A series of strong storms will move across the region into next week. The strongest storms are expected later today through Thursday, over the weekend, and again early next week. Widespread damaging winds are expected from late this afternoon into Thursday morning. Heavy precipitation will keep flooding threats elevated and mountain travel impacts at the forefront into next week. Flood Watch through Friday morning. High Wind Warning from 10 AM this morning to 4 PM PST Thursday. Flash Flood Watch from this afternoon through Thursday morning. Winter Storm Warning from 7 AM this morning to 4 AM PST Friday.
Discussion
Impressive satellite picture off the coast early this morning as the strong approaching system continues to mature. Cloud tops continue to cool and lightning detection is picking up some strikes indicative of continued strengthening. Ahead of the system, it’s the quiet before the storm with relatively light winds and patches of thick fog across portions of the Central Valley. The break in the weather which began Tuesday afternoon is about to end.
The warm-sector will spread across the region this morning bringing widespread light to moderate precipitation. Snow levels will start out around 3-4k ft across the northern mountains and 4-5k ft in the northern Sierra, but are forecast to rise considerably later today and tonight before settling in around 5-6k ft on Thursday. Several feet of snowfall accumulation is likely across the higher passes through Thursday.
Some areas will see a break in the rain this afternoon as the warm front lifts north, but gusty southerly winds will begin to increase this afternoon as surface gradient tightens ahead of the approaching cold front.
The strong southerly winds will peak overnight when widespread power outages will be possible as gusts reach 50-70 mph across the Central Valley.
The period of heaviest precipitation will occur late this afternoon into Thursday as the front moves through. With stronger southerly flow, the pattern favors the heaviest QPF in the mountains north of Redding and across the Feather Basin in eastern Butte and western Plumas counties where 6-8 inches of rain are forecast. The foothills on the west side of the Central Valley may also see some orographic enhancement with strong southeast winds ahead of the front.
Flooding on creeks, streams and small rivers will likely develop tonight and Thursday as runoff from the heavier precipitation works its way downstream.
Some of the recent burn scars will also be at elevated risk of mud and debris flow, particularly tonight.
As flood, wind and snow impacts rise, travel will become increasingly difficult, and will become especially treacherous overnight tonight into Thursday.
A relative break in weather is expected Thursday night through early Saturday, then another moderate to strong AR will affect the region over the weekend bringing more heavy precipitation and gusty winds.
Extended Discussion (Sunday through Wednesday)
Clusters and ensembles support continuing a very wet and windy pattern into next week. Storms are forecast to affect the region continuously with only brief respites in between. Currently, it’s looking like a moderate to strong AR will be winding down later Sunday, then another will quickly move into the region Monday and Tuesday, followed by another around the middle of next week.
The cumulative effect of the repeated rounds of moderate to heavy rain will lead to the potential for more widespread flooding with increasingly severe impacts.
Snow levels are forecast to mainly stay in the 4-6k ft range with brief rises as warm sectors with each wave move through, but accumulations will likely be measured in feet over the passes (GEF plumes for KBLU (around 5k ft elevation) show an average of around 2.5 ft of snow accumulation by early next week with a significant number of ensemble members showing 4-5 ft of accumulation by the end next week. Amounts over the higher passes will likely be significantly higher).
In addition to the rain, several more bouts of strong southerly winds will be possible early next week.