EV Posted June 16, 2004 Share Posted June 16, 2004 I'm trying to get a read on weather forecasts for this weekend. Now, instead of listing the freezing level on the Rainier forecast, they are showing the snow level. QUESTION: What is the difference between freezing level and snow level? Thanks. Quote Link to comment Share on other sites More sharing options...
iain Posted June 16, 2004 Share Posted June 16, 2004 Snow level is generally considered to be around 1000' below the forecasted freezing level Quote Link to comment Share on other sites More sharing options...
EV Posted June 16, 2004 Author Share Posted June 16, 2004 Thanks, Iain Quote Link to comment Share on other sites More sharing options...
robert Posted June 16, 2004 Share Posted June 16, 2004 They report a freezing level when there is no forecast for precip. If there is then they report a snow level. Here is from the current NWS Cascades forecast. THURSDAY NIGHT...CLEAR. FREEZING LEVEL 11000 FEET. EAST WIND IN THE PASSES AROUND 15 MPH. FRIDAY...MOSTLY SUNNY. CHANCE OF SHOWERS IN THE AFTERNOON. SNOW LEVEL 9000 FEET. Quote Link to comment Share on other sites More sharing options...
Ricardo_Montalban Posted June 16, 2004 Share Posted June 16, 2004 there's also a 'free air freezing level', which is the freezing level when there are no earth obstructions interfering with the local wind (etc.?) patterns. i have no idea how to relate the FAFL reading to what is happening on the mountain. anyone... anyone... Quote Link to comment Share on other sites More sharing options...
gslater Posted June 16, 2004 Share Posted June 16, 2004 there's also a 'free air freezing level', which is the freezing level when there are no earth obstructions interfering with the local wind (etc.?) patterns. i have no idea how to relate the FAFL reading to what is happening on the mountain. anyone... anyone... I think reporting free air freezing level is basically a way for them to report where the natural freezling level is, with the subtle implication that it can vary quite a bit from that due to local topography and microclimate effects. Quote Link to comment Share on other sites More sharing options...
iain Posted June 16, 2004 Share Posted June 16, 2004 Yes, those free-air levels come from the soundings that are released each day from weather balloons around the world (in fact they are all released at exactly the same time each day!) This generates data that can be found at places like: http://weather.uwyo.edu/upperair/sounding.html A SKEW-T diagram is generated from this data. They are pretty helpful to determine if you are going to break out of the clouds at a higher elevation, or if you will be socked-in at the summit. Pretty cool, and entirely free for the public. Quote Link to comment Share on other sites More sharing options...
Ricardo_Montalban Posted June 16, 2004 Share Posted June 16, 2004 Iain, what part of the diagram indicates the cloud cover roof? The Scew-T looks similar to the meteograms I've tried to use in the past but have not been able to read accurately Meteogram1: (better but not currently working) http://www.emc.ncep.noaa.gov/mmb/meteograms/images/726980.cloud.gif Meteogram2: http://grads.iges.org/pix/pdxeta.gif thanks! Quote Link to comment Share on other sites More sharing options...
Gaper_Jeffy Posted June 17, 2004 Share Posted June 17, 2004 On the theme of current weather, I always like to read the Seattle NWS forecast discussion as there's always a bit of nerdy humor in it. Today the forecast starts with, "A VERY NICE DAY TODAY WITH SEVERE CLEAR CONDITIONS." Severe clear conditions? Next line, "THE FORECAST IS TRICKER THAN AT FIRST GLANCE." Quote Link to comment Share on other sites More sharing options...
iain Posted June 17, 2004 Share Posted June 17, 2004 Iain, what part of the diagram indicates the cloud cover roof? Here's a great description of a skew-T diagram: http://meteora.ucsd.edu/weather/cdf/text/how_to_read_skewt.html Basically every skew-T has both a temperature and dewpoint tempature line drawn on the chart. The dewpoint temperature is always even or lower than the air temperature, which is the dewpoint depression. When the temp lines are close together, the air is becoming saturated, and clouds form. When they are far apart, the humidity is low. When the lines are close together at low altitude, you are likely to be in a cloud bank getting wet. If you see the lines split apart at say, 8000ft, you might be treated to a nice cloud sea. The wind barbs on the far right of the skew-T give you an idea of what the winds are doing aloft. Very valuable for climbing. Hope that helps. Here is the current skew-T for Salem, Oregon: As you can see, the dewpoint temperature and temperature lines are far apart and evenly-spaced, so things are relatively dry out there throughout the upper air column. Pressure in mb is on the y-axis and temp in °C on the x-axis. So for example, with today's Salem morning sounding you could expect clear skies at 10k ft (10k ft is usually about 700mb) with winds out of the ENE at 0-15 knots and temps around 4°C. Pretty cool, eh? Quote Link to comment Share on other sites More sharing options...
iain Posted June 17, 2004 Share Posted June 17, 2004 Here's an example from that site I mentioned, again, Salem, OR in October: According to this diagram, you would break out of the clouds around 12,000ft, and the winds would be about 35 knots out of the west. So in Oregon, you wouldn't break out of the clouds. Quote Link to comment Share on other sites More sharing options...
ivan Posted June 17, 2004 Share Posted June 17, 2004 the skew-t graph and explanation are excellent...now where is the source of said skew-t's? i didn't find them after a casual search through the national weather service page. Quote Link to comment Share on other sites More sharing options...
iain Posted June 17, 2004 Share Posted June 17, 2004 yeah they are not too popular with the general public, but are used by meterologists all the time, so you have to go to university web sites to get the data usually. Here is one that has all the soundings: http://twister.sbs.ohio-state.edu/ Go to the "upper air" section. There are a bunch of universities that have this info out there. The skew-T is not a very friendly diagram, but once you can read it, there's a ton of info crammed in there. Quote Link to comment Share on other sites More sharing options...
ivan Posted June 17, 2004 Share Posted June 17, 2004 (edited) you da man, iain! it's almost as if you nothing to do all day but sit around in front of a computer.... Edited June 17, 2004 by ivan Quote Link to comment Share on other sites More sharing options...
iain Posted June 17, 2004 Share Posted June 17, 2004 behold the web lackey Quote Link to comment Share on other sites More sharing options...
Ricardo_Montalban Posted June 17, 2004 Share Posted June 17, 2004 S'Weet! Thanks! Quote Link to comment Share on other sites More sharing options...
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