Hello all! Happy Pi day! I hope you’ve enjoyed the warmth lately. It’s been a nice reprieve from the cold we’ve endured this month. March temperatures are running close to 6º below average so far this month so it’s definitely been a cold March up to this point. This article is about an 5 minute read.

Some snow fell overnight on the Palmer Divide and a good bit of snow fell in the high country (looking at the central mountains near Aspen and crested Butte). The mountains will be clear and dry through Tuesday night as well.

We have some great weather in the forecast for Monday and Tuesday with plenty of sunshine and warmth expected. Highs Monday will be in the mid 50s but on Tuesday, we’ll be approaching 70º and it’ll feel oh so nice outside.

Our big changes start to occur Wednesday when our next storm begins to move into the picture. There are a few things to know about March storms. 1) the location of a storm has huge implications of how much moisture or snow we can get. More moisture = higher snow/rain totals. 2) temperatures can be variable. We’ll be at 70º Tuesday and likely near 60º Wednesday before the big cool down begins. 3) Elevation plays a big role in impacts and they can vary a lot depending on if you’re at 5,000 feet or 6,000 feet.

Here’s what we know so far:
~ There’s a trough with an associated cold front that will move through Colorado Wednesday.
~ There’s a lot of moisture with this storm
~ Temperatures will be very warm initially – so rain in Denver is a likelihood to start
~ Current models are suggesting a impactful snowstorm Wednesday night to Thursday

Here’s what we don’t know so far:
~ The exact track of the developing storm
~ How much cold air will be brought in and how fast
~ Snow totals – they are so dependent on many factors

Again, storm location is very important with Spring snowstorms. For there to be a lot of snow (like our big March blizzards or bomb cyclones), a low pressure needs to develop and track over southeastern Colorado. When a storm sets up in this location, winds that flow counterclockwise push air directly up the mountains and the Palmer Divide and when air is forced upwards, it condenses and forms clouds and moisture. Usually with these setups, cold air is also pulled in from the north so many times, these result in snowstorms.

The incoming storm – as of Monday morning – looks to be setting up in northern NM or northern TX. *Almost* in a perfect position but a bit further south than we’d like it. The last few model runs have shown this storm inching a bit further north and that is a trend we have to watch closely. Regardless, a storm in the Texas panhandle is adequate enough to provide us with upslope flow.

We’ll watch a cold front push across Colorado Wednesday afternoon and that will allow for cold air to filter into our area. Initially, light to moderate rain showers will develop and that will help to cool our atmosphere even faster so at some point Wednesday night, we’ll see our rain switch over to snow – and it could be VERY heavy at times since temperatures may be above freezing.

The rain/snow line will be elevation dependent. When the precipitation starts late Wednesday morning to the early afternoon, snow levels will be around 7,000 feet or so. So areas along the Palmer Divide and in the Foothills may never see rain but all snow during this event. Once the cold air settles in and we get some evaporative cooling from the rain, the snow levels will eventually drop to 6,000 feet and then lower to 5,000 feet and less.

Everyone will see a switch over to snow by Thursday morning at the latest and then we will watch the snow continue for Thursday. Timing on when this storms moves out will have to be watched closely too because a storm that lingers longer produces higher snow totals but if it’s a fast mover, we can expect lighter totals. Right now, the storm looks to exit Thursday afternoon to evening.

The potential for big impacts to Thursday morning’s commute are likely right now. With rain falling initially, then turning to snow with freezing temperatures, icy conditions are almost a guarantee for Thursday morning.

I’m not going to post specific totals right now but I will post ranges of what is looking possible right now.

Heck of a range, huh? So ensembles are basically different outputs from the same model. We’re looking at the EURO model above and each line (there are 50 of them) are forecasts from the EURO model but the starting weather situation (temp, precip, wind) is altered slightly so show different possible outcomes. This is for Denver Airport – so areas that are normally favored by upslope like Boulder, Castle Rock, Bailey and other Foothill locations could expect a different (likely higher) range than this.

Ultimately, this storm is tricky and although we’re within 72 hours of the event beginning, there’s still quite a bit to be worked out. Especially since the storm hasn’t even developed yet.

There’s a 100% chance of rain from this system in Denver and I’d say there’s a 100% chance of snow into Thursday morning as well. What’s in question here is how much cold air will move in and then how much snow will fall after that.

TBD but keep checking back because this forecast WILL change quite a bit. Here’s a look at how much moisture may fall with this storm

The NAM model is another model I look at for forecast. This is a short term model (it only goes 3-5 days out rather than 10-15 days like the EURO or GFS) so the clarity is usually much better with this model. It’s showing a lot of moisture from Pueblo to Denver. Potentially more than an inch of liquid. That’s a lot considering our annual liquid total is 14-15″.

Lots to watch but prepare for a rain/snowy Wednesday afternoon to Thursday afternoon with much colder temperatures. We warm up and dry out this upcoming weekend but another storm looks possible by early next week and that could also be a big storm to watch.

~ Andy

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