July 27, 2018 – Excessive heat continues through Friday for the northern Sacramento valley and surrounding foothills and portions of the northern San Joaquin valley. A little less hot this weekend through the middle of next week with a gradual decrease in high temperatures but temperatures will remain above average.
Discussion (Today through Saturday)
We will be in a quiet weather pattern over the next several days. The strong upper level ridge that has brought the heat will be drifting south on Friday and we will see slight height falls across NorCal.
Temperatures are still expected to be hot though pushing as hot as 110 in the north but a bit cooler in the south valley where we will see a Delta influence. An Excessive Heat Warning will remain in effect for the northern and central Sac Valley with a Heat Advisory for the remainder of the valley and foothills on Friday.
Smoke will continue to be an issue over the northern valley and the Sierra due to the Carr and Ferguson Fire. The upper level ridge will be pushing back north into the weekend but it will be setting up a bit further to the east than what we saw over this last heat wave. Hot temperatures are still expected but the heat concerns will mainly be for sensitive groups. This will allow the heat products to expire at 8 PM Friday evening and current thinking is we will not need to extend them into the weekend. A lack of moisture, forcing and instability will keep mountain thunderstorm chances out of the forecast.
Extended Discussion (Tuesday through Friday)
Extended period starts out Tuesday with a high pressure ridge over the western U.S. for fair skies and daytime temperatures a few degrees above normal for this time of year. If forecast models verify then NorCal will be under southwest flow aloft between the ridge and a trough of low pressure developing along off the Pacific Northwest coast.
This stable southwest flow should keep monsoon moisture and afternoon thunderstorm activity east and south of the forecast area. Extended models push the upper trough eastward into Oregon and Washington going into mid week displacing the western U.S. ridge inland a bit. This should bring a very gradual cooling trend.
By Friday, NorCal should be under mainly westerly flow and a fairly flattened upper level ridge bringing daytime temperatures down to near or just slightly above normal.