Tuesday was a breezy and rainy day around Western Washington. Some of the heaviest rain and strongest winds came from 3-4 PM, when a cold front moved through the region, bringing strong winds and heavy rain.
But how do we know this was a cold front...and what is a frontal passage? Let’s take a look at the weather chart from my home weather station that shows a good example of the frontal passage.
Outlined in the red rectangle (from top to bottom) are the charts of temperature, winds+gusts, wind direction, rain+rain rate, and atmospheric pressure. But first, we need to know what a frontal passage is.
During the frontal passage, a cold front “passes” by a location. The cold front is the “front” of the advancing mass of colder air. It is typically warmer ahead of a cold front, and more rain is found ahead of the front in the rain shield. The heaviest rain and strongest wind is in and very close to the frontal boundary itself.
Now that we have learned what a frontal passage is, let’s refer back to the chart above. During Tuesday’s frontal passage (and any other frontal passage):
Temperature will decrease
Winds and wind gusts will increase, and winds will change from S-SE to W-SW
Rain and the rain rate will intensify
Atmospheric pressure will stop falling, reach its lowest point, and rise after the frontal passage
All of these things can be observed in the chart above, and they happened today.
Winds gusted 20-45 mph on Tuesday. The strongest winds were during the frontal passage (37 mph gust at my house!). Below is a NWS map showing peak gusts.
Winds will subside through Tuesday night, and Wednesday will be calmer with a chance of rain.
We will be under the influence of a high pressure ridge from late Wednesday through the weekend. There’s a slight chance of rain on Friday night and another chance of rain by Sunday night.
Enjoy the break in the weather...and I hope you enjoyed learning about frontal passages!
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