SUMMARY:

Here is a summary of the steps and tools used to forecast freezing drizzle.

1.  Assess synoptic situation for weak convergence near a trough line or a low pressure center.  Also look for possible overrunning from a system south of the forecast area.

2.  Use FOUS60 Layer temperatures to locate 755-1000mb freezing drizzle thermal profile.  Look for temperatures between 0C and -10C in the lower level cloud deck.  

3.  700mb vertical velocity should indicate weak lift or subsidence.

4. Check low level relative humidity trends to see if moisture will be available.  The FOUS60 Layer 1 relative humidity should be greater than or equal to 85% and should be drier aloft.  

5.  FOUS14 should indicate lowering ceilings and dropping visibility.  

6.  Look for FOUS14 surface temperatures between 20F and 32F.  

Use actual RAOBS and forecast soundings to help identify trends in temperatures, saturation and cloud depth.  

Monitor Doppler radar pictures for freezing drizzle/super cooled water in clouds.  Call the National Weather Service to switch to clear air mode to identify freezing drizzle more easily.