I checked the forecast for today for my zip code (18344), and after a few
clicks & pop-up ads, I got the following :


Thursday, May 13 Temp °F Feels Like Dew Point Precip. Humid. Wind

11 AM Partly Cloudy 76° 78° 60° 20% 59% From the South at 5 mph
12 PM Partly Cloudy 78° 80° 60° 20% 54% From the South at 6 mph
1 PM Isolated T-Storms 79° 80° 60° 30% 52% From the South at 7 mph
2 PM Isolated T-Storms 79° 80° 60° 30% 52% From the South at 8 mph
3 PM Isolated T-Storms 79° 80° 60° 30% 51% From the South at 8 mph
4 PM Isolated T-Storms 78° 79° 59° 30% 51% From the South at 8 mph
5 PM Isolated T-Storms 77° 79° 58° 30% 52% From the South at 8 mph
6 PM Isolated T-Storms 76° 78° 58° 30% 54% From the South at 7 mph
7 PM Isolated T-Storms 74° 74° 58° 30% 57% From the South Southeast at 6 mph
8 PM Isolated T-Storms 72° 72° 58° 30% 61% From the South Southeast at 6 mph
9 PM Isolated T-Storms 69° 69° 58° 30% 66% From the Southeast at 6 mph
10 PM Partly Cloudy 67° 67° 58° 20% 72% From the Southeast at 6 mph
11 PM Partly Cloudy 65° 65° 57° 20% 77% From the Southeast at 6 mph

Friday, May 14
12 AM Partly Cloudy 63° 63° 57° 20% 81% From the East Southeast at 6 mph
1 AM Partly Cloudy 61° 61° 57° 20% 85% From the East Southeast at 4 mph
2 AM Partly Cloudy 60° 60° 56° 20% 87% From the East Southeast at 4 mph
3 AM Partly Cloudy 59° 59° 56° 20% 88% From the Southeast at 4 mph
4 AM Mostly Cloudy 59° 59° 55° 20% 88% From the Southeast at 4 mph
5 AM Mostly Cloudy 58° 58° 54° 20% 88% From the Southeast at 4 mph


The temperatures are good - 77 at MPO (which I don't think is in zip 18344,
actually) and my location. That was updated at 10:30 AM though.

Their day/night forecast is for a high/low of 80/57 and precip probabilities
of 30/30 %.

The thing I find most peculiar is the precipitation probabilities. If
they are hourly probabilities, this would imply a very large likelihood
of precip during both day and nighttime periods. If the probabilities
are considered independent, the likelihood of precip from 11 AM to 8 PM
is 1 - (.2^2 * .7^7) = .947 = 94.7 %. They are not close to being independent
events though - if thunderstorms do form, it is likely precip will occur
a few hours of the day. Yet if the probability each hour is 30 %, the
daily probability should be much greater - because the storms won't persist
all day.

So the correct interpretation of the forecasts shown above is that there's
a 30 % chance of precip today, and if it does occur, it'll persist all day
(i.e., occur each of those hours the probability is 30 %). That is obviously
not what they mean, but if the daily probability is 30 %, those for each
hour should be much lower.

Note that the nighttime probabilities are almost the same as the daytime
ones - 20 % every hour between 10 PM & 5 AM. I can't believe precip is
nearly as likely those times as it is between 2 & 7 PM.

I am thinking the probability is about 70 % for the daytime period now
and 20 % for the nighttime - hourly probability would be about 5 % ending
at 12 PM, peaking at about 25-30 % ending at 5 PM, then decreasing to about
10 % ending at 10 PM and to near 0 % ending at 5 AM. Saying that is one
thing, programming a computer to think like that another.

Maybe I am overestimating a bit, though storms are common over the elevated
locations during warm & humid days. We had some hail as large as 3/8 inch
diameter yesterday.


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