Dwindling precipitation chances on Friday to precede a nice weekend
Thursday, November 20, 2025
Temperatures are in the upper forties on this Thursday mid-afternoon in Steamboat Springs with partly sunny skies. Precipitation chances have diminished for Friday, leaving only some upper-elevation snow showers and cooler temperatures. Warmer temperatures return for the weekend, including mostly sunny skies for Opening Day at the Steamboat Ski Resort on Saturday.
Thank you to those who attended my presentation on Tuesday night at the library, and no one should have been surprised by the quick shower that passed through early Wednesday morning. I want to elaborate on a couple of questions I received regarding snowfall forecasts and wind direction.
Shown are four panels from the NAM forecast made at 11 am today and valid for 5 am Friday. Remember the first panel in the upper left represents the atmosphere at around 18,000′, or half its total depth, with the red denoting storm energy, or spin.
The second panel in the lower left is a forecast for the mountain-top level of around 12,000′, with green and orange denoting high and low relative humidities, respectively, and the third panel in the upper right is the surface pressure pattern.
In all of these, I have drawn green arrows indicating the wind direction at these three levels, which tend to follow along the black lines. These indicate constant height surfaces, or isoheights, in the first two panels and pressure surfaces, or isobars, in the third. Note the split flow, where the northern part of the jet stream flows across southern Canada and the southern part, which is comprised of a large eddy off the southern California coast, a smaller eddy in western Kansas, and a ridge of high pressure over the Southeast. Also note the counterclockwise circulation around the eddies, with clockwise circulation around the high pressure areas in the Dakotas and the Southeast. Generally, the denser the isoheights and isobars, the faster the winds.
The fourth panel in the lower right indicates precipitation, and I neglected to mention that this is a quantitative precipitation forecast, or QPF. The multicolored bar at the bottom of this panel indicates liquid forecast amounts, in millimeters, forecast to fall in the previous six hours, highlighted by the green arrows over coastal British Columbia, southern California, and Missouri. The dark blue indicates a range between 50 and 75 mm, while the light green indicates a range between 125 and 150 mm.
The final step for snow forecasting is converting the forecast liquid water into snow, which is temperature-dependent. A first-order estimate is 10:1, which represents dense snow, while the light and dry powder is around 20:1 or higher. This conversion adds complexity to already difficult forecasts.
Finally, I have added total accumulated snowfall underlying the forecast radar returns shown in the Rapid Refresh radar forecast, found by selecting NCEP in the MODEL DATA menu. Selecting a d(prog)/dt for 18Z Friday explicitly shows the dwindling forecast snow amounts over the last four runs. Since the Tuesday talk, those snow amounts went up to as high as 8” in the Wednesday 18Z, or 11 am, forecast, to nothing from today’s forecast. This was due to the changing forecast track of the eddy, which moved from northeastern Colorado to western Kansas.
There may be some spotty showers around Friday, but other than temperatures in town falling to the low forties, several degrees above our average of thirty-nine degrees, not much weather is expected from the grazing eddy.
A transient ridge of high pressure behind the departing eddy and ahead of the California eddy will make for a mostly sunny Opening Day at the Steamboat Ski Resort, with high temperatures in town rising back to the upper-forties. The California eddy is forecast to enter Arizona on Saturday and approach the Four Corners on Sunday, bringing precipitation to Arizona, New Mexico, and southern and eastern Colorado, but only some clouds to our area, allowing high temperatures to stay in the upper forties.
Meanwhile, a northern Pacific wave of energy moving across the Gulf of Alaska is forecast to cross the Pacific Northwest coast late in the weekend, ingesting some cold western Canadian air as it brings a cold front into our area around Monday night. Moisture is limited with this front and the cool northwest flow that follows through Thanksgiving, but there is some hope for snow.
Enjoy the nice weekend, and I’ll have more details about the cold front early next holiday week and what follows in my next regularly scheduled weather narrative on Sunday afternoon.
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