1	NOAA’s National Weather Service Improving Forecast Techniques and Procedures For Significant Lake Effect Snow Bands Across Northern New York and Vermont.
2	Discuss Items Examine 10 Year Statistics (Storm Data, WES Cases, WFO Buf website) Lake Effect Impacts (Transportation, Economy) Discuss Two Events (Hybrid/Traditional) Hybrid Arctic/Warm Front Enhancing multi lake effect snow band from Lake Ontario Traditional (well organized/quasi-stationary single band on sw flw/interacts with arctic boundary) Roles of Low-Level Boundaries in moving band downwind of Lake Ontario Useful Forecasting Parameters (snowfall rates/amounts/duration) -Shear, Instability, Lift, Moisture
3	Events vs. Months
4	Snowfall vs. Frequency
5	Events vs. Years
6	Forecast Problems? Horizontal displacement of heavy lake effect snow squalls up to 350 km down wind of Lake Ontario Intensity of lake effect snow band (rate of snowfall) Impacts of strong low level winds on snowfall accumulations
7	Useful Forecasting Parameters Treat very much like convection (Moisture, Instability, Lift, Shear) Moisture (1000-700mb), PWS, Sfc Dwpts Instability (Lake Induced Capes, 1000-700mb Lapse Rates)
8	Useful Forecasting Parameters Examine Low Level Shear/Wind Fields (Bufkit soundings, convective worksheets from AWIPS, and UA data analysis Cloud Base (CCL) to Echo Top Shear (0.5-3.0km) Magnitude of low level wind field very important to horizontal displacement of significant snowfall downwind of Lake Ontario Lift (enhanced by sfc boundary (warm or cold front), SW upslope flw)
9	Topo Map of CWA
10	6 Feb 2006 Event Well established single lake effect snow band (eventually interacted with arctic boundary) Caused numerous problems across our CWA (I-89, I-87 closed due to multi car accidents) Snowfall rates of up to 4 inches per hour, along with near zero visibilities Produced warning criteria snowfall across our CWA 300km downwind of Lake Ontario
11	Water Vapor 02-22z
12	250mb 12z 02/06/06
13	500mb 12z 02/06/06
14	850mb 12z 02/06/06
15	13z Surface
16	Vis Sat Loop 12z Thru 17z
17	Mosaic 15z thru 21z
18	12Z BUF Sounding 4 to 6 hrs Prior to Event
19	12Z Modified Buf Sounding Adjusted for Lake Temp of 36F
20	12z Buf Hodograph
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22	1-3km Cumulative Shear (RUC 40km at 18z)
23	1000-700mb Lapse Rates (RUC 40km at 18z)
24	1000-700mb Relative Humidity (RUC 40km at 18z)
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28	Improving Lake Effect Snow Forecasting Develop AWIPS procedures with colors/images displaying favorable lake effect parameters Increase forecaster situational awareness of lake effect events Develop checklist/decision tree very much like severe weather checklist Moisture, lift, shear, instability
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32	Near Whiteout Conditions Light winds within heaviest lake effect band (UVV’s/low level convergence) Large snowflake size (per max upward motions in saturated cloud layer in favorable dendritic snow growth region) Low snow density led to quick snowfall accumulations
33	Accident Near Swanton on I-89
34	Conclusion Cloud layer wind around 40 knots aided to transfer moisture/band 200-300km downwind of Lake Ontario Well established cutoff circulation from Sfc to 250mb led to limited shear and helped to transfer significant lake effect snow 200-300 km downwind of Lake Ontario Uni-directional flow between 250-260˚ Cloud layer (0.5-3km) shear (CCL to Echo Top)≤ 30˚ Favorable for single well organized band (Niziol 1987) 30˚ to 60˚ of shear multi band event/un-organized/less propagation downwind (Produces less snowfall amounts and rates) (Niziol 1987)
35	Conclusion Conts. Surface wind ≤ 20 knots enhances moisture and increases parcel time over the warmer waters Surface wind > 20 knots increases crystal fragmentation on the ground and causes higher snow density (less accumulation) (Roebber and Schultz 2002) >80% RH values between 1000-700mb and in favorable dendrite snow growth region with upward vertically velocities enhances snowfall accumulation rates Surface dewpoints near 20F and PW around 0.30” Southwest low level flow is enhanced by upslope lift from the Adirondacks and Western Slopes of The Green Mtns >8.0˚C/km 1000-700mb lapse rates and CAPE values between 200-400 J/kg create deep layer instability for convective bands producing very heavy snowfall rates Sfc front combined with strong 5h PVA helped to enhance lift and transfer significant snowfall 300 km downwind of Lake Ontario
36	Future Work Develop composite study of events from past 10 years Examine more sounding/real-time data Develop rules of thumb for lake effect snow events, along with checklist Continue with spread sheet of significant lake effect parameters