Join Alias Columns SQL - postgresql

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