textproduct: San Joaquin Valley

KEY MESSAGES

1. Temperatures will remain about 10-15 degrees above normal today before a relieving cool down Friday into this weekend.

2. A Heat Advisory remains in place expiring this evening throughout the Central Valley with a widespread Moderate Heat Risk.

3. There is a marginal risk for excessive rainfall in the Mojave Desert and along southern portions of the Sierra Nevada mountains this coming Sunday.

4. Although low confidence, a 60-70% probability exists for 72 hour snow accumulation greater than 2 inches above 9000 feet from Sunday into Wednesday morning.

DISCUSSION

Time for your favorite part of the day, reading the Area Forecast Discussion (with some sarcasm)! We are reaching the end of the sweltering October heat, fantabulous! The chances for highs to reach the triple digits in the San Joaquin Valley are at 20 to 35 percent today and 15 percent or less tomorrow. Temperatures will still be in the low to mid 90s by Friday, so while not a huge change, it is a welcoming relief both to us and our air conditioners. This is thanks to the persistent ridge of high pressure finally weakening. The bully has been defeated!

Now for the fun part, queue the drumrolls! We are in store for a significant change in temperatures and the overall weather this weekend into beginning of next week. Near seasonal temperatures are in store for Saturday. Chances for water falling from the sky also enter the forecast for Sunday into next week. Freezing temperatures arrive Sunday, with a 20 to 35 percent chance of highs of 70 degrees or lower and a 55 to 70 percent chance of highs of 75 degrees or less, including over the valley and desert (shivering!). The deep upper-level trough moving from the Pacific Northwest will combine with another trough from the Pacific to form a stronger trough. The Jet stream dynamics will pull in tropical moisture from Tropical Storm Rachel, though the storm's actual track is mainly over northern Baja California and into the southeastern CA desert. The latest National Hurricane Center's forecast cone indicates the most likely scenario is Rachel making landfall as a tropical storm over northern Baja early Sunday morning, moving northeastward through the Southwestern states by late Sunday afternoon. On Sunday and Monday, we are carrying at least a slight chance of precipitation over much of the forecast area. The most favorable locations for heavier rain will be over the Mojave Desert in eastern Kern County and southern Sierra Nevada, as the Weather Prediction Center continues to show a marginal risk (5-15% chance) of excessive rainfall for at least Sunday. A 60-70% probability exists for 72 hour snow accumulation greater than 2 inches above 9000 feet from Sunday into Wednesday morning. Is Frosty the Snowman coming in October!? It is a good and early opportunity to play Frosty's favorite game, freeze tag!(get it?). Overall, this is a low to moderate confidence forecast for this particular period, but confidence in precipitation has been increasing as model runs update with the approaching disturbance. Now, for the Valley, instead of the cooking outside joke, you can either choose to collect rain water to boil instead of tap water, or you can shower outside instead of inside! Or both!

Cooler than average temperatures prevail throughout next week, while slight chances of precipitation remain over at least the mountains and desert. Drier weather returns by midweek while cooler temperatures continue. After the trough, the jet stream displays a zonal ridge like pattern, which we expect will force temperatures to return to seasonal averages of 80s. Hoorah!

AVIATION

VFR conditions will prevail for the next 24 hours.

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

Heat Advisory until 10 PM PDT this evening for CAZ300>322.