Decoding Guide

Freezing Level Analysis

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Description:
The Freezing Level Analysis depicts freezing level at individual stations, as well as general contours.

Issuance:
0000 and 1200 UTC

Data Sources:
Upper air analysis

Depiction:
Solid white lines are contours of the lowest freezing level and are drawn for 4,000 foot intervals and labeled in hundreds of feet MSL. When a station reports more than one crossing of the 32 degree isotherm, the lowest crossing is used in the analysis. A dashed line represents the 32 degree isotherm at the surface and will outline an area of stations reports "BF" (below freezing).

Example:

Freezing levels for individual stations are depicted in green. The following examples show how to decode the observations.

Examples:

Plotted	Interpretation
	Entire observation is below freezing
	Freezing Level is at 2,800 feet; Temperatures below freezing above 2,800 feet.
	Freezing level at 12,000 feet; Temperatures above 12,000 feet are below freezing.
	Temperatures are below freezing from the surface to 5,100 feet; above freezing from 5,100 to 11,000 feet and below freezing above 11,000 feet.
	Lowest freezing level is at 300 feet; below freezing from 300 feet to 3,400 feet; above freezing from 3,400 to 9,000 feet and below freezing above 9,000 feet. (See illustration below)
	Data is missing.

Plotted Value	Interpretation