textproduct: San Joaquin Valley

KEY MESSAGES

1. Moderate to Major Heat Risk on Tuesday and Wednesday.

2. 30% probability of thunderstorms along the high Sierra and eastern Kern deserts through the week.

3. Slow moving mountain thunderstorms can produce excessive rainfall.

4. Dry lightning strikes in the high Sierra this week, 10% probability of occurrence, away from the excessive rainfall.

DISCUSSION

Heat Dome high pressure sitting over the upper Mid-West is now shifting back over the West as Central California starts a Heat Wave. As high pressure rebounds over the West, will see temperatures warming, with the addition of humidity, to increase the Heat Risk during the Mid-Week period. While Probability of Exceedance (PoE) of reaching 105 degrees Today will stay below 50 percent, a warm-up is expected as PoE of reaching 105 degrees by Mid-week does goes up to above 60 percent. PoE of 108 degrees will also hit the 10-20 percent range over Kern County. Furthermore, PoE of Minimum temperatures falling below 75 degrees is less then 10 percent. Warm Night. These ingredients and ranges will lead to the issuance of a Heat Advisory from Tuesday through at least Thursday. A brief cool-down is expected by the end of the week and into the weekend.

Four Corners high is indicative of monsoonal type moisture surging northward and into Central California. Doppler radar is showing showers pushing up with mostly light to moderate rain seen so far. Ensemble model guidance shows a rise in the probability of measurable precipitation in the 80-90 percent range least a tenth of an inch (0.10) over 24 hours. Ensembles even show a 50-60 percent probability of receiving a quarter of an inch (0.25) across the Sierra Nevada Today. With higher probabilities of high precipitation values, excessive rainfall will be a problem across the Sierra Nevada and will monitor for possible flash flood this afternoon. While percentage do drop on Tuesday, ensemble analysis still has a 25-50 percent chance of receiving a tenth of an inch on Tuesday. There is also a 20 to 30 percent probability for thunderstorms across this area each day from Today through at least Thursday as there is little deviation in the synoptic pattern through the middle of next week.

Climate Prediction Center (CPC) is indicating that the extended time frame of the 6 to 10 day period will remain on the warm side. Current CPC analysis has a 50-60 percent chance that temperatures will likely be above normal conditions.

AVIATION

High Sierra thunderstorms after 18Z Mon could lead to mountain obscuration through at least 03Z Tue. Otherwise, VFR is expected across the central California interior 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

None.