September 11, 2017/pm
Summary: Scattered light showers as of the time of this writing had broken out over western Fresno and Madera Counties. This activity was moving northwestward at a rapid pace. Upper level low pressure is near 400 miles to the west/southwest of San Luis Obispo and is forecast to drift further north through Tuesday. It will then move inland over central California Wednesday. By early Thursday morning, this feature will be merging into a trough of low pressure moving into California with considerably cooler weather.
Satellite imagery over southern California is showing generally partly cloudy skies from the Coachella Valley northward with a few showers beginning to show up. If model information is correct, the daytime heating process will cause thunderstorms to flare up which will move rapidly towards the Kern County mountains and the Sierra Nevada. It’s possible some of this activity could reach into the San Joaquin Valley tonight with a lesser chance Tuesday and Wednesday as the most active portion of the low will be over its northern flank. By Tuesday night, it will be over northern California.
Still, as the low drags across our area Wednesday, we need to maintain a small chance of isolated showers and thunderstorms in the forecast. Even though a trough will be moving through Thursday, no rain is expected, but considerable cooling will occur as readings fall into the mid 80s.
A slow warm up is due over the weekend, but a lingering trough of low pressure will remain over the west, allowing near to only slight above average temperatures. Of note also is the pattern beginning early next week which gives the possibility of a tropical system moving up the Baja peninsula. The projected configuration during this period will be out of the southwest, so most of the moisture should move into Arizona and New Mexico, but this is something we’ll definitely need to keep tabs on.
Forecast: Variable cloudiness tonight with a chance of widely scattered showers and isolated thunderstorms. Partly cloudy Tuesday through Wednesday with a small chance of scattered showers and isolated thunderstorms. Becoming mostly clear Wednesday night with mostly clear skies Thursday through Monday.
Temperatures: Lows tonight will be in the upper 60s to the mid 70s. Highs Tuesday will warm into the mid 90s. Lows Tuesday night will fall into the mid 60s to the lower 70s. Temperatures will warm into the lower 90s Wednesday.
Next update: September 11