Updated: Tuesday, May 31, 2016 07:08 AM
High pressure is bringing us summerlike weather this week. Temperatures are going to reflect this pattern through Saturday, but a cooling trend may occur as early as Sunday as an upper level closed low pressure approaches the coastline.
This morning is clear and mild, with a morning low of 63°. Temperatures are running about 3°-5° warmer than 24 hours ago. Today should see mostly sunny skies and warmer temperatures as the ridge builds into the region. The high this afternoon is predicted at 91° which is 5° warmer than Monday's high. Normal (measured at De Sabla) for this time of year is 79°. The low tonight is expected to only drop to 69°. Winds could be gusty at times this morning out of the northeast at 9-14 mph, especially out near the Feather River Canyon. Elsewhere, winds should be light and variable this morning, becoming west to southwest this afternoon up to 6-7 mph.
Wednesday and Thursday should see the ridge of high pressure flatten out a bit and shift slightly to the east in response to a trough of low pressure passing through the Pacific Northwest. This may bring a slight cooling effect to our region on Wednesday through Thursday. Wednesday's high is predicted at 90°, and 88° on Thursday. Overnight lows are expected to be near 65°. Any shower activity from the trough passing through the Pacific Northwest is expected to remain well to the north of Magalia as subsidence (sinking air) squashes any upward movement of any clouds.
Friday should see the ridge rebuild over us and bring the afternoon high temperature back to near 92°. Saturday could better that at 93° as the ridge axis passes over us. The low temperature on Saturday morning is only expected to drop to 70°, so sleeping may be lousy. As the upper low nears the coastline, there will be a token 5% chance of measurable precipitation on Friday and Saturday in Magalia, but will likely not happen. There is a better chance of showers in the higher mountain areas.
By Sunday, temperatures should start to cool down as the onshore air flow increases and the ridge shifts to the east of us. The upper low is predicted to reach the Central California coastline on Sunday morning, and possibly linger over Central California for a couple of days. The old saying "cutoff low, weatherman's woe" describes the forecast with this low as it is hard to predict the movement of these kinds of low pressure areas as they are not steered by the jet stream. It doesn't look to be a particularly deep low pressure cell, but still may create enough instability in the atmosphere to increase the odds of precipitation in Magalia to a 10% chance by Monday and Tuesday. A trough of low pressure will likely merge with the upper low over Central California by around the middle of the week and continue the chance of showers over Northern California, especially over the higher mountains. Snow levels are expected to be in the 13,000' range, so should not be an issue driving over the mountain passes. Have a great Tuesday. Bob