DISCUSSION
Upper level disturbance is now pushing through the Northern Rockies with a strong northwest wind flow in its wake. The strong west to northwest flow pattern aloft supported the cool down observed over the region. Temperatures are expected to remain blow their seasonal normal values as marine air surged into the region. While the cooler air continues to filter through the region, surface pressure gradients continue to relax and allow winds to diminish. Allowed the wind advisory for the Eastern side of the Tehachapi (Mojave Slopes) Mountains to expire this morning as speeds have dropped below criteria. As the disturbance pushes further eastward, will see an upward bump in temperatures ahead of the next (stronger) disturbance pushing into the region early next week.

Probability of Exceedance (PoE) of having wind gusts reach 45 mph dropped to near zero this afternoon. With this and observations showing a downward trend, allowed the strong winds to diminish today. At this point, will begin mixing out the air- mass over the region as temperatures start a weak warming trend for the first half of the weekend. While PoE of reaching a temperature of 95 degrees across the San Joaquin Valley remains below 10 percent on Friday, PoE rises to 20 to 30 percent on Saturday. Even with 100 degree temperatures unlikely over the next 3 days, a few spot could reach the upper 90s on Saturday.
All of that changes on Sunday as another disturbance (a strong one) enters the region. Ensemble temperature analysis shows the onset of cooler air (cold front) between 11 AM and 5 PM on Sunday. Will lean closer to 5 PM as temperatures trend slightly downward. At that point, PoE of 95 degrees returns to values near zero. Yet, PoE remains at near 40 to 50 percent for reading near 90 degrees. Therefore, not a big cool down at the start.

Change in the weather starts on Monday as ensembles shows the onset of precipitation as early as Sunday Night (near 11 PM)
when the Probability of Precipitation (PoP) rises to above 10 percent. During the day on Monday, ensembles show the 30 percent PoP line over Fresno County before the disturbance lifts northeast Monday night. With the help of orographic lift, PoP over the Sierra Nevada north of Kings Canyon show values between 60 and 70 percent during the day. In addition, Probability of Thunder rises to near 15 percent over the higher terrain from Yosemite to Kings Canyon on Monday. As for frozen precipitation, ensemble snow level analysis has the 25th to 75th percentiles between 8000 feet to 9000 feet, respectively. The mean sits at around 8500 feet from Fresno County northward. On Monday, snowfall probabilities for the favor area of Tioga Pass as listed as follows:

Tioga Pass (Yosemite) 24 Hour snowfall 65% >1 inch 48% >2 inches 15% >4 inches 3% >5 inches

While lingering showers will continue into Monday Night, minimal accumulation is expected as the disturbance pushes out of the area. Longer range ensemble analysis shows another disturbance making an attempt to swing across the area. Current ensemble cluster upper-air analysis has the third disturbance tracking further north and weaker over Central California. Therefore, while light precipitation can not be ruled out near Yosemite on Wednesday, will expect minimal accumulation impacts. However, temperature-wise the district will struggle to make any returns to triple digits during the next week period.

AVIATION
Areas of MVFR and local IFR visibilities near wildfires.
Otherwise, VFR conditions will prevail across the central CA interior over the next 24 hours.

AIR QUALITY ISSUES
ISSUED: 09/11/2024 14:35 EXPIRES: 09/12/2024 23:59 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
None.