I set up a WF station and also installed weewx. Most of the readings on the WF app closely parallel those on weewx, except for barometric pressure. That consistently reads .3 to .4 inches higher on the WF app, but the weewx reading is closer to that reported by Accu-Weather. For example, just now the WF app reads 29.932 (wish I could set it to round to two places) while weewx reads 29.60. Accu-Weather reports 29.59. The elevation of my station and the sensors are accurately set, and the elevation is set the same in weewx. What would explain the difference in readings?
Are you sure that you are looking at the correct type in WeeWX?
https://github.com/weewx/weewx/wiki/Barometer,-pressure,-and-altimeter
The skin (using NeoWx at the moment) says Barometer. I used to work as a CWO (certified weather observer) and I understand about lapse rates. It’s weewx that offers a figure closer to published figures; that’s why I posted here. I’ve been comparing barometer figures in both weewx and WF app to Accu-Weather because they publish barometer; the ATIS and METAR use altimeter. So far (and I’ve only been running the station a few days) weewx has agreed with Accu-Weather more closely. I have read the discussion on CL and will observe if the two get closer over time.
Oh, and I do wish I could set the precision displayed on the app. As an IFR pilot, three figures to the right of the decimal just looks wrong to me…
Do you have the Elevation set correctly in the App?
Set to 8475 MSL, which agrees with my Garmin. Air is set to 8 AGL and Sky to 27 AGL. In weewx, station elevation is set to 8483 to correspond to Air.
MSL is that meters above sea level?
Never mind, I see that is mean see level
While the sensor’s absolute precision is to two decimal places the relative precision is to three decimal places. This means that smaller changes in pressure can be detected than if only two decimals were displayed. I’m so used to rounding in Physics that it doesn’t bother me to see the third digit, in fact I prefer seeing it so I don’t have to wonder if rounding or truncating is taking place behind the scenes.
I wonder if I could somehow sneak into your airplane and add a third digit to the altimeter… 
switch to metric units and the problem goes away. It shows mbar with 1 decimal place, which happens to be the exact accuracy of the barometric sensor. (in inches it is around 0.003 inch)