September 19, 2019 – Showers linger across the mountains today, with dry and mild weather returning through the early weekend. Another system skims the area Sunday possibly bringing additional chances for mountain precipitation. Breezy north winds may be seen across the Valley early next week.
Radar shows a few showers continuing early this morning across eastern Shasta County and across the far northern Sierra Nevada close to the center of the upper low over northeast California. Elsewhere, skies remain partly to mostly cloudy over the mountains while clear skies cover much of the Central Valley. Current temperatures are cooler compared to 24 hours ago across much of the area and range from the mid 30s in the mountain valleys to the lower 60s across milder portions of the Central Valley.
Besides some lingering showers in the northern Sierra today as the low shifts east, dry weather is expected to linger into the weekend. Northerly winds return through Friday in the Sacramento Valley, but won’t be overly strong. As ridging rebuilds, temperatures rise to near average with Valley temperatures ranging from the mid 80s to around 90 degrees by Saturday.
The next upstream trough is forecast to move into the area on Sunday bringing a chance of showers to the northern mountains and northern Sierra Nevada and cooling temperatures a bit.
Extended Discussion (Monday through Thursday)
To commence the week, amplified flow returns to the West Coast as an elongated trough dives down toward northern California/Nevada. Details in the eventual placement of this system remain nebulous as dictated by the forecast spread. While spatial differences have decreased in recent model cycles, ensemble members still show enough solutions with an upper low track through northern California that it cannot be discounted. Ensemble means continue to favor a more eastward solution over far western Nevada which will remain the preferred route in the forecast package.
The current ramifications of this solution would be dry, northerly winds which will reduce relative humidities early next week, thus elevating wildfire concerns. At this juncture, the gustiest winds would be on Monday with winds speeds over the Sacramento Valley in the 20 to 30 mph range. Farther east into the foothills and Sierra, local gradients favor more of a east-northeasterly flow, potentially gusty at times.
In addition to the winds, high temperatures will remain warm, especially on Tuesday with readings likely approaching the mid 90s given 700-mb temperatures in the 12-14C range. There will be a potential cool down later in the week although it depends on the position of the mentioned upper low which stalls over the Desert Southwest. In terms of precipitation, while the threat is low, some isolated showers are possible Monday over the high Sierra (south of I-80).