12:20 PM MDT, Sunday, April 26, 2015
As advertised, a wet storm is here and is likely to persist into early Monday, and perhaps into late Monday, especially from Colorado Springs and southward. The snow level should slowly move down tonight and it’s possible that some wet snowflakes will occur in the lower elevations. But little or no accumulation is expected below 7000 feet. Heavy accumulation of 6 inches or more is likely to be limited to areas above 8000 feet, with perhaps more than a foot above 10,000 feet.
The precipitation should become more showery Monday with dry periods and perhaps a little sun breaking through for Denver, Boulder, and Cheyenne. The precipitation will probably linger a little longer south of Denver, and especially south of Pueblo.
Tuesday should be mainly dry and warmer with only a slight chance of s shower or sprinkle. Pleasant spring weather should be in full force on Wednesday.
12:45 PM, Friday, April 24, 2015
The pattern this weekend favors increasing chance for precipitation, peaking Sunday into early Monday. But there should be pleasant dry periods too, especially early to mid day on Saturday.
Scattered showers and thundershowers are likely late this afternoon and evening and again late Saturday, but not everyone is likely to get wet. Precipitation should be in the form of rain all the way up to around 9000 feet.
On Sunday a storm system and cooler weather is expected to have impacts statewide (including snow on the higher passes and mountain areas). For the Front Range region, expect damp weather all day Sunday although it appears that it could be late in the day when it is most likely. Rain is expected in the Colorado Springs-Denver-Boulder-Fort Collins area, and most likely Cheyenne too. Even Nederland should start as rain, but snow levels will probably drop to around 6500 or 7000 feet Sunday night. Significant accumulation of wet snow (more than 6 inches) will probably be mainly in areas around 9000 feet and higher.
12:30 PM, Saturday, April 18, 2015
The main moisture band from this very slow storm system rotated west and is impacting mainly western Colorado on Saturday. But it’s not over for the Front Range. Our partly sunny intervals will likely be interrupted by periods with increased clouds and precipitation through Monday, although the dry hours should outnumber the wet hours.
During Saturday night a weak cold front in eastern Colorado will increase the chance that where there is precipitation it will mix with or turn to snow even in the lower elevations. Only minor accumulations are expected.
Some mountain areas of the Front Range may pick up another 6 inches through Sunday, less in the foothills. Accumulations in the lower elevations are likely to be light (0 to 2 inches), with high melting rates during dry periods on Sunday.
12:30 PM, Friday, April 17, 2015
The wettest part of the storm is over for most of the Front Range region, but the storm system isn’t going far and is likely to impact the weather in Colorado and Wyoming through the weekend.
The precipitation Friday afternoon is likely to become more intermittent, and it already has south of Denver. It should be mainly rain below 6000 feet, but more snow accumulation (maybe 6-12 inches) is likely in the Front Range mountains, especially north of I-70 and above 7000 feet. A few spots may see a few showers or a thunderstorm that produce brief heavy rain (or snow) and maybe some small hail. We have already seen a few of those along the Front Range.
It appears that the weekend may feature more dry hours than wet hours, but don’t expect a mostly sunny Spring weekend. Occasional periods of thickening clouds and precipitation are likely, and maybe a few heavier showers or a thundershower in the afternoons. By Saturday night or Sunday morning slightly colder air may work down from the north and result in more snow than rain even in the lower elevations. A major storm is not expected, but accumulating snow (1-6 inches) at all elevations is possible Saturday night and/or Sunday in and along the Front Range.
It could be Tuesday next week before it feels like Spring again. But the storm track is likely to stay active, so there may be more wet weather by this time next week.
12:15 PM, Thursday, April 16, 2015
The worst of the storm is likely to last at least through Friday morning, but unsettled weather with some periods of precipitation are likely into the weekend. At 11AM the first round of heavy precipitation at UCAR’s Center Green campus in Boulder had ended and resulted in 2.7 inches of snow that contained 0.45 of liquid. That’s a 6-to-1 ratio… very wet snow!
Additional periods of moderate and heavy precipitation are likely into Friday. The heaviest is likely from Denver to Cheyenne and nearby mountains with storm totals of 1-3 inches of liquid equivalent by Friday night. Significant precipitation is likely in Colorado Springs, but totals should be lower there.
For the Front Range above 7000 feet, 12-30 inches is likely from Pikes Peak northward, with the heaviest probably in Boulder and Larimer counties of Colorado and the Laramie Range in Wyoming. For the foothills from 6000-7000 feet, expect 6-12 inches of dense snow.
For elevations below 6000 feet, there is still uncertainty, with rain likely mixing in. Accumulations are likely to be highly variable over short distances, from 1-8 inches, with some accumulation on roads during periods of heavier snow. Historically, a progression from snow to rain is uncommon in this region, but this appears to be a storm where that will probably happen. So the chance of more than 8 inches snow is quite small, but you should probably not park under trees that have leafed out, just in case.
12:30 PM, Wednesday, April 15, 2015
We are more certain about the storm track today and it is looking likely that there will be heavy precipitation in the Front Range region from Denver to Cheyenne. The big uncertainty today is whether it will be cold enough below 6000 feet to result in heavy snow.
A cold front has moved across the Wyoming border into Colorado at noon, and this afternoon will start turning cooler. Showers and maybe a thundershower may develop, especially along the Front Range north of Boulder County and in Wyoming.
The heaviest part of the storm is likely Thursday and Friday in southeastern Wyoming and near the Wyoming border in Colorado. For the Denver-Boulder area and the nearby foothills, it will likely be late Thursday and Friday when the heaviest precipitation occurs.
The atmosphere should be cold enough for snow down to lower elevations Wednesday night and Thursday morning, but there will likely be little if any precipitation, except to the north in and around the Cheyenne area. During the day Thursday the atmosphere is likely to become more moist and a little warmer throughout the area, probably too warm for snow below 7000 feet. Although it will cool off once the precipitation intensifies late Thursday, it might not be enough to push the snow levels much below 5500 feet by Friday morning.
For the mountains of the Front Range from metro Denver to Laramie: heavy wet snow, 1-2 feet by Friday night; 6-12 inches between 6000 and 7000 feet where it will likely start as rain.
Urban corridor, Denver-Boulder-Fort Collins- Cheyenne: Mainly rain in Colorado, but some wet snow accumulation is likely Thursday night into Friday morning. The accumulation may be very variable from 0-6 inches. In the Cheyenne area there is a better chance for heavier accumulations. For the Denver-Boulder area, we can’t rule out much heavier snow if the temperature is just a degree or two colder, but right now that looks like a small chance, maybe about 20%. The total liquid (rain plus melted snow) will probably range 1-3 inches in and along the Front Range from the Denver area northward. Precipitation is likely from Colorado Springs southward, but it appears that area will be south of the heaviest precipitation.
6:30 AM, Wednesday, April 15, 2015
There is now more consensus that a long, wet storm will impact the Front Range region beginning late today, but the impacts today will likely be minor. The heaviest part of the storm is likely to begin early Thursday in southeastern Wyoming, and late Thursday in the Denver-Boulder area.
Heavy wet snow is likely in the mountains late Thursday into Friday. In the Denver-Boulder area it appears that a large portion of the precipitation will fall as rain, but accumulating snow may occur by Friday morning.
I will update later today after analyzing the morning data.
12:55 PM, Tuesday, April 14, 2015
A potent Pacific storm system moved onshore today and will be taking shape as it moves eastward into the Rocky Mountain region. The storm appears to be splitting. Some of our weather model guidance- particularly the reliable GFS model- has the northern part of the split storm becoming dominant and tracking into eastern Wyoming. This would put the heaviest precipitation north and east of Cheyenne, with minor amounts for the Colorado Front Range. However, a few model simulations from the GFS, along with the European and Canadian models, have the southern part of the split storm becoming dominant as it moves very slowly through the four corners region and northern New Mexico from late Wed through early Saturday. That would put the heaviest precipitation in eastern Colorado and southeastern Wyoming.
This is a notable amount of uncertainty for a storm that is within 36 hours of starting. I’m a bit more inclined to trust the guidance in the wetter direction, but I am certainly not very confident. Whatever the outcome, Wednesday is likely to start mild and then turn cooler late in the day with some showery precipitation (rain in the lower elevations). It is likely to be windy at times both before and after the cold front.
Thursday is when the uncertainty starts to play out. The “minor precipitation” scenario would likely bring some unsettled showery weather Thursday, with drier & milder by Saturday.
The “big precip” scenario would likely see the main event late Thursday into Friday for the Colorado Front Range, maybe earlier in Cheyenne. Temperatures are likely to be marginal for snow below 6000 feet. I should point out that the wettest scenarios suggest multiple inches of liquid equivalent in and along the Front Range, and that would probably be mainly heavy snow in the mountains and possibly heavy wet snow in the lower elevations Thursday night.
I will update tomorrow. The storm will be completely inland so hopefully it will be better resolved by the observing network.
12:45 PM, Monday, April 13, 2015
Weather nerds of the Front Range are excited about the possibility of a big storm later this week. As the storm system rolls in from the Pacific and moisture is drawn up from the Gulf of Mexico, there are some scenarios played out by weather models that would result in major rain/snow for some part of the Front Range region. But it’s not a done deal! There is a real possibility that the storm will take on an orientation and track that either does not produce a big wet storm in Colorado/Wyoming, or is big only in a portion of the area.
Here’s what can be said confidently now: weather should become colder and more unsettled late Wednesday thru Friday. There is a chance this could evolve into a big storm. Stay tuned!
5:45 AM, Wednesday, April 8, 2015
A Spring storm is moving through Colorado today and tonight, but the result should be only slightly cooler than average temperatures Thursday, and minor precipitation amounts late today or early Thursday,
The best chance for precipitation is in the mountains near the continental divide, but even there the snow accumulations should be minor. For the Front Range urban corridor, there is a small chance for a few showers or a thundershower late Wednesday or Wednesday night, but some areas may get by with no measurable rain. Gusty west-northwest winds may develop along the Front Range for a brief period late Wednesday or Wednesday night.
Expect warmer weather to return Friday.