Cooling trend, with a side of smoke

July 3, 2018 – Dry with a cooling trend over the next couple days. Some smoke near wildfires. Daytime highs by Wednesday near or slightly below normal. A slight warm up for the end of the week.

Discussion

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Weak upper trough along the coast will bring more cooling today with daytime highs expected to come in around normal for this time of year. Most locations will see continued onshore flow carrying smoke and haze from the Lake and Yolo county wildfires eastward into the southern Sacramento and Northern San Joaquin valleys. An upper low dropping out of the Gulf of Alaska and into the Eastern Pacific will dig a trough along the west coast bringing still more cooling on Independence Day Wednesday. Daytime highs are forecast to come in around 5 degrees below normal. Stable southwest flow aloft will bring fair skies for evening fireworks. Upper trough moves little on Thursday so expect very little change in the forecast or temperatures. Upper trough lifts into the Pacific Northwest on Friday allowing western U.S. ridge to retrograde back west a bit and bring the start of a warming trend. Current GFS moisture proggs show some upper moisture from Hurricane Fabio being pulled into Norcal on Friday so some scattered clouds are likely.

Extended discussion (Saturday through Tuesday)

Deep trough centered off the West Coast will lift to the northeast for the start of the long term period as ridge of high pressure extends into NorCal from the east. Therefore, dry conditions and slightly warmer temperatures can be expected across the region. Locations across the northern Sacramento Valley could see daytime temperatures reaching the 100 degree this weekend into early next week. Meanwhile, the Delta-influenced areas could remain in the 90s given some onshore flow. Look for temperatures in the 70s to 90s over the foothills/mountains. Locally breezy winds expected at times, mainly over the mountains.