Last Storm for a While Sunday into Monday

Last Storm for a While Sunday into Monday

 MARCH 8, 2014

It’s been a rather active last few weeks compared to the pattern we’ve seen over the last several months to a year! While we’re still in a major drought, the recent storms have helped out slightly to moderately locally, and we’ve got one last storm to go before we dry out for what looks to be at least one to two weeks.

This next storm will have another atmospheric river associated with it, including a long fetch of precipitable water values of 1 – 1.3″ extending into the east-central Pacific, northwest of Hawaii. A large upper low in the Gulf of Alaska is what’s driving this plume southward, ahead of a cold front. The system will loose a considerable amount of dynamic force as it gets south of the north coast, however a modest upper-level jet and decent lift, which in addition to a southwest flow in the mid-levels, will promote decent orographic lift in the northern sierra. In the valley, it appears rain-shadowing may limit precipitation quite a bit in the western central valley, but along the eastern side of the valley lift/banking against the foothills and western slope will support better precipitation potential.

700mb vertical velocity plotted through the 4km NAM, valid for 5am Monday. Areas of warm color indicate upward lift, with purples associated with the strongest lift and precipitation.

Timing is a little tough with this system, as pre-frontal showers are possible by mid to late-afternoon, with precipitation forming in the northern sierra and foothills of Butte county by early afternoon. The rest of the region should receive precipitation from the front by mid to late-evening, lingering into the early morning hours, clearing out by mid to late-morning. A bit instability may lead to a few showers through the day Monday, but nothing widespread or strong convection appears likely at the moment.

Snow levels will start out quite high, AOA 8000 – 9000ft, but may lower off a bit early Monday, perhaps down to 6000ft.

Rainfall amounts will range from a few hundredths to a quarter inch in the valley, to a quarter to half an inch in the foothills, half an inch to an inch in the higher elevations of the western slope, and 1 – 2.5″ in orographically favored south/southwest slopes from Placer to Shasta counties.

4km NAM’s forecast QPF through Tuesday. It ain’t much for the valley, but more notable in the higher elevations.

Stronger ridging slides overhead through Tuesday and is currently expected to remain overhead through at least the end of next week, at least according to current models. Highs by the end of next week could enter the mid to upper-70s to low 80s by weekend in the valley, with 40s to 50s in the highest elevations and 60s and 70s in the foothills.

Forecast highs next Saturday (March 15th).

And that’s about it! I wish there was more to write about, but really this coming storm isn’t too significant, the convective potential seems to be lacking, and the ridging behind it doesn’t need much explaining as to what it’ll bring besides increasingly warm temperatures.

If/whenever a storm presents itself, expect an update!