Marine Weather and Tide Forecast for Atwater, CA

KEY MESSAGES...

1. Winter Storm Warning in effect for the Sierra Nevada above 7,000 ft.

2. An elevated risk for fire starts in eastern Tulare and Kern Counties.

3. An approaching cut-off low brings periods of heavy rainfall and mountain snow by early Tuesday, with favorable conditions for convective weather afterwards.

DISCUSSION...

A Winter Storm Warning is in effect for the Sierra Nevada above 7,000 ft, with accumulations of 3 to 5 inches above this level, increasing to 12 to 18 inches at the highest levels. Winds could gust as high as 75 mph along the Sierra Crest.

Current satellite imagery shows the storm system that will impact Central California this week just off the coast of the western CONUS. In the meantime, the lingering influence of the ridge over the area will keep temperatures a bit above normal today, with highs in the low- to mid-80s across the Valley, creating a minor heat risk, particularly for vulnerable populations. As the trough moves into the area, expect below- average temperatures Tuesday and Wednesday, with Valley highs in the 60s to low 70s Tuesday, slowly rebounding to climatological normals later in the week.

Looking to the more active weather, the system is expected to arrive Monday evening and continue through Wednesday afternoon.
The majority of the precipitation is expected late Tuesday morning through the afternoon as a large rain band moves through the region during that time period, and the most impacted areas are expected to be the Sierra Nevada and its foothills. Current probabilities for a half-inch of rainfall are 40-50% near Fresno, increasing to 65-75% toward Merced. There is also a Marginal Risk (at least 5%) for excessive rainfall in that area, along with the San Joaquin Valley from Visalia to Los Banos as the crow flies.

With regards to wind, on Tuesday, there is a 50-70% chance of 64 mph gusts or higher along the Mojave Desert Slopes, increasing to 60-95% along the Sierra Crest.

As the main rain band moves through the region Tuesday afternoon, the chances for thunderstorms increases into the 30 to 45% range in the Valley from Porterville north. The southern half of the Valley can expect a 15-30% chance of thunderstorms.
This is due to the increased dynamics behind the initial wave combined with the newly fallen moisture and afternoon heating.
As of today, the Storm Prediction Center has put this area under a general risk for thunderstorms. Severe thunderstorms are not expected. However, any cell that forms still comes with the risk for small hail, frequent lightning, gusty winds, and localized flooding.

After this system moves east and the precipitation moves on, a weak trough may still hang around aloft, with current ensemble models continuing to agree with that forecast. A second, albeit weaker, cut-off low may develop later this week and produce some precipitation by the weekend, particularly in the Sierra Nevadas.

AVIATION
VFR conditions expected across the area for the next 24 hours, with MVFR in and near thunderstorms.

AIR QUALITY ISSUES

Pockets of minor air quality issues may affect vulnerable populations today.

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
Winter Storm Warning from late tonight through Wednesday afternoon for CAZ323-326>328-330.