textproduct: San Joaquin Valley

KEY MESSAGES

1. High temepratures will likely be about 10-15 degrees above normal today before a quick cooldown starting Saturday.

2. High wind gusts over 35 mph are likely this afternoon into Sunday night (65-80% chance) over the San Luis Reservoir with a Lake Wind Advisory issued.

3. There is a marginal risk for excessive rainfall in the Mojave Desert and along southern portions of the Sierra Nevada mountains this coming Sunday.

4. There is around a 50-65% chance for 72 hour snowfall greater than 2 inches above 9000 feet from Sunday into Wednesday morning.

DISCUSSION

Fall is clearly here as we are well into October, but the weather has not been resembling fall. Temperatures this week have been about 10-15 degrees above average, with some near record heat in the San Joaquin Valley over the past few days. Relief from this intense heat is expected with a strong, deep upper-level trough likely move into our area this weekend. Today however, temperatures will likely remain well above average with the influence of an upper-level ridge remaining over our area. The probability of temperatures reaching above 95 degrees today is about 50-65% across the Central Valley. However, the Heat Advisory has expired as temperatures have cooled slightly today, resulting in only a Minor Heat Risk across the Valley today. In addition, localized winds are likely to exceed 30 mph over the San Luis Reservoir from this evening through Sunday evening (80-95% chance), hence a Lake Wind Advisory has been issued for that area.

The influence of the strong trough in our area will result in much cooler temperatures. Temperatures will begin to cool tomorrow with closer to average high temperatures for this time of year (average temperatures are around the low to mid-80s throughout the Valley). By Sunday, the probability of temperatures exceeding 75 degrees will only be around 30-45% across the Valley, with temperatures well below average for this time of year. Probabilities of temperatures exceeding 75 degrees will be much lower Monday (5-10% chance), with Monday likely being the coldest of the next several days. A slight warm up in temperatures will begin Tuesday before temperatures warm much more significantly by mid to late week next week. In addition to the significant cooldown in temperatures, remnants of Tropical Storm Rachel will impact our area, especially along the Sierra Nevada mountains and Mojave Desert. Rain will likely begin to move into the Sierra Nevada mountains by Saturday afternoon or late Saturday evening, with the exact timeframe of rainfall still a little uncertain. By Sunday rainfall will potentially move into the Valley as well, with the probability of rainfall exceeding .1 inch at around 20-35% across the Valley. Therefore, only light rainfall if any rainfall at all is expected across the Valley. The probability of 24 hour rainfall exceeding .1 inches will be about 60- 75% on Sunday and Monday of next week along the Sierra Nevada mountains and the Mojave Desert, before rain chances begin to decrease as the week progresses.

Wind gusts exceeding 30 mph are likely in typical wind prone areas (65-80% chance along high elevations of the Sierra Nevada mountains and the Mojave Desert slopes) from early Saturday morning through early Monday morning. In addition, snowfall is expected along high elevations of the Sierra Nevada mountains above 9000 ft, with a 50-65% chance from Sunday into Wednesday morning of seeing at least 2 inches of snowfall over 72 hours. There will be localized areas well above 9000 feet that will likely see more significant accumulations, with a 50-65% chance of seeing at least 6 inches of snowfall over 72 hours over the highest elevations.

The Climate Prediction Center (CPC) has us in a 33-50% chance of above normal temperatures in the 6-10 day outlook, and about a 33-50% chance for below normal precipitation in that time period. There will be a change in the weather pattern by mid to late week next week with temperatures likely warming up to above normal for this time of year. By next Friday, the probability of temperatures exceeding 85 degrees will be at about 55-70% across the Valley. The 8-14 day outlook looks to be similar to the 6-10 day outlook with likely above normal temperatures and below normal precipitation for this time of year.

AVIATION

VFR conditions will prevail for the next 24 hours. Winds will likely exceed 10 mph out of the northwest over Bakersfield by late this afternoon into this evening.

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

Lake Wind Advisory until 11 PM PDT Sunday for CAZ300.