Expect frosty 4-leaf clovers this St. Patrick’s Day

Weather

Here's your St. Patty's Day forecast

PORTLAND, Ore. (KOIN) — A frosty St. Patty’s Day to you! You’ll need more than a four-leaf clover to warm up this morning.

Clear skies and near freezing temperatures will start the day, and just as quickly, we’ll warm up to near 60 again. Your morning conditions will be accompanied by a light breeze which will make it feel a few degrees cooler.

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Our dominant offshore winds will turn onshore (from the west) this afternoon. That means low clouds return to the coast and may creep into the valley. A weak area of low pressure cruises by the coast tonight and it may help encourage a little drizzle to fall from those clouds along the coast.

The valley will likely miss out on this light variety precipitation, but will see more clouds. So we’re mostly dry this week and are now feeling more spring-like with afternoon temps in the upper 50’s to low 60’s. 

Does it feel like the vernal equinox is rushing up on you? Perhaps you’ve memorized your spouse’s birthday based on the normal first day of spring: March 20. Yes and yes, but now we must accept the fact that spring is sprouting one day early: Thursday March 19 at 8:49 p.m. PDT. 

According to the Farmers Almanac, “For much of the last century, the spring equinox has occurred on March 20 or 21. This year, however, the equinox happens on the 19th in all U.S. time zones, making it the earliest spring we’ll have seen in our lives (so far). The last time spring arrived this early was in 1896—a whopping 124 years ago!”

So why the sudden rush, Spring? Blame it on the leap year. Get ready, there’s a lot of numbers involved to explain this calendar dilemma.

According to OMSI Director of Space Science Education, Jim Todd,  “As seen from Portland on March 19 and 20, the noon sun will reach its mid-point in the sky near 45 degrees from the southern horizon.  On the day of an equinox, it is good day for finding due east and due west from your own backyard.

Just go outside around sunset or sunrise and notice the location of the sun on the horizon with respect to familiar landmarks.

Because of the 23.4 degree tilt of the Earth’s axis, we receive the Sun’s rays most directly in the summer. In the winter, when we are tilted away from the Sun, the rays pass through the atmosphere at a greater slant, bringing lower temperatures. If the Earth rotated on an axis perpendicular to the plane of the Earth’s orbit around the Sun, there would be no variation in day lengths or temperatures throughout the year, and we would not have seasons.

In reality, March 16th is when day and night are both closest to 12 hours from Portland, Oregon, sunrise at 7:20 a.m. and sunset at 7:18 p.m.. 

At the 45th latitude North, the time it takes for the sun to fully rise and set, which is several minutes, is added to the day and subtracted from the night, and therefore the equinox day lasts a little longer than 12 hours. Another reason why the day is longer than 12 hours on an equinox is that the Earth’s atmosphere refracts sunlight. 

After March 17th, the daylights will be longer than nighttime until September 25th, after the autumnal equinox.

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