textproduct: San Joaquin Valley

KEY MESSAGES

1. Lake Wind Advisory for San Luis Reservoir and Lake Isabella through 11 PM PDT Thursday, July 9. Beware of unsettled waters.

2. Slow but steady warmup this week, with widespread Moderate Heat Risk by the weekend and isolated areas of Major Heat Risk.

3. Hot, dry, and windy conditions will create elevated fire risk, particularly in eastern Kern and Tulare Counties.

4. Increased chance for Sierra Nevada thunderstorms late this weekend into next week with monsoonal moisture pushing into our region.

5. Practice safety around lakes, rivers, and streams, as water is still running cold.

DISCUSSION

Lake Wind Advisory for San Luis Reservoir and Lake Isabella through 11 PM PDT Thursday, July 9. Sustained winds to 25 mph and gusts as high as 40 mph will create hazardous conditions for small craft and high-profile vehicles.

Zonal flow prevails at the moment as a high pressure sits over the Four Corners region, bringing the area dry and warm conditions, with high temperatures a bit above normal. The high pressure will retrograde westward over the next day or two, bringing further increased temperatures. High temperatures in the Valley today will be in the upper 90s, increasing to the upper 90s and low 100s Thursday. Desert highs will be in the low 100s today, increasing to 105 to 115 tomorrow.

As the high moves westward, winds will increase in the desert. Maximum wind gusts will be 20-25 mph in the Valley today and 15-20 mph Thursday. In eastern Kern and Tulare Counties, maximum wind gusts will be 35-45 mph today, increasing to 40-55 mph tomorrow. These winds will be hazardous to drivers in the area, particularly those in high-profile vehicles.

Relative humidity will also decrease as the high moves westward. Minimum relative humidities will be 20-25% in the Valley today, decreasing to 14-18% tomorrow. In the desert, minimum relative humidities will be 6-10% today, decreasing to 4-8% tomorrow.

The distinct combination of above-average temperatures, windy conditions, and dry air will create concerning fire conditions in eastern Kern and Tulare Counties Wednesday through Friday.

As we move into the weekend, the high will migrate northeastward. This will alter overall flow to a southeasterly direction, bringing a surge of monsoon moisture to the region. As this happens, lightning chances will increase along the Sierra Crest and into the desert, with a 5-10% probability of lightning Sunday, increasing to 10-30% on Monday and continuing similarly through at least the early part of the week. Despite the surge of moisture, there will also be a dry lightning risk associated with some storms.

As the heat continues, be sure to take appropriate precautions and check in on and make arrangements for vulnerable people and animals. Brachycephalic (short-nose) breeds will have particular difficulties with the heat and should be kept indoors.

If driving or boating in an area with a Wind Advisory, take appropriate precautions.

Water temperatures are still in the upper 60s and low 70s and much colder near water flowing from higher elevations. Exercise cold water safety at all times.

AVIATION

VFR conditions expected across the area for the next 24 hours.

FIRE WEATHER

Warmer and drier conditions are moving into the area today and tomorrow. Minimum relative humidities will be 20-25% in the Valley today, decreasing to 14-18% tomorrow. In the desert, minimum relative humidities will be 6-10% today, decreasing to 4-8% tomorrow. Meanwhile, gusty winds will prevail in eastern Kern and Tulare Counties (maximum wind gusts will be 35-45 mph today, increasing to 40-55 mph tomorrow). This combination of heat, dry air, and wind will create elevated fire concerns in the aforementioned areas today through Friday. A surge of monsoon moisture will arrive later Sunday. While this will improve humidities slightly, it will create a notable increase in lightning chances, including the possibility of dry lightning.

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

Lake Wind Advisory until 11 PM PDT Thursday for CAZ300-332.