Periods of moderate to heavy rain, high elevation snow, and isolated thunderstorm chances continue today through Wednesday. Wind Advisory from 10 PM this evening to 7 AM Tuesday for Central Sacramento Valley-Northeast Foothills/Sacramento Valley- Northern Sacramento Valley. Quieter and seasonable weather is then anticipated late week into next weekend.
Discussion
Early this morning, mostly cloudy skies are evident across interior NorCal via latest GOES-West imagery. Scattered rain showers and a few embedded thunderstorms are also present along and west of the I- 5 corridor at this time. This activity looks to gradually spread east-northeastward through the overnight, becoming more widespread by the morning.
Resultant overnight low temperatures will remain comparatively mild, with Valley lows in the mid to upper 40s and upper 20s to low 30s in the mountains.
Precipitation chances will continue across the early week period and through Wednesday before tapering off throughout the day on Thursday.
Latest probabilities of exceeding 1″ of QPF during this time frame remain high, in the 90 to 100% range across the region, with probabilities of exceeding 3″ in the 30 to 60% range in the Valley and 70 to 90% range over the mountains.
Despite this being a relatively warm system, high elevation accumulating snow is still expected. Snow levels generally remain in the 7500 to 8000 foot range for much of the event until they drop to the 6500 to 7500 foot range late Tuesday into Wednesday. This will likely keep the bulk of the accumulating snowfall to high elevation mountain peak levels. Latest probabilities of exceeding 4″ of snowfall for elevations greater than 7000 feet are in the 50 to 90% range, with probabilities of exceeding 8″ in the 40 to 80% range. Best chances for heaviest snowfall are expected near Lassen Peak and for areas south of the Highway 50 corridor.
Furthermore, a 15 to 25% chance for isolated thunderstorms will remain possible through Tuesday. This is the result of increasing moisture to the region, amidst a fairly mild temperatures regime, leading to some weak instability. Best chances for thunderstorm development will be across portions of the Delta, Valley, and adjacent foothills locations. With any thunderstorms that do develop, gusty winds, brief heavy rainfall, and small hail will be the primary hazards.
Gusty southerly winds will also increase later today into Tuesday morning as the trough begins to move further inland. Sustained winds of 15 to 25 mph are anticipated with occasional gusts 30 to 45 mph. Strongest winds are expected over the northern Sacramento Valley and across the Sierra. Resultant probabilities of wind gusts exceeding 40 mph for these areas are in the 40 to 70% range.
Extended Discussion (Friday through Monday)
Late week into next weekend is expected to see much quieter weather across much of the region as troughing over southern California dominates the weather pattern. A weak shortwave embedded in this pattern may bring some isolated showers to portions of the forecast area early in the weekend, but rainfall totals look to remain light and generally confined to the mountains. Otherwise, seasonable temperatures prevail through the long term period.