After record warmth Wednesday, the News5 Weather Team is tracking our next weather maker tomorrow - as a large upper-level trough moves in from the west. Follow along below for the latest updates to this developing system.
Several of our higher resolution forecast models are beginning to be in-range for this system. These higher resolution models allow us to zero in on timing and impacts of winter storm systems. When we look at these models, we're also thinking about how certain models tend to perform in our region in various types of weather set-ups. But what we can say: higher resolution data is good. These models have more forecast points, which better models the topography of southern Colorado.
This storm system has thus far showed surprising consistency in all the models.
Here's the basic set-up right now:
A large ridge of high pressure that's given southern Colorado record breaking warmth early this week slides east Thursday morning. As it does so, our upper-level wind pattern strengthens, leading to gusty downslope southwesterly winds. This is a common pattern in southern Colorado as high pressure leaves the region.
Humidity levels will be low - criteria for a Fire Weather Warning are sub-15% relative humidity values, and wind gusts above 25 mph, for a minimum of 3 hours. As of now, no Fire Weather Warnings have been issued, but a grass fire earlier this afternoon shows the relatively enhanced risk that already exists.
Winds Thursday morning will already be gusting to 45+ mph along the east slopes of Pikes Peak, and around 30-40 mph along the US-24 corridor between Manitou Springs and Divide. If your morning commute takes you that way, expect gusty breezes. In Pueblo, your morning commute sees wind gusts of 20-30 mph. During the day, winds will be strongest in gap regions and the Sangres - Walsenburg, La Veta, and areas in Las Animas County, 2.5 hours south of Colorado Springs.
This gusty downslope wind warms temperatures Thursday to 15-20 degrees above seasonable norms, into the upper 60s to low 70s, but cooler than Wednesday's temps.
Thursday evening, a cold front swings through - cooling temperatures significantly ahead of the clouds and precipitation, which will arrive Friday. This set up is known as an "ana front." Snow begins Friday, heavy at times through your day, and continuing Friday night into Saturday morning. The greatest impacts will be felt Friday night - when temperatures are colder and snow will adhere to roadways better.
The latest News5 snow map reflects relatively low totals due to the fast moving nature of the system and questions on the placement of mesoscale banding features.
By Saturday afternoon, the entire system is out of here, but Saturday night will be bitterly cold with single digit lows.
What we don't know:
1. Timing: The sooner this system arrives, the less snow southern Colorado gets. This is due to a combination of how the various layers in our atmosphere align. Think of a sandwich; everything has to line up to make it work. An earlier arriving storm equals worse alignment - and above freezing temperatures Friday during the day. That means the warm roads will initially melt any snow that falls. The latest runs are bringing the system in earlier, reducing snow totals.
2. Strength of low: We know where the area of low pressure will be Friday morning - leading to upslope flow. The stronger the low is, the stronger the upslope, and thus the more intense snow and snow banding might be.
3. Small-scale factors. Events like this often see banding snow, enhanced by terrain features on the scale of the Pikes Peak massif. This can only be resolved 12 hours or less in advance of the storm. That’s why you sometimes see the snowfall forecast change very close to the time the snow begins to fall. At this time scale, we've got a sense of the set-up.
Track this storm through the morning, including snow totals and updated forecasts, on the First Alert 5 Weather stream, which can be viewed on the KOAA News5 app for your Roku, FireTV, AppleTV or AndroidTV.
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