A question for Garth F.; 'favorable orographics'

I hope Garth Ferber might be persuaded to offer a little insight into the term 'favorable orographics' as applied to potential new snow. I see the term, or more likely this year, its opposite in the NWAC mountain forecasts from time to time, and the following questions occur to me:<br><br>What factors are important in creating favorable orographics? What factors lead to unfavorable orographics?<br><br>Do these terms, as used in the forecasts apply east of the Cascade crest? That is, after the air has already been orograpically lifted as much as it's going to be.<br><br>My various teachers always told me that there is no such thing as a dumb question, but maybe I'll prove them wrong yet! <br><br>Larry

Well, I'm not Garth, but can give an abbreviated answer. Orographics is short for orographic lift, or air being forced to rise over some sort of terrain feature (mountains). Since the Cascades run N-S, westerlies (wind from the west) is the best for driving moist air into the mountains. Usually the stronger the better. Some instability in the mid-upper troposphere is also helpful (an upper level trough, or cold air above warmer air), so once the air gets going upwards, it keeps rising because it is warmer than the surrounding air. So the two best things are instability and strong westerlies. This is typically the situation after a cold front moves through and the lagging upper level trough follows (and for stronger events a convergence zone will form as the westerlies are diverted around the Olympics and down the strait).<br><br>They usually don't apply to places east of the crest, since most of the moisture is already precipitated out before the air gets there. But sometimes storms can ride over the Cascades in a ridge, or a 'dirty ridge', then move down the backside of the Cascades in eastern Washington. In this case, wrap around moisture might do something similar on the east slopes. Or a storm might move from south west to northeast from Oregon into eastern Washington. I think this is faily common along the Front Range in Colorado, and along the Bridger range in Montana - Bridger Bowl's biggest dumps are ones that slide down east side of the mountains from the north.

Matt explained it well. Not being a trained weather geek, my interpretation of NWAC mountain forecasts is the result of a sort of "code breaking" over many years of observation. The real weather guys decode patterns in the weather; I decode patterns in what the weather guys say. My translation for "favorable orographics" would be instability plus a convergence zone, like Matt said.<br><br>I realized that I was becoming sort of a weather geek myself when I described the snow condition on a tour--with a completely straight face--as having an "unfavorable density profile." My ski partner (from another part of the country) just about split a gut. I thought, "What, doesn't everybody talk that way?"<br><br>Obviously, I've spent too much time reading Garth's (and Mark's and Kenny's) forecasts.  

Good answers that I don't need to add much to. Maybe I have spent to much time writing forecasts. I use the term orographic flow here in the Northwest for significant westerly flow and moisture. Instability usually follows cold fronts in the flow and contributes to snowfall with a cooling trend. There can also be a lot of west flow and relatively stable moisture that accompanies a warm front with a warming trend.

By the way its a little scary when I log into the TAY see my name right away in the discussion topics. ???