June 20, 2018 – A few high clouds are moving into NorCal early this morning ahead of the approaching short-wave as the upper ridge is displaced to the east. Current temperatures are within a few degrees of readings from 24 hours ago and generally range from the mid 40s in the mountain valleys to the 60s to lower 70s across the Central Valley.
Highs today are expected to be similar to Tuesday’s as the incoming short-wave temporarily halts the warming trend.
The moderate Delta Breeze will continue and may bring a few degrees of cooling to areas influenced by it. Deep convection later today is expected to remain along the OR/CA border and northward into the PacNW.
The warming trend will return Thursday as ridging strengthens along the West Coast. Widespread triple digits return to the valley on Friday as surface flow becomes northerly and the Delta Breeze diminishes. It appears that the heat will peak on Saturday with much of the valley forecast to be around 105 along with breezy north winds.
Extended discussion (Sunday through Wednesday)
Hot conditions continue on Sunday, but a cooling trend begins that will bring near normal temperatures for the rest of the extended period.
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Sunday morning should be quite warm, remaining in the upper 60s to mid 70s for the Valley, foothills, and Delta, and even into the lower mountains. This is due to a warm airmass and breezy northerly winds late Saturday into Sunday morning. As the ridge axis shifts eastward later Sunday, onshore develops. This could bring cooler temperatures to Delta breeze influenced areas, keeping temperatures there below triple digit levels. The northern and central Sacramento Valley could actually see temperatures as hot or even a little hotter than Saturday, though, with projected highs of 106 at Redding and Red Bluff.
Temperatures on Monday morning will be noticeable cooler across the area. Minimums in the Delta and Sacramento metro area may drop into the 50s, with other areas also seeing a 5-10 degree drop compared to early Sunday. Afternoon highs are expected to remain below triple digits across the area. Near to slightly above normal temperatures continue through mid week.