postgresql - Join Alias Columns SQL

Question

I am trying struggling with joining alias named columns. Overall, I want an output with the with date, hour, and the actual and forecasted (most recent before 10am on the previous day) windspeeds.

With the below code I get:

ERROR: column "date" does not exist
LINE xx: ...ast_prep.lat AND meso.lon = forecast_prep.lon AND Date ...

I cannot figure out how to get SQL to join these named columns.
Thanks. And yes, I am a SQL newbie.

with forecast_prep as (
  SELECT
    date_trunc('day', foretime)::date AS Foredate,
    extract(hour from foretime)+1 AS foreHE, 
    lat,
    lon,
    windspeed,
    max(as_of) AS as_of
  FROM weather.forecast
  WHERE date_trunc('day', foretime)::date-as_of>= interval '16 hours'
  GROUP BY Foredate, foreHE, lat, lon, windspeed)
SELECT
  meso.station,
  date_trunc('day', meso.timestmp)::date AS Date,
  extract(hour from meso.timestmp)+1 AS HE, 
  CAST(AVG(meso.windspd) as numeric(19,2)) As Actual,
  forecast_prep.windspeed, 
  forecast_prep.as_of
FROM weather.meso
  INNER JOIN forecast_prep ON (
    meso.lat = forecast_prep.lat AND
    meso.lon = forecast_prep.lon AND
    Date = Foredate AND ----<<<< Error here
    HE = foreHE)
WHERE
  (meso.timestmp Between '2016-02-01' And '2016-02-02') AND
  (meso.station='KSBN')
GROUP BY meso.station, Date, HE, forecast_prep.windspeed, forecast_prep.as_of
ORDER BY Date, HE ASC

Here are the table structures:

-- Table: weather.forecast

-- DROP TABLE weather.forecast;

CREATE TABLE weather.forecast
(
  foretime timestamp without time zone NOT NULL,
  as_of timestamp without time zone NOT NULL, -- in UTC
  summary text,
  precipintensity numeric(8,4),
  precipprob numeric(2,2),
  temperature numeric(5,2),
  apptemp numeric(5,2),
  dewpoint numeric(5,2),
  humidity numeric(2,2),
  windspeed numeric(5,2),
  windbearing numeric(4,1),
  visibility numeric(5,2),
  cloudcover numeric(4,2),
  pressure numeric(6,2),
  ozone numeric(5,2),
  preciptype text,
  lat numeric(8,6) NOT NULL,
  lon numeric(9,6) NOT NULL,
  CONSTRAINT forecast_pkey PRIMARY KEY (foretime, as_of, lat, lon)


-- Table: weather.meso

-- DROP TABLE weather.meso;

CREATE TABLE weather.meso
(
  timestmp timestamp without time zone NOT NULL,
  station text NOT NULL,
  lat numeric NOT NULL,
  lon numeric NOT NULL,
  tmp numeric,
  hum numeric,
  windspd numeric,
  winddir integer,
  dew numeric,
  CONSTRAINT meso_pkey PRIMARY KEY (timestmp, station, lat, lon)

Answer 1

'Date' alias can't be seen from there.

You can use few tables after WITH, so I'll advice you to move second select there.

I'm not completly sure about weather.meso table structure but by guesing based on your query, this should work:

WITH
    forecast_prep AS (
        SELECT
              date_trunc('day', foretime) :: DATE AS Foredate,
              extract(HOUR FROM foretime) + 1     AS foreHE,
              lat,
              lon,
              max(windspeed) as windspeed,
              max(as_of)                          AS as_of
        FROM weather.forecast
        WHERE date_trunc('day', foretime) :: DATE - as_of >= INTERVAL '16 hours'
        GROUP BY Foredate, foreHE, lat, lon
   ),
   tmp AS (
      SELECT
        meso.station,
        meso.lat,
        meso.lon,
        meso.timestmp,
        date_trunc('day', meso.timestmp) :: DATE  AS Date,
        extract(HOUR FROM meso.timestmp) + 1      AS HE,
        CAST(AVG(meso.windspd) AS NUMERIC(19, 2)) AS Actual
      FROM weather.meso
      GROUP BY station, lat, lon, timestmp, Date, HE
   )
SELECT 
    tmp.station, tmp.Date, tmp.HE, tmp.Actual, forecast_prep.windspeed, forecast_prep.as_of
FROM tmp
INNER JOIN forecast_prep ON (
    tmp.lat = forecast_prep.lat 
    AND tmp.lon = forecast_prep.lon 
    AND tmp.Date = forecast_prep.Foredate
    AND tmp.HE = forecast_prep.foreHE
)
WHERE 
    (tmp.timestmp BETWEEN '2016-02-01' AND '2016-02-02') 
    AND (tmp.station = 'KSBN')
GROUP BY 
    tmp.station, tmp.Date, tmp.HE, forecast_prep.windspeed, forecast_prep.as_of, tmp.Actual
ORDER BY tmp.Date, tmp.HE ASC;

Like in first example right here https://www.postgresql.org/docs/8.4/static/queries-with.html