Thunderstorm on Christmas Eve? They are in the Fresno Forecast

The relatively mild weather we’ve been enjoying will end abruptly early Tuesday with the arrival of a new storm system that could bring thunderstorms to the Fresno area on Tuesday and drop daily highs this week back into the 50s.

Tuesday’s forecast calls for rain and possibly afternoon thunderstorms in the Valley and snow in the Sierra, with 6 to 10 inches forecast and potentially up to a foot in some places, said Andy Bollenbacher, a meteorologist with the National Weather Service in Hanford.

Snow will start at 7,500 feet and then drop down to 6,000 feet, he said.

A winter storm warning will be in effect for the central Sierra on Tuesday.

Depending on conditions, some graupel — small snowballs that form when ice sticks to snowflakes — may fall in the Fresno area during thunderstorms. However, there will not be enough to last for a white Christmas, Bollenbacher said.

People heading east from the valley to the upper Mojave should be prepared for wind gusts of up to 45 mph on Tuesday on the Sierra’s soft slopes.

The fog returns on Christmas Day

When the rain ends in Fresno on Thursday, the Valley will face the possibility of dense fog again, and that could affect a weekend warm-up, Bollenbacher said.

“This time of year the sun angle is really weak. This means that it is quite easy to form fog. So you could theoretically see a temperature forecast of 65, and then the reality is like 58, because you had fog all day and it was difficult to burn off or blend out in the afternoon hours, and the temperature forecasts have gone wrong,’ he said. “So basically what I’m telling you is there’s a potential for a warm up over the weekend, but we’ll have to see what the fog actually allows the afternoon highs to be.”

There is also a small chance that rain will return to the valley on Thursday, although not all forecast models agree with that prediction, Bollenbacher said.

Forecast highs and lows for Fresno for this week: Monday 64, overnight low 57; Tuesday, 53, low of 43; Wednesday, 52, low of 44; Thursday, 54, low of 48; Friday, 56, low of 48; Saturday, 60, low of 48; and Sunday 62.