textproduct: San Joaquin Valley

KEY MESSAGES

1. A warming trend will continue this week with afternoon temperatures approaching 20 to 25 degrees above average today 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

The high pressure ridge aloft continues to bring well above normal (possibly record-breaking) temperatures to the region through Saturday, with highs in the Valley expected to be in the lower 90's during this time period. The highs in the Mojave Desert are likely to be a few degrees higher, into the mid to upper 90's. Chances for highs of 95 degrees on Friday (expected to be the warmest day) in the Valley are 50 to 75% on the west side and 25 to 50% closer to the center and on the east side, indicating slightly cooler temperatures in the center of the Valley, and warmer highs on the west side into the Coastal Range. Chances for triple digits in the Mojave Desert are currently 5 to 15% in much of the area, as well as the Valley.

Moving into the weekend, this ridge is expected to weaken into a more zonal flow, with the possibility for small shortwave trough to move through the region as well. This will lead to a significant decrease in temperatures, bringing them down into the 80's in the Valley and the lower 90's in the desert, which would still be several degrees above normal, but will likely bring the Heat Risk down out of the minor to moderate range. These above normal temperatures are also likely to stick around into the long range forecast, as the CPC continues to have the southwest in likely above normal temperatures for 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 wild fire potential remains at little or no risk.

AIR QUALITY ISSUES

None.

CERTAINTY

The level of certainty for days 1 and 2 is medium. 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.