Marine Weather and Tide Forecast for Eureka, CA

Key Messages
/issued 1026 PM PDT Tue Jun 17 2025/

* Minor HeatRisk interior valleys through Thursday. Areas of moderate HeatRisk on Wednesday northeast Trinity and Lake.

* Gusty coastal northerlies expected Wednesday and Thursday afternoons.

* Strong westerly and northwest breezes and substantial cooling for interior valleys and ridges Thursday through Saturday.

* 10% chance of thunderstorms northern coastal waters and near Del Norte County Friday afternoon and evening.

* Interior warming and drying trend Sunday into early next week.

DISCUSSION... /issued 1026 PM PDT Tue Jun 17 2025/ Hot weather to continue with daytime temperatures generally peaking into the lower to mid 90s on Wednesday in Trinity, Lake and SE-NE interior Mendocino. Minor HeatRisk is forecast through Thursday except for areas of moderate HeatRisk in NE Trinity and portions of Lake on Wed where temps peak into the upper 90s. Temperatures are forecast to drop well below seasonal averages (by 15-20F degrees) Friday and Saturday, and then recover slightly on Sunday. Hot and drier weather with highs in the 80's forecast to return in the interior Monday and Tuesday next week.

Broad flat ridge with above normal 500mb heights will continue to result in modest interior warming through Wed. Strengthening northerlies offshore should scour out the stratus on Wed with daytime heating and mixing. In fact HRRR indicates a 70-90% chance of northerly peak gusts around 35-40 mph around Cape Mendocino and Pt St George late in the day into the evening Wed. And the King Range range too will probably have strong gusts to 40 mph or more by Wed evening. ECMWF ensemble has a much wider distribution with an average around 30-35 mph for the coastal headlands. ECMWF ensemble distribution is pegging Thu with stronger gusts near 40 mph for headlands, particularly Pt St George. NBM indicates much lower or near zero chances for gusts > 40 MPH.

Prime concern heading into the latter portion of the week (Thu-Fri)
will be stronger west-northwest winds across the interior valleys and interior ridges. Gusts to 20-30 mph are probable. A few of venturi-effect ridges may even gusts 40-50 mph or so as an unseasonably cold 500mb low drops down from the Gulf of AK. Humidity generally increases as we head into Fri and Sat, however portions of southern Lake and eastern Trinty may have much lower RH's - around 20-25%. With the trough enhancing diurnally westerly and northwesterlies, locally critical fire weather conditions will be possible. Risk for small fast spreading grass or brush fires will increase.

This upper trough/surface front will probably generate some light rain for the northern most zones; Del Norte, northern Humboldt and perhaps northern higher terrain of Trinity. NBM indicates a 30% chance for 0.25 inches of rain or more in Del Norte County in 24 hours late Friday into early Saturday. There may even by some isolated thunder too, mostly over the northern waters with 500mb temps plunging to -25C. Overall not much rain, but just enough to have impacts on outdoor activities and projects. So stay tuned for more details. Depending on how quickly clouds clear out and if winds die down and decouple over the weekend, there is even a chance of early morning frost in the valleys of mostly Trinity County this weekend. It will be considerably colder in the mountains too, so those venturing to the high mountains should be prepared for near or subfreezing temperatures in the mornings.

Considerable variability arises with the models over the weekend into early next week. Upper level trough lingers over the area or just to the east over the Great Basin this weekend. Trend is for the trough to lift out and fill, so interior temperatures should warm each day Sun-Tue. There is still an outside chance for some showers with perturbations pin-wheeling around the backside of the trough.
Overall no clear signs for thunder or a major warm up at this time.

AVIATION
(12Z TAFs) A fairly shallow marine layer is bringing low clouds and patchy fog which is producing IFR to LIFR conditions this morning. Gusty NNW winds building in the mid- late morning are forecasted to lift and likely dissipate most of the stratus by 2100Z. These winds will be strongest on ridges, river valleys, and coastal headlands. VFR conditions are expected to hold with light, variable winds in the inland areas this morning. This evening and tonight the HRRR is showing a return of stratus to the Humboldt coast. Confidence is low to moderate on this. Later tonight it make it north into KCEC but confidence is lower on this. MKK

MARINE
/issued 1026 PM PDT Tue Jun 17 2025/ The calmer conditions of Tuesday will be short lived as stronger winds return to the southern waters Wednesday and Thursday. Small craft advisories have been issued for the southern water through Wednesday morning. Winds will build through the day Wednesday bringing gale force gusts to the southern outer waters downwind of Cape Mendocino. Near gale to gale force gusts may push further into portions of the inner waters during the afternoon, especially Thursday. A gale warning remains in place for the southern outer waters. A small mid- period NW swell 4-5 ft at 14 seconds will contribute to the sea state Thursday afternoon, producing combined seas 8 to 10 feet. The sea state will begin to diminish on Friday as low pressure system approaches the region, disrupting the wind pattern. This late season cold front is expected to bring gentle- to-moderate breezes and a small mid- period NW swell to the coastal waters.

FIRE WEATHER
Northwesterly afternoon winds remain breezy in the interior through Wednesday, particularly in southern Mendocino and Lake. High temperatures are forecast to rise a few degrees, continuing the warm and dry trend. RH recoveries remain good, but afternoon RHs dip into the teens or low 20s, which does present a localized elevated fire weather threat in the afternoons and evenings. Winds spike up Thursday and Friday with stronger, gusty winds possible in the eastern portions of the area in the afternoons. Min RHs are forecast to be higher each day. A cold upper low is forecast to dive south into the region late this week and into the weekend. This will bring cooler temperatures and a chance for light rain to the area.

EKA WATCHES/WARNINGS/ADVISORIES
CA...
None.
NORTHWEST CALIFORNIA COASTAL WATERS...
Small Craft Advisory from 5 PM this afternoon to 9 PM PDT Thursday for PZZ450-470.

Small Craft Advisory until 9 PM PDT Thursday for PZZ455.

Small Craft Advisory until 3 PM PDT this afternoon for PZZ475.

Gale Warning from 3 PM this afternoon to 3 PM PDT Thursday for PZZ475.