textproduct: San Joaquin Valley

KEY MESSAGES

1. Warm conditions are expected through the weekend with temperatures across the area likely about 5-10 degrees above normal.

2. A Red Flag Warning remains in effect through tonight for the Sierra Nevada mountains above 4000 feet for high winds and low relative humidity values.

3. A Wind Advisory remains in effect for the Mojave Desert through tonight with gusts up to 60 mph.

4. A pattern change remains likely by early next week with temperatures cooling quickly to well below average for this time of year, and a chance of rainfall throughout the area (low confidence).

DISCUSSION

Fall like conditions have been in place for the past week or so after a very hot start to the month of October. Temperatures however will be well above average for the next few days due to the influence of a ridge of a high pressure over our area. The probability of temperatures above 90 degrees today is around 25-40% across most of the Central Valley today, with higher localized probabilities in the southern Valley (75-90%). Tomorrow looks to be the hottest day of the near future with the probability of temperatures above 90 degrees at around 50-65% through most of the Valley, with the southern Valley at around 80-95%. Temperatures will begin to cool by Sunday with the probability of exceeding 90 degrees only at around 35-50%.

A low pressure system is currently south of our area with an "omega block" pattern, high pressure to our north and low pressure to our south, influencing our area. This pattern has led to higher localized easterly wind gusts, especially along the mountain slopes and desert. A Red Flag Warning remains in effect for the Sierra Nevada mountains above 4000 feet through 10 pm tonight. There are localized areas along higher elevations that have had observed wind gusts around 45-60 mph, especially north of Tehachapi and south of the Sequoia National Forest. In addition, low relative humidity values (RHs) remain in place for the same area mentioned previously (below 25%). A Wind Advisory also remains in effect for the Mojave Desert through the rest of today. The probability of wind gusts exceeding 35 mph will be around 65-80% through much of the desert today before winds gusts begin to alleviate overnight. The low pressure system currently south of our region will continue to move southwest, leading to a significant decrease in wind gusts by this weekend. Therefore, the Red Flag Warning and Wind Advisory will expire tonight.

The vast majority of ensemble runs have reached a consensus that there will be a change in the overall weather pattern by early next week with a deep trough moving into our area off the Pacific Coast. Temperatures will therefore cool significantly after Sunday. The probability of temperatures exceeding 80 degrees will be at around 50-65% in the northern Valley and 80-95% in the southern Valley on Monday of next week. By Tuesday, temperatures will cool significantly with only about a 30-45% chance of temperatures exceeding 75 degrees through much of the Valley. In addition, wind gusts along the Sierra Crest and Mojave Desert slopes will increase by early next week and remain strong through the middle of next week. The probability of wind gusts above 35 mph will be at around 50-65% on Monday and Tuesday. The potential closed low pressure system moving into our area could lead to precipitation by mid-week next week throughout the entire area. However, the exact amounts of precipitation remain difficult to determine currently given that this system remains several days out. If rainfall does impact the area, the majority of rainfall that does fall would most likely be on Wednesday and Thursday of next week. In addition, along the Sierra Crest snowfall will be likely around the same timeframe. However, there is a wide range in snowfall totals along higher elevations and the exact details with regards to snowfall totals remain nebulous.

With temperatures cooling significantly by early next week the CPC has us in a 33-50% chance for below normal temperatures in the 6-10 day outlook. In terms of precipitation, the CPC has about a 50-70% chance of above average precipitation over the next 6-10 days, and about average precipitation over the next 8-14 days.

AVIATION

VFR conditions will prevail for the next 24 hours. Gusty winds will remain in place through Bakersfield throughout the day today with winds shifting from out of the southeast to out of the northeast, and gusts exceeding 20 mph through late this evening.

FIRE WEATHER

A Red Flag Warning remains in effect through tonight for areas above 4,000 feet. Easterly wind gusts exceeding 40 mph were recently observed north of Tehachapi and south of the Sequoia National Forest. Low relative humidity values below 25% remain in place in this area as well. Minimum relative humidity values will likely remain around 15-25% today with dry conditions continuing into this weekend. However, wind gusts will likely decrease substantially by tonight reducing the threat for fire spread.

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

Wind Advisory until 10 PM PDT this evening for CAZ337>339. Red Flag Warning until 10 PM PDT this evening for CAZ592>597.