HERE COMES THE MOISTURE. HIT AND MISS THUNDERSHOWERS NEXT 36 HOURS.

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As of Sunday morning, deep monsoonal moisture, around 2-3 times our average at this time of year, continues to stream north through California.

You can see the cloudiness this is causing across the state at midday Sunday. (Image 1) Lightning was already occurring (green, red and yellow) as thundercells ramp up over the desert areas of California.

This monsoonal moisture is bring driven north by high pressure to our north, and low pressure to our west. (Image 2) As of Sunday, deep moisture had made its way to the Bay Area. (Image 3)

The amount of moisture in the air will make it feel muggy today and Monday. Precipitable water in the atmosphere…one measure…is pretty much like the midwest in the summer. (Image 4) Deep moisture is in place, and will be for the next 24-36 hours. (Image 5)

THUNDERSHOWERS

Moisture alone isn’t enough to create thundershowers. You need an upward push in the atmosphere. This will come with two weak impulses in the upper atmosphere that will rotate into the area over the next day or two.

As these pass over the North Bay, showers will be more likely. The first will be late Sunday into early Monday, when the “K Index”, a measure of moisture and instability, will be highest. (Image 6)

The highest K index will be inland, but may reach reach 30 on this scale across the North Bay. 40 and above is considered necessary for thundershowers in most cases.

Still, there is a 20-30 percent chance of thundershowers over the area sometime late Sunday to mid-morning Monday. And, some of the high resolution models are hinting at high cloud tops, (Image 7), and also showers around our area early Monday morning. This is around 4-5 AM Monday.(Image 8)

The next chance for showers will be late Monday to early Tuesday. The “K index” will be similar to early Monday according to some of the high resolution models. You can see that here. (Image 9)

After that, there are signs that most of the thunderstorm threat will move out of our region. But there is one last wild card.

As Hurricane Frank moves north from the Baja coast, there is a chance it could throw some moisture and a few showers our way. This is a low chance right now, but it is worth watching. (Image 10) This would be in the late Tuesday time frame.