UpstreamWX

A planning-reference weather briefing for caving and canyoneering. It gathers official and modeled weather, assesses four life-safety hazards — flash flooding, lightning, heat, and cold/wet hypothermia — and shows the reasoning. It never tells you whether to go.

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Free · No account required · Works in your browser

UpstreamWX map view showing the upstream watershed for Pettyjohn's Cave on a dark topo basemap
Install it on your phone

UpstreamWX installs as an app straight from your browser — no app store, no account. Open the app, then:

Who makes UpstreamWX

UpstreamWX is built and maintained by Southeast Expedition Medical, a small team of cavers and wilderness medicine practitioners. We built the briefing tool we wanted for our own trips: one place that pulls the official forecast, the ensemble models, and the upstream watershed together, and shows the reasoning behind the risk assessment. It is free, has no ads, and asks for no personal data.

info@upstreamwx.com
Support UpstreamWX

Running UpstreamWX has real costs: the servers that process the GEFS and REFS ensembles, the map and watershed data, and the time to keep the app up to date. It stays free because people who find it useful chip in. If it saved you time planning a trip, a donation helps keep it online for the next expedition.

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How this works
The deterministic engine Why identical inputs always produce an identical posture.

Every hazard posture, confidence level, and window of concern is decided by a deterministic, documented rule engine. Identical inputs always produce an identical result. The language model used for summary generation only frames the wording of the summary. It can never compute, raise, or lower a posture.

  • Four hazards are scored independently on a common scale (Minimal, Elevated, High, Extreme).
  • Each hazard applies only in the expedition phases where it is relevant (approach, technical span, egress) and per activity type. A cave technical span is treated as isolated from surface weather and shows flash flood only.
  • The overall expedition posture is the maximum across all applicable hazards, and every hazard stays visible, so a high lightning posture on approach is never hidden behind a low flood posture.
  • A confidence qualifier per hazard comes from GEFS ensemble agreement and cross-source consistency, including GEFS and REFS agreement on same-day windows.
Data sourcing The official and modeled weather sources behind each hazard.

Providers sit behind a common interface, so the engine never depends on a specific source. If a non-mandatory source is unavailable the briefing still renders, marking that input as unavailable.

NWS API api.weather.gov
Forecast discussions (AFD), watches, warnings, advisories, and NWS Heat Index categories. The authoritative anchor and a mandatory source.
Open-Meteo HRRR-derived fields
Derived numerical fields (QPF, precip probability, CAPE / lifted index, temperature, humidity, apparent temperature, wind) feeding all four hazard models.
GEFS (in-house) NCEP GRIB2, processed server-side
Global Ensemble Forecast System member-exceedance probabilities of precip and a convective proxy over the upstream domain, covering the full multi-day planning horizon at ~25 km resolution.
REFS (in-house) ~3 km, same-day ~6 to 36 h
Rapid Ensemble Forecast System (RRFS Ensemble) neighborhood probabilities — 1 h / 3 h QPF, lightning, reflectivity — that sharpen the same-day window at ~3 km. Where both GEFS and REFS are in range, the engine takes the higher posture; REFS is authoritative for confidence.
SPC outlook Storm Prediction Center
Categorical and probabilistic severe and thunderstorm outlook, a secondary cross-check for lightning.
USGS NHD / WBD NLDI and Watershed Boundary Dataset
The stream network and watershed boundaries used to delineate the upstream contributing basin (a pour-point trace, with a HUC-12 fallback).
The upstream watershed Why a slot can flood under a clear sky — and how we account for it.

Flash-flood risk is assessed over the upstream contributing basin — the land that drains toward your point, not the point itself. This matters because a slot can flood under a clear sky from rain falling miles upstream. Aggregating probability over the drainage area is what catches that. Your coordinate is snapped onto the mapped stream network, the exact upstream basin is delineated, and ensemble precipitation probabilities are aggregated across it.

Surface delineation is a defensible proxy for canyoneering, but in karst terrain it is a rough estimate at best — underground drainage can cut across surface basins. Flash-flood risk is intentionally assessed on the coarse global GEFS grid (~0.5°, ~25 km) for the planning horizon — which buffers the watershed edges and partly accounts for subsurface drainage — sharpened inside the same-day window by the 3 km REFS ensemble. User judgment is always required.

Reference only. Not a forecast, not a decision. UpstreamWX surfaces hazard information and links to authoritative NWS sources; it never issues a go/no-go or an all-clear. The data can be incomplete, delayed, or wrong, and a cave or slot canyon can flood from rain you never see. The decision to enter, continue, or turn around always rests with you and your party.

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