Denver Area Snowfall Event Feedback

David Barjenbruch, a forecaster at the Denver/Boulder WFO working with SPoRT and NESDIS to evaluate the NESDIS Snowfall Rate product this winter, provided a nice case study for consideration.  He writes:

We received more snow across the Front Range of Colorado on Wednesday, January 21, and just wanted to attach a few comparisons of SFR, radar, obs, and METARS.  At 17Z, the SFR unfortunately missed the moderate snow across the Denver metro area (KDEN…1mm water in last hour…and KBJC 1/2 mile visibility in moderate snow, and 1/4 mile at KAPA…0.8mm water in last hour). Area of main concern is highlighted in pink, while at the same time it also overestimated snow toward the east toward ITR in eastern Colorado.

Comparison between radar and SFR product at 17Z on 21 Jan 2015

Comparison between radar (left) and SFR Product (right) at 17Z on 21 Jan 2015.  Circled area denotes region where SFR missed accumulating precipitation in the Front Range.  SFR overestimates snow in eastern CO.

 

Comparison between radar and SFR at 20Z on 21 Jan 2015.

Comparison between radar (left) and SFR Product (right) at 20Z on 21 Jan 2015.  SFR captures some of the snow in southern CO but continues to overestimate snowfall in parts of eastern CO.

After a fairly widespread precipitation event Wednesday morning, the snow turned more convective in the afternoon.  Checking the 2320Z radar, we had an intense convective cell which moved southwest across the western sections of the Denver metro area (highlighted in pink again).  This particular cluster of convection produced anywhere from 1.5 to 3″ of snow (2-5.5mm water) in an hour or less.

Comparison between radar and SFR Product at 2320Z on 21 Jan 2015.

Comparison between radar and SFR Product at 2320Z on 21 Jan 2015.  Circled area denotes convective snowfall that was not captured by the SFR.

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