1. Stephen Rodriguez, Jr. National Weather Service Chicago, IL

2. Introduction  Brief background.  Purpose of Study.  Synoptic background and forcing mechanisms.  Synoptic/Mesoscale features: Moisture, Forcing, Instability.  Conclusions.

3. Radar Storm Evolution

5. Observed Snowfall Totals CHICAGO

6. Wind Gusts/Visbys/Lightning 1/4 MILE VISBYS. 65 STRIKES!

7. Purpose of Study  Synoptic/Mesoscale Overview.  Pattern Recognition/Conceptual Models.  “How to Forecast” Blizzards?  What are we forecasting?

8. Purpose - NWS Blizzard Definition  Sustained wind or frequent gusts to 35 miles an hour or greater; and  Considerable falling and/or blowing snow (i.e., reducing visibility frequently to less than ¼ mile).  For a period of 3 hours or longer.

9. Purpose - Blizzard Elements  Heavy snowfall.  Snow efficiency.  Strong winds.

10. Synoptic Overview 300 MB 02/02/11 00Z

11. Synoptic Overview 700 MB 02/02/11 00Z

12. Synoptic Overview 850 MB 02/02/11 00Z

13. Synoptic Overview SFC 02/02/11 00Z

14. Synoptic Overview 02/02/00 00Z ROAB KDVN

15. 00Z Low/Isallobaric Component 03Z06Z

16. Well-Mixed Environment 04Z RUC Sounding

17. Moisture 850 MB Moisture Transport

18. Moisture TROWAL structure identifiable by 02Z-3Z. CHICAGO

19. Forcing - Deformation

20. Forcing - Isentropic Lift 22Z/00Z/02Z RUC 290K Persistent isentropic lift from late afternoon through late evening. CHICAGO

21. Forcing - Frontogenesis RUC 02Z ORD MSN EVV

22. Instability - EPV ORDEVVMSN RUC 02Z

23. Instability – CAPE/Lapse Rates 04Z RUC Sounding NORTH CENTRAL ILLINOIS

24. Snow Efficiency NORTH CENTRAL ILLINOIS 00Z-03Z

25. Conclusions - Review  Copious amounts of moisture.  Persistent strong forcing due to both synoptic/meso forcing mechanisms.  Instability – an added benefit.  Snow efficiency.

26. Conclusions – Key Factors  Heavy Snowfall – Yes!  Snow efficiency – Yes!  Strong winds – Yes! Yes! Yes!!!

27. Blizzard Climatology

28. Conclusions – Lessons Learned  Stick to “base” data.  Pattern Recognition of three elements.  All come together – Blizzard.

29. Questions?  References:  NOAA/NWS/Storm Prediction Center  Schwartz, 2001.