Skyview Weather

Thunder in February?

Just after noon today a line of light precipitation moved through the region from the west bringing gusty winds and dropping temperatures.  As the line moved over Denver it was met with warm, northeasterly winds ranging from 15-25 mph which provided a good convergence zone towards the southeast metro area enabling for a bit of convection which yielded some thundersnow southeast of Parker and into northwestern Elbert County.  Lightning during a snow storm is one of the more rare occurrences in weather.  Generally you need warm moist surface air and cold dry air aloft in order to get the type of storm to produce lightning.  In this case, relatively moist air was being advected at the surface while much colder air was aloft, almost like a spring storm set up.  This allowed rapid storm development along with lightning, while temperatures remained cold enough to only produce sleet and snow.  Below is a screen capture of the thundersnow cell as it moved just east of the Parker area:

 

Morning Frost in Northeast Metro

This morning, February 11th, frigid temperatures in the low teens along with a dense low level cloud bank created some spectacular frost on tree branches in the northeast metro area.  The type of frost is similar to snowflake formation and allowed for light flurry conditions from pieces of frost gently blowing/falling off.  Here are a some pictures of this mornings frost!

 

 

Super Blood Wolf Moon

Last night a rare total lunar eclipse could be seen between 9:41pm and 10:41pm.  This specific lunar eclipse was referred to as a Super Blood Wolf Moon.  Wolf, for the first full moon in January and blood since the light refracted from the sun passing through the Earth’s atmosphere giving the moon a reddish hue.  It was an amazing spectacle to behold last night and unfortunately if you missed it there will not be another Super Blood Wolf Moon until May 26, 2021, and will only last for 15 minutes instead of the hour last nights Super Blood Wolf Moon lasted.  In case you haven’t seen any photos here are a couple I was able to grab with the full moon before the eclipse at the bottom for reference:

Fast moving storm to bring more snow to Colorado on Monday

A storm system will move across the Rockies today, bringing another shot of snow to the Colorado mountains during the daytime hours, with Eastern Colorado getting a round of snowfall tonight.  While this will not be as big of a snowfall producer for the high country as last Friday’s storm, we will see some quick bursts of heavier snow along with gusty winds as a cold front races across the state, which will impact road and travel conditions for the end of the holiday weekend. 

The Denver metro area (southern areas most favored) down to the Palmer Divide will also get in on the action tonight as the system moves east of the Continental Divide.

This morning’s infrared satellite image shows this low pressure system located over Utah and racing toward Colorado (image source: College of DuPage).

 

 

The short-range HRRR model projects snow to fill in across the western and central mountains of Colorado by around midday today (image source: weathermodels.com).

 

The heaviest snowfall across the high country is likely during the afternoon hours, though lighter snow showers will linger through the overnight period as well across northern and central Colorado.  Snowfall amounts of 6″ or greater will be possible across the higher elevations and mountain passes

Lesser amounts are expected across most of the mountain towns and valleys across ski country, but cold temperatures arriving with the cold front will allow snow to easily accumulate on pavement, and strong winds today and tonight will result in areas of blowing and drifting snow.

In general, the highest snowfall amounts are expected across the central and northern mountains.

Tonight, the system will swing into Eastern Colorado and a strong cold front will move across the plains and I-25 corridor, leading to a quick drop in temperatures with snow projected to fill in by late this evening, per the 12z run of the HRRR model (image source: weathermodels.com).

 

The exact track of the low pressure system is still in question, even this close to the event, which makes the Front Range snowfall forecast a bit more tricky.  Most of the models are projecting a minor snowfall event across the I-25 corridor, with northerly winds favoring southern Denver metro southward to the Palmer Divide.  On the other hand, the northerly winds will be much less favorable from downtown Denver north to Ft. Collins, as these areas will be experiencing a drier downsloping effect.

If the low pressure center were to track farther south than projected, then the potential for higher snowfall totals would exist.  But as it stands now, the Palmer Divide region will have the best chance of seeing meaningful snow amounts, as will the far northeast plains of Colorado where blizzard-like conditions will even be possible given the strong winds forecasted. 

Temperatures will quickly fall into the 20s tonight behind the cold front, so snow that does fall across the I-25 corridor will accumulate on road surfaces and could lead to a slick morning commute on Tuesday, especially in Douglas and Northern El Paso Counties, and into southern/central Denver metro as well.

Lingering snow should quickly taper off during the morning hours Tuesday before drying out Tuesday afternoon.  Temperatures will remain chilly on Tuesday, though, with continued breezy northerly winds.

Heavy snow tonight west of the Divide in Colorado

A Pacific storm system is moving into Western Colorado tonight with heavy snowfall amounts expected across much of the higher terrain of Colorado west of the Continental Divide.  This storm system has already produced several feet of snow across the Sierra Nevada in California, as well as heavy snow in Utah.  

Colorado’s mountains are now getting in on the action as well, with southwest flow favoring the San Juan and Elk Ranges south of I-70 initially.  The image below shows the most relative humidity analysis at the 7,000-millibar relative, which corresponds to roughly 10,000′ of elevation and is a good measure of moisture for the mountain areas of Colorado.

 

 

Later tonight, a gradual shift in the upper level flow from southwest to west, and eventually northwest, will allow the mountain areas along and north of I-70 to pick up heavy snowfall amounts as well.  By Friday morning, most of Colorado’s mountain areas west of the Continental Divide will have picked up impressive snowfall amounts, with double digit totals likely for many ski areas.  Road conditions will quickly deteriorate tonight through Friday morning throughout the Colorado’s high country, making for a challenging Friday morning commute.

East of the Continental Divide, this storm will mostly be a miss for the Front Range cities due to a lack of upslope flow.  However, a cold front will arrive Friday morning as the low pressure system swings across the Continental Divide, and banded snow showers are expected to develop across the I-25 corridor during the daytime hours.

Winds from the north/northwest will be unfavorable for Denver snow, with most areas east of the mountains expected to receive snowfall amounts of less than an inch, except perhaps under isolated heavier bands or across the Palmer Divide.  Temperatures near freezing as well as the timing during the daytime hours should also limit road impacts across the Denver area and I-25 corridor.

Looking farther out, the next system is slated to reach Colorado on Monday, and at this time there appears to be a chance for Denver to see a more meaningful snowfall event Monday night or Tuesday.

Colorado High Country Snow

A Pacific storm is approaching Colorado’s High Country today bringing winter weather across the Rockies over the next couple of days and will impact travel conditions as well as bring beneficial moisture to the mountains.  With this storm, all mountain areas will be impacted, with higher snow totals along higher elevations and west facing slopes.  Best chances for snow per NWS are as follows:

Expected Snowfall - Official NWS Forecast

A 10% chance of seeing higher amounts:

Maximum Potential Snow Accumulation

Generally snowfall amounts should fall into the 1-3″ range with higher elevations looking more in the 4-8″ with isolated higher amounts possible on west facing slopes up to 12″ possible with this storm.  Here is a look at the percent chance of 4″ or more across the Colorado High Country:

And a percent chance of greater than 8″:

Snow has just started creeping into the western portion of the state with snow increasing today and falling through the day tomorrow.  Expect some travel delays, specifically along higher elevations including mountain passes.  If you have the chance to get up to the High Country to ski, it should be a good time to ride some fresh powder this week without having the weekend rush of people!  

Sublimation?

Most people know what evaporation is, when a liquid transfers into a gas, such as wet roads after a rain storm when the sun shines and you can see steam rising from the surface.  When temperatures are cold, generally below freezing, snow will also behave in the same matter as liquid water, but this process is referred to as sublimation and not evaporation.  Sublimation is the transfer of a solid into a gas, in this case ice turning into steam directly before melting.  Unfortunately sublimation does not provide the ground with any beneficial moisture since all the moisture is released back into the atmosphere.  A good time to catch this phenomenon visually is in the early morning as the sun rises providing just enough heat, while surface temperatures are well below freezing.  Here is an image I took Sunday morning when temperatures were hovering around 20 degrees at the surface and the sunlight was just hitting some frost on the fence allowing for sublimation.  In order to confirm it was sublimation and not evaporation was that the fence never became wet or even looked like there was any type of moisture on it once all the frost sublimated into the air.

Another process that can create sublimation is wind.  Cold, windy days with below freezing temperatures where snow does not melt by warmth, but visually dissipates is usually caused by sublimation as well.  The tell tale sign this has occurred will be that the top layer of snow is smooth and crunchy with dry, crumbling snow below and the ground is still hard and dry beneath.  This indicates that the moisture from the snow has sublimated into the atmosphere and did not melt into the ground below.  Sublimation is a process that is not beneficial for providing drought relief, although, fortunately it does not occur that often since Colorado needs all the moisture it can get!    

 

Variable Snow Totals Along the Front Range

Friday’s winter storm dropped a healthy amount of liquid precipitation along the Front Range, but snow totals proved highly variable due to marginal storm temperatures. Much of the snowfall at the lowest elevations did not stick to road surfaces, and also compacted significantly due to the high moisture content. Rain also mixed with snow over the northern and central metro area throughout the day on Friday, further diminishing potential impacts on road surfaces. Below, you’ll find a collection of local storm reports showing a high degree of variability.

Shaffers Crossing (3N) 18”
Tiny Town (3S) 16.5”
Aspen Park 13.4”
Perry Park 12”
Golden (3SW) 10.9”
Elizabeth (2E) 10”
Highlands Ranch 8.3”
Castle Pines (3S) 7.1”
Boulder (3NW) 4.5”
Aurora (3SSE) 4”
Englewood 2.8”
Lakewood 2.7”
Denver (2E) 2.2”
DIA 1.3”
Fort Collins (3SW) 0.2”

The storm generally favored areas west of Interstate 25 and south of Interstate 70. The Foothills of Jefferson County, Douglas County, and areas along the Palmer Divide saw the most precipitation, where more than 1.00″ of liquid was observed in some areas. Higher foothills near Conifer topped the scales with 15-18″ of snowfall observed.

Heavy snowfall west of Conifer 01/12/19.

Light snow showers and flurries remain possible on Saturday, but little accumulation is expected. By early afternoon, there’s a good chance for breaking skies to help melt the recent snowfall. Temperatures will slowly rebound this week as high pressure steadily builds into the Rocky Mountains. Eyes then turn towards our next period of unsettled weather, perhaps arriving on Friday as a trough of low pressure takes aim at Colorado.

The Next Round of High Country Snow

Snowfall for the Colorado High Country started out strong this season with many ski resorts opening early for the first time in a decade.  Unfortunately as we’ve moved into 2019 the snow has been both, less frequent and very few days with high accumulations.  This has lead to snow pack totals to creep closer to 100% in the northwest, with a statewide total of only 95% as seen below:

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

Currently a storm is headed towards Colorado from the Pacific which will bring some beneficial snowfall to the High Country.  This snow should start impacting the region Thursday afternoon and could last into early Saturday morning before pushing eastward and out of Colorado.  Best chances for snow with this storm will be in the central Rockies along the Continental Divide which is generally the case with west to east storms.  Here are the percent probabilities provided by NWS for an inch or above snowfall over the next two days:

It appears there will a good chance for the entire state to see at least some snowfall, but as the accumulations go up, the probabilities drop significantly as seen below on areas expecting more than 4″:

This indicates that there will be a good chance to see snow over the next couple of days, although amounts will most likely be minimal.  At this time there is a lot of model uncertainty as is usually the case with west/northwest to east/southeast storms.  Considering the pattern we have been in, the snowfall amounts indicated below seem more likely:

Expected Snowfall - Official NWS Forecast

Although I would expect totals in the southern, central Rockies and along the Continental Divide, especially western facing slopes receiving amounts closer to these:

The NWS only has a 10% chance for amounts in the 6-12″ range for the Colorado High Country, but I would certainly give a 50% chance to at least see half of those amounts across portions of the Continental Divide, the San Juans and Sangre de Christo ranges! 

 

 

 

 

 

New Years Even Snow Across The Denver Metro

A blustery storm system moved through Colorado New Years Eve bringing snow across the region along with very cold temperatures.  Unfortunately temperatures were too cold to enable good dendrite growth leading to most falling snow to be a very light, powdery snow.  Strong winds from the north throughout the day caused blowing snow and poor visibility with small drifting in some areas.  Preliminary snow totals this morning around 8:30 AM via local storm reports are as follows:

Snow favored the western and south side of the Denver Metro Area with totals ranging from 2-4″.  Denver, north and east had less accumulations between 1-1.5″ reported with DIA’s official total coming in at only 0.5″ from New Years Eve’s storm.  Hopefully this will lead to a more active winter as Denver has seen little to no snow so far this season.