For most summers, during July or August there is an intrusion of "monsoon" moisture from the southwest into our region, resulting in showers and thunderstorms...and this year will be no different.
Such thunderstorms can be both good and bad. Good at providing needed rain and lessening fire risk, but bad if lightning starts fires.
The predicted totals through Friday morning (seen below) range from a few tenths to a half inch, with higher values along the coast.
The wet fun will begin later this afternoon and evening as convection and thunderstorms build near the crest of the Cascades (see forecast for 5 PM below).
Why this wet bounty?
Two things are occurring together. The upper-level pattern includes an approaching upper-level trough (500 hPa, about 18,000 ft shown for tomorrow morning). Such troughs produce upward motion (which helps initiate cumulus clouds) and bring in moisture from the south.
Such "monsoon" moisture and unstable air from the southwest are evident in the forecast below.
Total water vapor content of the atmosphere this evening.
Blue and red are higher values
Enjoy the show overnight!
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