We provide our final thoughts on the snow event taking shape for Wednesday evening and night, including a timeline for the storm and our snowfall forecast map.
J
ust as we had hoped for in our forecast update yesterday, the weather models have come into better agreement on the large-scale factors influencing the approaching storm system!
On the downside (if you want snow), the passing jet streak just won’t hit the timeline correctly across the area. Any concentrated lift and associated heavy snow bands will form to the south of the Denver area this evening. During the afternoon, we could see a few jet-forced rain bands develop across the Metro area before the colder air arrives this evening.
NAM 250 mb wind forecast (left) and HRRR simulated radar (right) for 6PM Wednesday evening
However, on the plus-side, the developing closed-low across southwestern Colorado late this evening has been confirmed by all primary weather models. This is a major point of uncertainty yesterday, and with its formation, upslope from the surface up to around 11,000 feet elevation will develop across the Front Range tonight. It could turn out to be rather juicy and strong from the northeast between 9PM and 3AM. This would favor portions of Boulder and Jefferson Counties in and near the Foothills, as well as the Palmer Divide.
700 mb temperature and wind forecast for Wednesday night at midnight from the GFS (left) and NAM (right) models
A combination of this brief but deep upslope, elevated moisture, and broad lift from the passing trough (below) will lead to a period of accumulating snowfall this evening and through the overnight hours tonight.
GFS 500 mb vorticity map for Wednesday night
Timeline
Wednesday will begin fairly decent with partly sunny skies and mild temperatures, especially on the western suburbs. An initial cool boundary will impact the area from east to west this morning, but most areas will get into the 50’s for highs. Winds will be breezy from the northwest or northeast, depending on your location. A secondary surge of colder air will move into the Metro area by mid-afternoon with temperatures dropping and increasing cloud cover.
As things come together by early evening, scattered showers should begin break out, likely beginning as a brief period of rain across the lower elevations. With the jet screaming past during this time and a tiny amount of CAPE available, it’s possible there could be one or two rumbles of thunder mixed in. As temperatures quickly cool into the low to middle 30’s around sunset, any rain will quickly mix and change to all snow. We think the evening commute should be largely okay since temperatures will be warm enough for only rain or melting snow. Also, the precipitation may hold off until just after the commute window.
During the evening hours, snow could be moderate to heavy at times, especially south of I-70 and west of US-36. Light snow will linger south and west of Denver into the early morning hours Thursday before quickly tapering off as energy exits and winds turn dry and northerly. The morning commute on Thursday will be dicey in spots that see the higher totals.
High temperatures on Thursday will bounce back to near 40 degrees.
Snow Amounts
Given the track of the storm, the best lift will generally be south of Interstate 70 this evening, but we also have to consider the influence of brief but deep northeasterly upslope across the area. These two facets will lead to snow totals being highest south and west of Denver. Areas north and east of the Metro area will ultimately see almost no snow. And of course, let’s not forget: this storm will exit as quickly as it arrives. The window for accumulating snow is just eight to twelve hours for most of us.
Here’s our snowfall forecast map:
If your location comes up short tonight, don’t worry….another chance of snow is taking shape for the entire area this weekend. We’ll talk more about that system in the coming days. Happy Wednesday!
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