Saturday PM Update: Snowfall Forecast

Let's run through today's models and begin to get a bit more specific on this next system.

I've looked through all global models, and now the short-rangers. I've looked through today's 12z runs of the big guns, the 18z run of the 4km NAM, and the 15z of the SREF. There is a pretty good agreement on timing and strength of the cold air and QPF amounts and placement. The average QPF for Denver remains below 0.25" – which works out to 2.5 to 4" of snowfall depending on snow ratio.

Let's discuss timing first. The cold front sits near Sterling as of 3pm Saturday. That cold front will make its way to the Front Range overnight and Sunday. In Denver, we will remain quiet overnight as clouds increase and take over. Temperatures will be near freezing Sunday morning with a breeze. For Denver, the overnight will be cloudy; meanwhile the Plains could see some patchy fog and freezing fog as the cold air moves through. This is a potential icing concern for them.

The breeze will strengthen throughout the day Sunday -- blowing in much colder temperatures. So, many will hit the lower 40s by midday and then you'll notice them cool the rest of the afternoon into Sunday night. There is good model agreement on this.

As those temperatures drop, clouds will thicken and there'll be some areas of rain and snow in the afternoon, becoming all snow by Sunday evening. With this combination, there will be a chance for some icing on all surfaces by Sunday night. There is a good agreement that the initial cold front will have the lowest probability of precipitation.

Very similar system to many we've seen this season
Sunday night through Monday will continue the snow chance, and most of the accumulation will likely be on Monday. SREF is a good representative for the larger scale models; all reflecting a peak in snow chance midday/afternoon Monday.

Right now, it appears to be a system similar to so many we've had this season so far. Within all model's QPF, accumulation will be highest in the foothills and across the Palmer Divide with 3 to 6". Many than in the foothills could see more than that, where some areas will have more than a foot thanks to upslope and jet stream dynamics. This is nicely consistent among all global models, and now the short-rangers.

For most of the metro areas from Denver to Fort Collins this is another small snow. QPF trends are averaging less than 0.25" of precipitation. GFS and NAM profiles indicate a snow ratio of 10:1 to 15:1 during peak hours of accumulation. This will amount to a range of 1 to 4" based on current QPF. Thankfully, this has been relatively consistent. Further, MOS statistics have been consistent, and SREF probabilities nearing consistency. All indicate the most likely statistical range of snow to be between 0 to 3 inches for Denver. The probability quickly drops for totals 4" or greater. This method doesn't include jet induced snow banding, however.

GFS 500 hPa 18z Mon | Relative vorticity and wind | Weather5280 Models

Banded snowfall the wildcard
There could be smaller isolated areas that benefit from higher intensity snow, where measurements could be more than that. This will come down to jet stream placement during the day Monday. Should a narrow area of more intense snow develop due to the jet, totals could climb to more than 6" for isolated areas. Since 4km NAM and 18z GFS both show the potential for snow banding, it is entirely possible. Now, we just need to wait and see who actually gets that enhanced zone of heavier snowfall.

Snowfall forecast issued 4pm Sat, Feb 14. Possible adjustments to be made Saturday night into early Sunday.

The jet stream will be critical in another regard too. We'll see quick clearing and warming with the jet cranking up on the heels of this system. The snow chance is from Sunday through late Monday, then the system will begin to clear Tuesday. Although not super cold, this is a chilly system. Monday highs in the 30s, lows in the teens and single digits for Monday night, then 30s again Tuesday. By Wednesday and Thursday we will have warmed quickly to the 40s and 50s.

Matt Makens

Matt Makens has won 5 Emmys for his weather coverage. He has the seal of approval from the NWA and is a certified Broadcast Meteorologist as designated by the AMS. He works for Colorado's Own Ch 2.

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