textproduct: San Joaquin Valley

KEY MESSAGES

1. A warming trend will continue today through next week with afternoon temperatures approaching 10 degrees above average by the weekend.

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

DISCUSSION

An upper level ridge of high pressure is currently centered off the California coast this morning, having moved northward from the coast of Baja California over the last 24 hours. Subsidence linked to the area of high pressure is keeping conditions over central California clear and dry once again, with a warming trend continuing from Wednesday. Temperatures are expected to hold in the mid to upper 70s for Friday and Saturday as the high pressure erodes to the south, setting up west-to-east zonal flow across the area during the early weekend period. However, as Sunday approaches, there is high confidence in a stronger area of high pressure developing in the east Pacific which will center over central California through the early portion of next week. Sinking air and light winds at the center of the high will trap heat nearer to the surface and continue the warming trend from the previous days. However, afternoon temperatures will be substantially greater than over the weekend, with upwards of 20 degrees above season averages on Wednesday. Ensemble guidance from the NBM expresses a 90 to 100 percent probability for highs to exceed 90 degrees in the San Joaquin Valley midweek, with an additional 50 to 60 percent probability to exceed 95 degrees. Many of the projected temepratures across the valley areas will be nearing or breaking daily record highs, with all-time monthly records also in jeopardy for some locations. While temperatures will fall by a handful of degrees towards the end of next week, little change is expected in the synoptic pattern until the following week, which will result in above average temperatures continuing during this time.

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 which will fall between 10 and 20 percent, and for the high Sierra, dropping to 20 to 25 percent. This will coincide with a sharp decrease in 100- and 1000-hr dead fuel moistures and an increase in ERC in these areas, however values remain below critical thresholds and significant 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.