Rain Chances Tonight, Big Cool Down this Weekend

Good afternoon folks!!

Cloudy skies from this morning have transitioned into partly sunny skies this afternoon. Thanks to the cloud cover from this morning and a steady wind out of the NE, high temperatures for today should top out in the middle 50s across much of the area.

The rain chances are on the increase as we head into tonight, thanks to an elongated middle to upper-level trough moving through the region with a strengthening jet stream over the Ohio Valley. The strengthening of upper-level winds indicates divergence aloft and convergence in the lower-levels of the atmosphere. The peak strengthening of the shortwave will likely happen over eastern KY as the SW low-level jet kicks it into gear during the overnight hours. PWAT (Precipitable Water) values are suppose to reach about an inch just east of Bowling Green area. Precipitable Water is the measure of the depth of liquid water at the surface that would result after precipitating all of the water vapor in a vertical column over a given location, usually extending from the surface to 300 mb (NWS Glossary, 2009). The response or result will be numerous rain showers throughout south central Kentucky.

Below: NAM 09Z 11-09-2018 PWAT & Sfc-400mb Mean Wind

For your Friday, rain chances stick around for the morning hours as the upper-level trough axis and surface low pressure move northeastward. Light rain showers will exit the region heading into the early afternoon hours with partly cloudy skies sticking around for the rest of the day. High temperatures across the area on Friday will have a hard time getting out of the 40s thanks to the persistent cloud cover and a steady wind out of the NW. The figure below shows CAA (Cold Air Advection) filtering into the area from the north throughout the day on Friday.

Below: NAM 18Z 9-9-18 850mb Theta-e & Winds

Friday night, high pressure will build into the area from the west. Cloudy skies from earlier in the day will move out of the area during the early evening hours, giving way to mostly clear skies. Temperatures throughout the evening hours and into the early morning hours will cool quite a bit thanks to the mostly clear skies. Temperature cools off more under clear skies, because heat that is emitted from the earth’s surface escapes freely into the atmosphere resulting in cooler temperatures. Low temperatures across the area for Friday night will struggle getting out of the 20s.

Surface high pressure that moved into the area from the west will dominate the region the whole weekend. High pressure over the area means that conditions will remain dry and cool. High temperature for the Bowling Green area will climb into the upper 30s, possibly hitting 40°.

Forecast

Tonight: Rain with otherwise cloudy skies. Low around 42° with NE winds at 5-10 mph. Precipitation totals less than a quarter inch.

Friday: Showers mainly in the morning hours. High temperature of 48° with NW wind at 5-10 mph. Precipitation totals during the morning hours of less than a quarter inch.

Friday night: Partly cloudy skies with a low of 28°. NW winds at 5-10 mph.

Saturday: Sunny skies, High of 40°. NW winds at 3-8 mph.

 

 

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