What is the best alternative to WeatherX Forecast on iPhone?

Barometer & Altimeter & Thermo, S tier, #1 in barometer.

Is there a free alternative to WeatherX Forecast?

Yes: Barometer & Altimeter & Thermo (S tier, #1) is free to download, with in-app purchases.

Yes. 2 apps rank above it in barometer: Barometer & Altimeter & Thermo (#1), Thermometer++ App (#2).

WeatherX Forecast is A tier, #3 of 6 in barometer. Here is everything that competes with it on iPhone, in tier order.

1
Barometer & Altimeter & ThermoShigher tier
Free + IAP · ★ 4.8 · 9,616 ratings · score 93
Measures atmospheric pressure and altitude, using GPS, device sensors and nearby weather station data.
2
Thermometer++ AppA
Free download · ★ 4.7 · 7,288 ratings · score 83
Shows current outdoor temperature, humidity, pressure, and wind for your location or a location chosen on a map.
4
Thermo-hygrometerB
$3.99 · ★ 4.7 · 1,914 ratings · score 80
Shows outdoor temperature, feels-like, humidity, pressure and discomfort index for your location on analog-style gauges.
5
Gauges: Speedometer & SensorsB
Free download · ★ 4.6 · 3,079 ratings · score 78
Live gauges for iPhone and iPad measuring speed, altitude, pressure, compass, sound, light and other sensors.
6
eWeather HD - Weather & AlertsC
$3.99 · ★ 4.7 · 8,819 ratings · score 69
Weather app with hourly and 15-day forecasts, radar, lightning tracking, severe alerts, tides and air quality.

What is the best alternative to WeatherX Forecast on iPhone?: Barometer & Altimeter & Thermo, S tier, #1 in barometer.
Is there a free alternative to WeatherX Forecast?: Yes: Barometer & Altimeter & Thermo (S tier, #1) is free to download, with in-app purchases.
Does anything rank above WeatherX Forecast?: Yes. 2 apps rank above it in barometer: Barometer & Altimeter & Thermo (#1), Thermometer++ App (#2).