June 11, 2019 – Well above normal temperatures today. A very slow cooling trend through the weekend but remaining warmer than normal. A light chance of mountain thunderstorms Wednesday and Thursday and again early next week. Otherwise, fair skies through the extended period.
Upper level ridge axis centers over the west coast today bringing the warmest temperatures overall for the week. Daytime highs today are forecast to 15 to 20 degrees above normal. Current forecast puts highs just under records but one or two may fall today.
An excessive heat warming remains in effect for today. Upper ridge axis slips just east of the state overnight allowing for a slight onshore flow to begin through the delta. Overnight minimums should be about the same as this mornings which means that most valley locations will be dropping into the 70s by late this evening. Have therefore decided to end the excessive heat warming by 06z Wednesday.
Upper ridge axis shifts into the Great Basin by Wednesday afternoon allowing a more onshore flow and slightly cooler temperatures during the day on Wednesday. GFS continues to bring in possible short wave disturbance and isolated mountain showers Wednesday afternoon. Other models hint at this as well so put in a few isolated afternoon thunderstorms at the highest elevations.
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A very weak shortwave trough crosses NorCal on Thursday for a bit more cooling, delta wind and a threat of isolated thunderstorms over the highest terrain. Flat upper level ridging pushes in over the west coast on Friday but continued onshore flow will keep daytime highs level. Subsidence under the building ridge should keep mountain shower threat out of the Friday forecast.
Extended Discussion (Saturday through Tuesday)
Upper troughing over CA will keep a slight chance of afternoon to evening showers or thunderstorms over higher terrain of 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.