Heat advisory in effect through tomorrow

June 10, 2019 – Hot temperatures today through mid-week will bring excessive heat concerns to most of Valley. A little cooler but still well above normal temperatures for the second half of the week. No precipitation in the forecast for the forecast area through the end of the week.

Discussion

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A high pressure ridge amplifying over the west coast will bring increasing temperatures today and Tuesday. Daytime highs today are expected to range from 10 to 15 degrees above normal and Tuesday may see highs 15 to 20 degrees above normal. For the most part, daytime highs are predicted to come in just shy of records but one or two might fall over the next couple of days.

Subsidence under the ridge will bring continued very dry and stable conditions. Winds should remain fairly light which should reduce fire weather concerns compared to this past weekend.

Upper ridge axis is forecast to shift east of the state on Wednesday bringing a more onshore flow and slightly cooler temperatures. Even with this cooling, daytime highs will remain well above normal.

There is still some question as to threat of afternoon showers over the mountains. GFS has been painting in afternoon showers during this timeframe for the last several days while operational ECMWF has not. NBM and consensus models starting to come in line with idea of isolated afternoon mountain showers but will wait to see if this trend continues before introducing a shower threat mid week.

Slight breakdown in upper ridge and continued onshore flow brings a little more cooling Thursday but again highs are expected to remain about 10 degrees above normal. Surface humidity and overall atmospheric moisture continue to rise on Thursday so need to continue to monitor for afternoon mountain shower threat.

Extended Discussion (Friday through Monday)

Upper ridging gradually gives way to upper troughing over NorCal through the weekend into early next week. Models diverge on strength of upper trough and ensemble spread is significant. For now, forecast advertises a threat of afternoon showers and thunderstorms over the Sierra Nevada Sunday and Monday.

Above normal daytime temperatures expected through the extended period with mostly 90s in the Central Valley and 70s and 80s for the mountains and foothills.