textproduct: Eureka

AVIATION UPDATE (18Z)

Coastal stratus remains across the entire western seaboard today. Expect IFR/LIFR conditions for most of the day along coastal terminals. Slight clearing is possible, yet not expected from 19Z-00Z, better changes are for areas near large river deltas compared to areas near steeper terrain. If it does clear, overcast skies will return later this afternoon between 02-04Z for most of the North Coast before developing to fog late this evening. Winds will build to 10-15kts or so and will be mostly northerly for most of the day along the coast. Wind directions this will be dictated by coastal eddies forming and migrating along the coastline.

Inland areas are expected to remain VFR with gusty afternoon winds developing during the peak heating of the day. Upslope winds will form through the morning and midday before NW winds dominate the interior areas of NW CA. Anomalously hot temperatures for the inland areas could lead to density altitude issues this afternoon as well, be aware.

PREV DISCUSSION

/issued 153 AM PDT Sat Aug 8 2026/

KEY MESSAGES...

* Moderate to major heat risk continues peaking on today in most areas. Temperatures diminish slowly next week, but most areas remain the upper 90s to around 100 through mid-week.

* Stronger afternoon valley winds and low relative humidity will elevate fire danger this weekend.

* There is the potential for thunderstorms late next week or over the weekend.

SYNOPSIS...Persistent high pressure aloft will remain through the weekend. Inland areas continue to see above normal temperatures through the weekend bringing moderate to major heat risk. Coastal areas will have improved chances of clearing over the weekend. Temperatures are expected to start gradually cooling next week. An upper level trough off the coast may bring monsoon moisture and the potential for thunderstorms late next week or next weekend.

DISCUSSION...A steady ridge of high pressure remains entrenched over the west coast leading to warm to VERY hot temperatures for the inland areas. Most inland valleys can expect high temperatures between 100-110F through the weekend. The coast continues to offer some relief from this heat. Offshore stratus is blanketing much of the western seaboard from the Mexican boarder up to Canada overnight into Saturday. However, above average SSTs and offshore flow will limit the development of overcast conditions through the weekend.

Increased warming continues across the interior increasing the HeatRisk with moderate to major HeatRisk now being indicated. The heat is expected to peak on Saturday, particularly over Lake County, where conditions are on the edge of warranting an excessive heat warning instead of only an advisory. Regardless, this persistent heat will be dangerous for anyone working outside and everyone in the interior portions of all of Northern California should be drinking plenty of fluids and taking breaks in the shade to avoid heat stroke or heat exhaustion.

The aforementioned mentioned daytime interior heating will tighten the surface pressure gradient over NW CA forcing stronger onshore (NW) sea breezes each afternoon and evening. With very dry conditions across the interior this will result in increase fire weather concerns. For more details, see the fire weather section below.

The upper level ridge that has settled over the area will finally see some weakening and should migrate eastward. A secondary high pressure system is forecasted to set up over the Pacific which will lead to weak troughing settling over the west coast. This should allow temperatures to cool several degrees back to around normal for this time of year and could lead to increased likelihood of afternoon clearing of coastal stratus. This may also start to bring the threat for inland thunderstorms late next week or next weekend.

MARINE...Significant wave heights are starting to increase, especially over the outer waters. Satellite imagery and surface observations shows northerly nearshore winds of around 10-20kts. The wind field increases in speed further away from the coastline. This increase in wind speed means that waves in the outer waters are likely larger and steeper than the nearshore buoys are recording. This afternoon through Sunday northerly winds will continue to increase. Downwind of Cape Mendocino and Point St. George, stronger northerlies are expected with gale force winds likely (>50% probability). These forecasted winds called for a Gale Warning to be issued for the outer waters from Saturday late morning through the remainder of the weekend, and likely longer if long range models hold strong. The inner waters are more likely to see moderate to fresh breezes through the weekend. Waves could still be steep due to propagation from short period seas in the outer waters entering the area. These stronger northerly winds are likely to last through most of the coming work week.

Plan your seafaring outings accordingly and always feel free to reach out for any addition information regarding the marine forecast for NW CA.

FIRE WEATHER...In Mendocino and Lake counties the higher elevations, generally at least above 2,500 feet are seeing very conditions this morning with RH in the 20s or even lower as of 1am. Some of those locations are also 5 to 10 mph northwest winds with local gusts to 25 in the windiest areas. These breezy conditions are expected to expand to much of the area for several hours this afternoon bringing critical fire weather Trinity, northern and eastern Mendocino, and Lake Counties due to low RH values and increased afternoon winds. While the duration of the winds are shorter than needed for Red Flag status, it is important to remember that even a single spark could start a wildfire in these conditions. Tonight the higher elevations will likely be dry again, although maybe not quite as dry as this morning. Sunday afternoon breezy winds are expected again for several hours, but the RH is expected to be slightly higher than on Saturday.

Next week temperatures are expected to start cooling off as the ridge of high pressure gets pushed to the east. It is starting to look like there will be the potential for some thunderstorms next Friday or Saturday. There is still a lot of uncertainty on this, but it definitely needs to be watched as it gets closer.

COASTAL FLOODING...Sea levels continue to run approximately 0.8 ft above the predicted tide level in Humboldt Bay. Tides will become more amplified early next week following the normal lunar cycle. The predicted tide at the North Spit is 7.95 ft MLLW at 10:21 pm on Monday the 10th and then 7.99 ft MLLW at 11:17 pm on Tuesday the 11th. If the tide continues to run at around 0.8 ft above predicted, this could result in minor coastal flooding around Humboldt Bay with minor impacts in King Salmon and possibly a few other locations around the bay.

EKA WATCHES/WARNINGS/ADVISORIES

CA... Heat Advisory until 11 PM PDT this evening for CAZ105-106.

Heat Advisory until 10 PM PDT Sunday for CAZ108-110>114- 116>120.

NORTHWEST CALIFORNIA COASTAL WATERS... Small Craft Advisory from 3 PM this afternoon to 10 PM PDT Sunday for PZZ450-455.

Small Craft Advisory until 3 PM PDT this afternoon for PZZ470-475.

Gale Warning from 3 PM this afternoon to 3 AM PDT Tuesday for PZZ470.

Gale Warning from 3 PM this afternoon to 10 AM PDT Monday for PZZ475.