Barometric Pressure Forecast for Tracy, California
Barometric pressure forecast for Tracy, California — sitting at the mouth of the Altamont Pass where Bay Area marine air spills into the San Joaquin Valley. See current barometric pressure and what it means for weather-sensitive people.
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Pressure and weather in Tracy
Tracy occupies an unusual gap in California's geography: the western edge of the San Joaquin Valley, directly downwind of the Altamont Pass, which is one of the few low breaks in the Coast Ranges between the ocean and the Central Valley. On summer afternoons cool marine air is drawn through that gap by the valley's thermal low, producing the delta breeze that arrives most evenings and drops the temperature ten or fifteen degrees in an hour. That is a wind and temperature event, though, not a barometric pressure event — the thermal low is shallow and the barometer barely notices. What actually moves current barometric pressure here is the winter storm track. From November into March, atmospheric rivers aimed at central California make landfall and cross the Coast Ranges, and each one brings a genuine fall and recovery in pressure over a day or two. Between those storms the Great Basin high can build in and lock down a strong inversion, which is when tule fog forms on the valley floor and sits for days under a stubbornly high barometer. Spring frontal passages taper off through April. Summer is the flattest stretch of the year, with weeks of near-identical readings under the Pacific high. A barometric pressure forecast for Tracy is most useful from late autumn through early spring.
What this means for you
Can barometric pressure cause headaches? In Tracy the honest answer is that most of the year the barometer is too quiet to blame, which makes the winter storm sequence stand out sharply when it arrives. If you get a weather migraine, the days to watch are the ones ahead of an atmospheric river landfall. Use this barometric pressure forecast with Pressure Pal as a migraine tracker app to see pressure change today before the next system crosses the Coast Ranges.