March 29, 2019 – Lingering light showers possible over the mountains mainly north of I-80 today. Otherwise, dry conditions expected across most of the region Friday into the weekend. Unsettled weather returns early next week with the potential for a wetter system late next week.
Latest radar imagery shows decreasing shower coverage this morning, except for some light activity over the Sierra and portions of Shasta County. Guidance keeps some lingering showers over mainly the Shasta, Coastal, and Western Plumas mountains today. Elsewhere, dry conditions are anticipated with daytime highs a few degrees below seasonal normals.
Gradual warming trend and dry conditions are expected this weekend as upper ridging builds across interior NorCal. High temperatures will be in the low to mid 70s across the Valley, and 40s to 60s over the mountains. These forecast highs range from 2 to 8 degrees above normal. Some breezy northerly winds could develop Saturday; gusts up to 20 mph could be possible.
Ridge axis shifts east of the forecast area Monday afternoon as Pacific system approaches from the west. Latest models indicate a slower arrival, and keep precipitation mainly over the Coastal range and western Shasta mountains Monday afternoon. Precipitation may spread southward late Monday evening, but model differences are evident. Early QPF amounts indicate around 0.50-1″ of liquid equivalent over the mountains through Monday evening. Snow levels are expected to rise above 7500 feet Monday.
Extended Discussion (Tuesday through Friday)
Lingering showers continue into the start of the extended period Tuesday as and upper shortwave through shifts eastward out of the region. Weak upper ridging slides over the state on Wednesday for a break in precipitation some areas. This ridge is fairly flat, however, and another shortwave passing through the Pacific Northwest will continue a threat of shower activity over the northern mountains. Timing varies some but models shift the upper ridge axis east of the state by Thursday afternoon allowing next Pacific cold front into the state for another round of rain and mountain snow. Confidence in timing is increasing on this system but strength varies. GFS currently shows a fairly low impact event Thursday while ECMWF brings heavier precipitation. Current ECMWF would bring significant valley rainfall and with below pass level snow levels, significant travel difficulties. Wet pattern continues into Friday and into the weekend as atmospheric river remains aimed into the north state.