Sunday, February 27, 2011

Light Snow Across Metro Tucson Early This Morning

When I got up this morning it was raining here at the house (a bit after 5 am) but but after 5:30 am it began snowing very lightly and now the precipitation has ended here (6:30 am). The front, and attendant precipitation band, moved eastward very rapidly. The four graphics above show the surface plot (NCAR RAP) around 2 am (all times MST) and regional radar about the same time. the bottom two graphics show the same for just before 6 am (note that bottom radar shows composite radar product from TUS - since the RAP radar products use base-scan data, their regional plot becomes a real mess due to blockage as the precipitation band moved into southeast Arizona, where coverage is only from TUS radar).
Yesterday's WRF-GFS was within about about 2 hours of the frontal passage time (see early post below) at TUS (front moved by right around 3 am) and light snow began at the airport at 4:46 am. The lower surface chart shows that snow was occurring at Tucson, Nogales, and Ft. Huachuca at that time. At 6 am we had 0.24" in the gauge here and the eastern Pima County ALERT gauges indicate 100% coverage of precipitation. Amounts at 6 am were about 1/10 to 4/10s of an inch, with accurate readings not available where mostly, or all snow, fell. Temperatures across the metro area stayed just above freezing (again as forecast by yesterday's WRF) and there appears to be accumulations around the edges of the city, where elevations are a bit higher.

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