textproduct: San Joaquin Valley

KEY MESSAGES

1. Temperatures will remain above average through the weekend. Record highs are possible again in the valley areas.

2. Practice cold water safety, as waterways will be running cold and fast over the next several days.

3. There is good confidence for a storm to pass through central California next Monday through Wednesday, bringing valley rain, mountain snow and strong winds to the region.

DISCUSSION

Temperatures will continue to be well above normal for this time of year due to southwest flow aloft, along with drier conditions for much of the region through the weekend. The Mojave Desert can expect RH's in the mid to low teens through at least Monday, along with mid to upper 20's in the Valley and Sierra Nevada. Rivers will continue to run cold and fast as rapid snowmelt continues to come down from the mountains due to warmer temperatures.

There is good confidence for a pattern change by Tuesday morning, with a shallow trough expected to move in by that time. This will lead to a drop in temperatures through the week as the trough moves through the region, as well as a chance for light precipitation int he Sierra Nevada and its Foothills. Currently the chance for a quarter inch of rainfall Wednesday morning, the height of the event, is 40 to 60% from Fresno County northwards. During that same timeframe, the Valley has a 20 to 30% chance for a tenth of an inch. These values have seen a drop-off in intensity as the models continue to resolve to a weaker trough with each run, so the actual rainfall may be lighter for the region as a whole. Snow levels with this system are expected to be around 7000 to 8000 feet, consistent with previous runs. Actual snow amounts have followed the same trend of becoming lighter than former runs, with current probabilities on Wednesday for 3 inches of new snow at 20 to 40%, with the higher elevations seeing a stronger chance for that amount.

After that weak disturbance moves east, a trough moving through the Northwest is expected to lead to further cooling for the region, as well as continued strong winds along the mountain crests and the desert slopes through Thursday. This trough moves east, another ridge is expected to build in after it, marking the return for warming temperatures starting Friday into next weekend. The CPC has also indicated this return, as above normal temperatures are in both the 6 to 10 and 8 to 14 day outlooks, with the latter showing a further extent into our region. The precipitation outlook shifts from near normal for the 6 to 10 day outlook into leaning below normal in the 8 to 14 day outlook, indicating a return to the dry pattern seen for much of this month.

AVIATION

VFR conditions will prevail across central California across the next 24 hours.

FIRE WEATHER

Temepratures will continue to rise into the weekend with RH values falling as a result, curing fine fuels across the region and leading to conditions conducive for sporadic grass fires to develop. Light terrain driven winds expected through the weekend. Strong winds return on Monday, mainly over the higher terrain. No precipitation is expected through the weekend. A storm will enter the region on Monday with a chance of rain and snow on Tuesday and Wednesday.

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.