Photo by Charley Knoderer


Procedure Descriptions:







Snowfall relative to Upper Level Features


  1. Synoptic Climatologies


  2. Goree and Younkin 1966: Used 50 cases 1963-65 (including 50 developing or occluding which reached severe intensity). Good old fashioned study. Results are based on hand analysis using storm relative coordinates.

    They found the most favorable location for the occurrence of heavy snow to be:

    Browne & Younkin (1970): Used 81 heavy snow occurrences between 1965-67. Related heavy snow to the 850mb low center


  3. Koontz "Heavy Snow Forecasting Aids"







Cook Method (Cook, 1980)



Amount of snow:

Location of snow:

Type of precipitation:
see the temperature section under forecast ingredients.

Additional notes:


Cloudiness and precipitation increase under warm advection 
and decrease under cold advection at 200mb.

One need not to worry about moisture in developing storms.  
If the dynamics are strong, moisture will find its way into 
the storm.  Initially dry conditions serve only to delay the 
precipitation a few hours.

Cold advection in mid-troposphere (700mb) indicates downward 
motion and warm advection upward motion.  use this to adjust 
the forecast derived from the 200mb chart.

Warm air at 200mb reflects cold air at 500mb. If the storm is 
not strong enough to affect the 200mb temps, heavy snow 
usually doesn't occur.

Expect continued digging if the cold pocket at 200mb is 
southeast of 500mb low; expect recurvature if the cold pocket 
at 200mb is northeast of 500mb low.

The vorticity maximum at 500mb tends to move toward 200mb cold 
pockets.  If the 200mb cold pocket develops northeast of a 500mb 
low, the low will recurve in 24 hours.  

The 200mb warm pocket usually coincides with 500mb vorticity 
maximum, especially in well-developed systems.  

The direction of movement of a vorticity maximum at t = 12 
to t = 36 hours will be parallel to a line connecting 200mb 
warm and cold pockets at t = 0.  

If the 200mb warm pocket is ill-defined or shows an elongated 
warm sector then the 500mb vorticity maximum is used as the 
200mb warm pocket.  

Limitations:

Do not use for large scale cyclonic flow over North America 
with short waves moving through or cutoff lows in SW US that 
have been stationary for 24 hours.  

For winter storms only (mid october - march 10).  

Don't use near lakes, hills, mountains.





Garcia Method



from Garcia (1994):




The Technique (Garcia, 1994): Description of steps to predict snowfall amounts


Appendix B from Garcia (1994): "Rules of Thumb" for heavy snow placement



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