Storm Series to Drench Pasadena This Week

After enjoying one final sunny day Monday with temperatures in the low 70s, Pasadena residents should prepare for a dramatic shift as a series of storms will bring periods of rain, much colder temperatures and possible local flooding through much of the week, according to National Weather Service forecasters.

The most significant rainfall is forecast for Wednesday evening and overnight as a vigorous cold front sweeps through the area.

“Very good confidence that this will be a moderate storm with the potential to create local flooding and debris flows,” National Weather Service forecasters said in their Monday morning report.

Rainfall totals of 1-2 inches are expected for valley locations like Pasadena, with rain rates potentially exceeding half an inch per hour. Forecasters predict a three-hour to six-hour period of moderate to heavy rain, with enough atmospheric instability to produce thunderstorms that could generate rainfall rates approaching one inch per hour.

The pleasant weather begins to change Monday night as the first storm system approaches. A 30% chance of rain will develop after 11 p.m., though precipitation amounts will remain minimal overnight, with less than a tenth of an inch expected.

Tuesday brings a 60% chance of rain with a high near 60 degrees. New precipitation amounts between a tenth and quarter of an inch are possible, followed by a brief decrease in rain chances Tuesday night.

The cold front will move over the area overnight Wednesday into the predawn hours of Thursday. Steady rain will turn to showers Thursday morning, with the chance of precipitation at 80%.

The temperature trend shows a steady decline through the week, with Wednesday reaching only around 60 degrees before Thursday plunges to the mid-50s — a striking 10 to 15 degrees below normal for mid-March.

The weekend outlook shows improving conditions Saturday before another system may bring light rain on Sunday. Temperatures will rise noticeably to the mid-60s by Saturday.

Here is the latest forecast for Pasadena from the National Weather Service as of 3:18 a.m. on Monday, March 10:

Today: Sunny, with a high near 71. North wind 5 to 10 mph becoming south in the morning.

Tonight: A 30 percent chance of rain after 11:00 p,m. Mostly cloudy, with a low around 47. Southwest wind 5 to 10 mph becoming east southeast after midnight. New precipitation amounts of less than a tenth of an inch possible.

Tuesday: Rain likely. Mostly cloudy, with a high near 60. East southeast wind 5 to 10 mph. Chance of precipitation is 60%. New precipitation amounts between a tenth and quarter of an inch possible.

Tuesday Night: A 20 percent chance of rain before 11:00 p.m. Partly cloudy, with a low around 47. East wind 5 to 10 mph.

Wednesday: A 50 percent chance of rain. Mostly cloudy, with a high near 60. South wind 5 to 10 mph, with gusts as high as 15 mph. New precipitation amounts between a tenth and quarter of an inch possible.

Wednesday Night: Rain. Low around 46. Chance of precipitation is 100%.

Thursday: Showers. High near 56. Chance of precipitation is 80%.

Thursday Night: A chance of showers before 11:00 p.m. Partly cloudy, with a low around 38.

Friday: A slight chance of rain after 11:00 a.m. Partly sunny, with a high near 58.

Friday Night: A slight chance of rain before 11:00 p.m. Mostly cloudy, with a low around 44.

Saturday: Partly sunny, with a high near 63.

Saturday Night: Partly cloudy, with a low around 47.

Sunday: Partly sunny, with a high near 65.