textproduct: San Joaquin Valley

KEY MESSAGES

1. Below average temperatures and dry conditions are expected for the next several days.

2. A disturbance moving south from near Alaska and a low pressure system tracking south of us and coming off the Pacific Ocean could potentially bring the next chance for precipitation in our area by this coming weekend (low confidence).

DISCUSSION

A trough that is currently over the Pacific Northwest is beggining to dig south and have more of an influence on our region. Temperatures are expected to remain below average for the next several days with dry conditions. The probability of temperatures exceeding 70 degrees is at about 65-80% across the valley today. Temperatures are expected to decrease further after today with the probability of temperatures exceeding 70 degrees only at about 40-55% tomorrow and Thursday across the valley. In addition, low relative humidity will remain in place today and tomorrow given that an area of low pressure will remain well north of our region, with minimum relative humidity values at around 15-25% across the mountains and foothills.

A more potent upper-level low will move south from Canada (near Alaska) and influence our weather this coming weekend, with even cooler temperatures and the potential for precipitation across our area. By Saturday and Sunday, likely the coolest days, the probability of high temperatures remaining below 67 degrees is at around 55-70% across much of the valley. In addition to the influence of this strong trough, there is the potential for precipitation to move into our region from off the Pacific Ocean, with a low pressure system tracking well south of here near the California Mexico boarder. Given that the main area of low pressure will remain to our south, precipitation will likely be limited in the valley if it does rain at all. The highest probabilities of greater than .1 inch of rainfall over 48 hours in the San Jauquin Valley is at around 25-45% by early Monday morning; there are similar probabilites in the Mojave Desert. There are higher probabilites however in the mountains and foothills of around 50-65%. If rainfall does occur it would likely be between late in the day Saturday and late in the day Sunday, but the exact timeframes are difficult to determine this far out. In addition to rainfall, there is a possibility of snow at higher elevations along the Sierra Nevada. There would only be minor snowfall totals as of now however, with only a 20-40% chance of at least 2 inches of snowfall above 8,000 feet in elevation. There remains a possibility that no precipitation will occur at all, with a 40-55% chance in the valley and Mojave Desert, and a 20-30% chance in the foothills and mountains.

The majority of ensemble members and model runs continue to indicate that a ridge of high pressure will influence our area early next week. With that change in pattern, temperatures are expected to at least warm up slightly from the cooler conditions this weekend to closer to average for this time of year, with a 50-65% chance of temperatures exceeding 70 degrees by Tuesday of next week. Some models are indicating that the ridge will move out of our area by middle of next week resulting in potentially cooler conditions further out into the long term. The Climate Prediction Center (CPC) has our area with near normal temperatures in the 8-14 Day Outlook and a 40-60% chance for above normal precipitation.

AVIATION

There is a potential for visibility to be slightly reduced over KBFL early tomorrow morning resulting in MVFR conditions. Otherwise, VFR conditions will prevail 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.