NorCal spring showers

Filed in Uncategorized by on May 2, 2007 5 Comments

A very weak May-like system brought some sprinkles and light showers to NorCal this morning…nothing of any real singificance. Outside of isolated thundershowers in the far north, today’s weather was rather unexciting. Tomorrow will be mostly dry in most places, but another disturbance diving down west side of the Gulf of Alaska trough will renew shower chances across the northern 2/3 of the state late Thursday into Friday. Rainfall amounts will be a bit higher than the precious system, but still on the light side (generally 0.15 to 0.35 in. at best). There is the outside chance of an isolated thunderstorm, mainly in the Central Valley, but convective chances really will be minimal with this system. After Friday, strong high pressure builds back into the region and 850 mb temps rise significantly going into the weekend and beyond, when inland highs could climb back into the 90s.

The most recent snow survey for California drainage basins paints an even drier picture than the April 1st survey did. Statewide, snowpack water content averaged an abysmal 27% of the May 1st average. More northern basins fared decidedly better than those in the Southern Sierras; the Northern Sacramento River basin scored a positively drenching 52% of normal while the San Joaquin River drainage had a spectacularly low 8% of average snowpack water content. All hydrologic regions, however, scored a collective 30% or lower. We’ll make it through this summer…as reservior levels are still near average for this time of year thanks to a series of good snow accumulations in NorCal the past few years previous to this one…but peak flows on snow-fed rivers and streams will occur in just a couple of weeks and there will be very little water to replentish reserviors once June comes around. Reservoir level percent of normal values will start to drop rapidly once summer sets in…and we may begin to see some concerned water managers by the end of August. Everything, at this point, hinges on 2007-2008 precipitation: if it’s not above average, we’re going to have water shortages. A unusually hot summer wouldn’t help, either…