textproduct: San Joaquin Valley

KEY MESSAGES

1. Dry conditions continue for the next several days with near average temperatures today before temperatures cooldown to below average.

2. A disturbance dropping southeast from near Alaska will bring the next chance for precipitation in our area by this coming weekend (low confidence).

DISCUSSION

A strong trough is currently evident over the Pacific Northwest region. Mainly zonal flow will be evident over our area however for the next couple of days. The trough will then begin to dig south and have more prolific impacts in our region by the middle to end of this coming week. Temperatures will likely remain near average today with about a 40-60% chance for temperatures above 75 degrees in the San Joaquin Valley. However, a cooldown will be in store by tomorrow as the weak ridge of high pressure that was influencing our weather this past weekend continues to move out of the area. There is a possibility for temperatures to remain below 70 degrees across the valley tomorrow with this cooldown (30-45%). A similar pattern will remain in place across our area for the remainder of the work week. Drier conditions will also prevail for the next couple of days with the influence of the strong trough remaining to our north. Minimum relative humidity values will therefore be below 20% across the Sierra Nevada Mountains and the Mojave Desert through the middle of this week before increasing substantially by Thursday and Friday. Despite the reduction in minimum relative humidity values, there are no major fire weather concerns given the rainfall last week across the region.

There remains a possibility for precipitation throughout the area this coming weekend with a disturbance moving southwest from near Alaska. There is still a lot of variability within individual model runs however given that this system is several days out. Precipitation could potentially begin in the Sierra Nevada Mountains as early as Friday before more widespread precipitation could impact the entire area sometime Saturday night. As mentioned before, there is still a lot of uncertainty with regards to the exact track and amounts of precipitation in our area, and there remains a possibility that there will not be rainfall across the valley at all. The highest probability of at least .1 inch of rainfall over 24 hours is around 35-50% by Sunday afternoon across the valley. There is also a 45-55% chance of exceeding .1 inch of rainfall in the Mojave Desert and a 50-65% chance in the Sierra Nevada Mountains. These chances are subject to change however as we progress closer to this event. The chances of rainfall decrease dramatically by Monday of next as the potential disturbance moves out our region.

The majority of model guidance and ensembles currently indicate the most likely scenario would be for a ridge of high pressure to influence our area by the beginning of next week. However, some individual models still indicate a strong trough over our region in that timeframe with a lot of uncertainty in the overall weather pattern as we move into the long term. The Climate Prediction Center (CPC) has us in a 33-40% chance for below average temperatures and a 60-70% chance for above average precipitation in the 6-10 Day Outlook. The 8-14 Day Outlook has us with near normal temperatures and a 40-60% chance of above average precipitation.

AVIATION

A reduction in visibility remains possible over KMCE leading to potentially IFR of LIFR conditions from late tonight through mid-morning tomorrow. 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.