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A cloudy, but generally mild and dry weekend will slowly progress into a stormier pattern by the middle of next week. Valley temperatures will range from the upper 50s to the lower 60s through Tuesday, after which a cold front will drop highs into the 40s by Thursday. Storms accompanying next week’s cold front could be significant, with snow levels lowering to Lake Tahoe level at the least.

barometer

Marci wrote me to tell me that her son just got a new weather set. She knew that the barometer needed to be set to Reno’s elevation, and wondered how to calibrate it. I told her to set it to 29.89 inches of mercury (the pressure at the time), and Bob’s your uncle, Luke will be on his way to meteorological harmony.

Marci thanked me, but then said “It’s marked in ‘hPa,’ not inches. Does that make a difference?”

hPa chart

Indeed it does. hPa stands for hectopascal, or 100 Pascals. A Pascal is the standard metric unit of pressure. One atmosphere of pressure (the approximate pressure you will find at sea level) equals just over 100,000 Pascals. So a hectopascal is roughly equal to one thousandth of an atmosphere, and is exactly equal to one millibar.

It actually makes more sense to use hPa for pressure when it comes to the international community, but we Yanks just have to be different, and we’ve adopted inches of mercury as our public standard.

 

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