TAFs will always be pessimistic because the forecaster has to throw in anything remotely likely under the PROB30 heading.
The UK F215 is even more pessimistic, throwing in everything including the kitchen sink, and then adding moderate icing in all cloud even if the wx is CAVOK.
So one needs to have a physical look at the actual wx. One can use
weather radar,
sferics,
satellite IR images, etc.
And a quick look at the
MSLP chart will give you plenty of clues. The troughs (their actual position is meaningless; the forecaster just draws them in randomly) mean a PROB30 TEMPO of TS, and sure enough for EGKK you now have, for tomorrow,
PROB30 TEMPO 1313/1318 4000 +SHRA
I am no forecaster and would never suggest anybody can beat those who do it for a living, but it's not hard to get a rough grip on what is coming. It's just that in the PPL people spend hours on the stupid slide rule when they could be learning to read wx data presented to them on a plate, using that new fangled method (never mentioned in my PPL) called the
internet 
A while ago I knocked up
this pic, largely from the POV of high altitude IFR. It is self explanatory. One interesting thing I found repeatedly is that you get TS where there is a change from a cold to a warm front.