Area Forecast Discussion
Issued by NWS Eureka, CA
Issued by NWS Eureka, CA
668 FXUS66 KEKA 172231 AFDEKA AREA FORECAST DISCUSSION National Weather Service Eureka CA 331 PM PDT Tue Sep 17 2024 .SYNOPSIS...Another round of light rain showers is expected to spread across the area from north to south this afternoon and evening in Del Norte and northern Humboldt counties and working south tonight and Wednesday. A drying and warming trend is expected late in the week. && .DISCUSSION...As of 2PM PDT, Doppler radar depict weak returns moving onshore along the Redwood Coast. Meanwhile, an upper level trough continues to move down along the west coast. This feature is expected to become in a negatively tilted trough while evolve into a closed low just near the NW California Coast late this evening. As that occur, the precipitable water content is expected to increase up to 1.2 inch late this afternoon and evening, with chances of precipitation increasing across Del Norte and Humboldt counties. Light to moderate rainfall is expected late this afternoon and evening over Del Norte and northern Humboldt, with the heaviest rainfall over west- southwest facing higher terrain of Del Norte. Precipitation will be mainly across Humboldt and Del Norte for the rest of the day. Periods of light rain are expected to spread south and east overnight and into Wednesday as the low continue drifting southward. Rainfall total amounts are forecast to range from 0.30 to 0.10 inch for Del Norte and Humboldt counties, with less tenth of an inch to few hundredthsmost likely elsewhere. Showers will gradually taper off Wednesday morning from north to south with lingering showers through Wednesday afternoon as the low continue moving toward southern California. In addition, a weakly unstable post-frontal airmass will aid in a slight chance (15-20%) of isolated thunderstorms development across the eastern portion of the Mendocino, southern Trinity and Lake counties on Wednesday afternoon into evening. Wednesday night the low moves south and out of the area fairly quickly. This is expected to bring offshore flow that may keep the coastal areas clear. Inland areas could see some frost in the coldest spots, especially if there is little to no rainfall to help generate low clouds. Thursday highs are expected to rebound into the mid 80s with upper 80s to low 90s for the weekend. The current NBM shows these temperatures continuing into early next week. && .AVIATION...Inconsistent IFR conditions this morning have given way to mostly VFR conditions this afternoon with approaching low pressure helping to lift low level clouds. Conditions are expected to deterioate this evening, especially along the Humboldt and Del Norte Coast as light rain showers cross the area. Conditions will likely be inconsistent with periods of IFR ceilings and visibilities during heavier rain. Rain is most likely right along the coast between 1700 tonight and 0200 early tomorrow morning. As rain moves out IFR ceilings will likely linger (60% chance) through Wednesday morning before clearing to at least MVFR conditions by early afternoon. /JHW && .MARINE...Mostly gentle, northerly winds have built in today with short period seas falling below 5 feet. Light rain over the northern waters this evening will be the only notable feature. Northerly winds will increase Wednesday into Thursday with gusts above 21 kts in the outer waters by early Wednesday afternoon. Short period seas will build in response with heights up to 10 feet at 8 seconds in the far outer waters. Most models keep the steepest waves out of the inner waters except right around Cape Mendocino. Besides short period waves, the sea state will be modified through Thursday by a minor northwest, mid-period swell up to 5 feet. With high pressure generally building over the eastern Pacific, moderate to strong northerlies will continue for the outer waters through the week and likely into the weekend. There is a less than 20% chance of any gale force gusts though near gale force gusts are possible in the northern outer waters Friday. The chances of steep seas pushing into the inner waters will increase Friday into Saturday as passing shortwave pushes strong winds closer to shore. /JHW && .EKA WATCHES/WARNINGS/ADVISORIES... CA... None. NORTHWEST CALIFORNIA COASTAL WATERS... None. && $$ Visit us at https://www.weather.gov/eureka Follow us on Facebook and Twitter at: https://www.facebook.com/NWSEureka https://www.twitter.com/NWSEureka For forecast zone information see the forecast zone map online: https://www.weather.gov/images/eka/zonemap.png