textproduct: San Joaquin Valley

UPDATE

Updated Aviation Section.

KEY MESSAGES

1. A warming trend will continue this week with afternoon temperatures approaching 10 to 15 degrees above average today and Monday and even warmer Tuesday through Saturday.

2. Daily and monthly record high maximum temperatures will be challenged this week.

3. Practice cold water safety, as waterways will be running cold and fast over the next several days.

DISCUSSION

Above average temperatures will dominate the headlines this week as the ridge of high pressure moves onshore today and tomorrow and strengthening. Latest NBM probabilities have continued to favor Tuesday as the start of the stretch of 90s as there is a 65 to 85 percent chance of highs hitting at least 90 degrees. Wednesday through Friday have a widespread 85 to 95 percent chance of hitting 90 degrees with a 40 to 60 percent chance of highs of at least 95 degrees. However, a 10 to 20 percent chance for triple digits loom from Wednesday through Saturday for the Valley. These temperatures will challenge both daily and even monthly record temperatures. The heat also will increase the snowmelt in the Sierra Nevada leading to higher flows of colder water. Practice cold water safety including wearing a life vest and be aware that even the most experienced swimmers can lose muscle control due to the cold water temperatures.

In the Desert, there is a 75 to 95 percent chance of highs of at least 95 degrees Wednesday through Friday. Friday and Saturday have a 10 to 40 percent chance of hitting triple digits in the Desert despite Saturday's 95 degree probabilities lowering to 55 to 80 degrees. The probabilities continue to lower on Sunday to a 20 to 40 percent chance for 95 degrees.

Latest ensembles agree the ridge will begin to weaken and become more zonal next weekend. However, things will remain warm with a 75 to 85 percent chance on Saturday and 40 to 60 percent chance on Sunday of highs to hit 90 degrees in the Valley. The CPC continue to send strong signals of above average temperatures and dry conditions in both the 6-10 and 8-14 day outlooks.

AVIATION

VFR conditions are expected for the next 24 hours.

FIRE WEATHER

Warming air temperatures and steady dew point temperatures will lead to a decrease in minimum relative humidities, especially for the Mojave Desert, high Sierra, and Coastal Range. This will coincide with a sharp decrease in 100- and 1000-hr dead fuel moistures and an increase in ERC in these areas. Rapid curing of fine fuels will bring about some risk for isolated grass fires. However, live fuel moisture remains below critical thresholds and significant wildland fire potential remains at little or no risk.

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.