It’s a long ways out, so bear with us here, but as things stand today next week has all the makings to deliver our first real cold shot of the year to eastern Colorado. While these setups aren’t typically big snow producers for Denver, should things align just right, we’d likely be looking at our best shot for our first measurable snowfall of the year. Until then, our mostly tranquil weather continues, with an outside chance we see a few rain or snow showers Friday evening.
High confidence, sort of
We talk a lot here about teleconnections and how they help predict our weather pattern. A few that we watch for the delivery of cold air for eastern Colorado are the AO, NAO and EPO, which are all set to go negative by next week if the current forecasting holds.
Below are GFS outputs for the EPO and AO. The solid blue line indicates where we’ve come from since the end of October, the black line the forecast. Note in both the dip around November 1st, this was our last system. Both are set to go negative by next week, and both are cold signals for the eastern ⅔ of the United States.
We’ll need to watch these carefully over the coming days as there are still some conflicting signals, which depending on how they fluctuate will push the colder air further east across the central and eastern United States, or further west from Colorado eastward. As it stands, both the ECMWF and GFS keep the PNA positive next week and dip the NAO slightly negative, which would favor a more eastern bias for the coldest temperatures. Regardless, all major models are supportive of our coldest temperatures of the season by early next week.
Influence of typhoon Nuri
A few week’s back Matt discussed the impact of pacific Typhoons on the United States. Should things come together for next week, part of the culprit for will be the energy from typhoon Nuri in the western Pacific. It is forecast to recurve and strengthen over the coming days and not surprisingly will have big impacts on our weather going forward.
N Pac storm to likely be among strongest storms on record outside tropics: http://t.co/e0XHZ8k0id pic.twitter.com/9aU4IZnpUw— Capital Weather Gang (@capitalweather) November 5, 2014
Quick glance at temperatures
While positioning of the coldest air next week isn’t a done deal, it’s looking like a good bet many east of the Rockies will be impacted. Temperatures from 20 - 30 degrees below normal will be possible with this airmass, and if model trends hold eastern Colorado will see temperatures well below normal somewhere in the Monday through Wednesday timeframe.
Here are the 18z GFS ensemble mean 850hpa temperature anomalies for early Wednesday next week (in Celsius), with its operational run for 2 meter temperatures 18z Tuesday below (in Fahrenheit), the Euro looks mighty similar. Brr!
As mentioned above, snow chances are the greater question mark at this point, but they’re also not something we start to narrow in on until we get closer to the event. For what it’s worth, the 12z GFS showed the most QPF with this system (below), while other models are all but dry. Again, these setups are not typically huge snow producers for us, but every once and awhile can deliver.