1. Synoptic Patterns Responsible for Snowfall

2. A “Typical” NWFS Event: 10-11 Feb 2005
NWFS = Snowfall w/ 850 hPa NW ( °) Flow

3. Rising Air Motions
Sinking Air Motions

4. 11 Feb 2006: Heavy NWFS

5. Significant blowing and drifting of snow frequently occurs . . .

6. Leading to sizeable drifts on roads even during light events

7. Synoptic Ingredients of NWFS
Perry (2006), Ph.D. Diss.

8. Windward vs. Leeward Slopes in Periods of NWF
Perry and Konrad (2006), Climate Research

9. Accumulation During a Typical NWFS Event
Perry and Lee (2007), Unpublished

10. Annual Snowfall in the GSMNP, 1990-2004
Perry et al. (2007), Proceedings of the Eastern Snow Conference

11. 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

12. More Snow in the NC High Country

13. No Snow in the NC High Country

14. 25 Jan 2006 Radar
40+ cm in SE WV

15. Collaborative Efforts with Dr. Sandra YuterNW
Flow

16. MRR Summary: 17-19 Feb 2007 (5.5” snow, 0.24” swe, 23:1)
WSR-88D Coverage
Echo Tops < 6,000 ft

17. 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

18. MRR Summary: 15-16 Apr 2007 (4.4” snow, 0.48” swe, 9:1)
WSR-88D Coverage

19. 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

20. 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.

21. MRR Summary: 27-29 Feb 2008 (8.3” snow, 0.39” swe, 21:1)
WSR-88D Coverage

22. Skew-T Plots

23. 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

24. Byers 1965

25. Libbrecht 2007

27. 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

28. Questions?