1. A Case Study of the 18 th January 2015 High-Impact Light Freezing Rain Event Across the Northern Mid-Atlantic Region Heather Sheffield Meteorologist Steven M. Zubrick Science Operations Officer NOAA/NWS Weather Forecast Office, Sterling, VA

2. Storm Total Summary January 18, 2015 = Ice-related incident Credit: Google Earth Harford Baltimore Howard

3. Selected Impacts- Maryland Howard County 49-car pile up on a down-hill slope towards the Patapsco River on Highway 40 Baltimore County 30-car pile up near the intersection of Highway 40 and I-70 Accident involving a Maryland Transit Administration (MTA) bus in western Baltimore Harford County Accident in Forest Hill resulting in one fatality and three injuries

4. Outline Meteorology Pre-event conditions Synoptic & meso-scale Observations and radar Model Performance MOS guidance Nam soundings Hi-resolution models HRRR, RAP and SSEO  Summary

5. Pre-event Jan 2015 Weather The coldest Jan1-Jan17 Average Minimum Temperature in the last 15 years (2000-2015)

6. Synoptic Overview…

11. Observations…

12. 00 Z Baltimore

13. 06 Z DC PHL Wilmington Martin State Temperatures have dropped into the U20s L30s along and west of I-95 Variable winds in E PA/S NJ Baltimore

14. 09 Z Temperatures have risen to above freezing around DC and south of Baltimore MD Light winds become NE DC Baltimore

15. 12 Z Temperatures have increased across the Baltimore/DC metropolitan region Light NE winds continue in E PA and S NJ DC Baltimore Traffic accidents occurred between 11-12Z…So what happened?

16. 12z IAD RAOB Road temps 28-33 degrees around Baltimore- MD Chart

17. 09Z <32° >32° DC Baltimore

18. 12Z <32° >32°

19. Radar Loop 0954-1229Z KLWX 88D 0.5 deg Base Refl

20. 9:54Z

21. 9:59Z

22. 10:04Z

23. 10:09Z

24. 10:14Z

25. 10:19Z

26. 10:24Z

27. 10:29Z

28. 10:34Z

29. 10:39Z

30. 10:44Z

31. 10:49Z

32. 10:54Z

33. 10:59Z

34. 11:04Z

35. 11:09Z

36. 11:14Z

37. 11:19Z

38. 11:25Z

39. 11:31Z

40. 11:37Z

41. 11:43Z

42. 11:48Z

43. 11:54Z

44. 12:00Z

45. 12:06Z

46. 12:12Z

47. 12:17Z

48. 12:23Z

49. 12:29Z How did the models perform?

50. Model Performance MOS Guidance NAM soundings at KMTN and KILG HRRR and RAP forecast Courtesy G. Manikin, NOAA/NWS Environmental Modeling Center SPC SSEO forecast

51. MOS Guidance

52. 12 Z KILG-Wilmington KMTN-Martin State

53. KMTN/KILG 1200Z 00z NAM Run

54. 00,03,06z RAP/HRRR Forecasts VT 12z SUN PRECIP TYPE Courtesy: G. Manikin, NCEP/EMC

55. HRRR Forecasts valid 12z Sunday Courtesy: G. Manikin, NCEP/EMC

56. HRRR Forecasts valid 14z Sunday Courtesy: G. Manikin, NCEP/EMC

57. SPC Storm Scale Ensemble of Opportunity- SSEO 10z 11z 12z 13z 14z 15z Run 150117 12z

58. Summary Traffic accidents occurred due to light freezing rain Cold early January 2015 for Baltimore Radiational cooling may have caused pressure differences and led to a NE flow from E PA/S NJ Light radar echoes moved across I-95 as warm air advection occurred a few hundred feet off the surface Upstream forecast soundings may have hinted at future conditions in northeast Maryland Hi-res models showed freezing rain, especially HRRR, RAP and SSEO MOS: GFS and NAM too cold Potential freezing rain events require a high level of situational awareness Monitor all surface observations, METARs, road temps and mesonets

59. Summary Northeast flow from E PA/S NJ settled in valleys where the ground was very cold =Ice-related Incidents Northeast MD topography

60. Acknowledgments Steve Zubrick, NWS Sterling Brian LaSorsa, NWS Sterling James Lee, NWS Sterling Geoff Manikin, NOAA/NWS Environmental Modeling Center Questions?