Cold Trough From Gulf of Alaska Will Chill Pasadena Through Next Weekend

A cool and showery weather pattern will affect Pasadena this week as a storm system off the coast sweeps through and then exits the region. A few showers are expected in the Los Angeles Basin this morning, with locally gusty northeast winds possible across the mountain and foothill areas of the Southland.

A slight warm-up is forecast for  Monday, with low clouds possible over much of the San Gabriel Valley. Temperatures will likely still remain below normal as moderate onshore flow develops ahead of the next system. Gusty southwest winds could develop across the interior portions of the area.

Starting Tuesday, a cold trough of low pressure moving through the Gulf of Alaska will dig south into southwestern United States, bringing a very cold and windy weather pattern. As winds diminish and skies clear, a very cold and dry air mass will bring the potential for frost conditions for Tuesday night and early Wednesday.

A very cold air mass will remain across the region into Wednesday, with a vast majority of valley locations struggling to reach 60 degrees for a high temperature. Dry weather is expected for Thursday, followed by another storm system moving in on Friday. There is a large spread of precipitation amounts and forecast timing for the weekend, with an extended period of cooler-than-normal weather likely to continue.

Sunday will bring isolated showers, with partly sunny conditions and a high near 61. Sunday night will be mostly cloudy, with a low around 43. Monday will be partly sunny, with a high near 63, and a 20 percent chance of showers Monday night. Tuesday will have a 20 percent chance of showers before 10 a.m., mostly cloudy, with a high near 57.

Here is the detailed forecast from the National Weather Service:

Sunday: Isolated showers. Partly sunny, with a high near 61. Southwest wind around 5 mph. Chance of precipitation is 20%.

Sunday Night: Mostly cloudy, with a low around 43. Southwest wind 5 to 10 mph becoming northeast in the evening. Winds could gust as high as 15 mph.

Monday: Partly sunny, with a high near 63. Northeast wind 5 to 10 mph becoming south in the morning.

Monday Night: A 20 percent chance of showers. Mostly cloudy, with a low around 45. South southeast wind 5 to 10 mph.

Tuesday: A 20 percent chance of showers before 10am. Mostly cloudy, with a high near 57.

Tuesday Night: Patchy frost after 10 pm. Otherwise, mostly clear, with a low around 35. Breezy.

Wednesday: Patchy frost before 10 am. Otherwise, sunny, with a high near 58.

Wednesday Night: Clear, with a low around 38.

Thursday: Sunny, with a high near 61.

Thursday Night: Partly cloudy, with a low around 40.

Friday: A slight chance of rain. Mostly cloudy, with a high near 61.

Friday Night: A chance of rain. Mostly cloudy, with a low around 43.

Saturday: A chance of rain. Mostly cloudy, with a high near 61.