Radiosonde Skew-T
Observed soundings for Quillayute, Salem, Spokane, and Port Hardy, rendered with MetPy from IEM's RAOB data feed. Skew-Ts are useful for eyeballing freezing level and temperature inversions, the dendritic growth zone (DGZ), estimating snow level, wind shear, and convective potential. Read more about understanding a Skew-T here.
Click a site to see the most recent sounding for that location. Give about 30 seconds for the chart to load. Quillayte, Port Hardy, and Salem are launched upwind of the Cascades, so they are often representative of what the Cascades will see. Hover the chart to read temperature, dew point, and parcel values at any level, in metric or imperial units.
Sounding Diagnostics
- Freezing Level
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- Snow Level (Saturated Column)
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- Snow Level (Modeled)
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- Thermal-wind signal
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- Dendritic growth zone
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What is this?
The height above ground where the air temperature first drops to 0°C as you go up. On its own this doesn't tell you where snow reaches the ground -- see the two Snow Level estimates below.
What is this?
Assumes the air below the clouds has already been moistened by falling precipitation, which is what typically happens once a storm has been going for a while. This is usually the more realistic number during an active, steady storm.
What is this?
Uses this sounding's actual measured dewpoints instead of assuming saturation. When the air is this dry, a falling snowflake loses moisture to its surroundings (sublimates) instead of warming up and melting, so it can survive much closer to the ground than the temperature alone would suggest. If this sounding was measured before precipitation started, this number can look surprisingly low -- once it's actually been snowing or raining for a while, the real snow level is likely closer to the Saturated Column estimate above.
What is this?
Whether the wind veers (turns clockwise with height, implying warm advection) or backs (turns counterclockwise, implying cold advection) between the surface and roughly 1-2.5 km up, estimated from the thermal-wind relationship.
What is this?
The depth (in km AGL) of the layer between -12°C and -18°C, where stellar dendrite snowflakes grow most efficiently. Shaded blue on the skew-T above.
Convection
- MLCAPE
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- MUCAPE · source height
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What is this?
Mixed-Layer CAPE: convective available potential energy for a parcel representing the average of roughly the lowest 100 hPa. More conservative and generally preferred by severe-weather forecasters, since it reflects what the atmosphere is actually doing as a whole rather than a single hot spot.
What is this?
Most-Unstable CAPE: the maximum energy available to a parcel lifted from the single most unstable level in the sounding. Tells you the absolute maximum energy potential available to a storm, even if that level isn't at the surface (e.g. the ground is cold but a warm, moist layer sits just above it).
Freezing Level & Snow Level Trend
Recorded automatically every few hours from observed soundings (last 2 days shown by default -- drag to pan/zoom further back), so you can see how a level actually evolved versus what was forecast.
No recorded history yet for this station -- check back after the next automated update.