Synoptic Patterns Responsible for Snowfall
A “Typical” NWFS Event: 10-11 Feb 2005 NWFS = Snowfall w/ 850 hPa NW (270-360°) Flow
Rising Air Motions Sinking Air Motions
11 Feb 2006: Heavy NWFS
Significant blowing and drifting of snow frequently occurs . . .
Leading to sizeable drifts on roads even during light events
Synoptic Ingredients of NWFS Perry (2006), Ph.D. Diss.
Windward vs. Leeward Slopes in Periods of NWF Perry and Konrad (2006), Climate Research
Accumulation During a Typical NWFS Event Perry and Lee (2007), Unpublished
Annual Snowfall in the GSMNP, 1990-2004 Perry et al. (2007), Proceedings of the Eastern Snow Conference
57 48 Low-level southeast flow attributed the least amount of snowfall for both high and lower elevations. Southeast flow into the Smoky Mountains produce downslope conditions, especially for the lower elevations of east Tennessee. 1 5
More Snow in the NC High Country
No Snow in the NC High Country
25 Jan 2006 Radar 40+ cm in SE WV
Collaborative Efforts with Dr. Sandra Yuter NW Flow
MRR Summary: 17-19 Feb 2007 (5.5” snow, 0.24” swe, 23:1) WSR-88D Coverage Echo Tops < 6,000 ft
MRR Summary: 17-19 Feb 2007 (5.5” snow, 0.24” swe, 23:1) 0.1” 0.01” 10:1 1.6” 0.09” 18:1 2.8” 0.12” 23:1 0.5” 0.01” 50:1 0.5” 0.01” 50:1
MRR Summary: 15-16 Apr 2007 (4.4” snow, 0.48” swe, 9:1) WSR-88D Coverage
MRR Summary: 15-16 Apr 2007 (4.4” snow, 0.48” swe, 9:1) 3.9” 0.40” 10:1 0.5” 0.08” 6:1 Graupel
2007-2013 Snow Season Activities Model Analysis – Compare numerical model output (QPF, moist layer thickness, and moist layer temperature profiles) to observations on Poga Mountain; includes balloon releases (w/ D. Miller). Snow Density – Relate snow density observations to meteorological parameters and develop guidelines for forecasting snow density (crucial for forecasting snowfall). Spatial Patterns – Utilize a dense network of volunteer precipitation observers as part of the CoCoRaHS network to improve understanding of the spatial patterns of snowfall.
MRR Summary: 27-29 Feb 2008 (8.3” snow, 0.39” swe, 21:1) WSR-88D Coverage
Skew-T Plots
MRR Summary: 1-2 Mar 2009 (11.1” snow, 0.94” swe, 12:1) 3.9” 0.40” 10:1 0.5” 0.08” 6:1 Graupel
Byers 1965
Libbrecht 2007
Summary and Conclusions Spatial patterns of NWFS are strongly controlled by topography. Over 50% of mean annual snowfall at higher elevations and along windward slopes occurs in association with low-level NW flow. Antecedent upstream air trajectories with a Great Lakes connection help to enhance snowfall. Ongoing research on Poga Mt. in Flat Springs, NC, has highlighted the following: Shallow and convective nature of NWFS. Exceptional snow density variability. Dominance of NWFS
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