Denver, Colorado

The State of the Atmosphere: Monday, April 21, 2014

Posted by @BrendansWeather
With another beautiful spring weekend under our belt, it's time to start looking at what the coming week has in store for us. The coming week looks to start warm and windy across eastern Colorado, but big changes could be on the way by the middle of next weekend, with a chance for isolated storms across extreme eastern Colorado for the middle of the week.

NAM 10m Wind Wed | WeatherBell
Warm and Windy
We've got Tuesday as the pick day of the week temperature-wise this week, though none of the next five days look particularly chilly. The average high this time of year is 63 for Denver, we'll better that each of the next several days, with highs near 80 degrees on Tuesday.

The big downside to the warm temperatures through the middle of the week will be the breezy conditions across the state. I would expect we'll see a Red Flag Warning get hoisted for portions of eastern Colorado by the middle of the week as temperatures will be warm, humidities low, and winds gusty. There is already a Fire Weather Watch in effect for much of southeast Colorado for Wednesday.

Severe Weather Threat
Despite all the mild temperatures, our storm track remains active. We saw some rain this last weekend, and there's a chance we see more by the coming weekend -- even an outside chance we see a good soaking storm.

First we'll be tracking a severe weather threat across Texas, Oklahoma, and Kansas as we head into the Wednesday (day 3) timeframe. As it stands right now, impacts on the severe weather front from this system appear low for Colorado -- but proximity reminds us it's the time of year when severe weather starts to become more common here in Colorado.

The Storm Prediction Center has issued a "slight risk" outlook for the areas outlined below.

SPC Day 3 Risk MesoMap

The biggest threat at this time appears to be for hail and damaging wind. That said, there will very likely be tornadic activity with this severe weather outbreak -- so if you live within the highlighted risk area, or have travel plans that take you across this area Wednesday, please make plans accordingly. We'll continue to update as the week progresses.

Weekend Soaker?
Our focus across northeast Colorado quickly shifts to next weekend after Wednesday. The GFS operational has been remarkably consistent in bringing a big upper level trough across the state this weekend and plentiful moisture. In fact, it's 12z brings more than 1.5" QPF to DEN Sunday through Monday night. This would mean a big time rain event for lower elevations and likely a good late season snow for higher elevations.

Plenty of uncertainty remains with regard to this system. That being said, even the deterministic ECMWF appears to be trying to come around to a bit wetter solution for the state after being largely dry previous runs. The GFS ensemble control run also looks more promising with it's 12z run, though ensemble members have been rather all over the place over recent days. Here's a look at the GEFS ensemble control run at 500 hpa for this coming Sunday -- a mean upper level low tracking across Colorado. Eventual track will be a huge factor with this system.

GEFS Ensemble 500mb

The differences between the GFS and EURO are significant enough that it's worth a good degree of caution before getting too excited about this system. Also let's keep in mind we are still nearly a week out, though this trough has been on the radar for some time.

Here's a look at the 0z EURO (left) and 12z GFS (right) at 500mb for next Sunday. Notice how much deeper and slower the GFS is compared to the EURO.

EURO 06z Mon 500GFS 06z Mon 500

Somewhat surprisingly I might actually be favoring a deeper solution with this system as the GFS is trying to do over the faster more open solution on the EURO. One reason for this is it's clear the EURO has been trying to move toward a deeper solution over the last few runs. Another is that there might be enough blocking out in front of this system to slow it down. Even the Canadian that comes in rather unorganized, but then slows and deepens as it moves across Colorado Sunday -- a solution that would actually favor eastern plains over Front Range communities.

A lot to watch over the coming days. It's fair to say the State of the Atmosphere is active! We'll push updates throughout the week.

Watching for the Chance for Storms this Easter Weekend

Posted by @BrendansWeather
A relatively warm weather pattern will stick with us through the weekend and into early next week. Temperatures Friday have soared to near 80 degrees across the metro. While we expect cooler temperatures for both Saturday and Sunday, both days should still be mostly pleasant with highs in the upper 60s to near 70 degrees.

The big weather story over the next few days will be the chance for scattered rain and storms across eastern Colorado. The unsettled weather will also mean a chance for rain and snow showers at higher elevations, so if your plans take you west for the weekend, please plan accordingly. We don't expect the weekend to turn into a soaker, but as you can see in the NAM simulated reflectivity for Saturday afternoon there are widely scattered storms across the state.

NAM Simulated Radar

Same is true for Sunday when we might have a bit more moisture to work with. Timing will be key in if we see more rain Saturday PM vs Sunday. Like earlier this week, and frankly with any luck at all, rain chances may be greatest south of Denver where it's needed most. While still a 'hole' over southeast Colorado, it's good to see some moisture trying to return to that part of the state. The GFS is pretty excited in spots about precipitation totals by Monday, but don't take this too literally. . .

GFS Total Precip

Here's another look from NOAA's HPC -- shows widespread light QPF for state through Monday.


By early next week we dry it out and warm it up once more. Temperatures by Tuesday could be even warmer than today!

We'll post updates through the weekend should anything change rain-wise -- otherwise, wishing everyone a great weekend from all of us at Weather5280!

Storm on Track, Keeps Best Precipitation South of Denver

Posted by @BrendansWeather
As we discussed yesterday, another storm will begin to affect Colorado today through Thursday bringing at least a slight chance of rain and snow to Denver.

The eventual track of this system was the biggest uncertainty yesterday, as only a slight shift would mean a greater or lesser chance for shower activity in Denver and the northern Front Range communities. 18z model runs yesterday trended south, away from Denver, and the 0z runs last night did little to change this idea. We'll stick with cool and unsettled for Denver this afternoon through Thursday, but temperatures are not looking as chilly Thursday as they once were, and precipitation chances will be low.

South of Denver the forecast remains interesting. The National Weather Service has issued a Winter Weather Advisory for areas west of Colorado Springs which we outlined yesterday could have the best chance for appreciable snowfall. Currently thinking 4 to 8 inches will be possible there (at elevations >6700 ft), but will need to watch for another southern shift in precipitation.

Should the NAM pan out, this will be a good little snow for the southern Front Range, with good soaking rain trying to push east into the southeast plains. . .

NAM Total Snowfall Thru FridayNAM Total Precip Thru Friday

The hi-res HRRR looks very similar, though may try and keep bulk of moisture south of Colorado Springs.

HRRR Precip Type Accumulation

Notice how both of these models keep Denver and northeast Colorado virtually dry through Friday. This could very well be the case -- but we think there will be just enough ingredients in place to keep a chance for showers this afternoon and overnight Wednesday into Thursday for the Denver area. Again, not expecting much in the form of measurable precipitation in the city, but something to keep in mind if you're headed out and about, especially if you're headed south.

Temperatures will spring back nicely Friday, with highs expected back near 70 degrees for much of eastern Colorado by Friday.

GFS 2m Temps

Easter weekend looks mostly pleasant for the state, but we'll need to track the chance for thunderstorms Saturday, and at least a slight chance for rain on Sunday. Neither day of the weekend looks particularly cold however, with highs in the 60s likely both days.

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.