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A nice start to autumn; why not equal day and night on the equinox?

Thunderstorm chances return Tuesday PM

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The 2019 autumnal equinox is at 2:50 a.m. CDT this Monday. What does “equinox” mean? According to the Merriam-Webster dictionary:

Equinox descends from aequus, the Latin word for "equal," and nox, the Latin word for "night"

Sunrise and sunset tables show 12 hours and 8 minutes between sunrise and sunset in the Twin Cities this Monday. Why do have more than 12 hours of daylight?

According to timeanddate.com:

On the equinoxes, the geometric center of the sun is above the horizon for 12 hours, and you might think that the length of the day (hours of daylight) would be 12 hours too.

However, ‘sunrise’ is defined as the moment the upper edge of the sun's disk becomes visible above the horizon – not when the center of the sun is visible. In the same sense, ‘sunset’ refers to the moment the Sun's upper edge, not the center, disappears below the horizon. 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.

By the way, the sun rises due east and sets due west on the autumnal and vernal (spring) equinoxes:

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Illustration courtesy of SkyandTelescope.com.

Nice start to autumn

Most of Minnesota and western Wisconsin will enjoy plenty of sunshine on Monday. Many areas will see highs in the 70s:

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Monday forecast highs
National Weather Service

There’ll be some 60s in northeastern Minnesota.

Highs will be well into the 70s in most locations on Tuesday, with some spots in the south reaching 80 or warmer:

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Tuesday forecast highs
National Weather Service

The Twin Cities metro area will reach at least the upper 70s Tuesday afternoon, with a shot at 80.

Metro area highs retreat to the upper 60s Wednesday through Friday.

Thunderstorm chances late Tuesday

Some showers and thunderstorms are expected to move into northern and western Minnesota Tuesday afternoon, then spread southeastward. Showers and t-storms could arrive in Twin Cities late Tuesday afternoon or Tuesday evening.

The National Oceanic and Atmospheric Administration's North American Mesoscale forecast model shows the potential rain pattern Tuesday and Tuesday evening:

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NOAA NAM simulated radar Tuesday morning through Tuesday evening
Tropicaltidbits.com

It’ll rain in some spots that look dry in the loop, but the loop illustrates the general rain pattern within the NAM model.

Some strong or severe t-storms will be possible late Tuesday afternoon and Tuesday evening.  Updated weather information can be heard on the MPR network, and you’ll also see updated weather info on the MPR News live weather blog.

Tropical updates

Forecasters are watching two tropical storms in the Atlantic basin. Tropical storm Jerry could affect Bermuda early this week, while tropical storm Karen could move near or over Puerto Rico.

The National Hurricane Center shows this track for Jerry:

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Forecast track of Tropical Storm Jerry
NWS National Hurricane Center

Here’s a portion of the Sunday evening update from the National Hurricane Center:

Jerry is moving toward the north-northwest near 9 mph (15 km/h). A turn toward the north is expected on Monday, followed by a turn toward the north-northeast on Tuesday, and toward the northeast on Wednesday. On the forecast track, the center of Jerry is expected to pass near Bermuda Tuesday night. Maximum sustained winds are near 65 mph (100 km/h) with higher gusts. Little change in strength is forecast during the next 48 hours. Tropical-storm-force winds extend outward up to 105 miles (165 km) from the center.

The National Hurricane Center shows this track for Karen:

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Forecast track of Tropical Storm Karen
NWS National Hurricane Center

Here’s a portion of the Sunday evening update from the National Hurricane Center:

Karen is moving generally toward the west-northwest near 13 mph (20 km/h). A turn toward the northwest is forecast to occur later tonight or on Monday, followed by a turn toward the north on Tuesday. On the forecast track, the center of Karen will continue to move away from the Windward Islands this evening, and then move across the eastern Caribbean Sea tonight and Monday. On Tuesday, Karen is expected to pass near or over Puerto Rico and the Virgin Islands. Maximum sustained winds are near 40 mph (65 km/h) with higher gusts. Little change in strength is forecast during the next 48 hours.

Tropical storm updates are issued every three hours or so.