Periods of rain with high elevation snow today, along with scattered thunderstorms in the Valley. Another wet, warmer system early week bringing moderate to heavy rain, high elevation snow, and renewed flooding concerns.
Upper level trough is pushing east over the far part of the state. This short wave has been bringing widespread showers to the area with some locally moderate to heavier rain in the northern San Joaquin Valley. It has also kept skies mainly cloudy across the region. This has had a major impact on instability and our thunderstorm chances and was always the wild card for today. Meso– Analysis is estimating 100-250 j/kg of ML-CAPE from about Sacramento north to Chico. HRRR runs are still favoring the northern San Joaquin Valley to about Sacramento for scattered thunderstorms this afternoon which doesn’t seem reasonable at this point and the HRRR has been under doing these showers all morning. The better thunderstorm chances today will likely be south of our area into Hanford’s area. We still could see some isolated thunderstorms mainly over the central and southern Sacramento Valley. Model soundings are still showing good hodographs, sufficient 0-1 km shear, high PWATs, and CAPE in the hail growth zone. This would indicate that we could see some stronger storms but cloud cover has likely modified these sounds some. Still will have to keep an eye on any thunderstorms that develop but heavy rain at this point looks to be the biggest threat.
This will bring the return of periods of heavy rain and heavy mountain snow. Models are in slightly better agreement but still seeing a wider range in the 500 mb pattern than what you would like to see this close to the event. The GEFS continues to be slower and a bit further south with the southern part of the trough. Overall there is good agreement with QPF though, it’s looking like 1.50-3″ in the Valley and 3-7″ over the foothills and mountains.
Snow levels will be 5500-6500 feet into Monday rising to pass level Tuesday as the burnt of the storm hits us. Snow levels fall Wednesday falling back down to 3500-5000 feet. Several more feet of snow is expected over the Sierra with this storm. This will bring travel issues at times mainly as you get to the passes.
We will also see gusty southerly winds with this system. 850 mb wind increase to 45-70 knots Tuesday morning into the afternoon. This will result in winds gusting 45-60 mph across much of the area and up to 70+ mph over the higher Sierra.
With another warmer and wetter storm in the forecast for Monday- Tuesday flooding is a concern. Streams, creeks, and rivers will continue to rise as we see additional rain and snow melt. Some urban and street flooding will also be possible mainly Monday night through Tuesday. Streams, creeks, and rivers of most concern will be those coming out of the Sierra. A few showers will linger on Wednesday mainly over the mountains. Upper level ridge will build in later in the day bringing the return of dry weather.
Extended Discussion (Thursday through Sunday)
Dry weather forecast for Thursday into early Friday as short wave upper ridging moves through.
Another storm is progged later Saturday into Sunday. Model differences exist with timing and associated precip amounts resulting in some forecast uncertainties at this time.