A look at the weekend storm system: Thu to Sun

04/14/25 8:30pm: I'm getting excited for the weekend storm system although uncertainty is still high and devil is in the details. Snow amounts, especially for the front-range will all depend on the upper-level low track but all models show a large, prolonged storm system impacting CO from Thu afternoon to Sun morning (coming in two phases).

Prior to this a short-wave with some snow for the mountains from 12pm Wed to 6am Thu (1-3" in spots).

As I mentioned yesterday models show a northern branch (colder) trough merging with a cut-off low coming from the southern subtropical branch. This setup will bring good rain/snow to almost the entire state (as it is a large storm system with several phases).

And with the main trough being positively tilted and the upper-level low developing west of CO (in UT) this storm will produce some good upslope flow along the front-range (Den/Bou) and drag down some much colder air from Canada (turning rain to snow on Fri).

Main impacts for both the north-central mountains and northern front-range will be from 12pm Thu to 6am Sun (with biggest impacts likely Fri night through Sat mid-morning), cold-air and heavy snow in spots especially Fri night so heads up there.

Hard to pin down details right now but generally speaking models show 0.5" to 1.0" of liquid precip for Den/Bou and the front-range, with half coming as rain, half as snow: could be >4" of snow for urban corridor and >8" for the foothills, uncertainty is high.

For much of the central mountains (north-central, south-central and southwest CO) it could be 0.75" to 1.50" of liquid, mostly in the form of snow above 9k ft...so it could pile up in spots to 8-16"+ for some of the ski areas and mountain passes / higher terrain. Of course will all depend on low track, how much east to west flow, etc. High uncertainty right now but the skiing is likely going to be getting good again with some pow.

First image loop show the complex flow pattern via forecast 500mb vorticity / wind from latest ECMWF. Images 2 and 3 compare forecast total liquid precip from now through 6am Sun from latest ECMWF and GFS models, take with big grain of salt. Last image shows forecast total snowfall from NWS Blend of Models from now through 6am Sun....gives idea of model trends but amounts / details will certainly be different than it depicts.