July 7, 2020 – Dry weather with seasonably warm temperatures for the week.
Discussion
Upper level trough has brought onshore flow with breezy conditions and cooler temperatures. Gusty winds have been a factor in enhanced fire weather conditions, with grass fires reported in the area this evening. Humidity levels are increasing overnight, though, and this should help to mitigate fire weather conditions to some degree. The surface pressure gradient has relaxed, from a high of 10.3 mb between San Francisco to Sacramento at 01Z, down to 6.2 mb at 09Z. Winds generally are decreasing, though at 2 am were continuing to gust up to 31 mph at Fairfield, 25 mph at Stockton.
Temperatures under the onshore flow have been 2 to 8 degrees cooler than last night. Lows this morning will be generally in the mid to upper 50’s in the Valley and Delta. Afternoon highs will be near normal levels.
The upper level pattern will flatten out as the trough exits to the east. Four Corners ridging will gradually expand westward into the region. Temperatures increase a few degrees on Wednesday, then a few more by Thursday, with Valley highs in the mid to upper 90s. While temperatures will be 1 to 5 degrees abover normal, Heat Risk is expected to be generally at low risk levels for those sensitive to heat.
Upper trough will transition into more of a flat ridge through the week with a another quick moving trough passing mainly north of the area late Thursday. Temperatures will be near or just slightly above normal through the week with dry weather and generally light winds, except breezy at times through the Delta.
Extended Discussion (Saturday through Tuesday)
The upper level ridge will be set up over the four corners region extending west into SoCal with troughing over the PacNW. This will bring warmer temperatures for the weekend across NorCal with highs near 100 in the Valley. Troughing over the PacNW will begin to push east early next week. This will bring a slight cooling trend.