I'll try to do a simple write up and if anyone has any further questions I'll try my best. I'm technically just a "journeyman" in the Air Force WX career field. I had a little bit of a head start over class mates having learned weather earning my pilot's license.
So reaching back to what I said previously about 00Z and 12Z soundings. The biggest takeaway I can summarize as a pilot that went through Air Force WX school - is what are you actually looking at? A 00Z and 12Z analysis chart is the only charts you will look at that are actual weather. Worse than that though - I don't know if this holds true on the civilian side - but the Air Force's Analysis charts are computer analyzed and have to be
reanalyzed and adjusted in much the same way that the model charts do that I previously talked about.
So my process begins with pulling up the Satellite image for 00/12Z - whatever is appropriate for time or region of the world I'm working. With some training and practice (I'll attempt a write up for this later hopefully) you should be able to draw an analysis chart based on what you see in the satellite photo. Now you compare your 00/12Z satellite to your 00/12z analysis and reanalyze the analysis moving features as needed to match real life (satellite). Remember, 00/12Z, satellite and radar is the only "real" weather you will ever look at.
What about SFC measurements you might say though, isn't that real weather ? Yes and no. Placement of the ASOS/AWOS can affect the data as well as limitations of the equipment itself. The most prominent example being clouds. We could look at the FMQ-19 readout and it say CLR but when we go outside there was most definitely clouds. Therein lies another issue - send 5 observers out to take an augmented observation and you'll get 5 different METARS. Mine might say FEW 025 while the next guy/gals says SCT030 while the laser beam on the FMQ-19 is hitting the side of the cloud and saying 045.
They're just clouds who cares? Well, part of reading an analysis chart and predicting weather is finding moisture - so clouds are your real life weather that confirms your analysis charts. As the last two posters have said - you hypothesize about what happens and then compare and see what actually happens. This is part of the old school 27 states of the sky method and clouds (satellite or observed) and radar are your verification products.
So, as a pilot the concern becomes - how bad will it be? i.e. I'm cool with flying through light green radar returns but dark green or yellow makes me nervous. The BASIC ingredients for any rain can be broken down into an acronym we use in Wx called MILE. Moisture Instability Lift Exhaust. In the Air Force we have enhanced SkewT which gives us all kinds of values to indicate these kind of things LI, CAPE, CINH, PWI, TT, KI, SSI etc etc you can literally spend all day lost in the sauce but I mention this to refer back to what I previously said about the work already being done for you in local and mesoscale forecast discussions.
Simply though -
- Moisture - dewpoint depression less than 6 aka Isodrosotherms, these are areas moist enough generally speaking to produce rain
- Instability - all those values I talked about in the previous paragraph, could literally write a page long description of each value... SkewT mastery CBT in previously linked COMET course can be a good start...
- Lift - fairly simply orographic or isentropic but also low level jets, low level convergence/confluence, cyclonic turning, troughing, etc, etc again lengthy subject
- Exhaust - upper level divergence/diffluence
I feel this is a good time to mention one of my favorite resources that I forgot to mention earlie, as it can probably explain a lot of these single specific areas of interest way better than me -
http://www.theweatherprediction.com/ .
Basically, once you've reanalyzed the analysis and made the necessary adjustment then you make your hypothesis. You look for the four ingredients above, there are numerous ways to do so (SkewT, hodographs,various charts), there is no one size fits all answer. Unfortunately there is no 'if the PWI is 0.50 and CAPE is 1250' we will get Heavy Rain. There are threshold numbers certainly that indicate you may but as previously stated I've seen it both ways in real life, we had all the ingredients and it didn't happen and had only some of the ingredients and it did happen and it will happen at different thresholds depending on where you are in the world. In the Air Force we have FRM, Forecaster Reference Material - which are basically lists of these ingredients specifically for that local location. In other words we have FRMs for each base and each bases thresholds are different.
Once you made your hypothesis, then you adjust your 00/12Z model to match your (re)analysis and compare/adjust it also to radar images. Then you run the model out with adjustments as a way to verify your hypothesis. If your guess and the model don't match which is very likely is the model over/under estimating over/under performing ? That goes back to the Initializing, Continuity and Consistency of models step. These steps though done initially in a certain order they are also continually done throughout the process. Advantage again to the Wx folk as this process is a 24/7 process but again you can access the model discussions linked previously.
Again, just trying to give an overall big picture kind of - this is what you can do, hopefully you added a few more tools to the toolbag type approach. There are as many different ways to interpret the weather as there are weatherman.