A Pacific cold front, all day.

Summary

January 22, 2026. A Pacific cold front trailed across the Sonoran Desert from a parent low pressure system off Baja California, depositing 0.89 inches of cold rain at the El Encanto cooperator gauge between 06:42 and 16:14 MST. NWS Tucson issued no advisories. The storm was unremarkable except for cumulative October–January rainfall before it (Tucson at 11% of normal for the season-to-date), which made this the largest event in 78 days.

Why winter storms behave differently

Two reasons winter storms work differently than monsoon for our subsystems.

Slower percolation. Tucson clay-loam absorbs water at roughly 0.2–0.4 in/hr in summer when the soil is warm and unsaturated; in winter, with cool soil temperatures and the residual moisture from the previous storm, infiltration drops to 0.10–0.20 in/hr. A 0.89″ storm at 0.10 in/hr will hold standing water in the basin for 8–9 hours rather than the 2–3 hours it would in summer.

Different tree state. Native Sonoran legumes — velvet mesquite, palo verde, ironwood — are largely or fully dormant in late January. They drink very little. The water captured in winter mostly recharges deep-soil moisture, which the trees access in March and April for the spring growth flush. This is desirable for tree health but doesn't show up immediately as visible above-ground growth.

Gauges

Field notes

Crew: Marisol and Daniel on a small estimate visit at the Barrio Viejo property, walking the lot in rain gear. Antón and Ben at Bay 3 doing winter inventory and rebuilding the controller dashboards in storage. June at home reviewing the previous week's telemetry data.

Marisol noted no overflow on any of the right-of-way basins she could see during the day. The Barrio Viejo cistern took the storm to within 4 inches of overflow — about 1,200 gallons of new capture from the storm — and the small basin under the courtyard pomegranate held standing water from approximately 10:30 until past sunset.