Isolated thunderstorms possible today

April 20, 2019 – Showers and thunderstorms are forecast for today as a low pressure system moves inland. Temperatures will be significantly cooler today, with a warming trend starting Sunday and lasting through the middle of next week.

Discussion

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A trough will swing inland today which will bring showers and thunderstorms to the region. Hi-res model guidance and ensemble forecasts suggest that we could see a few rounds of this activity. The first round will be later this morning and should stay confined to northern portion of the Valley, in Shasta Co and likely east of I-5 likely. The second shot for showers and thunderstorms will be later this afternoon and evening, with the potential be more scattered to widespread, especially over the northern valley and surrounding mountains. Convective ingredients support heavier rain and perhaps even some small hail. Temperatures for the day will be 10-15 degrees cooler than yesterday and much closer to our seasonal normal for this time of year.

As the low continues to exit the region, high pressure start to build to our west. Dry and milder weather is expected for Sunday, with warming accelerating into next week. Expect to see temperatures about 10-15 degrees above normal again through mid next week.

Extended Discussion (Wednesday through Saturday)

Upper ridge over the southwest U.S. Wednesday starts out the extended period under fair skies and well above normal temperatures. Daytime highs Wednesday could reach up to 20 degrees above normal Upper ridge axis shifts east of the state by Thursday for a little cooling but Thursday should remain dry under the ridge. Extended models hint at some form of shortwave disturbance bringing showers across the northeast corner of the state Thursday evening. Stability progs indicated enough instability for a thunderstorm threat in this area as well. Models differ on details so confidence is low but shower threat will remain in the forecast across the northern zones through Friday. End of extended forecast looks dry next Saturday but model confidence remains low.