wxgeek's weather-Dry Mild Start, Cold/Snowy End-Update Jan 9

Update Wed Jan 9

Yet another dry and mild day across CO. Some high clouds and breezy westerly winds at times. Quite a contrast to the drenching occurring in Texas. Many areas have received 2-5 inches of rain the past 36 hours, and another 1-3 inches expected through Thursday morning. Flood warnings in effect for most of TX east of I-35. This should help with the drought conditions there. This system will move north and east Thursday and Friday.

For CO, we will have one more dry and mild day before winter returns. Models have now come into good agreement, unfortunately for eastern CO, that now means little if any snow. Models take the upper level trough into UT on Thursday, and then move the majority of energy to the west and north of CO on Friday. Surafce low now forms over northeast CO on Friday, so no real upslope flow is forecast for eastern CO, only perhaps some light northeast flow across the far northeast plains by Friday evening. Flow remains westerly across the foothills through this entire event, so a dusting to an inch is the most likely snow outcome from this system on Friday, with many areas not even getting a dusting. Best chance for snow in the foothills will likely be with the cold frontal passage, which looks to occur early Friday morning, between 4 am and 7 am. Temps will drop steadily after frontal passage, but only flurries possible after that.

A different story for the mountains of western CO. System will move into western CO Thursday night bringing moderate snow along with gusty westerly winds, so travel across the high country will be difficult to impossible Thursday night into Friday afternoon. Snow should diminish by Friday evening west of the Divide, Most areas will se 6-12 inches, with higher amounts possible at higher elevations over west facing slopes.

For the remainder of the weekend, the upper trough will sag over the central Rockies, with another disturbance dropping into this trough on Monday to reinforce the cold air already in place. Thus temps will remain very cold from Friday through Tuesday over CO. The Mountains may see some flurries from Saturday night into Monday, but little if an additional snow now expected for the foothills and plains. I will mention, that as this minor disturbance drops into CO Sunday/Monday, it could produce more snow that models currently suggest if the track changes slightly, so forecast for Sunday/Monday could change.

Models then build an upper ridge back across CO next week, so dry conditions with temps back near seasonal norms for Tuesday through next weekend. Models hinting at precip chances for the following week.
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"Climatology is what you expect, Weather is what you get".

"It is better to be roughly right than precisely wrong".

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Update Tue Jan 8

Partly coudy and breezy today as a mountain wave has set up across northern CO under brisk northwest flow aloft, although still quite a mild day for early January. Flow aloft becomes southwesterly on Wednesday in advance of our upcoming upper trough later in the week. As flow aloft turns southwesterly, temps will rise even more on Wednesday and Thursday, and gusty south to southwest winds will develop across the foothills and adjacent plains. Temps expected to be 10-15 degrees above normal next couple of days.

Winter still expected to make a return on Friday. Models in much better agreement today, so better confidence in forecast for Friday through Sunday. Upper level trough will move into the Great Basin Thursday, and move across CO on Friday. The upper trough will split as it moves across CO, with the northern piece moving off to the northeast, and the southern portion will remain anchored over CO through early next week. This pattern would result in the following forecast:

Snow will move into western CO Thursday night into Friday morning, mostly west of Vail Pass. Snow will move east during the day on Friday, as a cold front moves through CO. Cold front should move through the foothills early Friday morning, which will increase chances for snow across the foothills and plains by late Friday morning and afternoon. Snow may persist into Friday evening/night for the foothills and plains as temps drop dramatically behind cold front. Models hinting at some upslope flow behind front, but pretty limited, so snow amounts for the foothills and plains look to be in the 1/2 to 2 inch range at this time. Mountains west of the Divide will receive higher amounts, likely in the 6-12 inch range from Thursday night into Saturday morning. Temps on Saturday will be very cold, with high temps in 5-15 deg F range foothills, and 15-20 deg F range plains. Low temps Saturday night near zero. Anyone planning to attend the Broncos game, bring the arctic gear.

As the upper trough lingers over CO through the weekend, expect periods of light snow or flurries from Saturday through Monday. Best chance for additional accumulations will be in the mountains west of the Divide, although the foothills and adjacent plains could pick up an additional 1-2 inches during this period. Temps will also remain very cold Saturday through Monday as arctic air mass remains in place.

As the upper trough finally begins to move east on Tuesday, temps will begin to moderate. Models showing very strong northerly winds on the back side of the upper trough will pass over CO Tuesday night, so we could see some pretty strong northerly winds over the foothills and adjacent plains Tuesday night into Wednesday morning. Models then indicate more seasonal temps and dry conditions across CO for the remainder of next week into next weekend as upper ridge builds over the western US. Next precip chances according to long range model not until Jan 23/24. So unless we get a pretty big storm in late January, looks like another below average snow month in January. We have lots of catching up to do.
_________________
"Climatology is what you expect, Weather is what you get".

"It is better to be roughly right than precisely wrong".

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Update Mon Jan 7

Warm and dry pattern to persist across CO through Thursday. High temps 5-15 degrees above average for this time of year.

Then winter will re-appear Friday or Saturday, depending on which model is correct. GFS and ECMWF beginning to converge, but still have some significant differences for the system later this week. GFS continues to be faster, wetter and colder than the Euro solution. GFS solution would spread snow into western CO Thursday night, and move snow into eastern CO by Friday afternoon with decent upslope flow into Saturday morning. Euro solution delays the upper trough by about 12 hours, so snow would not move into western CO until Friday morning, and there would be limited upslope and thus less snow for eastern CO. Euro also would not have as cold of temps on Saturday as the GFS. Still not certain which model will be correct, although the Euro model tends to be better at these time frames. NAM and the Canadian models are trending toward the Euro solution, so seems that may be the more likely scenario. Snow amounts would not be heavy in either scenario for the foothills and plains. Amounts likely to be in the 1-4 inch range using the Euro solution. Snow would end early Saturday in either scenario, so likely not much snow during the Broncos game on Saturday. Temps woudl be in the teens to low 20's on Saturday under the GFS solution, and 5-10 degrees warmer for the Euro solution. Hopefully some better consensus by Tuesday or Wednesday this week.

Medium range models continue to call for cold temps to persist into early next week, with another chance for snow Tuesday. Temps begin to warm by late next week under a dry pattern. Longer range models indicate this dry pattern may persist into late January across CO.
_________________
"Climatology is what you expect, Weather is what you get".

"It is better to be roughly right than precisely wrong".

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Another warm and dry day across the state today, as upper ridge moves across CO with warm temps aloft. Upper level low currently spinning over central CA will dive southeast into southern AZ on Monday, then into northern Mexico on Tuesday, and west TX on Wednesday. This will result in more dry and mild weather across CO to start this week. As this upper low moves closer to TX, the Lone Start state will see an abundance of rain beginning Tuesday and will continue into Wednesday. Up to 5 inches of rain is expected in portions of central and eastern TX, so flooding is a possibility. This system will then move northeast and bring rain into OK, AR and LA Wednesday and then into the midwest and Great Lakes by Thursday. Across CO, we will see temps 5-10 degrees above seasonal norms this week. As next upper level trough approaches, southwest winds will increase on Wednesday night into Thursday.

Next system to affect CO will move into the Great Basin by Thursday. GFS and Euro model handling this system a little differently, so hard to be too confident in a specific forecast at this time. GFS moves a closed upper low into southern UT Friday morning, then moves an open upper trough across CO Friday night into Saturday morning. At the surface, a cold front will drop south across CO Friday morning, bringing snow and cold temps to most of CO Friday into Saturday morning. The ECMWF (Euro) model moves an open upper trough across CO on Saturday, which would bring less snow and not as cold of temps to eastern CO. Not sure which model solution will be more accurate at this time, but overall we can expect much colder temps by next Saturday, with a chance for snow from Friday into Saturday. Currently looks like the mountains will get the majority of snow, but we should see some in the foothills and adjacent plains. Looks likely the Broncos game on Saturday will be played in cold temps, with the possibility of some snow.

Beyond that, models suggest another upper level trough will move from Alaska southeast into CO by next Monday, so another round of snow and very cold temps for early next week. This is related to a high amplitude upper ridge building in the eastern Pacific, moving storms up into Alaska then driving them southeast into the Inter-Mountain West. This pattern may persist into late next week, so temps look to remain cold all of next week.
_________________
"Climatology is what you expect, Weather is what you get".

"It is better to be roughly right than precisely wrong".

Bump for Jan 7 update

Bump for Tue Jan 8 Update

Bump for Jan 9 update