Hi guys, I wanted to do a quick forecast post for the upcoming storm system because I’ve already had quite a few questions about it on here and in a few other places. I will warn you, it’s long, but it’s definitely worth the read.
Current Model Forecast-
Based off of the current model run, yes, we are supposed to see very heavy snow Monday Night through Thursday of next week. Snow predictions are currently 18-24″ for most of the urban corridor. If this verifies, it will be a true Colorado blizzard and you should buy all the milk and bread that you can immediately. I’m still not sure why only milk and bread. Does everyone make French Toast during blizzards and this is just something that I’ve never experienced? But, I digress.
Why the Current Forecast Can’t be Trusted and Weather Stations Seem to be Split on the Forecast-
In order to bring Colorado these really intense and long snow storms, a lot of factors have to line up perfectly. This storm is no different. We need the low pressure to be in just the right place to produce the winds that sling moisture against the mountains and give us upslope blizzards. This critical position of the low is what makes these storm systems so difficult to predict for Denver. You can see the forecast low pressure for the storm system to the right. As it sits in this image (the blue circles on the Colorado/Kansas border), it’s in the perfect spot to give Denver a ton of snow, but when the new models runs are started, they incorporate current meteorological data which will make them adjust their diagnosis of the upcoming days. Most often, the change has to deal with the storm system position. So, if the low in the image is shifted because of new data, it can take the snow completely out of Denver.
These are the images in chronological order of accumulated snow predicted by the GFS model for the runs from yesterday morning through today. You’ll notice the first image shows 12+ inches of snow for the Denver Metro area. The next three runs had shifted the low pressure to the east which meant that Denver was getting only a couple inches of snow, if any. This type of oscillation in snowfall and system position happens a lot with winter storms and that is one of the main reasons that they’re so difficult to predict. This oscillation of position and Denver snowfall has been happening since I noticed this system over a week ago.
This uncertainty creates a problem with all forecasters. There is a chance of an epic snow storm, but the next model run could reveal that it is too far east to create good snow. So, it becomes, do you tell people about the storm system and run the risk of looking like and idiot when there’s only an inch of snow on the ground (this happened a couple times last winter) or do you call for a little snow and then wind up with feet? The answer to this question boils down to one factor; time.
Because the atmosphere is a chaotic system, trying to predict it far in advance is a nightmare for reasons similar to the one above, but as we get closer in time to when the event is supposed to happen, the forecast approves dramatically. So, the opposite of what I want to do is sprout off large storm totals only to have to redact them when we get closer and the model forecasts improve. Realistically, the models are pretty good at resolving systems 24-48 hours in advance so, I’ll be waiting until tomorrow night and/or Sunday to make any crazy predictions.
Your Wall of Text Blows and I Just Want a Quick Forecast-
Alright, here’s my forecast! Gun to my head, I’d say we will get some significant snow. The last four model runs have agreed on the position of the system and the European model that correctly made the forecast for Hurricane Sandy is on board with where the system will set up. With that being said, 72 hours prior to an event is an eternity in the forecast world. So, here’s my suggestion. Err on the side of caution. Get groceries and gas now so that if and/or when things line up and the news stations go ballistic, you won’t have to deal with the chaos that will be gas stations and grocery stores. If nothing happens, you got a couple errands out of the way early. When I’m not trying to be practical, I’m wishcasting the hell out of this storm, but only time will tell.