Lingering moisture trapped underneath a surface inversion in the wake of a departing winter storm allowed dense fog to form across portions of eastern Utah.
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The episode as NWS GJT wrote it up.
Lingering moisture trapped underneath a surface inversion in the wake of a departing winter storm allowed dense fog to form across portions of eastern Utah.
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 Jan 7, 9:21 PM MST, 1 hour 9 minutes earlier.
Area Forecast Discussion National Weather Service GRAND JUNCTION CO 921 PM MST Sun Jan 7 2018 .UPDATE... Issued at 917 PM MST Sun Jan 7 2018 Some low clouds and fog are being reported in 3 areas this evening. The first is along the I-70 corridor from De Beque to Glenwood Springs where ceilings have remained at around 800 to 1000 feet all day. Another area is just north of Moab up to I-70, west to Green River and east to the Utah/Colorado border. The final area is a small swath between Delta and Montrose. Over the last hour, reports have been received of visibilities dropping to 1/4 mile at Montrose so issued a dense fog advisory for that area. Latest satellite shows some low clouds now forming over the Redlands dropping southeastward. Will be keeping an eye on all these areas overnight and will add these areas to dense fog advisory if needed. && .SHORT TERM...(Tonight through Monday night) Issued at 342 PM MST Sun Jan 7 2018 Cloud bases are beginning to gradually lift and skies are beginning to clear over most of the region as a weak transitory ridge of high pressure builds overhead, though some locations remain trapped under a low cloud deck. Forecast models for some of the lower valley locations across eastern Utah and western Colorado indicate the presence of a good bit of low level moisture overnight which will result in some areas of fog. As far as temperatures tonight, strong radiational cooling under mostly clear skies will keep overnight lows several degrees cooler than last night. Benign weather will persist through the first part of Monday before southwesterly flow increases over the region. Warm air advection paired with embedded ripples in the flow will allow clouds and the chance for isolated to scattered showers to increase Monday evening, continuing through Monday night. Temperatures will be on the mild side on Monday with daytime highs sitting some 10 to almost 15 degrees above normal. Snow levels will also remain relatively high at the onset of precipitation Monday evening and most accumulations will be confined to elevations above 9000 feet with amounts of 1 to 4 inches possible through daybreak Tuesday. Meanwhile, off the west coast, a broad upper level trough will split on Monday evening with a cutoff low developing just offshore of California by Tuesday morning. This closed low will be a big storm to watch as we head into the long term period. .LONG TERM...(Tuesday through Sunday) Issued at 342 PM MST Sun Jan 7 2018 Unsettled southwesterly flow will persist on Tuesday as the aforementioned closed low drops into the southern Great Basin. Isolated to scattered rain and snow showers will continue before increasing in coverage during the latter half of Tuesday. The closed low will progress towards the Four Corners during the evening hours with an abundance of moisture wrapped around the low spreading into our forecast area. As mentioned by the previous forecaster, the tap of Pacific moisture will result in a significant increase in both precipitable water and specific humidity values. Additionally, a cold front will be working its way through the region overnight which will provide favorable lift for precipitation. Numerous to potentially widespread showers can be expected through Wednesday before the Four Corners low lifts into the Plains. The forecast area will remain under the influence of an upper level trough through daybreak Thursday which will allow 700mb temperatures to plummet to -8 to -16 degrees C across the region. This will also result in showers continuing over the northern and central mountains. Now, in regards to snowfall amounts and uncertainty. There is the potential for this system to produce significant snowfall with new accumulations of 8 to 14 inches for the mountains and amounts close to 2 feet possible across the higher southern mountain peaks. Higher valley snowfall may vary between 1 and 4 inches. The greatest accumulations are expected Tuesday night through Wednesday morning. However, there is some uncertainty in regards to the exact track and mild nature of the system. The latest model runs have been trending further south, which could drastically impact snow levels and projected snow totals. Given this, decided not to issue any highlights with this package and instead opted for a Special Weather Statement which can be found on our website at weather.gov/gjt. Behind the departure of the trough conditions will generally clear before another quick moving shortwave brushes the northern half of the area on Friday. A strong ridge of high pressure looks to build over the western United States for the weekend which will allow for dry conditions under mostly sunny skies to prevail and temperatures to rebound. && .AVIATION...(For the 00Z TAFS through 00Z Monday evening) Issued at 433 PM MST Sun Jan 7 2018 Biggest concern for the overnight hours will be fog and some low ceilings for a few TAF sites. Right now, KMTJ and KRIL are socked in under a low cloud deck and have been all day. Do not anticipate breaking out now and fog will likely develop too. MVFR/IFR conditions will be common for those sites. KVEL and KCNY may also see some low ceilings and visibility thanks to low level moisture continuing. Other sites should remain VFR with some concern for KASE and KEGE so will keep an eye on things for those airports over the next few hours. Remaining TAF sites will remain VFR under clear to mostly clear skies. The next system will bring some high clouds to the area tomorrow dropping through the afternoon and evening. Expect that the TAF sites down in the muck now will mix out tomorrow morning after 17Z or so and TAF reflects this thinking. && .GJT WATCHES/WARNINGS/ADVISORIES... CO...Dense Fog Advisory until 9 AM MST Monday for COZ011. UT...None. && UPDATE...TGR SHORT TERM...MMS LONG TERM...MMS AVIATION...TGR
Hazardous Weather Outlook National Weather Service GRAND JUNCTION CO 432 AM MST Sun Jan 7 2018 COZ001>014-017>023-UTZ022>025-027>029-081145- 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- 432 AM MST Sun Jan 7 2018 This hazardous weather outlook is for eastern Utah and western Colorado. .DAY ONE...Today and Tonight Snow showers are expected to linger over Colorado's mountains through the early part of the day bringing an additional 1 to 3 inches. Meanwhile, valley fog will be prevalent along the I-70 corridor, the Uncompahgre River Basin, the Gunnison Basin and portions of the eastern Uinta Basin through the mid to latter part of the morning. Conditions improve during the afternoon. .DAYS TWO THROUGH SEVEN...Monday through Saturday The next chance for significant snowfall will be Tuesday evening into Wednesday. Initial snowfall output suggest advisory level snow for some mountain areas. However, until model agreement improves details will be limited. .SPOTTER INFORMATION STATEMENT... Spotter activation will not be needed.
PRELIMINARY LOCAL STORM REPORT
NATIONAL WEATHER SERVICE GRAND JUNCTION CO
549 PM MST SUN JAN 7 2018
..TIME... ...EVENT... ...CITY LOCATION... ...LAT.LON...
..DATE... ....MAG.... ..COUNTY LOCATION..ST.. ...SOURCE....
..REMARKS..
1000 AM SNOW 5 NE BAYFIELD 37.27N 107.52W
01/07/2018 M1.5 INCH LA PLATA CO PUBLIC
MEASURED AT 10AM.
&&
TGRPRELIMINARY LOCAL STORM REPORT
NATIONAL WEATHER SERVICE GRAND JUNCTION CO
907 PM MST SUN JAN 7 2018
..TIME... ...EVENT... ...CITY LOCATION... ...LAT.LON...
..DATE... ....MAG.... ..COUNTY LOCATION..ST.. ...SOURCE....
..REMARKS..
0930 AM SNOW 2 N COLLBRAN 39.27N 107.96W
01/07/2018 M3.0 INCH MESA CO PUBLIC
SNOW FELL FROM 3AM - 930AM.
&&
TGRThe national radar mosaic for the moment the first event began.
1 dense fog. Local standard time, as filed.
Dense fog developed across portions of the Grand Flat in east-central Utah, including Interstate 70. The visibility dropped below 1/4 mile for several hours.
After NWS Directive 10-1605, the rules offices file Storm Data by.
Every storm in Utah in 2018Every state in 2018This day in weather historyWarnings in Utah, January 2018
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: 726485.