Scattered showers and thunderstorms over the mountains, dry and warming up elsewhere

May 7, 2019 – Afternoon and evening mountain showers and thunderstorms are possible this week. Warmer through the rest of the week.

Discussion

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Mostly clear skies cover the region early this morning. Gusty southerly winds are not as strong this morning compared to early Monday, but onshore gradients continue and we`re expecting some stratus inland around the Sacramento region again this morning. Current temperatures range from the mid 30s to mid 40s in the mountains to the upper 40s to upper 50s elsewhere.

Enough lingering moisture and instability remains for a few showers and thunderstorms to pop up with daytime heating across the northern Sierra and over portions of the Coast Range. Highs today will be warmer than Monday as onshore flow slackens and high pressure leads to some synoptic warming of the airmass.

A strengthening upper level ridge centered offshore the Pacific Northwest is expected to bring increasing subsidence which will limit any shower development on Wednesday. By Thursday and Friday, ensemble and latest operational runs indicate a retrograding low moving into central California from the Great Basin/Rockies supporting potential for showers/thunderstorms south of I-80.

High temperatures will gradually trend up through mid-week. Highs are expected to return to above average across the entire region Wednesday thru Friday, with the northern Sacramento Valley reaching the lower 90s.

Extended Discussion (Saturday through Tuesday)

Little change to the extended forecast as models and ensembles continue to show the rex block like pattern over the west. An upper level low will likely be situated over central or southern CA this weekend while ridging to our north noses inland and then gradually sags southwards. This will bring mostly dry conditions to the area; however, there is a chance for isolated to scattered showers and thunderstorms over the mountains. Long range and ensemble guidance then shows split flow over northern CA on Monday, with a broad trough forming over the Pacific. This could bring additional showers and thunderstorms to the region, but impacts and timing confidence remain low at this point.