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The State of the Atmosphere: Monday, February 4th, 2019

The state of the atmosphere was far too nice yesterday to sit inside and write about it. If you didn't get a chance to get out and enjoy the mild weather this weekend, you'll have another chance today (and perhaps tomorrow) before temperatures start to cool for the remainder of the week.

Teleconnections to start the month of February indicate a cold and unsettled pattern for much of the Western United States, with a bias toward colder than average weather across eastern Colorado as well. Both the PNA and EPO teleconnections are forecast to remain negative over the next 10 days, while the WPO turns positive. These are all cold signals for the west in January and in the case of PNA/EPO much of the northern tier/pushing east. So, while it was warm over the weekend and today, we expect the next 10 days to overall be of the colder variety.

source: Mad US Weather

There's good agreement in the modeling for this to be the case. Take a look at the five day 500mb anomaly forecast ending next Monday from the Euro: mean trough in the west, ridging going up in the east:

At 850mb this paints a very cold picture across the Northern Rockies and Western United States. For Northeast Colorado, the coldest anomalies are expected across the far northeast Plains, with perhaps some warmer days mixed in for those of us immediately adjacent to the mountains. All in all, however, a the warmth we saw this weekend will quickly be a thing of the past:

Tuesday will likely be another pretty mild day across Northeast Colorado, though not as warm as today or this weekend. Wednesday a cold front will drop south across the Plains, and bring with it a chilly and unsettled change to the area:

Right now it doesn't look like a huge snow event for most of Northeast Colorado, though snow showers at least appear likely by Wednesday. The NAM and GFS both agree that the best chance of snow will come later in the day Wednesday (perhaps for the evening rush?) but differ on how much snow we see around here.

The NAM is more bullish with a slightly more favorable track. It shows several inches of snow from Denver north to the Wyoming state line, with heaviest totals along and west of I-25. The GFS is quicker and a bit further north with its track, and therefore is advertising lower totals, though still some accumulation for the area with a very cold shallow upslope flow developing Wednesday PM.

The Euro has been pretty consistently less bullish on snow for the urban corridor, but a look at its ensemble mean shows the potential for a couple of inches for the area in that Wednesday/Wednesday night timeframe:

Our gamblers show the potential too. Below are the three-day probabilities. Upwards of 50% chance for Boulder to see 2" of snow, with decent odds Denver sees something as well. Further south the probabilities are lower:

We'll keep an eye on Wednesday and offer another update as we get closer. For now, plan on temperatures turning colder and a least a chance for snow returning to the forecast by Wednesday. Right now not looking like a blockbuster storm, but the track is in the ballpark to deliver a few inches to some locales so let's see how things look tonight and tomorrow.

Looking ahead a bit... not a great signal for snow across eastern Colorado through the middle of the month, despite temperatures forecast to cool. We discussed this in our February outlook for Insiders, but in general, the pattern will be more favorable for areas west of the Continental Divide. Now, that's not to see we won't get lucky... the storm track will be quite active for a while, so it won't take much for one to line up for us. We see the system on Wednesday trying, with the next system to watch already on its heels this weekend.

The Euro ensemble forecast insists below average snow for most of us east of the Divide over the next 15 days:

With colder than average temperatures, though the worst of the cold largely north and west of our area:

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This is a collaborative post from multiple authors at Weather5280.

Denver, Colorado
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