Flash Flood Watches are in effect in Northern California ahead of rain expected to develop along the US West Coast Wednesday morning, November 21, 2018. After that, a parade of storms is expected to march through the weekend. Meanwhile, Air Quality Alerts are expected to remain in effect over parts of Southern California until the fires are extinguished.
A deep upper-level trough will move onshore over the West Coast early Wednesday, November 21 into Thursday morning, November 22 (Thanksgiving), NWS forecaster Ziegenfelder said November 20.
Rain will develop along the West Coast early Wednesday morning and expand inland to the Northern Intermountain Region/Great Basin by Thanksgiving morning.
Flash Flood Watch for the burn scars is in effect Wednesday afternoon through Friday morning, NWS office in Sacramento said November 20.
Ash, mud and debris flows is possible for the burn scars.
"There is a marginal with embedded slight risk of excessive rainfall over California from Wednesday morning into Thursday morning," Ziegenfelder added.
"As the trough moves inland the snow levels will lower over the Cascades and the Sierras. Snow will begin over the higher elevations of the Cascades and Sierras by Wednesday afternoon continuing into Thursday morning. Overnight Wednesday, snow will develop over parts of Northern California and the Southern Cascades."
"After the arrival of Wednesday’s rain, it’s going to be a parade of storms through the weekend as several more waves of moisture and energy swing through," Weather Nation meteorologist Merry Matthews said.
"It is important to stay up-to-date to changes with this forecast. The timing of this event makes for higher impacts as more people frequent the highways and interstates for the Holidays. Debris flows, mudslides can shut down area roads quickly so be sure to plan your routes accordingly," she concludes.
Flash Flood Watch for the burn scars is in effect Wednesday afternoon through Friday morning. A Winter Storm Watch is in effect Wednesday Afternoon and Wednesday night above 6500 ft.— NWS Sacramento (@NWSSacramento) November 20, 2018
Ash, mud and debris flows possible for the burn scars. Accumulating snow above 6500 ft. #CAwx pic.twitter.com/cw5AMXJCD8
With rain back in the forecast, previously burned areas will experience ash flow. If the rain becomes heavy over one of these burned areas, debris flow may be possible. Be prepared if you live near an affected area. #CAwx pic.twitter.com/ihRACDAp4a— NWS Sacramento (@NWSSacramento) November 19, 2018
Rain still on track across SW Calif Wed afternoon into early Thu morning. Main threats will be rockslides, mudslides, minor debris flows across #WoolseyFire and #HillFire burn areas. Greatest threat along Hwy 1 and canyon roadways. #LArain #LAWeather #cawx pic.twitter.com/a44RCA6XRy— NWS Los Angeles (@NWSLosAngeles) November 19, 2018
Strong inversions will allow wildfire smoke to continue to impact interior Norcal today although air quality is slowly getting better most areas. Rainfall spreading over Norcal on Wednesday should clear the air considerably. #cawx pic.twitter.com/LKa2b1d7uy— NWS Sacramento (@NWSSacramento) November 20, 2018
Featured image credit: NWS Los Angeles
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