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I use https://flightplanning.navcanada.ca to get METARs and TAFs for my local stations. While listening to CYPK tower at work I noticed something in the header of my VLC:
That's a METAR! But why doesn't it show up at NAV CANADA?
That got me wondering where those reports/forecasts actually come from. After the station observes weather, does it report it to a central service? Does the station itself predict the future conditions to create the TAF?
METAR
The METAR always refers to a specific airport and is obtained right then and there. That is at the airport.
It is a report of current conditions, usually hourly.
In the US, the FAA polls all systems remotely and disseminates the reports in METAR format. No word on wether this is via phone, mobile or radio, if that is what you are asking.
In Germany, the DWD, the german weather service, provides the reports. It can be assumed, that the situation is similar and that the stations are polled.
Weather stations have wide-ranging capabilities and operators, so the reported parameters may be different.
METAR reports may be reviewed by an individual before being transmitted, but the vast majority are reported automatically.
METAR reports are used for aviation weather, by definition, as a "Meteorological Terminal Area Report".
TAF
The TAF is a forecast. It is updated only 4 times a day and is provided by a human forecaster on the ground. Most larger airports have a meteorologist.
FORMAT
Both METAR and TAF use similar format, but each contains elements distinct from the other. For example, a TAF may contain a FM (from) or BECMG (becoming), but a METAR never will.
DATA SOURCES
You can use https://www.checkwx.com/ to check both. Or http://tgftp.nws.noaa.gov/weather/current/ if you want the raw data.
Though this reference is second-hand information, the author suggests that the National Weather Service explains why some reporting stations do not get collated or transmitted by agencies like the FAA or Nav Canada. Here's what he says:
Many local airports across the state, as well as the country, have been fortunate to generate the funding to purchase AWOS equipment to obtain current weather conditions for their location. While establishing these sites however, they are generally not fully informed of the requirements needed to make this data available over the worldwide network used by the FAA and NWS. The FAA controls the stream of data from small airports such as these and requires the individual sites to purchase additional equipment and pay a monthly fee to send the data in to their system.
