Area Forecast Discussion
Issued by NWS Eureka, CA
Issued by NWS Eureka, CA
375 FXUS66 KEKA 162014 AFDEKA AREA FORECAST DISCUSSION National Weather Service Eureka CA 114 PM PDT Wed Jul 16 2025 .SYNOPSIS...Inland temperatures trend low and remain warm and dry into the weekend. The coastal stratus will remain more persistent over the coastal regions, lowering the daytime highs for some areas. && .DISCUSSION...Upper troughing to the north through the Pacific Northwest is suppressing high pressure over our region today. Inland temperatures are forecast to be a few degrees cooler Thursday as the trough to the north slightly deepens. The low-level inversion has strengthened, and will remain strong to moderately strong this week. Well defined coastal eddies and strengthening southerly return flow along the coast this afternoon is generally maintaining the coastal stratus. A weak shortwave trough remains off the coast Wednesday and most of Thursday. In response, the marine layer will further deepen and contribute to more diurnally present coastal stratus. This will hold daytime highs down a bit where clearing does not occur. There is a very slight chance (less than 5%) for dry thunderstorms in northern Trinity County Wednesday and Thursday afternoons. Model soundings show very limited elevated instability and available moisture, with a good amount of CIN. Some cumulus clouds are observed on visible satellite. Instability will improve air quality in the afternoon, except immediately downwind from the fire. JJW && .AVIATION...(18Z TAFs) A large southerly reversals along the NW coast today is creating IFR/LIFR conditions with low ceilings. Satellite imagery shows these clouds beginning to evaporate within inland river valleys, yet along the coast conditions are not expected to improve (and if they do it will not last long). LAMP guidance shows a likely chance (30-40%) of IFR conditions through the daylight hours today at KACV and KCEC, and this can be expected along the Mendocino coast as well. IFR/LIFR conditions are very likely (>80%) to return tonight to the north coast beginning around 03Z due to low ceilings returning. Inland, VFR conditions are expected with potential for smokey visibilities as well as diurnal winds and light elevated winds (Southerly, ~15kt at 1500ft AGL) in Trinity, interior Humboldt and NE Mendocino counties. The HiRes-ARW model shows fog (>97% RH) encroaching over the Russian and Eel River valleys again tonight and early tomorrow morning leading to potential LIFR conditions. && .MARINE...Coastal trapped eddies are present in both the northern and southern inner waters this morning as seen by satellite imagery. Expect light southerly breezes close to shore with low clouds and possible fog/drizzle. With these calmer winds, the steep seas are forecast to calm through today. Over the next few days, moderate breezes are expected through Friday. Stratus, drizzle, and fog are expected as well with potentially degraded visibilities, especially at nighttime and in the early mornings. && .FIRE WEATHER...There is a very slight chance (less than 5%) for dry thunderstorms in northern Trinity County Wednesday and Thursday afternoons. Model soundings show very limited elevated instability and available moisture, along with a good amount of CIN. Some cumulus clouds are observed on visible satellite. The instability will improve ventilation. The deepened marine layer will continue to maintain marine influence farther inland from the coast. Further deepening is likely through Thursday. A weak shortwave trough will increase southerly to southwesterly winds locally Wednesday and Thursday afternoons in Lake and Southern Mendocino counties. Inland temperatures will inch slighlty higher late this week while conditions remain warm and dry. Minimum RH will drop into the low 20s to mid teens with some increasing westerly winds through Saturday before trending higher Sunday and into next week. JJW && .EKA WATCHES/WARNINGS/ADVISORIES... CA... None. NORTHWEST CALIFORNIA COASTAL WATERS... None. && $$ NOTE: The full forecast discussion is now regularly issued between 10 am/pm and 1 pm/am. Additional updates will be issued as needed. 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