Monthly Archives: April 2016

Cold, damp weekend

9:30 AM, Friday, April 29, 2016

The large and cold storm system did not produce as much mountain snow last night as expected, but there is still more on the way. The main storm center will move slowly eastward across southern Colorado today and tonight which will result in periods of snow (and rain in some low elevation areas). The storm is likely to become nearly stationary on the central high plains this weekend and be close enough to continue periods of clouds and precipitation for the Front Range region.

 

Accumulation through Saturday morning:

Mountains, foothills, and Palmer Divide above 6500 feet: 5-12 inches (the heaviest is a little more likely south of I-70 and in the Pikes Peak region).

Urban corridor below 6500 feet: no accumulation in some areas, 1-4 inches in other locations. Accumulation is a little more likely south of I-70.

 

Saturday afternoon through Monday:

There is likely to be some intervals of drying and maybe even some breaks in the overcast.  But it is also likely that there will be multi-hour periods with mountain snow and low elevation rain (maybe a little snow).  Little or no additional snow is expected in the low elevations after Saturday morning, and only light amounts in the mountains.

 

 

 

 

Wet, slushy, cold

6:30 AM, Thursday, April 28, 2016

I’ve been on the road with limited access to internet, but hopefully you are aware of the storm coming in. It should be a cold wet period through the weekend with the main precipitation period coming this afternoon through Friday. Precipitation will likely be mainly rain with some snow in the lower elevations, and mainly snow in the foothills, mountains, and Palmer Divide.

 

A storm system is moving into the four corners region today and then it will move slowly eastward into the central Great Plains Saturday. Rain and maybe some thunderstorms will likely develop this afternoon in the plains (rain and snow in the foothills and mountains). Precipitation should become all snow down into the foothills this evening, and may into parts of the urban corridor by morning.

 

Mountains, foothills, Palmer Divide through Saturday morning: around 4-12″ between 6000 and 7000 feet, and 1-2 feet above 7000 feet.

Urban corridor and plains through Saturday morning: Some areas may get no accumulation, most areas probably 1-4 inches, and a few spots may get more. Snow accumulates most efficiently this time of year at night and in the early morning.The forecast assumes that precipitation will be rain most of the night. An unexpected early changeover can add to accumulations. Precipitation is likely to become more intermittent Friday night. Areas of northeastern Boulder County (Longmont), Weld and eastern Larimer County may be most slow to change to snow.

 

Cool, unsettled week of weather to end April

5:00 pm, Sunday, April 24, 2016

 

An active storm track across the West this week will keep temperatures cooler than average after Monday. There is also likely to be periods with clouds and some rain or snow. But at this point a major precipitation events appears unlikely.

 

A strong storm is likely to track across northern Colorado Tuesday and Tuesday night, which is a track that would keep the heaviest precipitation to the north, and result in relatively minor effects in the Front Range region. But some snow is likely in the mountains, and some showery rain or rain changing to snow in the low elevations. That storm is likely to trigger severe thunderstorms on the Great Plains late Tuesday, and there may be a few thunderstorms develop in eastern Colorado either Monday or Tuesday afternoons.

 

Although drier weather is likely Wednesday, it will be cold in the upper atmosphere which can cause a few showers to develop during the afternoon. The chance for showers may increase Thursday as another storm approaches from the west.

 

 

Gusty winds Sunday

1:10 PM, Friday, April 22, 2016

Happy Earth Day everyone!

We are in for a relatively nice weekend, especially Saturday when temperatures are likely to be in the 70s along the Front Range urban corridor.  A fast-moving storm should pass by to our north Saturday evening. There is a small chance for a few showers at that time, mainly in the mountains. Sunday should be a bit cooler, but not cold. The main impact this weekend may be from gusty northwest winds Sunday along the Front Range and on the plains of northeastern Colorado and southeastern Wyoming.

 

The next chance for s storm in the region is late Tuesday, but there is still a lot of uncertainty with that one.

 

 

A weekend of rain and snow

12:45 PM, Friday, April 15, 2016

The much anticipated storm is about to begin this Friday afternoon with rain in all but the highest elevations at first, and then snow at most elevations by Saturday morning. This storm brings the risk of heavy, wet accumulation on grass, trees, and power lines in the urban corridor Saturday morning into early Sunday. Slushy roads will probably occur in places in the low elevations, and snowpacked roads higher up.

 

Areas above 6500 feet elevation:

Mountains, foothills, Palmer Divide: 1-4 feet by Sunday morning, with the heavier end of that range above 9000 feet elevation. Some minor additional snow may occur intermittently Sunday afternoon and Monday.

 

Areas below 6500 feet elevation:

Rain and maybe a thunderstorm Friday afternoon and night. Rain changes to snow in most areas by Saturday daybreak (there may be a few areas that are still getting rain). Mainly snow Saturday and Saturday night, with intervals of heavy snow.

Accumulations through Sunday morning in the urban corridor will likely be very variable:

Fort Collins, Longmont, Niwot, Lyons, DIA: 5-11 inches (the higher end is more  likely if it’s already accumulating by daybreak Saturday)

Boulder, Louisville, Broomfield, metro Denver: 8-14 inches (the higher end is more likely if it’s already accumulating by daybreak Saturday)

Cheyenne and South Denver suburbs, Castle Rock: 12-18 inches

Colorado Springs: 5-10 inches north and west side, 0-5 as you move south and east

 

At this time of year snow accumulates more efficiently at night (or at least early and late in the day).  If the changeover Saturday occurs well before sunrise, that increases the chance for the heavier accumulations. Also, moderate or heavy snow Saturday evening will boost the odds of getting the heavier amounts (and boost the odds of tree damage).

 

Sunday and Monday: unsettled and cool weather, but probably not much additional accumulation.

Significant wet snow in lower elevations has become more likely

12:45 PM, Thursday, April 14, 2015

The big weekend storm from Friday afternoon through Sunday morning (and some lingering effects into Monday) is looking like it will bring wet snow accumulation, possibly heavy, to the Front Range urban corridor beginning Friday night or in the predawn hours on Saturday.

 

Front Range mountains and foothills (above 6500 feet): this is the relatively easy part. Heavy snow (rain at first Friday afternoon in the foothills). Accumulations 1-4 feet, heaviest above 9000 feet. It appears that Nederland and the high points of the Palmer Divide may see 2-3 feet.

 

Below 6500 feet:

Rain and maybe a strong thunderstorm with hail Friday afternoon and evening. The changeover to snow should occur after dark and maybe after midnight. Some heavy, wet snow is probable by daybreak Saturday.

Snow intensity is likely to vary  Saturday through Sunday morning, with moderate to heavy periods and some lulls. After Sunday morning precipitation will probably be more intermittent and lighter.

 

Accumulation below 6500 feet:

5-15 inches, highly variable, and I will update this tomorrow.

  • The higher end of that range is a little more likely along the west and south sides of metro Denver (including Boulder and Broomfield), and in the Cheyenne area.
  • The lower end of that range is a little more likely in places where northeast winds are a “downslope” direction, such as Lyons and many parts of Weld and northeastern Larimer counties.
  • The greatest accumulation will be in grassy areas, but dense slush is likely on roads, especially in heavy snow areas.
  • Broken tree limbs and power disruptions are likely.

 

Why the variability? At the time of year enough of the sun’s energy gets through the clouds to enhance melting. The most efficient accumulation will be at night, or during heavy daytime precipitation when cooling from evaporation is greatest. During light precipitation intervals melting is likely to take over.

 

 

 

Big wet snow in mountains, wet on plains

1:30 PM, Wednesday, April 13, 2016

A long-duration period of wet weather (Friday-Monday) is likely to bring heavy snow to the mountains, and a mix a rain and wet snow in the lower foothills and plains.

 

The center of the storm system is slower than we thought a couple days ago, and likely to spin in place near or just south of the four corners region this weekend. In fact it may just slowly weaken in place and never move east of us. The impacts for the Front Range region may come as intervals of heavy precipitation separated by intervals of a relative lull, with heavier precipitation less likely by Monday.

 

The initial precipitation (Friday afternoon or evening) is likely to be rain and maybe some thunder at most elevations. There may even be a strong thunderstorm with hail and heavy rain, especially out on the high plains. Snow levels will probably work there way down to the lower foothills by Saturday morning. In the urban corridor, the changeover to snow will probably be very variable, but it’s too early to call right now.

 

Potential accumulations through the weekend:

Mountains and Palmer Divide above 7000 feet: 1-2 feet (and likely more in some local areas, especially above treeline)

Lower foothills (and Cheyenne): Highly variable from a few inches (after rain initially) to around a foot.

Colorado Springs, metro Denver, Boulder, Fort Collins: Mainly rain, but some heavy wet accumulation of a few inches in some local areas. Although a heavy wet snow is unlikely, it can’t be completely ruled out yet. Generally 1-2 inches of liquid is likely.

 

Historical perspective:

This storm is arriving almost 95 years to the day after the infamous Silver Lake snowstorm that produced 76 inches of snow in 24 hours on April 14-15, 1921, and 100 inches in 4 days. Silver Lake is in Boulder County at 10,240 feet elevation. Denver and Boulder had much less snow but saw a sloppy mess. Denver recorded 9 inches downtown. Boulder did not record the snow but reported 3.37″ of liquid and commented that the snow brought the city to a standstill.