Data Sources
National Weather Service: point metadata, forecast office, forecast zone, county zone, nearest observation stations, current observations, hourly forecast, daily forecast, and active alerts.
NOAA Storm Prediction Center: Day 1 convective outlook context and broad severe-weather risk categories where available.
Radar: recent public radar imagery is sampled near the selected point. The app can use national mosaic tiles and the nearest local NEXRAD site as a fallback or comparison source.
AirNow: current AQI and primary pollutant where an AirNow key is configured and a nearby observation is returned.
HDR local data: Madison-area snowday context can appear only when the selected location is near the supported school district area.
Update Cadence
The page refreshes weather data about every five minutes while open. Manual searches also reload the full forecast pipeline.
NWS observations update when nearby stations report. Hourly and daily forecast periods update on the NWS schedule. Alerts are fetched from the active NWS alert feed. Radar frames are checked from recent available imagery and may lag real time by several minutes.
Current Conditions
The Now card starts with the nearest usable NWS or METAR observation station. Temperature, wind, humidity, dew point, pressure, visibility, heat index, wind chill, and observed text come from that station when available.
The app shows station distance and report age in popups because a station 3 miles away and 9 minutes old is much more trustworthy than a station 25 miles away and 80 minutes old. If the observation is missing, stale, or far away, the app lowers confidence and falls back toward the NWS hourly forecast.
Condition Engine
HDR Weather keeps separate internal answers for observed condition, next-hour expectation, visual atmosphere, and confidence. That prevents a future rain chance or an alert headline from becoming the current weather condition by itself.
Rain or storms should only take over the current condition when the station reports precipitation or radar shows meaningful precipitation at or very near the point. Alerts add risk context, but an alert is not treated as the weather outside.
Radar Nowcast Method
The next-90-minute rain module samples radar imagery in rings around the selected point. The closest ring estimates what is happening at the location now. Wider rings help detect nearby precipitation that may arrive soon.
The sampler filters weak gray and blue speckle that often appears as radar noise. Meaningful returns need enough strength and enough coverage around the point before they count as rain. Recent frames are compared to estimate whether precipitation is increasing, fading, or moving closer.
The output becomes 5-minute buckets for the next 90 minutes. Radar drives short-term rain timing when the signal is strong enough. NWS hourly precipitation probability stays in the background as forecast context, especially when radar is quiet or unavailable.
Alert Geometry
NWS alerts sometimes include mapped polygons. When a polygon is present, HDR Weather checks whether the selected latitude and longitude are inside it. This allows the app to say an alert includes the location instead of only saying an alert is nearby.
Some alerts are area-based without detailed geometry. Those are shown as broader local-area alerts and are not treated as precise point matches.
Forecast Views
Hourly cards and charts use the official NWS hourly point forecast. Daily cards merge day and night periods into app-style days, but the detail popup preserves the NWS day and night discussion.
Detail popups include small accuracy labels such as station age and distance, radar sampling, NWS hourly forecast, SPC outlook, AirNow observation, or alert geometry checks.
Severe Weather
Active NWS warnings, watches, and advisories are the official hazard source. SPC outlooks are used as broad regional context, not as a point-specific warning.
Storm wording is supposed to require relevant evidence: an active point alert, strong radar signal, high short-term thunderstorm probability, or a meaningful SPC setup. A low rain chance alone should not produce storm language.
Known Limitations
Radar tile sampling is useful but imperfect. Terrain blockage, radar range, bright banding, hail contamination, mixed precipitation, ground clutter, and delayed frames can all affect what the app sees.
Observation stations may be several miles from the selected point. A station can report clear weather while rain is falling nearby, or report rain after a shower has already moved away from the selected point.
Alert polygons and forecast zones can be larger than a neighborhood. Even when an alert includes a point, the worst weather may pass north or south of that exact spot.
Why This Can Differ From Apple Weather
Apple Weather blends many sources and model outputs into a polished consumer forecast. It may smooth or reinterpret NWS data before showing it.
HDR Weather intentionally leans closer to the official NWS feed and shows where the data came from. That can make the app less smooth at times, but it keeps watches, warnings, forecast wording, station observations, and radar context easier to audit.
