textproduct: San Joaquin Valley

KEY MESSAGES

1. Minor Heat Risk through Wednesday as temperatures remain around seasonal normal values.

2. Warmer temperatures dominate Thursday with a 30-50% chance of triple digits and greater than a 70% chance of a Moderate Heat Risk throughout the CWA.

DISCUSSION

The cut-off low pressure system that drove yesterday's mountainous thunderstorms will be moving east through the day today, leaving our area on the leeside of its axis. This will cause thunderstorm chances to fall off a cliff as drier air takes over. There will still be a shortwave trough influencing the weather in our region today, but that trough is expected to lift and move east, further away from our region as the day progresses. Temperatures will be slightly warmer today compared to yesterday, but will likely still remain below average. The probability of temperatures exceeding 90 degrees, which is around the average high for this time of year in the Central Valley, is only about 10-25%.

As the trough continues to lift and move further away from our region even after today, a ridge will be present over our area on Wednesday and Thursday. The presence of this ridge will result in a substantial warm up on Wednesday and Thursday. Thursday looks to be the hottest day of this week with valley highs expected to be in the upper 90's, with the southwest side of the valley seeing a 40- 60% chance for triple digits in the afternoon with the rest of the valley at 20% or less. There will also be a 55-70% chance for Moderate Heat Risk on Thursday, which has the largest affects on more sensitive groups, such as elderly people, children, and those with chronic illnesses.

The ridge will quickly move out of our region by Friday of next week with a trough moving in from the west. This will result in temperatures cooling quickly to close to average by Friday and Saturday. Slightly below normal temperatures are expected by Sunday into Monday of next week. Typical of the transitional season, this temperature rollercoaster is expected to continue through next week as troughs are able to dig further south and ridges become less able to produce summer-like conditions due to the reduced amount of sunlight in the day. The probability of precipitation looks to remain very low through at least the middle of next week. Looking to the long term forecast, the Climate Prediction Center has our CWA at a 40-50% chance of above normal temperatures for the 6 to 10 day and a 50-60% chance of above normal temperatures for the 8 to 14 day outlook (normal being in the upper 80's to around 90 for this time of year).

AVIATION

VFR conditions will prevail for the next 24 hours.

AIR QUALITY ISSUES

HNX AFD authors - edit this section manually UFN consult: HNX Site Page --> Bulletin listed there and http://ww2.valleyair.org/aqinfo/action_day_hnx.txt

CERTAINTY

The level of certainty for days 1 and 2 is high. The level of certainty for days 3 through 7 is high.

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.