spotter activation will not be needed.
The national radar mosaic for the moment the first event began.
1 winter weather, 1 winter storm. Local standard time, as filed.
Generally 6 to 12 inches of snow fell across the area. Winds gusted up to 45 mph at times.
Generally 5 to 9 inches of snow fell across the area with locally higher amounts of up to 16 inches estimated at the Mosby Mountain SNOTEL site. Much of the snow fell in 12 hours or less. Winds gusted up to 58 mph at times.
After NWS Directive 10-1605, the rules offices file Storm Data by.
Every storm in Utah in 2023Every state in 2023This day in weather historyWarnings in Utah, March 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 2026-09-24. Each event’s entry at NCEI: 1075377, 1075376.