A series of strong storms will move through the region 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 afternoon through Thursday morning. Heavy rainfall will keep flood threats elevated and mountain travel impacts front and center into next week. Flood Watch until Friday morning. High wind warning from 10:00 a.m. this morning to 4:00 p.m. PST Thursday. Flash Flood Watch from this afternoon to Thursday morning. Winter storm warning from 7:00 a.m. this morning to 4:00 a.m. PST Friday.
Impressive satellite image off the coast early this morning as the approaching strong system continues to mature. Cloud tops continue to cool and lightning detection picks up a few hits indicating continued strengthening. Ahead of the system, it is the calm before the storm with relatively light winds and patches of thick fog over parts of the central valley. The weather break that started on 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 around 3-4000 feet in the northern mountains and 4-5000 feet in the northern Sierra but are expected to increase significantly later today and tonight before settling around 5 to 6,000 feet Thursday. Several feet of snow accumulation is likely in the upper passes through Thursday.
Some areas will see a break in the rain this afternoon as the warm front rises to the north, but gusty southerly winds will begin to increase this afternoon as the surface gradient tightens before the approach of the cold front.
Strong southerly winds will peak overnight when widespread power outages are possible as gusts reach 50-70 mph in the Central Valley.
The heaviest period of precipitation will occur late this afternoon through Thursday as the front moves. With a stronger southerly flow, the pattern favors the heaviest QPF in the mountains north of Redding and across Feather Basin in eastern Butte and western Plumas counties where 6 to 8 inches of rain are forecast. The foothills on the west side of the Central Valley may also see orographic improvement with strong southeast winds ahead of the front.
Flooding on creeks, streams and small rivers will likely develop this evening and Thursday as runoff from the heavier rainfall heads downstream.
Some of the scars from recent burns will also be at high risk from mudslides and debris, especially tonight.
As the impacts of flooding, wind and snow increase, travel will become increasingly difficult and will become particularly dangerous overnight Thursday into Thursday.
A relative break in weather is expected from Thursday evening to Saturday morning, then another moderate to strong RA will affect the region over the weekend bringing more heavy precipitation and gusty winds.
In-Depth Discussion (Sunday to Wednesday)
Clusters and sets support a continuation of a very wet and windy pattern into next week. The storms are expected to affect the region continuously with only brief respites in between. Currently, it looks like a moderate to strong AR will end later on Sunday, then another will quickly move through the region Monday and Tuesday, followed by another around the middle of next week.
The cumulative effect of repeated rounds of moderate to heavy rains will lead to the possibility of more widespread flooding with increasingly severe impacts.
Snow levels are expected to remain mostly in the 4-6,000 foot range with brief increases as warmer sectors pass through each wave, but accumulations will likely be measured in feet over the cols (the GEF plumes for KBLU ( around 5,000 feet elevation) are showing an average of about 2.5 feet of snow accumulation early next week with a significant number of ensemble members showing 4-5 feet of snow accumulation by the end of next week. Quantities above the highest cols will likely be much higher).
In addition to the rain, several other episodes of strong southerly winds will be possible early next week.