Winter Weather Forecast Checklist

[Jeff Snyder]

I ran across these two links a few minutes ago... There an interesting read for those who want to better their snowfall forecast technique(s) more than just taking model QPF and applying a snow:liquid ratio... It has information on the Lemo method, Garcia's method, Cook's method, etc.

http://speedy.meteor.wisc.edu/~swetzel/win...er/methods.html

http://www.crh.noaa.gov/sgf/papers/wwchklst.htm

 

[Alex Lamers]

I would be interesting in using the Magic Chart technique but I can't find net vertical displacement values anywhere. Does anyone know where I can find these or perhaps derive them from something else?

Otherwise the rest of those look familiar .... particularly the Garcia method which I use frequently.

...Alex Lamers...

 

[Robert Dewey]

I notice that none of these techniques take into account the instability that may or may not be present. Instability is one of the most important aspects... If you have good CSI, or even pure convective instability (theta-e surfaces folding in/decreasing with height), and you have a relatively unidirectional profile, then heavy banded snow is a good bet (provided you also have deep moisture and good frontogenesis or other form of lift). I often notice the Garcia method underpredicts values when it comes to big storms that take place in very cold air, due to the low mixing ratios. According to the Garcia method, this last snowstorm we had (which dropped 12-14 inches), predicted a max of around 6 inches, as mixing ratios never got above 2-2.5 g/kg.

 

[rdale]

Garcia revised his method after the New Years Day blizzard around 7 years ago, it was published on the CRH website as a tech attachment I think back around 2000.

- Rob

 

[Jeff Snyder]

Garcia revised his method after the New Years Day blizzard around 7 years ago, it was published on the CRH website as a tech attachment I think back around 2000.

- Rob

Here is Garcia's updated method:

http://www.crh.noaa.gov/techpapers/memos/T...116/TM-116.html

From the paper: "This paper briefly examines the Southeast Wisconsin Blizzard of January 2, 1999 and emphasizes the necessity of factoring in the snowfall to meltwater conversion when the "area of concern" is under the influence of a frigid air mass, before and during a heavy snow event. It also addresses how jet streaks and couplets significantly alter the original isentropic snowfall to mixing ratio relationship and suggests a new forecast scale for such events, based on six published papers and informal local studies conducted at WFO Sullivan."