As we mentioned last week, after weeks of unseasonably warm weather, winter is back in the forecast for eastern Colorado for the early part of this coming week.
Overall, the flow for Colorado and the region is pretty benign early on Monday. Pictured below is the 500mb pattern from the EURO:
That pattern changes dramatically late Monday. By Tuesday morning, we have a fast moving wave "closing off" and continuing to intensify over the Panhandles:
She doesn't waste any time moving though... Notice how far east our little storm is by Wednesday morning (Lower Mississippi Valley):
So, what does this mean for us in terms of sensible weather?
Precipitation Type, Timing, and Impact for Denver:
Monday 4pm-8pm: Rain showers gradually changing over to snow late in timeframe.
Monday 8pm-12am Tuesday: Transition to wet snow continues with complete changeover likely by 10pm to 12am Tuesday. Wind picks up too...
Tuesday 12am-6am: Periods of wet snow, with occassional heavy bursts...especially for higher terrain to the west and south of the city. Gusty north wind causing blowing snow and reduced visibility.
Tuesday 6am-9am: Light snow ends from north to south. Roads will likely be challenging for the morning commute. This will be especially true for areas that see the most snow and for colder locations farther away from the city's core warmth. The most challenging travel conditions will likely be in the higher terrain to the west and south of Denver.
This system will mainly be an upslope event. These type of events really favor the Palmer Divide and areas along and west of I-25. In fact, the latest GFS (and many models for that matter) have little to no precipitation across the northeast Plains. There will be a sharp east/west gradient for snowfall across the I-25 corridor.
The biggest question is how much snow – and of course, that's a challenge. While it looks like a good chance for snowfall along the I-25 corridor, we'll have several factors working against with regard to accumulating snow.
First, the ground is much warmer than it was just a few weeks ago. Of the last 15 days, 12 have seen daytime highs more than 50° F in Denver, with six of those coming in at >60°. Overnight lows have also been well above normal (normal is 20° this time of year), with several nights this past week not even making it below freezing for overnight lows. So, snow will have a difficult time sticking, especially at the onset, and may eat into totals at lower elevations. Raised surfaces (grass and cars) will see snowfall accumulate first. While we are expecting some challenging travel conditions on Tuesday morning, travel conditions may end up worse IF paved surfaces cool fast enough/snowfall is heavy enough. Here is the latest GFS has soil temperature forecast for Colorado, well above freezing for Tuesday morning:
Next we have issues with air temperatures – and while we think we transition to snow pretty quickly with this system, any precipitation that falls as rain initially, will take away from snowfall totals in the end. And lastly, speed. This system will intensify over southern Colorado, but won't hang around. The main energy with this system will quickly dive south and east of Colorado on Tuesday.
With that, we think a few inches will be possible in Denver by late Tuesday morning, but at the moment we don't expect a huge snowfall in town. Areas to the west and south of Denver will fare better, as upslope will favor these locales and temperatures will be less of an issue.
Below is our initial snowfall forecast for Monday night into Tuesday. For Denver we are calling generally for 1 - 4" on the east side of I-25, and 2 - 5" on the west side. At higher elevations west and southwest of Denver, totals from 4 - 8" inches can be expected. We'll go with a middle of the road Bust Index for now, given concern about melting/rain and therefore low-end snowfall potential.
A few models have been a bit more gung-ho with snowfall totals, especially for the higher terrain south and west of Denver. With that, the potential for greater snowfall totals is there – but for the time being, we think this potential is much lower, and so we'll hedge lower with totals, especially given warm temperatures and any rain that may initially fall.
Of course we'll track the latest data tonight, and pass along any adjustments that need to be made Monday if needed. If you're not yet subscribed to Weather5280, please do so now!