1. The March 01/02 Non-Winter Weather Event: Part 1 Michael W. Cammarata Anthony W. Petrolito

2. WWA Timeline 507 AM EST Sat Feb 28 2009 Winter Storm Watch valid Sun March 1 Winter Storm Watch valid Sun March 1 700 pm EST through Mon March 2 700 am EST 700 pm EST through Mon March 2 700 am EST Far North Midlands (Lancaster, Chesterfield, Fairfield) Far North Midlands (Lancaster, Chesterfield, Fairfield) Potential for 1 – 3 in of Snow Potential for 1 – 3 in of Snow

3. WWA Timeline 347 PM EST Sat Feb 28 2009 Winter Storm Watch Continued for far northern Midlands from Sun Mar 1 1200 pm EST through Mon March 2 700 am EST Winter Storm Watch Continued for far northern Midlands from Sun Mar 1 1200 pm EST through Mon March 2 700 am EST Potential for 1 – 3 in of Snow Potential for 1 – 3 in of Snow Winter Weather Advisory issued for central Midlands from Sun Mar 1 1200 pm EST through Mon March 2 Winter Weather Advisory issued for central Midlands from Sun Mar 1 1200 pm EST through Mon March 2 700 am EST 700 am EST Up to 1 in of Snow Up to 1 in of Snow

4. WWA Timeline 357 AM EST Sun Mar 1 2009 All counties in the previous issuance (northern and central Midlands) were upgraded to Winter Storm Warning from Sun Mar 1 400 pm EST through Mon March 2 700 am EST All counties in the previous issuance (northern and central Midlands) were upgraded to Winter Storm Warning from Sun Mar 1 400 pm EST through Mon March 2 700 am EST 3-6 inches of Snow northern Midlands 3-6 inches of Snow northern Midlands 2-4 inches of Snow western Midlands 2-4 inches of Snow western Midlands 2 inches of Snow Columbia Metro Area 2 inches of Snow Columbia Metro Area Winter Weather Advisory issued for remainder of CWA (southern Midlands and CSRA) from Sun Mar 1 1200 pm EST through Mon March 2 700 am EST Winter Weather Advisory issued for remainder of CWA (southern Midlands and CSRA) from Sun Mar 1 1200 pm EST through Mon March 2 700 am EST Up to 1 inch of Snow Up to 1 inch of Snow

5. What Happened? Not too much 1 – 2 inches of snow in Lancaster County 0.5 inches of snow in Whitmire in Newberry County Trace in Columbia metro area

6. Objective of this presentation To arrive at an assessment of the certainty of snow for this event To arrive at an assessment of the certainty of snow for this event

7. HPC WWD Graphics issued 1254 am EST Sat Feb 28 2009 for the period 700 am Sunday Mar 01 2009 to 700 am Monday Mar 02 2009

8. HPC WWD Graphics issued 1227 pm EST Sat Feb 28 2009 for the period 700 pm Sunday Mar 01 2009 to 700 pm Monday Mar 02 2009

9. HPC WWD Graphics issued 1140 pm EST Sat Feb 28 2009 for the period 700 am Sunday Mar 01 2009 to 700 am Monday Mar 02 2009

10. SREF 21-hr forecast probability categorical snow (%) valid 700 pm EST Sunday Mon March 01 2009 Low snow probabilities central and east midlands 10 20 30 40 50 60 70

11. SREF 21-hr forecast probability categorical rain (%) valid 700 pm EST Sun March 01 2009 Highest rain probabilities across the Eastern Midlands 10 20 30 40 50 60 70 80

12. SREF 24-hr forecast probability categorical snow (%) valid 1000 pm EST Sun March 01 2009 Snow probabilities CAE CWA 60-70% Highest snow probabilities in the SC/NC Piedmont 10 20 30 40 50 60 70 80

13. SREF 24-hr forecast probability categorical rain (%) valid 1000 pm EST Sun March 01 2009 Low probabilities rain across CAE CWA at 03z. Probabilities favored snow over rain 10 20 30 40 50 60 70 30

14. NAM12 3-hr QPF (in.) and mean sea level surface pressure valid 1000 pm EST Sun March 01 2009 0.25-0.50 inches QPF forecast across Western Midlands and Piedmont

15. GFS40 6-hr QPF (in.) and mean sea level surface pressure valid 100 am EST Mon March 02 2009 GFS QPF similar to NAM with highest amounts West and North of CAE Models show sufficient QPF for accumulating snowfall across Central South Carolina/CSRA of Georgia with higher amounts north and west of CAE.

16. SREF 03-hr forecast mean sea level pressure and precipitable water (in.) valid 100 am EST Sun March 01 2009 Surface low over South Central Georgia

17. SREF 12-hr forecast mean sea level pressure and precipitable water (in.) valid 1000 am Sun March 01 2009 Surface low tracking northeast along SC coast Climatological favorable surface low track for heavy snow in central SC/CSRA is across central Florida Climatologically favored storm track

18. BUFKIT CAE Sounding and Precipitation Type Nomogram from 700 pm EST Sat Feb 28 run of NAM12 valid at 1000 pm EST Sun Mar 01 2009

19. BUFKIT CAE Time Section Overview 700 pm EST Sat Feb 28 2009 run of NAM12

21. BUFKIT CAE 2m T and Precipitation from 700 pm EST Sat Feb 28 2009 run of NAM12

22. BUFKIT CAE Energy Precipitation type diagram NAM12 23-hr forecast valid 6 pm Sunday evening Mar 01 2009

23. BUFKIT CAE Energy Precipitation type diagram NAM12 24-hr forecast valid 7 pm Sunday evening Mar 01 2009

24. BUFKIT CAE Energy Precipitation type diagram NAM12 25-hr forecast valid 8 pm Sunday evening Mar 01 2009

25. BUFKIT CAE Energy Precipitation type diagram NAM12 26-hr forecast valid 9 pm Sunday evening Mar 01 2009

26. BUFKIT CAE Energy Precipitation type diagram NAM12 29-hr forecast valid 12 am Mon Mar 02 2009

27. GFS MOS Guidance 700 pm EST model run Sat Feb 28 2009 Columbia, SC. GFS MOS Guidance 700 pm EST model run Sat Feb 28 2009 Columbia, SC. Temperatures above freezing from 0000-0600 UTC. 6-hr Probability of Precipitation 71 % ending at 0600 UTC. Conditional Probability of Snow 70-85 % from 0000-0600 UTC. Conditional Precipitation type from 0000-0600 UTC = snow. 24-hr snowfall accumulation ending at 1200 UTC = none to a trace.

28. NAM MOS Guidance 700 pm EST model run Sat Feb 28 2009 Columbia, SC. Temperatures at or above freezing from 0000-0600 UTC. 6-hr Probability of Precipitation 84 % ending at 0600 UTC. 24-hr snowfall accumulation ending at 1200 UTC = none to a trace.

29. CAE Hourly Temperature verification vs. GFS/NAM MOS Guidance 700 am EST Sun March 01 2009 to 900 am EST Mon March 02 2009 Guidance and observed temperatures were above freezing during the critical time period when snow was possible. RA RA RA RA RA RA RA RA RA RA RA RA RA RA UP SN UP Rain was the predominant precip type during the event. Brief period of light snow at the end of the event.

30. Soil/Surface Temperatures The three days preceding the event were relatively mild. Max and Min temperatures at CAE were as follows: The three days preceding the event were relatively mild. Max and Min temperatures at CAE were as follows: Feb 26 69 46 Feb 26 69 46 Feb 27 69 52 Feb 27 69 52 Feb 28 64 48 Feb 28 64 48 Soil temperatures were in the low to mid 50s Soil temperatures were in the low to mid 50s

31. So what can we say about certainty? Storm track was not the climatologically favored track Storm track was not the climatologically favored track Reliance upon wrap around precipitation on back side of dry slot in weak cold advection Reliance upon wrap around precipitation on back side of dry slot in weak cold advection Model forecasts did show adequate moisture in snow growth region and ample QPF Model forecasts did show adequate moisture in snow growth region and ample QPF Above freezing layer near surface Above freezing layer near surface

32. So what can we say about certainty? Mild weather prior to event and warm soil temperatures would be an inhibiting factor to snow accumulation Mild weather prior to event and warm soil temperatures would be an inhibiting factor to snow accumulation SREF probabilities favored snow but were not certain SREF probabilities favored snow but were not certain MOS Temperature forecasts were above freezing during the time of expected snow MOS Temperature forecasts were above freezing during the time of expected snow Energy Precipitation Type diagrams indicate that surface based warm layer would be a significant inhibiting factor for accumulating snow especially at CAE Energy Precipitation Type diagrams indicate that surface based warm layer would be a significant inhibiting factor for accumulating snow especially at CAE

33. The End (Part 1) Questions?

34. BUFKIT CLT Sounding and Precipitation type Nomogram (NAM12 27-hr forecast) valid 10 pm EST Sunday March 1

35. BUFKIT CLT Overview – from the 700 pm EST NAM model run Sat March 01 2009

37. BUFKIT CLT Energy Ptype diagram from 0000 UTC run of NAM March 1 2009

40. UZA GFS MOS Guidance 0000 UTC Sun March 01 2009 Rock Hill, SC. Temperatures at or above freezing from 0000-0600 UTC. 6-hr Probability of Precipitation 77 % ending at 0600 UTC. Conditional Probability of Snow 73-83 % from 0000-0600 UTC. Conditional Precipitation type from 0000-0600 UTC = snow. 24-hr snowfall accumulation ending at 1200 UTC = > trace < 2 inches.

41. UZA NAM MOS Guidance 0000 UTC Sun March 01 2009 Rock Hill, SC. Temperatures above freezing from 0000-0600 UTC. 6-hr Probability of Precipitation 89 % ending at 0600 UTC. 24-hr snowfall accumulation ending at 1200 UTC >= 8 inches.

42. UZA Hourly Temperature verification vs. GFS/NAM MOS Guidance 700 am EST Sun March 01 2009 to 0900 am EST Mon March 02 2009 Guidance and observed temperatures were at or above freezing during the critical time period when snow was possible. Rain mixing with snow at times early in the event…then a change over to snow after 700 pm. UP RA RA RA RA RA RA RA SN RA RA RA SN SN SN SN SN SN SN