National Weather Service - Discussion

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Area Forecast Discussion

National Weather Service - San Joaquin Valley / Hanford, CA
Issued: Monday, June 27 2022 - 2:55 AM PDT

SYNOPSIS... Unseasonably warm weather will occur across the forecast area through Tuesday, with a gradual lowering of temperatures starting midweek. A cooling trend will bring temperatures back to near normal levels is likely later this week. Winds over the favored locations are expected to increase later in the week.

DISCUSSION... Central California is in the middle of a heat wave as triple digit temperatures are expected yet again this Monday afternoon. Sunday saw widespread temperatures over the century mark as even some higher elevation locations approached to within a degree or two of the century mark (namely Yosemite) – which tells of the heat being experienced. With the axis of the upper ridge still over the West Coast today and the next disturbance taking a more northerly path, change in the weather may take longer to reach Central California. Currently, will maintain the Heat Advisory in place for Central California based on how 24 hour trends in temperature have shown such little change. Even further, the pattern has slowed down with possible change not occurring until closer to Mid-week when temperatures take a down turn more toward seasonal normal values.

Starting with High-Res short range ensemble solutions, the current ridge is slow to shift east and does not exit until early Wednesday. Therefore, with a slower and more northerly trajectory solution, will hold off on ending the heat advisory until closer to Wednesday night. Heat advisory that was expected to expire Monday night will now expire at around 9 PM PDT on Wednesday night. With probability of exceedance of reaching 100 degrees or above across the San Joaquin Valley at value from 60 to just over 80 percent, confidence is good that the heat wave will continue this afternoon. Ensemble mean value surface temperatures for Tuesday afternoon continue to show heat advisory level values. Therefore, extended the Heat Advisory through Tuesday evening as the cooling may not reach Central California until early Wednesday. Yet, cooling on Wednesday will only mean that temperatures range from the upper 90s to 104. By then the heat advisory will have ended. Probability of exceedance of reaching 100 degree struggles to reach above 30 percent by Thursday.

The cooling trend that will start around mid-week will continue for the remainder of the week as longer range ensemble solutions show the disturbance finally attempting the ride over the ridge (flatten it) and maintain a stronger westerly wind flow. A secondary disturbance during the weekend will help to re-enforce the surge of cooler air and extend the period of cooling. While the disturbance will mainly cross the Pacific Northwest, temperatures and winds will be affected across the Central California Interior as seen in mean value ensemble for those weather parameters. However, the disturbance will remain too far north to provide the area with precipitation. Will expect the period to remain dry as the cool westerly flow pushes Monsoonal moisture east and across the Four Corners area through early next week.

AVIATION... VFR conditions will prevail across the Central California Interior for at least the next 24 hours.

AIR QUALITY ISSUES... On Monday June 27 2022...Unhealthy for Sensitive Groups in Fresno and Kern Counties...and Sequoia National Park and Forest.

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 an/or to provide feedback.

HNX WATCHES/WARNINGS/ADVISORIES... Heat Advisory until 9 PM PDT Tuesday for CAZ300>317-319-321-332.