FZ LVL at SFC

[Richard]

As depicted on the 4 panel prog chart, why doesn't the freezing level at surface (blue zigzag line) follow the contours of mountain ranges?

Example:
[FONT=Verdana, Arial, Helvetica, sans-serif]KBIH [/FONT][FONT=Verdana, Arial, Helvetica, sans-serif]070556Z AUTO 02007KT 10SM OVC110 M01/M06 A2976 RMK AO2 SLP078 T10061061 10050 21011 51009 FZRANO TSNO [/FONT]

But the prog chart shows above fz at Eastern Sierra Bishop Airport, elevation 4100 msl.

 

[Richard]

Either:

• honestly, you have no idea what the heck I'm talking about.
• it's such a stupid question it doesn't merit an answer.
• I stumped y'all and any response you give would only reveal your ignorance.
• it's such a fundamental question I can hardly call myself a pilot because I cannot explain the discrepancy.
• who gives a rip?

Or all of the above.

 

[Dave Krall CFII]

As depicted on the 4 panel prog chart, why doesn't the freezing level at surface (blue zigzag line) follow the contours of mountain ranges?

Example:
[FONT=Verdana, Arial, Helvetica, sans-serif]KBIH [/FONT][FONT=Verdana, Arial, Helvetica, sans-serif]070556Z AUTO 02007KT 10SM OVC110 M01/M06 A2976 RMK AO2 SLP078 T10061061 10050 21011 51009 FZRANO TSNO [/FONT]

But the prog chart shows above fz at Eastern Sierra Bishop Airport, elevation 4100 msl.

Because it has irregular contours of warmer air.

 

[Richard]

Dave, oh the irony....

 

[Richard]

Because it has irregular contours of warmer air.

Perhaps I should have used an airport further away from the FZ LVL line. Also, I can hardly imagine an entire mtn range would be warmer at the sfc.

Thank you for your response, it gives me something to think about.

 

[Everskyward]

As depicted on the 4 panel prog chart, why doesn't the freezing level at surface (blue zigzag line) follow the contours of mountain ranges?

I think you are expecting a little too much accuracy and detail from such an itty-bitty chart, if you mean this one:

http://aviationweather.gov/data/products/swl/ll_12_4_cl_new.gif

Surface temperatures sometimes change significantly with elevation and time of day. If the chartmakers were going to be that accurate the prog chart would be huge and look like a topo map, especially out in the western states, and you would need a new one for every hour.

Is that what you were asking?