Actual rain this week?

Filed in Uncategorized by on April 17, 2007 21 Comments

It does appear that some wetting rains are likely across the state over the next few weeks. Many places have seen only sprinkles or light showers during the past 1-3 months, and have received only a few inches of rain over the entire winter. This week’s relatively widespread and significant precipitation will, therefore, be particularly noticable in the areas that have been so dry. A fairly potent low pressure area will develop and deepen a bit as it slides down the CA coast Thurs/Fri, dragging a cold front across CA ahead of the main cold-core low. The initial cold front will be pretty strong for this time of year…as instability will be present and cold air advection will be impressive. This system will not only have better dynamics than others that have fizzled as of late by will also have more moisture to work with. After the main cold front passes through, which could being brief heavy rain, gusty winds, and a few embedded thunderstorms, cold air aloft will settle in across the region and give rise to convective showers and thunderstorms. As always, thunderstorm activity will be most concentrated in the Central Valley and in some orographically favored locales in SoCal, but even coastal areas throughout the state stand a chance at hearing some thunder at some point on late Thurs/Fri. Some strong thunderstorms are likely Friday afternoon after daytime heating acts to further destabilize the atmosphere. There will be a brief break in the weather on Saturday before another significant…possibly even stronger…system swings in from the Gulf of Alaska. This second system for the weekend will being some fairly intense rainfall rates to NorCal if the latest runs of the GFS are correct, and would produce at least some light precipitation as far south as San Diego. Total rainfall from these two systems will be as high as the 3-4 inch range in the far northern part of the state, 0.75-2 inches in the Bay Area, and 0.25-1.0 inches in SoCal. Although rainfall of ths magnitude won’t end our dry spell/drought conditions by any means, every bit helps at this point and these cold systems do serve to bolster late-season Sierra snowpack. Stay tuned.