1. Better Forecasting Bureau
Forecasting Lake-effect Snow
November 10, 2011

2. What do we look at? Temperature difference Wind direction & wind shear
Moisture
Convergence/ lift

3. Temp difference
Ideally you want the temperature difference between the lake surface and 850 mb at least 13°C
Only a little warm air advection is good
Heat fluxes
Wind speed
Temperature differences

4. Wind direction Determines the type of lake-effect Long fetch is best
LLAP bands
Wind parallel rolls
Tea kettle (land breeze)
Vortices
Long fetch is best
Might have lake-to-lake connection
i.e. Georgian Bay, Lake Huron

5. Wind shear Less than 30° directional shear is best
Too much speed shear isn’t good for the band either

6. Moisture Boundary layer moisture at least 70%
No moisture, no lake-effect (simple as that)
Moisture from upstream can enhance moisture over the lake

7. Convergence Orographic lift Land breezes Frictional shear Tug Hill
Chautauqua Ridge
Land breezes
Frictional shear

8. Making the forecast Look at current obs! Look upstream
Look at everything else we mentioned (RUC & BUFKIT may help)

9. BUFKIT & Lake-effect Check current lake temp

10. Other sites worth checking
SPC Mesoanalysis
HRRR model
NWS Buffalo’s locally-run WRF model