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A measure of atmospheric moisture, known as precipitable water, ranges between 1.3 and 1.7 inches.

Precipitable water indexes — a measure of how much moisture is present in a column of air from the bottom to the top of the atmosphere — are approaching a remarkable three inches.

Precipitable water, an indicator of atmospheric moisture, was estimated up to 2.25 and 2.65 inches Wednesday evening between Alexandria and central Prince George’s County.

That lead to a record October PWAT, or precipitable water index, at Oakland.

Thursday “showed the highest level of precipitable water in the atmosphere, for winter, since 1948,” said Matt Moreland, meteorologist in charge of the National Weather Service office in Rancho Bernardo.