Trapped low level moisture led to areas of dense fog in the Eastern Uinta Basin.
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The episode as NWS GJT wrote it up.
Trapped low level moisture led to areas of dense fog in the Eastern Uinta Basin.
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 Dec 9, 11:02 PM MST, 1 hour 58 minutes earlier.
Area Forecast Discussion National Weather Service Grand Junction CO 1102 PM MST Mon Dec 9 2019 .SHORT TERM...(Tonight through Tuesday night) Issued at 312 PM MST Mon Dec 9 2019 Light convective showers are still occurring in northwest flow behind the departing trough as one last piece of energy moves through. Not much evidence of anything reaching the ground in the lower central valleys but the higher peaks appear to still be seeing some light snowfall. The higher passes remain wet with some patchy fog up high. Skies are improving from the northwest as drier air moves in with high pressure building to the west. Light snowfall may continue over the northern Park and Gore range through the overnight into Tuesday morning due to weak orographic flow but do not anticipate any significant accumulations. Temperatures tonight will be much colder than last night due to less cloud cover. Some patchy fog is possible in some areas that have seen recent moisture. In terms of a repeat performance in the Grand Valley as was seen last night into this morning, confidence is low as any lingering low level moisture will have been vacated. Dense fog is more common the night after a recent rain or snowfall, due to evaporation of moisture off the surface and advection of cooler air aloft. The ground has had sufficient time to dry, lessening the chance of this occurring. Tuesday afternoon will be met with dry conditions and mostly sunny skies, although some thin high cloud cover will be present. Temperatures should stay near to slightly above normal. .LONG TERM...(Wednesday through Monday) Issued at 312 PM MST Mon Dec 9 2019 A weak shortwave trough looks to move across the region on Wednesday but this is not bringing much moisture with it. Most models indicate very little to no precipitation but an increase in mid and high cloud cover. Some light snowfall is possible over the higher terrain, but chances are pretty low. Mostly dry conditions are expected through Thursday with temperatures staying near normal for daytime highs and overnight lows staying cold but above normal due to increased cloud cover. Westerly flow will set up Thursday into Friday as a 160 kt jet sets up over the northern California and southern Oregon coast, advecting in some Pacific moisture. This moisture will slam into the northern and central mountains as the jet shifts southward, with snow beginning Thursday night into Friday morning. This moist pattern will remain through the weekend as the upper level trough associated with this upper level jet moves through the region Saturday into Sunday, finally bringing much colder air with it as H7 temps drop into the -10C to -16C range by Sunday morning. Until then, snow levels appear higher where the high elevations in the northern and central mountains could see decent snowfall Friday into Saturday, spreading into the southern mountains late Saturday into Sunday. Snow levels appear to lower to all valley floors Saturday night into Sunday as this colder air advects in with cold front and trough passage. Hard to pinpoint amounts at this time but this is the next best chance for widespread precipitation and accumulating snowfall. Drier air moves in from the north on Monday but chances are some snow will be lingering behind this trough as orographics and lingering moisture take over with temperatures in that sweet dendritic zone. As expected, temperatures take a dive to below normal levels Sunday through early next week. && .AVIATION...(For the 06Z TAFS through 06Z Tuesday night) Issued at 1058 PM MST Mon Dec 9 2019 Some high clouds will move overhead tonight but any ceilings will be at or above 20K feet. Having said that, KHDN, KASE and KVEL are sitting at MVFR and IFR due to some low clouds that have formed over the last few minutes. Will need to keep an eye on things over the next few hours to see if they hang around. Next concern is fog for KVEL and KGJT. Expect some patch spots for the Grand Valley but a better chance for KVEL. With those high clouds though, might keep fog at bay. Again, later shifts will need to keep an eye out. Tomorrow, VFR conditions under mostly sunny skies. && .GJT WATCHES/WARNINGS/ADVISORIES... CO...None. UT...None. && SHORT TERM...MDA LONG TERM...MDA AVIATION...TGR
Hazardous Weather Outlook National Weather Service Grand Junction CO 314 PM MST Mon Dec 9 2019 COZ001>014-017>023-UTZ022>025-027>029-102215- 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- 314 PM MST Mon Dec 9 2019 This hazardous weather outlook is for eastern Utah and western Colorado. .DAY ONE...This Afternoon and Tonight Light snow will linger over the northern and central Colorado mountains through the evening with very little additional accumulation expected. Some patchy fog may develop overnight, especially in areas of recent precipitation. .DAYS TWO THROUGH SEVEN...Tuesday through Sunday The next chance for mountain snow arrives Friday and continues through Sunday, with lower valley rain changing over to snow Saturday night. .SPOTTER INFORMATION STATEMENT... Spotter activation will not be needed.
The national radar mosaic for the moment the first event began.
1 dense fog. Local standard time, as filed.
Dense fog was observed across the Eastern Uinta Basin including at the Vernal Regional Airport as visibility was reduced to less than one quarter of a mile for several hours.
After NWS Directive 10-1605, the rules offices file Storm Data by.
Every storm in Utah in 2019Every state in 2019This day in weather historyWarnings in Utah, December 2019
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: 861337.