Hypothetical sounding for Tmax exercise

Question

The 1200 UTC sounding above is at an inland location over the southeastern U.S. in early October. Winds aloft are very light, and the location is underneath a large scale ridge aloft. Scattered clouds are being reported in the surface observation. Using the plotted sounding, predict the afternoon maximum temperature.

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TMAX = °C

Answer: The correct answer is TMAX = 30°C.
Since we're under an upper-level ridge, we do not expect an air mass change during the day. It's early fall, so 850 hPa is an appropriate reference level. There are no inversions in the 4,000-6,000 feet layer, so we can use the dry adiabatic method for determining maximum temperature, given the surface observation of scattered clouds. From T850, proceed down dry adiabatically to the surface, which yields a surface value of 30°C for TMAX.

Note that there is some residual low-level moisture residing in a 100 hPa deep layer near the surface. Therefore, despite being under a ridge, one might expect the possibility of some scattered afternoon convection. In this case, the convective condensation level is at about 830 hPa, and proceeding down dry adiabatically from that level to the surface yields a convective temperature of 30°C, which matches the TMAX obtained via the dry adiabatic method.
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