Terpeast Posted December 15, 2012 Share Posted December 15, 2012 Does anyone have a group of sfc to mid-upper air maps of big front range snowstorms? I want to learn how to recognize a good set up for a significant front range storm a few days out on the models. Thanks! Link to comment Share on other sites More sharing options...
baroclinic_instability Posted December 15, 2012 Share Posted December 15, 2012 Don't have a list myself, but the setup that undoubtedly favors the Front Range more than any other is a closed low across the 4 corners and an arctic front diving through the High Plains. That supports a northerly barrier jet and a easterly upslope flow...which can result in epic snowstorms for them. Link to comment Share on other sites More sharing options...
baroclinic_instability Posted December 15, 2012 Share Posted December 15, 2012 Here you go. Some big events for them. You will notice something similar among all events...deep closed low over the 4 corners, long period of preceding leeside troughing and a favorable trajectory off the GOM. December 20, 2006. http://www.meteo.psu...2006/us1220.php December 28, 2006: http://www.meteo.psu...2006/us1228.php December 24, 1982: http://www.meteo.psu.edu/~fxg1/NARR/1982/us1224.php The mother of them all, March 17-19 2003: http://www.meteo.psu...2003/us0318.php Link to comment Share on other sites More sharing options...
Terpeast Posted December 15, 2012 Author Share Posted December 15, 2012 Here you go. Some big events for them. You will notice something similar among all events...deep closed low over the 4 corners, long period of preceding leeside troughing and a favorable trajectory off the GOM. December 20, 2006. http://www.meteo.psu...2006/us1220.php December 28, 2006: http://www.meteo.psu...2006/us1228.php December 24, 1982: http://www.meteo.psu...1982/us1224.php The mother of them all, March 17-19 2003: http://www.meteo.psu...2003/us0318.php Thanks for those! Looks to me that the jet stream splits before reaching the west coast, spawning off a closed low over the 4 corners while a neg tilted blocking ridge over the great lakes slows the flow down, allowing the storm to sit there for a bit. What strikes me as unique is that the thicknesses and 850mb temps seem quite warm in each case... for example March 2003 showed 540 thicknesses all the way up in Montana. I'm used to 540 thicknesses and 0 C 850mb temps as a general rule for snowstorms in the east... anything warmer than that would definitely result in rain. Maybe it is different in Colorado... could be a dumb question...do they use 700-850 or 500-850 thicknesses to determine ptype rather than 500-1000 due to elevation? Link to comment Share on other sites More sharing options...
baroclinic_instability Posted December 15, 2012 Share Posted December 15, 2012 Thanks for those! Looks to me that the jet stream splits before reaching the west coast, spawning off a closed low over the 4 corners while a neg tilted blocking ridge over the great lakes slows the flow down, allowing the storm to sit there for a bit. What strikes me as unique is that the thicknesses and 850mb temps seem quite warm in each case... for example March 2003 showed 540 thicknesses all the way up in Montana. I'm used to 540 thicknesses and 0 C 850mb temps as a general rule for snowstorms in the east... anything warmer than that would definitely result in rain. Maybe it is different in Colorado... could be a dumb question...do they use 700-850 or 500-850 thicknesses to determine ptype rather than 500-1000 due to elevation? Personally, I do not use thicknesses at all...so I am not the person to ask. But the typical thicknesses used out east will definitely not work in CO since the Front Range elevations range from 5000 feet to 7000 feet. With any closed low you can expect the thicknesses to be warmer than what you will expect. As for upper levels, you are right. There is no magic to what creates a good storm for the Front Range...they like slow moving closed lows and a persistent northerly low level flow. GOM moist air cools moist adiabatically quite a bit by the time it ascends the barrier jet, so it may be surprising how warm the 850T's might be while still supporting snow. Link to comment Share on other sites More sharing options...
Chinook Posted December 15, 2012 Share Posted December 15, 2012 They say thicknesses should be 552dm in this area. It actually doesn't matter too much. I have never seen rain from December 1st to February 28th here. Heavy freezing rain or sleet is not an issue. Temperatures at or around 700mb cannot have a melting layer to +3C or +5C for an ice storm. If 700mb is something like -5C, then likely the surface will cool to 0C by wet bulb. In every setup where we are getting precipitation, 700mb has been -5C or much colder, and the bergeron process is working well in the clouds above 700mb. Our only rain/snow question marks have been in October, March, and April. (maybe in November.) Even then, it tends to snow because the upper level system is cold. Link to comment Share on other sites More sharing options...
Terpeast Posted December 15, 2012 Author Share Posted December 15, 2012 This is very helpful, thanks guys. Link to comment Share on other sites More sharing options...
Chinook Posted December 15, 2012 Share Posted December 15, 2012 http://www.fortcollins.salsite.com/FortCollinsSnowstorms.htm You can look up charts for these (I don't have any charts for these on my web page) http://www.greatlakes.salsite.com/snowfall/20100325_colorado.png http://www.greatlakes.salsite.com/snowfall/20100220.png http://www.greatlakes.salsite.com/snowfall/20100425_colorado.png http://www.greatlakes.salsite.com/snowfall/20100513.png http://www.greatlakes.salsite.com/snowfall/20111028.png http://www.greatlakes.salsite.com/snowfall/20111104.png http://www.greatlakes.salsite.com/snowfall/20111204.png http://www.greatlakes.salsite.com/snowfall/20120205_colorado2.png Link to comment Share on other sites More sharing options...
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