Slightly cooler today, then warmer through the remainder of the week

May 6, 2019 – Mountain showers and thunderstorms are possible this week. Slightly cooler today, then warmer through the remainder of the week.

Discussion

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Satellite imagery shows the mid/upper level closed low along the central California coast slowly moving to the south-southeast. Mid and high clouds (and a few sprinkles), associated with the deformation zone to the north of the low, remain across the southern half of the forecast area. Current temperatures are mild ranging from the 40s in the mountains to the 50s to lower 60s elsewhere. Breezy/windy conditions continue through the Delta into the southern Sacramento Valley supported by a 6+ mb SFO-RNO gradient.

The low is forecast to continue moving southeast toward SoCal today before ejecting eastward Tuesday. Lingering instability, with daytime heating, is expected to be sufficient for scattered shower and thunderstorm development over higher terrain today and Tuesday. Strengthening ridging centered offshore the PacNW may cap off any shower development on Wednesday. By Thursday, ensemble and latest operational runs indicate a retrograding low moving into California from the Great Basin/Rockies supporting potential for showers/thunderstorms south of I-80.

High temperatures will cool a little more today, then gradually trend up through mid-week. Highs are expected to return to above- average across the entire region by Wednesday.

Extended Discussion (Friday through Monday)

Guidance continues to show the ridge over the Pacific nosing into the Pacific Northwest and British Columbia mid to late week, while the trough over desert southwest tilts positively. This will allow an upper level low pivot back into southern California which could bring showers and thunderstorms back to the mountains. The best chances look to be on Thursday and Friday for the mountains south of I-80 and Hwy 50. Come the weekend, the Pacific high looks to nudge its way southward in the Pacific Northwest which would bring dry and warm conditions to the region.