Spring Storm Delivers Feet of Snow, Great Moisture to Colorado

Mapping northeast Colorado's rain and snow from weekend storm
The forecast remains unsettled through Tuesday as our slow-moving system will take its time exiting. The central and southern mountains may see an additional 5 - 10" of snow tonight, but any rain and snow across lower elevations to the east will generally be light. With that, the biggest impacts from this system for us are likely done now, with impressive snow totals, severe storms, and big-time moisture all making for quite a weekend across the state.

Water vapor imagery from Saturday morning showing a big cutoff low spinning into northern Arizona then drifting east into northwest New Mexico. The bright whites across far eastern Colorado (halfway through the loop) is the severe weather we saw on Friday across the Plains.

Severe weather
As forecast, the system started off Friday by bringing severe weather to eastern Colorado and heavy rains to the plains. Below is a map of severe weather reports from Friday, with lots of hail reports, heavy rain, and even a tornado being spotted south of Eads, Colorado:

Below is GREAT photo taken of this tornado from Scott Longmore and Dan Bikos just south of Eads on Friday afternoon:

Photo credit Scott Longmore and Dan Bikos

Snow
On the cold side of this system, there was no doubt some very impressive snowfall totals! Rain and snow began at Denver International Airport during the 9 o’clock hour Friday night and didn’t let up until midday Sunday. This worked out to 38 consecutive hours of snow being reported officially for Denver, for a total of 12.1” at DIA, the official storm total for the city.

Related: Denver's top 5 April snowstorms (this was not one of them!).

As we discussed on Friday, this storm was certainly not an “equal opportunity” snowfall event. For those living across the northern urban corridor, it took a long time to see snow and for the most part totals ended up not all that impressive given warm surface temps and a prolonged period of rain Saturday. But oh how quickly conditions changed with just a little elevation – totals on the south side of Denver were over a foot in most locations, with totals across the Palmer Ridge flirting with two feet in many areas, and a few foothill locations logged more than four feet of snow.

As an example, take a look at the following three weather stations from across the region. The first, Thornton, reported temperatures from 33 - 34° all day Saturday, with a storm total of 7.3". The second, Highlands Ranch, averaged just a degree or two cooler all day Saturday then dipped into the 20s Saturday night, and saw more than double the snowfall as up north with 18.9" recorded at this station. Lastly, we look at Genesee, west of Denver (approximate elevation 7,600 ft), and see temperatures were no issue with highs in the 20s Saturday and an impressive storm total of 42.0". Of course, this is only part of the reason for the wide range in totals, but especially this time of year temperatures and elevation played a big role.

Area weather stations compared

From a forecast perspective, we’re pretty happy with how things worked out. For the northern urban corridor, we issued a Bust Index of 8 (high!) and are happy we did. At the same time, we had MUCH lower totals forecast in these areas, from 2 - 6” for Longmont, Loveland, and Greeley, to 3 - 7” for the Fort Collins area and north Denver suburbs. Fort Collins ended up with 5.4” (on target!) with 3.2” reported in Longmont, also right in range.

For Denver's southern suburbs and the Palmer Divide, we forecast 12 - 18" which also worked out pretty well. Our initial forecast called for 12 - 24" in this zone, which in the end we very well could have stuck to. Castle Rock ended up with 20.1" of snow with just about 24" recorded in Elizabeth. A bit closer to town we saw from 14 - 19" across Highlands Ranch, with upwards of 18" for southeast Aurora.

Here is an interactive map of snowfall totals from across the region, note a few 40"+ readings west of Denver!

And here is an interpolated plot of these totals (click points to explore totals, pan and zoom map):

Map of snowfall totals from the April 15 - 17, 2016 snowfall across northeast Colorado | Weather5280 Models

Which should look a lot like our forecast, with the exception of across the far eastern Plains where heavy snowfall never really materialized. In this case, we leaned a bit too heavily on the EURO, which overall did well, but was a bit too bullish on coverage out east. For points south of Denver we ended up a bit low, but I think overall impacts are implied with 18" forecast vs 20 - 25" recorded.

A few additional totals:

Location Forecast Total Bust?
Pinecliffe 1 - 3' 51.3" Boom!
Genesee 1 - 3' 42.0" Boom!
Elizabeth 12 - 18" 24.0" Boom!
Castle Rock 12 - 18" 20.0" Boom!
Highlands Ranch 12 - 18" 19.0" 👍
Boulder 7 - 14" 18.3" Boom!
Bennett 12 - 18" 16.7" 👍
SW Westminster 7 - 14" 13.6" 👍
Denver (official) 7 - 14" 12.1" 👍
Arvada 7 - 14" 11.5" 👍
Fort Collins 3 - 7" 5.4" 👍
Longmont 2 - 6" 3.2" 👍

Precipitation
There were a lot of uncertainties about this storm, but one thing we felt very confident about was that it would deliver a lot of moisture to the region and that it did.

Denver International Airport is reporting 1.39" of liquid from this weekend's storm, which (like our last event) is actually on the low-end of reports. In Boulder, where CoCoRaHS reporter Matthew Kelsch lives, precipitation totals of over 2.0" were common, with 15 - 20" of snow. Nevertheless, this storm puts Denver's precipitation totals for the month at 1.53", which is 0.71" above normal, great news!

The latest precipitation analysis (below) from the last five days shows pretty good totals across the state. Of course, we would have liked to have seen better snowfall for our southwest mountains where snowpack continues to hurt, but great to see some moisture for southeast Colorado, the eastern Plains, and of course the Front Range.

Totals over northeast Colorado ranged from 1 - 3 inches with a few locations across extreme eastern Colorado seeing upwards of 4 inches of rain with this system | WeatherBell Analytics

So, as we wrap this storm up over the next 24 hours or so, we look forward to some much warmer temperatures and plenty of melting of the second half of the week. After a very warm and dry February, it is so nice to see our forecast for a wet spring continue to unfold. As Brian Bledsoe mentioned last night, let's take all the moisture we put into the ground right now, to offset drought creep as long as possible for when this pattern eventually flips.

Brendan Heberton

Brendan is founder of Weather5280. He is co-founder of FreshyMap, and develops software for geospatial data analysis and visualization.

Denver, Colorado
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