textproduct: San Joaquin Valley

KEY MESSAGES

1. Another round of monsoonal moisture will bring chances for thunderstorms across the Sierra Nevada crest through the middle of the week.

2. High pressure over the region will maintain temperatures near season averages for most of this week.

DISCUSSION

High pressure will be asserting itself again in the upcoming week after a brief weakening towards the end of last week. The center of the ridge will position itself over the Great Basin/Four Corners region, resulting in south to southeast flow across central California. As with most flow from this portion of the country during the summer timeframe, a push of monsoonal moisture is again expected over the next few days as more saturated air is transported northward from the Gulf of California. The warm, saturated air will rise and condense over the Sierra Nevada during the afternoon periods, resulting in chances for thunderstorms, especially along the crest. Beginning today, there is a 20 to 30 percent probability for thunderstorm development in this area, with these chances returning each afternoon at least through Wednesday. Additional moisture already in place in the higher elevations due to outflow from Tropical Storm Elida may further enhance the available energy that can be tapped into. As opposed to the potential from last week, these storms will be on the wetter side, with at least a 40 to 50 percent probability for a wetting rain (more than 0.10") where these storms occur; additionally, there is a 30 to 40 percent probability for more than one quarter inch. Any storms that develop have potential for small hail, gusty and erratic winds, and locally intense rainfall rates. Cloud-to- ground lightning will also be a threat and has potential to spark new wildfires on dry fuels outside of storm.

At lower elevations, the high pressure will continue temperatures near to slightly above average through this week. In the San Joaquin Valley, there is a 50 to 60 percent probability for temperatures to exceed 100 degrees each day through Tuesday. These probabilities rise to 60 to 70 percent on Wednesday as the prevailing upper level flow briefly shifts to the southwest, then returns to around 50 to 60 percent for the remainder of the week. The increased pressure on area mountain ranges has potential for increased downsloping wind gusts, especially in the Mojave Desert. In this area, there is a 70 to 80 percent probability for maximum wind gusts to exceed 35 mph each day.

In the near-to-mid term, a continuation of the high pressure ridge is expected, leading to warmer temperatures and occasional influx of monsoon moisture. The Climate Prediction Center expresses a 50 to 60 percent probability for above average temperatures in the one- and two-week period. There is also a 33 to 40 percent probability for above average precipitation in the one-week outlook.

AVIATION

VFR conditions expected for the next 24 hours.

AIR QUALITY ISSUES

None.

CERTAINTY

The level of certainty for days 1 and 2 is high. The level of certainty for days 3 through 7 is medium.

Certainty levels include low...medium...and high. Please visit www.weather.gov/hnx/certainty.html for additional information and/or to provide feedback.

HNX WATCHES/WARNINGS/ADVISORIES

None.