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June 18, 2018 – A few clouds linger along the southern Cascade/northern Sierra crest and over the coast range, otherwise clear skies early this morning. Current temperatures are milder across most of the region compared to 24 hours ago and range from the mid to upper 30s inthe mountain valleys to the upper 50s to mid 60s across the Central Valley.
Weakening cyclonic flow will linger today as the weekend low moves toward the northern Rockies. Can’t rule out an isolated late-day shower or thunderstorm near Mt. Lassen, but much of the region will return to warm and dry weather today as highs are expected to warm about 10 degrees from Sunday’s readings.
Upper ridge builds across the area Tuesday and Wednesday before the next short-wave trough is forecast to dent the ridge on Thursday. Temperatures are expected to be seasonably hot with highs in the Central Valley forecast to range from the mid 90s to around 100. The threat of showers and thunderstorms with Thursday’s trough is expected to remain to the north along the Oregon/California border.
Extended discussion (Friday through Monday)
Dry and very warm weather is expected through the end of the week as Pacific upper level ridging expands eastward into the region and builds. Widespread triple digits are expected across the Valley by Friday, with even hotter temperatures expected on Saturday. This will bring the potential for moderate heat risk for sensitive groups including the elderly and the very young for Friday, potentially areas with areas of high risk on Saturday. Breezy north winds will bring lower humidity levels and increasing fire danger. Sunday may be slightly less hot, as a trough moving through the Pacific Northwest flattens the ridge and shifts the axis eastward. Cooler weather returns on Monday, with Valley highs dropping to around 90.