July 23, 2018 – Hotter weather returns this week, peaking mid-week. Potential for thunderstorms in the mountains continues through mid-week. Heat Advisory from noon Tuesday to 11 PM Thursday.
Skies have cleared out for the most part following Sunday afternoon and evening`s moist deep convection over the northern mountains and Sierra Nevada. Current temperatures are running about the same as 24 hours ago over most of the area and range from the lower 50s in the mountain valleys to the mid 80s at the north end of the Sacramento Valley. Hotter weather returns to the region this week as upper ridging extends northward. A brisk southwest breeze continues at Travis AFB, but coastal profiler day indicates the marine layer is gradually being squished. This will allow temperatures to gradually warm across the region through mid-week.
Highs across the northern half of the Sacramento Valley are expected to range from 105-110 Tuesday thru Thursday. Enough onshore flow thru the Delta is expected to linger to temper heat across the southern Sacramento Valley into the northern San Joaquin Valley.
Late-day thunderstorms will be possible along and east of the northern Sierra Nevada crest and near Mt Lassen the next few days, followed by drier conditions late this week.
Extended Discussion (Friday through Monday)
Upper level ridge axis continues to retrograde through the extended period. However, flow becomes more zonal over NorCal through early weekend, allowing for continued onshore flow and not much fluctuation in temperatures. Daytime temperatures expected to remain in the mid 90s to near 109 in the valley and 80s to 90s in the foothills and mountains.
The onshore flow will keep overnight temperatures in the low to mid 60s for most of the valley, up to the low 70s in the northern Sacramento valley. Dry conditions expected across the region.