wxgeek's weather-Cool/Wet This Week, Snow possible Fri Morning-Update 9/11

Update Thu Sep 11

Cold front moved into eastern CO this morning bringing low clouds, fog and drizzle into the plains and foothills. Clouds extend up to about 7000-7500 ft currently, so foggy conditions near the top of the cloud layer as it interacts with foothills. Second and stronger push of cold air associated with upper level disturbance moving southeast from the northern Rockies will move into eastern CO this evening. This push will reinforce cold air and push cloud deck up to about 11,000 - 12,000 ft. It will also bring showers, drizzle and light precip to the plains and eventually the foothills. Highest precip amounts will be east of I-25 and north of I-70 on the plains and fall mostly as rain. Temps will begin to fall this evening as surge of cold air moves in. Freezing level looks to lower to about 7000-8000 ft by 9 pm, then down to about 6000 ft by midnight. Mix of rain, snow and freezing drizzle expected across eastern CO through Friday morning, then gradual clearing will occur from north to south by late morning into early afternoon. For the foothills, snow accumulations of a trace to 1/2 inch will be common above 7000 ft, with some areas receiving 1-2 inches. At this time, I would expect major roadways to remain mostly wet with some slush between midnight and 9 am Friday, while secondary and dirt roads may have some snow and ice accumulation, especially above 8000 ft. Expect roads in the Urban Corridor to remain wet. Areas on the plains may pick up 1-2 inches on grassy surfaces, mostly north of I-70. Conditions will gradually improve during the afternoon. Expect the morning commute to be slow with some slick spots possible at higher elevations. Evening commute should be fine.

For those wondering if this is an unusually early snowfall ? A bit early, but by no means a record. Average first snowfall on Conifer Mountain is Sep 23. Earliest snowfall was Aug 30 in 1993, and next earliest was Sep 7 in 2001. Heaviest September snowfall was 17 inches in 1996, followed by 13.5 inches in 2009. Average September snowfall is about 3.8 inches on Conifer Mountain.

Weekend weather is looking very nice, temps climbing back to near seasonal norms and mostly sunny skies, with only some isolated showers across southwest and south central CO.

For next week, mostly dry weather with temps near seasonal norms with isolated mountain showers and thunderstorms. By late next week, CO may see increased precip chances as late monsoon moisture interacts with an upper trough from the west coast.

_________________
"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 Wed Sept 10

After a cool and soggy start to the day, general clearing this afternoon with temps near normal west of the Divide and below normal east of the Divide. Thursday should start out dry with temps remaining below seasonal norms. Some gusty westerly winds will be possible across higher terrain. By Thursday afternoon, a strong cold front that is bringing snow to the Northern Rockies today will move south over eastern CO and usher in moist upslope flow, with northeast winds of 10-25 mph behind front. Temps will rapidly drop behind front as well, and low clouds will envelop the plains and push up against the foothills by late afternoon and evening. Clouds should extend up to about 12,000 ft, so light precip and/or drizzle will develop over the plains and into the foothills by late afternoon and evening. Snow level will begin around 10,000 ft Thursday afternoon, but quickly lower to 5000-6000 ft by 9 pm to midnight. Heaviest precip will be across the far eastern plains, with lighter amounts across the Urban Corridor and foothills. Precip will persist overnight into early Friday morning, before gradual clearing late Friday morning. Fog, low clouds, freezing drizzle and snow could make driving difficult in the foothills from Thursday evening into Friday morning. For amounts, most areas likely to see a dusting to 1/2 inch, but favored areas could see 1-2 inches of snow above 6500-7500 ft. Urban Corridor and plains likely to see a mix of rain, snow and freezing drizzle but little if any accumulation below 6500 ft. Temps will be below freezing above 6500 ft from around 9 pm through 9 am Friday morning, so ground temps may be cold enough to support accumulation of snow or slush on asphalt, hence roads could be slick Thursday night into Friday morning, especially at higher elevations. Conditions will gradually improve late Friday morning into afternoon. Commute home Friday evening should be fine, but Friday morning could be messy. Precip not likely to make it farther west than the Front Range Crest, so from the Divide west will remain dry and mild.

Conditions return to more seasonal norms this weekend. Mostly dry statewide with temps climbing back to near seasonal norms. Only isolated showers mostly over the High Country possible. Next week remains mostly dry statewide with temps near seasonal norms. Isolated afternoon showers and thunderstorms possible mostly along the Divide. Some monsoon moisture may make it's way back into CO by next weekend, as another tropical system moves up the Baja coast.

_________________
"Climatology is what you expect, Weather is what you get".

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

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Upper trough currently located over eastern NV and will move east across CO today into tonight. Moist monsoon flow continues to bring substantial surface moisture into CO, so combination will produce significant rainfall today across western CO, with moderate amounts east of the Divide. Batch of showers moves across eastern CO this morning, with a new batch moving into western CO this morning. Precip will intensify this afternoon and evening statewide, with embedded thunderstorms. Storm motion today will be from the west at 15-25 mph, so flood potential fairly low due to fast moving storms, but some areas could pick up an inch in an hour in heavier storms. Areas west of the Divide could see localized flooding, as a Flash Flood Watch remains in effect. Precip likely to persist into nighttime hours across eastern CO, with snow level lowering to 10,000 - 11,000 ft overnight.

Wednesday is looking mostly dry with temps remaining below seasonal norms. Isolated showers will be possible mostly along the Divide. Thursday will be similar, with temps remaining below seasonal norms and mostly dry through Thursday afternoon.

Then things get interesting. Models have been suggesting that an upper trough will move from the northern Rockies into the Great Plains Thursday night into Friday morning. At the surface, a cold front supported by High pressure over the Northern Rockies will push into eastern CO Thursday afternoon and evening. This will create a push of easterly upslope flow into eastern CO Thursday eveining into Friday morning. The difficult part currently is predicting how much precip will be associated with this upslope flow. Moist layer is currently expected to be up to about 12,000 to 14,000 ft, so it should be deep enough to support drizzle and some light precipitation. The other interesting part is the air will be cold enough to drop snow levels down to about 6500-7500 ft Thursday night into Friday morning. Precip amounts look to remain on the light side, but with temps below freezing, we could see a mix of light snow and/or freezing drizzle above 7000 ft. Asphalt should be warm enough to melt most of the frozen precip, but higher elevations in the foothills could see our first dusting of the season. Low clouds and fog could also create difficult driving conditions in the foothills Thursday night into Friday morning. Conditions should improve after about Noon on Friday with warming temps and drier conditions, although temps will remain well below seasonal norms.

By Saturday, a return to warmer temps and mostly dry conditions will prevail statewide, with only isolated afternoon and evening showers possible across southerwest and south central CO. Similar day on tap for Sunday with temps warming back to near seasonal norms. For next week, temps at or above seasonal norms and mostly dry conditions as an upper ridge builds over teh western U.S. Some late monsoon moisture may move back into CO by next weekend.

_________________
"Climatology is what you expect, Weather is what you get".

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

Bump for 9/11 update