Immediately obvious was the broad area of IFR and even LIFR conditions. Based on the observed ceilings at the time, this was clearly over done. The RAP seemed to have a better handle, eliminating a lot of those low ceilings. Those working on the national scale opted to go with the RAP, assuming that it would be a lot easier for the local WFOs to more accurately add areas of C&V back in at their level, rather than send them a grid with a mess of widespread IFR and LIFR (accuracy debatable) that would require a large amount of editing and adjusting.
|20170815 1400 UTC National Blend (left) and RAP (right) ceiling and visibility forecast, 6-hour (20 UTC) forecast|
There was also more discussion on more versus less detail in the cloud grids. Below is the National Blend Sky Cover grid.
|National Blend Sky Cover grid from 1800 UTC on August 15th|
In this case, one of the mock local offices was Philly, and participants at that local level, smoothed out the Sky Cover grid in that area for better TAF generation.
|National Blend Sky Cover forecast zoomed in over Philly, the mock WFO forecasting at the local level|