Trapped low level moisture in the wake of a departing storm led to areas of dense fog in southeast Utah.
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The episode as NWS GJT wrote it up.
Trapped low level moisture in the wake of a departing storm led to areas of dense fog in southeast 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 4, 11:23 PM MST, 1 hour 7 minutes earlier.
Area Forecast Discussion National Weather Service Grand Junction CO 1123 PM MST Sat Jan 4 2020 .UPDATE... Issued at 1119 PM MST Sat Jan 4 2020 Low stratus and areas of dense fog continue to overtake the Grand Valley with satellite imagery showing the low level moisture spreading east across the valley. The Grand Flats and areas south toward Canyonlands National Park are also seeing an expansion of the cloud cover and fog. Several reports coming in of locally dense fog, especially near the rivers. Some icing also possible along bridges and overpasses. Thin cirrus is spreading in from the west and this may help to improve visibilities later tonight, but for now, will go with a Dense Fog Advisory with visibility restrictions down to a quarter mile or less for several more hours. && .SHORT TERM...(Tonight through Sunday night) Issued at 301 PM MST Sat Jan 4 2020 The transitory mid-level ridge over the area this morning has shifted east in response to a low-amplitude shortwave trough moving across the Great Basin. This disturbance has spread cirrus across the forecast area, but as mid-level moisture is lacking, no snow has fallen. Meanwhile, a stubborn near surface low-level inversion over the Grand Flat of eastern Utah has trapped a broad stratus shield across the area. Forecast soundings at KCNY showed the saturated layer trapped below the inversion clearly, and long story short, it doesn't appear that skies will be clearing there in the near term. As a result, have updated the sky grids with cloudy or mostly cloudy skies through Monday morning. The shortwave trough mentioned previously brushes the northern zones late this afternoon and early this evening. Very little moisture and lift associated with this feature, so expect only isolated snow showers to form over the northern Colorado mountains this evening. A tightening gradient with the trough's passage will bring brisk winds to the mountains, most notably at Monarch Pass. Fast, progressive flow continues on Sunday as another fast moving mid-level shortwave trough sweeps over the area during the afternoon and evening. This disturbance carries moderate moisture with it and will bring snowfall to the northern and central mountains Sunday night. Amounts appear to be similar or maybe a little higher than outlined in previous forecast discussion. Latest guidance suggests 3 to 6 inch accumulations with locally higher amounts for the Elkhead and Gore Ranges with additional snow coming Monday. Accumulations are expected to be significantly lower for the Flat Tops and central mountains. Confidence not quite there to pull the trigger on a Winter Weather Advisory just yet. The remainder of the area will remain dry, though clouds will be increased with the passage of this system. Temperatures will continue to hover near normal for most locations in the near term, though there will be exceptions to that rule across areas where low-level valley inversions persist. .LONG TERM...(Monday through Saturday) Issued at 301 PM MST Sat Jan 4 2020 We will be on the back side of the main trough on Monday. However a trailing wave and continued cold air advection will likely keep some light orographic snow going across our northern Colorado mountains through mid-day. Warm advection in the wake of this wave late in the afternoon should shut the snow down by sunset. By the storm's end there could be some significant snow amounts in the upper elevations of the Elkhead Park and northern Gore Ranges which is typical in this fast NW flow pattern. Broad ridging transitions from the Pacific Coast to the Rockies through mid-week with dirty flow bringing periods of high level cloudiness to the CWA. This will again be a battle of inversions and cloud cover. Expect some warming in the mid and upper elevations while the valleys remain on the cold side of normal into at least Tuesday. Wednesday is a 50/50 day for warming as a larger trough digs into the western CONUS and brings stronger winds aloft into our CWA. Though this is a bigger trough moving into the West...there is seems to be little organization with it attm. The lead energy moves through late Wednesday while the trailing energy carves out a sharper trough to our South heading into Friday. Without organized lift this is favoring the mountains for the better precipitation. There are the usual model differences showing up but the American model seems to be trending toward the EURO according to the latest progs in the early Friday timeframe. They are more consistent with the large wave pattern...developing strong anomalous heights into the northeast Pacific while the Bermuda High remains anchored over the Caribbean. This will favor a cooler and unsettled West with the high amplitude ridge in the Pacific limiting the extent of any AR to the coastal areas. A fetch of subtropical moisture to the central Rockies is beginning to show up on the horizon just outside this forecast period. Stay tuned for that. && .AVIATION...(For the 06Z TAFS through 06Z Sunday night) Issued at 1031 PM MST Sat Jan 4 2020 Low stratus remains persistent invof CNY keeping conditions IFR/LIFR with CIGS near 500 ft AGL. There is a small potential that this stratus deck will deteriorate some overnight but kept status quo with this TAF issuance. This cloud bank has slowly advected upvalley (eastward) now impacting KGJT as well. Cloud level happens to intersect the ground right near KGJT leading to consistent reduced sfc visibilities on the order of 1/2 mile or less. At KASE, winds in the 3-5 kft AGL layer will be in the 30-40 kt range near the 250 degree mark...while much lighter winds remain in place near the surface. Low clouds and vis remains a potential concern at KEGE around sunrise...but forecast confidence in a particular solution remains low. Otherwise, VFR expected at remaining sites with the next passing system expected to only produce some increased cloudiness and possible high peak flurries in the northern Colorado mtns. && .GJT WATCHES/WARNINGS/ADVISORIES... CO...Dense Fog Advisory until 9 AM MST Sunday for COZ006. UT...Dense Fog Advisory until 9 AM MST Sunday for UTZ027-029. && UPDATE...JDC SHORT TERM...NL LONG TERM...15 AVIATION...TGJT
Hazardous Weather Outlook National Weather Service Grand Junction CO 435 AM MST Sat Jan 4 2020 COZ001>014-017>023-UTZ022>025-027>029-051145- 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- 435 AM MST Sat Jan 4 2020 This hazardous weather outlook is for eastern Utah and western Colorado. .DAY ONE...Today and Tonight No hazardous weather is expected at this time. Dry weather will continue under mainly sunny skies. .DAYS TWO THROUGH SEVEN...Sunday through Friday A light snow event will move through the mountains of northern Colorado on Sunday afternoon through Monday morning. Expect 1-3 inches in these ranges with 6" or possibly more in the Park range. Watch for slick travel over Rabbit Ears Pass on Monday morning. .SPOTTER INFORMATION STATEMENT... Spotter activation will not be needed.
PRELIMINARY LOCAL STORM REPORT
NATIONAL WEATHER SERVICE GRAND JUNCTION CO
1117 PM MST SAT JAN 4 2020
..TIME... ...EVENT... ...CITY LOCATION... ...LAT.LON...
..DATE... ....MAG.... ..COUNTY LOCATION..ST.. ...SOURCE....
..REMARKS..
1105 PM DENSE FOG GRAND JCT. REDLANDS 39.09N 108.63W
01/04/2020 MESA CO NWS EMPLOYEE
1/16 TO 3/8 MILE VISIBILITY. SCATTERED SNOW
GRAIN SHOWERS MID TO LATE EVENING.
&&PRELIMINARY LOCAL STORM REPORT
NATIONAL WEATHER SERVICE GRAND JUNCTION CO
1120 PM MST SAT JAN 4 2020
..TIME... ...EVENT... ...CITY LOCATION... ...LAT.LON...
..DATE... ....MAG.... ..COUNTY LOCATION..ST.. ...SOURCE....
..REMARKS..
0948 PM DENSE FOG GRAND JCT. REGIONAL AP 39.12N 108.52W
01/04/2020 MESA CO NWS EMPLOYEE
1/4 MILE VISIBILITY IN FREEZING FOG.
&&PRELIMINARY LOCAL STORM REPORT
NATIONAL WEATHER SERVICE GRAND JUNCTION CO
1136 PM MST SAT JAN 4 2020
..TIME... ...EVENT... ...CITY LOCATION... ...LAT.LON...
..DATE... ....MAG.... ..COUNTY LOCATION..ST.. ...SOURCE....
..REMARKS..
1045 PM DENSE FOG GRAND JCT. 3NW 39.14N 108.59W
01/04/2020 MESA CO NWS EMPLOYEE
1/4 TO 1/2 MILE VISIBILITY IN FREEZING FOG.
&&The national radar mosaic for the moment the first event began.
2 dense fog. Local standard time, as filed.
Dense fog was observed across the area as visibility was reduced to less than one quarter of a mile for several hours.
Dense fog was observed across the area 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 2020Every state in 2020This day in weather historyWarnings in Utah, January 2020
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: 863741, 863742.