California's Sierras Get Over 10 Inches of Precipitation; Snow, Ice Coming to South

California's biggest rainstorm since December 2012 brought much-needed moisture to the state over the weekend, thanks to a very moist “Pineapple Express” atmospheric river of moisture from the Hawaiian Islands. The storm brought more than 2" of precipitation to most of Northern California, and more than 10" to the Northern Sierra Mountains, where as much as six feet of snow fell above 9,000'. Some locations saw more rain in a four-day period than they had during the previous eight months. San Francisco got 2.58" of rain Thursday through Sunday, which isn't far below the 4.24” of rain it received during the previous thirteen months. The city averages about 20" of rain per year. Water levels on the critical Central California reservoir Folsom Lake rose by twelve feet in one day between February 8 and 9, 2014. However, the lake remains at just 41% of its average capacity for this time of year, and is well below the record low levels set during 1977. California probably needs at least five more storms like this to pull them out of drought. Wunderground's weather historian Christopher C. Burt discusses the amazing January 2014 California heat wave in his Saturday post, and has a detailed update on precipitation totals from the past weekend's Pineapple Express storm in his latest post.


Figure 1. Observed precipitation for the 7-day period ending at 12 UTC on Monday, February 10, 2014. Portions of the northern Sierra Mountains received more than ten inches of precipitation. Image credit: NOAA/HPC.


Figure 2. Water levels on the critical Central California reservoir Folsom Lake rose by twelve feet in one day between February 8 and 9, 2014. However, the lake remains at just 41% of its average capacity for this time of year, and is well below the record low levels set during 1977. Image credit: California Department of Water Resources.

The forecast: a return to mostly dry conditions this week
The persistent and intense ridge of high pressure that has dominated the West Coast since December 2012, bringing California's record dry spell, has broken down over the past week. While the models show generally dry conditions for the state during the coming ten days, the ridge is not forecast to build back at anywhere near its former intensity, giving me some hope that the state will experience more rainy weather during the last half of February.


Figure 3. Predicted precipitation for the 7-day period ending on Monday, February 17, 2014. California will mostly be dry, with heavy rains confined to the far Northern Coast. Image credit: NOAA.

Significant winter storm takes aim at Southern U.S.
The Southern U.S. gets its second serious winter storm of 2014 this week, as Winter Storm Pax brings a dangerous mix of snow, sleet, and freezing rain. The snow and freezing rain action begins Monday night over Northeast Texas, Southeast Oklahoma, Southern Arkansas, and Northern Louisiana, then spreads eastwards on Tuesday into northern portions of Mississippi, Alabama, Georgia, and South Carolina, and over much of North Carolina. Atlanta, Georgia, which was shut down by the 2.6" of snow Winter Storm Leon brought to the city on January 28, is under a Winter Storm Watch. Snow and sleet are expected to begin on Tuesday morning. After warming afternoon temperatures bring a period of plain rain on Tuesday afternoon, the rain may change to freezing rain on Tuesday night and Wednesday, making travel dangerous or impossible. The greatest accumulations of freezing rain may fall in Central South Carolina, where up to 3/4" of ice is predicted. However, this is a complex forecast, and just a slight shift in the track of the storm or atmospheric conditions could greatly alter the amount of snow and freezing rain this storm brings. The storm will move up the Eastern Seaboard Wednesday night into Thursday, potentially bringing snow to major East Coast cities.

Jeff Masters