A deepening trough over the Pacific Northwest phased with a potent shortwave over the Baja Peninsula, pulling a strong jet northeastward toward the Four Corners. This, combined with generally clear skies that promoted deep mixing, allowed strong winds to reach the surface on the afternoon of the 20th.
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The episode as NWS GJT wrote it up.
A deepening trough over the Pacific Northwest phased with a potent shortwave over the Baja Peninsula, pulling a strong jet northeastward toward the Four Corners. This, combined with generally clear skies that promoted deep mixing, allowed strong winds to reach the surface on the afternoon of the 20th. This event was confined mainly to Southeast Utah and Southwest Colorado.
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 May 20, 11:02 AM MST, 58 minutes earlier. Its key messages:
Area Forecast Discussion National Weather Service Grand Junction CO 1202 PM MDT Mon May 20 2024 .KEY MESSAGES... - Warm and windy conditions today ahead of a cold front will drive temperatures back above climatology and winds will gust 30-40 mph around the region. - Showers and thunderstorms will develop along the front today. Storms will be capable of strong outflows and small hail. A few snow showers are also expected in the mountains behind the front Monday evening and into Tuesday morning. - Cooler temperatures behind the front Tuesday will keep afternoon highs 10 degrees below climatology. Temperatures return to near normal Wednesday and beyond. && .SHORT TERM /THROUGH TUESDAY/... Issued at 401 AM MDT Mon May 20 2024 A frontal boundary stretching northeast from the Great Basin to the Panhandle of Nebraska marks a rather abrupt moisture gradient here in the CWA this morning. Dewpoints are in the mid 40's across northwest Colorado, where light rainshowers have been observed much of the night. The moisture/front are situated along a strong jet streak turning the bend on the West Coast trough digging into the Great Basin this morning. Those strong winds aloft will gradually work their way over the Four Corners this morning and drive up wind speeds across the CWA this afternoon ahead of the approaching frontal boundary. The strongest winds will concentrate around the Four Corners today where southwesterly winds around 20-25 mph with gusts to around 35-40 mph can be expected. Held off on a wind advisory for now, due to the lack of widespread zone coverage down there. Forcing along the front holds across northeast UT and northwest CO into the afternoon hours. A few showers and thunderstorms are expected to develop this afternoon as the jet begins to pull the front through the region. Early activity will remain north of the Colorado River Valley, then begin to fill in during the early evening hours as the actual front swings in northwest to southeast. The front clears northwest Colorado by midnight and cooler, drier air quickly puts the brakes on showers up there. However, down south, showers and convection along the front will keep going into the overnight hours, likely not calming down until the early morning hours. Showers will likely hang up on the mountains through the night Monday into Tuesday, where accumulating snow above 10000 feet is expected thanks to the generous shot of cold air behind this front. Tuesday, we remain under the upper level trough as it lags the front. Gradient winds will remain blustery behind the front. Afternoon highs on Tuesday are expected to be nearly 20 degrees cooler. Showers and additional thunderstorms are expected across the region Tuesday as we see a series of shortwaves work through the upper trough during the day. Steep lapse rates will help out with some gusty outflows and small hail. && .LONG TERM /TUESDAY NIGHT THROUGH SUNDAY/... Issued at 401 AM MDT Mon May 20 2024 Tuesday night will finally see the axis of the prolonged trough slide east of the Divide with subsident, dry air quickly settling in behind it. Any lingering showers will diminish and denser cloud cover will begin to clear under the now northwest flow aloft. This will mean a sharp drop in temperatures compared to the last several nights with Tuesday night's lows trending some 10 degrees cooler. In the wake of the cold front subfreezing temperatures will be possible in portions of southwest and northwest Colorado, while the central Colorado and eastern Utah valleys will stay in the upper 30s to low 40s. No freeze highlights are needed at this time since the current forecast subfreezing temperatures correlates with our zones that do not have vegetation susceptible to damage. A quiet day is on tap for the Western Slope on Wednesday, though upper level flow will shift to the west as the next trough digs into the Pacific Northwest. Can't rule a few afternoon storms over the higher terrain once daytime heating kicks in but, overall, it'll be dry area-wide with temperatures beginning to rebound back to near normal. Models are beginning to come into better agreement regarding the evolution of the Pacific storm as it pushes across the Intermountain West Wednesday night before eventually tracking through Montana and Wyoming on Thursday as it splits off from the parent system. Flow will once again return to the southwest across eastern Utah and western Colorado by Wednesday evening so those overnight lows will quickly jump back to a few degrees above normal. The base of the northern wave looks to straddle the Wyoming / Colorado border on Thursday so expect isolated to scattered showers and storms to develop across northeast Utah and northwest Colorado that afternoon. Elsewhere will remain dry but breezy as the gradient tightens with the trough. The secondary wave looks to cross the forecast area sometime on Friday but there are some discrepancies regarding how far south it will drop. Depending on when this system pushes through we could be looking at unsettled conditions going through the weekend. But, not locking anything in at this moment as changes can be expected under this persistent longwave troughing pattern. && .AVIATION /18Z TAFS THROUGH 18Z TUESDAY/... Issued at 1202 AM MDT Mon May 20 2024 Winds will become gusty this afternoon and evening out ahead of an approaching strong cold front. Gusts of 30 to 40 mph will be common at most terminals. Showers and thunderstorms will also continue to develop along the front in northeast Utah and northwest Colorado before working south and east by this evening. The strongest storms will be capable of producing very strong winds and hail. Terminals will see periods of ILS breakpoint conditions this afternoon and into the overnight hours, especially mountain terminals, where rain and snow showers will likely hang up along the Divide overnight into Tuesday morning. More widespread showers are expected across mountain and adjacent valley TAF sites through much of the day Tuesday with MVFR ceilings and visibility possible. && .GJT WATCHES/WARNINGS/ADVISORIES... CO...None. UT...None. && SHORT TERM...LTB LONG TERM...MMS AVIATION...TGJT
Hazardous Weather Outlook National Weather Service Grand Junction CO 1243 PM MDT Mon May 20 2024 COZ003-006>014-017>023-UTZ022-025-027>029-211845- Roan and Tavaputs Plateaus-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-Tavaputs Plateau- Arches/Grand Flat-La Sal and Abajo Mountains- Canyonlands/Natural Bridges- 1243 PM MDT Mon May 20 2024 This Hazardous Weather Outlook is for northwest Colorado, southwest Colorado, west central Colorado, east central Utah and southeast Utah. .DAY ONE...This afternoon and tonight. Warm and windy conditions today ahead of a cold front will bring wind gusts 30 to 40 mph across the region. Near critical fire weather conditions this afternoon are expected around the Four Corners, where fuels remain sub-critical. Showers and thunderstorms along the front will work through the region this afternoon and into the overnight hours. Gusty outflows and small hail are expected in storms today. Accumulating mountain snows expected above 10000 feet tonight, as cold air behind the front lowers freezing levels. .DAYS TWO THROUGH SEVEN...Tuesday through Sunday. Scattered showers and thunderstorms will continue on Tuesday behind the front. Gusty outflow winds and small hail will remain a threat in thunderstorms on Tuesday. Quieter conditions return Wednesday into late week, when unsettled weather returns to the region. .SPOTTER INFORMATION STATEMENT... Spotter activation is not expected today or tonight, however spotters are encouraged to report excessive wind or any observed wind related damage to the National Weather Service in Grand Junction. COZ001-002-004-005-UTZ023-024-211845- Lower Yampa River Basin-Central Yampa River Basin- Elkhead and Park Mountains-Upper Yampa River Basin- Eastern Uinta Mountains-Eastern Uinta Basin- 1243 PM MDT Mon May 20 2024 This Hazardous Weather Outlook is for northwest Colorado and northeast Utah. .DAY ONE...This afternoon and tonight. Slightly cooler and windy conditions today ahead of a cold front will bring wind gusts 30 to 40 mph across the region. Showers and thunderstorms along the front will work through the region this afternoon and into the overnight hours. Gusty outflows with the potential to produce gusts in excess of 60 mph and small hail are expected with some storms today. Accumulating mountain snows expected above 10000 feet tonight, as cold air behind the front lowers freezing levels. .DAYS TWO THROUGH SEVEN...Tuesday through Sunday. Scattered showers and thunderstorms will continue on Tuesday behind the front. Gusty outflow winds and small hail will remain a threat in thunderstorms on Tuesday. Quieter conditions return Wednesday into late week, when unsettled weather returns to the region. .SPOTTER INFORMATION STATEMENT... Spotter activation is not expected today or tonight, however spotters are encouraged to report excessive wind or any observed wind related damage to the National Weather Service in Grand Junction.
Preliminary Local Storm Report
National Weather Service Grand Junction CO
1224 PM MDT Mon May 20 2024
..TIME... ...EVENT... ...CITY LOCATION... ...LAT.LON...
..DATE... ....MAG.... ..COUNTY LOCATION..ST.. ...SOURCE....
..REMARKS..
1203 PM Non-Tstm Wnd Gst 1 W Douglas Pass 39.60N 108.82W
05/20/2024 M50 MPH Garfield CO Mesonet
Mesonet station CO098 139s034 Douglas Pass.
&&Special Weather Statement
National Weather Service Grand Junction CO
1236 PM MDT Mon May 20 2024
UTZ024-201900-
Eastern Uinta Basin UT-
1236 PM MDT Mon May 20 2024
...A STRONG THUNDERSTORM WILL IMPACT WEST CENTRAL UINTAH COUNTY
THROUGH 100 PM MDT...
At 1236 PM MDT, Doppler radar was tracking a strong thunderstorm near
Fort Duchesne, moving east at 30 mph.
HAZARD...Wind gusts up to 50 mph and half inch hail.
SOURCE...Radar indicated.
IMPACT...Gusty winds could knock down tree limbs and blow around
unsecured objects. Minor hail damage to vegetation is
possible.
Locations impacted include...
Fort Duchesne, Randlett, and Maeser.
This includes U.S. Highway 40 in Utah between mile markers 118 and
141.
PRECAUTIONARY/PREPAREDNESS ACTIONS...
If outdoors, consider seeking shelter inside a building.
Frequent cloud to ground lightning is occurring with this storm.
Lightning can strike 10 miles away from a thunderstorm. Seek a safe
shelter inside a building or vehicle.
&&
LAT...LON 4018 10991 4030 10993 4046 10959 4020 10945
TIME...MOT...LOC 1836Z 259DEG 27KT 4028 10980
MAX HAIL SIZE...0.50 IN
MAX WIND GUST...50 MPH
MillerSpecial Weather Statement
National Weather Service Grand Junction CO
1257 PM MDT Mon May 20 2024
UTZ024-201930-
Eastern Uinta Basin UT-
1257 PM MDT Mon May 20 2024
...A STRONG THUNDERSTORM WILL IMPACT NORTHEASTERN UINTAH COUNTY
THROUGH 130 PM MDT...
At 1257 PM MDT, Doppler radar was tracking a strong thunderstorm near
Vernal, moving northeast at 35 mph.
HAZARD...Wind gusts up to 50 mph and pea size hail.
SOURCE...Radar indicated.
IMPACT...Gusty winds could knock down tree limbs and blow around
unsecured objects. Minor hail damage to vegetation is
possible.
Locations impacted include...
Vernal, Naples, and Maeser.
This includes the following highways...
U.S. Highway 40 in Utah between mile markers 133 and 161.
U.S. Highway 191 in Utah between mile markers 353 and 357.
PRECAUTIONARY/PREPAREDNESS ACTIONS...
If outdoors, consider seeking shelter inside a building.
&&
LAT...LON 4027 10962 4041 10971 4061 10939 4035 10917
TIME...MOT...LOC 1857Z 243DEG 30KT 4037 10957
MAX HAIL SIZE...0.25 IN
MAX WIND GUST...50 MPH
MillerThe national radar mosaic for the moment the first event began.
1 high wind. Local standard time, as filed.
Wind gusts across the zone ranged from 45 mph to near 60 mph. The peak wind gust of 59 mph was recorded at the KCNY ASOS at the Canyonlands Airport, north of Moab. This was the only wind gust to be recorded above 58 mph.
After NWS Directive 10-1605, the rules offices file Storm Data by.
Every storm in Utah in 2024Every state in 2024This day in weather historyWarnings in Utah, 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: 1181614.