June 28, 2018 – June 28, 2018 – Seasonable weather today. Warmer Friday with hot, dry, and breezy conditions over the weekend. Cooling trend returns early next week.
Fire Weather Watch from late Saturday night through Sunday evening
Mostly clear skies prevail across interior Northern California. A weak upper trough is currently passing through the region, which has kicked up the Delta Breeze. The upper trough has effectively mixed out the marine layer along the Bay Area coast, though a few patches of stratus can still be found in Napa Valley and in the East Bay. The upper trough axis will shift eastward later today, with flow aloft becoming more northwesterly.
Look for high temperatures today to reach the upper 80s to mid 90s across the Valley, with 70s to 80s over the mountains. These forecast highs are within a few degrees of normal. Warming trend will continue into Friday as the eastern Pacific ridge strengthens northward, and surface high pressure builds into the Pacific Northwest.
Locally breezy north winds are likely to develop starting late Thursday night, likely continuing Friday and into Saturday. Upper wind patterns suggest that the strongest winds are likely to occur during Friday night into Saturday morning, and again Saturday night into Sunday morning. Local north wind gusts upwards of 35 mph are possible in the usual wind prone spots: the western Sacramento Valley and adjacent Coastal Range, along with NE foothills.
A brief heat spell is expected Friday into Saturday, not unlike what occurred last week. Saturday looks to be the hottest day coming up, with Valley temperatures ranging from 100 to 108. Onshore flow looks to return starting on Sunday.
EXTENDED DISCUSSION (Monday through Thursday)
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Our ridge will be pushing back west to start the extended period as an upper level trough dips down into the PacNW. This will start to bring onshore flow on Sunday but winds don`t look to shift until afternoon/evening time. Still should see warm temperatures on Sunday but will be cooler in the southern Sac Valley due to the onshore flow.
A cooling trend will continue throughout the extended period as the upper level trough drops south over NorCal. Temperatures look very pleasant for the 4th of July with mid to upper 80s in the valley, 70s and 80s in the foothills and 60s and 70s in the mountains. That will be about 5-10 degrees below normal.
As the trough axis passes through on Tuesday we may see a light shower pop up in the northern mountains but looks unlikely at this time. A strong ridge will start to build in from the east towards the end of the week and that will start to warm temperatures back up.