August 7, 2018 – Slightly above normal temperatures through mid week with weak winds. Onshore flow increasing Thursday through Saturday with temperatures returning to near normal. Smoke from wildfires will continue to impact the air quality.
Discussion (Today through Thursday)
An upper level ridge will continue to build into NorCal through the mid part of the week. We will see 850 mb temps warm a few degrees compared to what we saw on Monday, this will bring afternoon highs a bit warmer running about 5 degrees above average in the valley. Smoke became quite heavy on Monday across the area and we should see similar conditions again on Tuesday especially given the weak winds at the surface and aloft. This may also hold temperatures down mainly where we see the thickest smoke.
Similar temperatures are expected on Wednesday and Thursday as the ridge continues to dominate our weather. Thursday we will start to see a trough approach from the west and this will bring an increase in winds and onshore flow. Models are showing 850 mb winds pushing above 20 knots in the valley north of Sacramento with a well mixed layer, gusts up to 25 mph will be possible in this area Thursday afternoon into the evening. This may also help to clear up some of the smoke.
The trough pushes into the PacNW on Friday and that will be the start of a gradual cooling trend. With the trough pushing the ridge back east we may see some monsoon moisture push back north but models are keeping it out of our area with it staying south and east.
Extended discussion (Saturday through Tuesday)
Short wave trough moves through the PacNW over the weekend with associated broad troughing over NorCal. This will result in slight cooling over the forecast area, but continued above normal temperatures. Locally breezy conditions expected in the Coastal Range and Delta and over higher mountain terrain, mainly afternoons into evenings.
Models differ into early next week with GFS brings another upper low into PacNW while EC expands Desert SW High back over NorCal. With uncertainties, current forecast trends towards climatology temperature wise early next week. Mainly dry weather expected with wildfire smoke likely to continue resulting in poor air quality.