Denver, Colorado

Next Storm Targets Southeast Colorado

Posted by @BrendansWeather
Rain and snow looks promising for drought-stricken southeast Colorado
We promised an April more active than March, and so far the month has delivered. Two weeks in and we've seen several good soaking storms across northeast Colorado, and great late-season snows for the high country. Another system arrives Wednesday, and will bring another round of cool and unsettled weather to eastern Colorado through Thursday.

This next system looks to favor southeast Colorado. The best chance for appreciable precipitation through Friday will be from I-70 south, and from the southern Front Range mountains east. While not an exact bullseye for heaviest precipitation over the part of the state hardest hit by drought, any bit of moisture will only help. Here's what the GFS has in mind for total precipitation through Friday, with the U.S. Drought Monitor graphic to the right for comparison.

GFS PrecipDrought Monitor


This system will be relatively warm, especially when compared to our last system. With that, much of the precipitation that does fall at lower elevations will be in the form of rain, or a rain snow mix. The best chance for accumulating snowfall at this time looks to be across the Palmer Divide, and at higher elevations across the Front Range foothills. There is actually pretty good agreement between the models here, with nearly all of them painting a bullseye of heaviest snow across Teller County, and western / northwestern Colorado Springs.

GFS Snowfall Map

The track of this system just doesn't favor much snow or rain for Denver. We'll go ahead and call it unsettled for Wednesday afternoon and Thursday, with at least a chance for rain and rain mixed with snow through the period. Temperatures will cool too -- after highs in the 60s Tuesday, we'll be back in the 40s across the metro for Thursday. Without a notable shift in track over the next 24 hours, we think locales to Denver's south will be favored with this storm.

Take a look at the SREF ensembles for Denver (left) and Colorado Springs (right). Both means show measurable precip through the period, but far more members are on board for COS. Mean QPF for DEN 09z was just 0.09 inches, while COS was 0.45 inches.

SREF Total Precip DENSREF Total Precip COS


We'll keep you posted as this system continues to develop and pass along updates as needed. The long and the short of it is plan for another round of cool and unsettled weather for Wednesday into Thursday, with winter driving conditions at higher elevations, especially Thursday morning.

Beyond Thursday the pattern continues to look active. The EPS Weeklies that came in last night confirm that (and they've been pretty spot on this spring), as well as all global models showing several more disturbances (with warmth in between) through the end of the month, and likely into May.



Spring Storm Recap

Posted by @brendansweather
Our latest spring storm is now well east of the area, bringing snow to Kansas and as far south as Oklahoma City this morning. While some locations did 'bust' low with snowfall from this system, overall (if we did grade our forecasts) I may not give it as bad a grade as some might expect. Snowfall totals from the storm ranged from a few inches to 15 inches, and brought another round of beneficial moisture to the state.

Bitter cold for April
This storm was impressive on many counts. Let's back up to Saturday afternoon when Denver climbed to 72 degrees at Denver International Airport. Twenty four hours later the temperature read 28 degrees with light snow, fog, and a stiff breeze. That's a 44 degree temperature swing in 24 hours, and over 50 degrees difference between Saturday afternoon's high, and Monday morning's low.

Unfortunately for the new buds on the trees, this storm brought with it some very cold temperatures for this time of year. While Denver bottomed out last night several degrees warmer than the record low for the date (19 degrees at last check, with the record low being 15), the Daily Camera is reporting that Boulder high 14 degrees this morning, a record low for the date.

Soaking storm
If you'll recall, we were fairly confident that this storm would bring good moisture,, and even that we'd see snow, but the question mark all week was -- how much snow would actually accumulate? The moisture certainly delivered. Here are the CoCoRaHS 24 hour precipitation reports as of 7am this morning, many locations seeing totals in excess of 0.5" from this storm.

CoCoRaHS Precip Totals Map

Snowfall totals
If we take a look at snowfall totals from the same report network, we see totals in Denver from 2 to 6 inches. For our forecast we had Denver split for totals going into this storm, with 5 to 8 inches forecast for the south/west/east metro, and 3 to 6 for the northern metro.

The Bust Index was relatively high across the board at a 5 out of 10. The Bust Index is the potential for actual totals to be LOWER than forecast. We left the BI relatively high given several factors: a) warm surface temperatures (it was 70 degrees for several days prior to the snow falling), b) daytime snowfall, as high sun angle this time of year is a snow-eater, and c) storm intensity -- the storm didn't have all the characteristics we look for in a good spring snow.

Decent snowfall totals nonetheless. And if you took our comparison to previous storms to heart, you'd notice totals this time were once again very similar to those systems. Had timing worked out with more of the precipitation coming after dark Sunday, many of these totals would be much higher this morning, especially with the cold temperatures that worked in behind the front.



The foothills did even better, with anywhere from a few inches to nearly 13 inches being reported. We had 8 - 12 inches forecast for the Front Range foothills, so generally speaking, not too far off.

CoCoRaHS Snowfall Map

We tried to stress that snow would have a hard time sticking with this storm, especially during daylight hours Sunday. We noted that roads would remain mostly wet, and even where 5 to 8 inches of snow fell in Denver there would be melting, before colder temperatures arrived for the second half of the storm. Some were left wanting more, and that's fair. For the snow lovers in the group this storm didn't necessarily over-perform.

A lot of what we try to do here at Weather5280 is explain the uncertainty behind forecasts, and why that uncertainty exists for any given storm. If we fell short on this storm, then we'll try better next time!

More snow in the forecast
Don't put away those jackets just yet. After a cool Monday temperatures will rebound nicely for Tuesday ahead of another cold front and chance for snow Wednesday into Thursday. We'll have more on this later in the day, but expect another chance for accumulating snow for some, and another shot of cold air for eastern Colorado.

Winter Returns for Sunday, Snow Likely Across Colorado

Posted by @brendansweather
GFS Precip Type Sunday | WeatherBell
We have little change overall to the going forecast. Rain is expected to change to snow overnight Saturday into early Sunday morning in Denver, with a Winter Storm Watch in effect from late tonight through Sunday evening for the metro area and Front Range. The watch could very likely be upgraded to a Winter Weather Advisory later this afternoon.

Snow totals will vary greatly depending on your locale. Higher elevations to the south and west of Denver will once again be favored for highest snowfall totals, with lesser totals across the northern suburbs of Denver. We continue to stick with slightly lower snow totals for Denver proper, with much of the accumulating snowfall being confined to grassy and raised surfaces. Models are very moist with this system, but the big question is how much melting will take place with warm surface temperatures and high sun angle Sunday. We've updated the snowfall map above with our latest thinking, and will continue to refine as needed.

With recent leafing, where snow accumulates, this could be a high impact event for your trees. The weight of this very wet, heavy snow will be a tremendous burden on them. Go out and gently shake the snow off trees if they start to look like the weight is taking a toll. We expect snow to be heavy at times, which will make travel difficult Sunday and Sunday night, with blowing snow causing reduced visibility.

In Denver roads will likely stay mostly just wet until after dark on Sunday. Where snow continues Sunday night expect some ice and slush to accumulate on roads, especially secondary ones. Be mindful that overpasses will become snow-packed before the warmer road surfaces. We have the potential to challenge our all time record low temp for the date which is 15 degrees with a couple of the models bring us into the teens by early Monday morning.

We'll continue to monitor all the latest here at Weather5280, and push updates as necessary as we head into the overnight hours Saturday and during the day Sunday. We'll be active on Twitter and likely the Live Blog throughout this event.

Thursday PM Update: Latest on Weekend Storm

Posted by @MattMakens247wx
In the previous post regarding this weekend's storm, I pointed out three things to watch:
  • Does the trough remain open or does it deepen.
  • Does the speed of the system change, with any potential slowdown.
  • Does the cold front have colder than expected temperatures.
Here's a brief update to these factors.

1) The trough remains open, although with slight deepening on the ECM and it's members. GFS and GEM deterministics and ensembles are similar in depth to previous runs in terms of strength. Currently the trough is a closed low off the California coast, that will open as it moves onshore and over the Rockies.

An additional question mark to add at this point is the amount of surface troughing as a result of the system moving off the Rockies onto the Front Range and Plains. As that system "stretches" out on this side of the Divide it can add enhanced energy to the system to provide higher than forecast snowfall/rainfall totals. This will be best determined when the system is actually over land, interacting with the mountainous west. A slower solution, to be pointed out in 2), will only help facilitate surface troughing and thus higher snowfall/rainfall.

2) The speed of the system has changed in ECM and GEM. The trough axis is slowest on ECM and doesn't clear our region until Monday morning. A longer period of precipitation has developed in the ECM, and to an extent in the GEM. These two globals are the highest snowfall producing models as a result. The speed with the GFS trough has not substantially changed.

3) The associated cold front has indeed changed impact. Sunday's high will likely be at 12:00am, with a substantial and continuous drop throughout the day. Sunday afternoon will be 30s and 20s by the evening. With this rapid cooling, rain will change to snowfall in all areas. How much rainfall versus snowfall can't accurately modeled at this time… there are still 3 days for speed of the trough and cold air to change. The speed at which that cold air arrives will affect the column and could cool it quickly enough that snow will develop early and therefore produce a higher total.

CIPS Analog Snowfall
At this moment it sure looks like a storm that you'll want to plan for in a few respects. First, if you want to fertilize, go ahead and do that Saturday while it's still warm out and it'll be ready for Sunday's moisture -- rain and snow. Sunday travel through elevations of 6,000feet and higher will become slick and slow. Below 6,000feet will likely have a rain/snow mix with slushing possible later in the day as temperatures drop. In areas of heavy snowfall, keep an eye on your trees (not many have budded and leafed, but branches will be vulnerable to heavy snow). Also, track that cold air as it settles into the 20s for Monday morning. . . any lingering moisture could make your Monday morning commute slower than normal.

We'll have additional updates as necessary as we head into the weekend, and keep you posted as this storm continues to develop.