textproduct: Eureka

KEY MESSAGES

* Moderate to major heat risk continues through the weekend for much of the interior peaking on Saturday in most areas.

* Temperatures diminish slightly 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.

* Coastal stratus to continue for much of the North Coast today and tonight with better chances for afternoon clearing this 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 remain mostly overcast Friday with better chances of clearing over the 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 today. Temperatures will struggle to reach the mid 60s for coastal communities due to this compressed marine layer. However, above average SSTs will limit the likelihood of any true daytime fog.

Increased warming remains today through Saturday 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 H5 ridge that has been settled over the area for so long 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.

AVIATION

Coastal stratus remains across the entire western seaboard today. expected IFR/LIFR conditions for most of the day along coastal terminals. Slight clearing is possible, yet not expected. If it does clear, overcast skies will return later this afternoon between 02-04Z for most of the North Coast. Winds will remain light (<08kt) for most of the day along the coast. Directions will be dictated by coastal eddies forming and migrating through the day. Overcast skies are expected to dissipate around noon for Saturday, especially near KACV with steady light to moderate winds tomorrow out of the NW. Inland areas are expected to remain VFr with gusty afternoon winds developing. Upslope winds will form through the morning and midday before NW winds dominate NW CA.

MARINE

Significant wave heights are currently low at observation buoys, around 3-4ft. 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. Entering this weekend, northerly winds will 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

Short-lived critical fire weather is expected Saturday afternoon for Trinity, northern Mendocino, and Lake Counties due to low RH values and increased afternoon winds. While winds are weaker than Red Flag status, it is important to remember that even a single spark could start a wildfire in these conditions. RH values in the teens to single digits are forecasted to briefly coincide with afternoon wind gusts from the NW. The areas of concern are mostly for the Upper Trinity River Valley and the eastern side of Clear Lake. Winds will enhance through the channeled terrain and over the lake likely causing conditions that could fuel explosive fire growth from 3pm - 7pm. While coverage and timing are localized, the threat of critical fire weather conditions remains.

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 10 PM PDT Sunday for CAZ108-110-111-113- 114-116>120.

Heat Advisory from 10 AM Saturday to 10 PM PDT Sunday for CAZ112.

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

Small Craft Advisory until 3 PM PDT Saturday for PZZ470.

Gale Warning from 3 PM Saturday to 10 AM PDT Monday for PZZ470-475.

Small Craft Advisory until 3 PM PDT Saturday for PZZ475.