textproduct: Eureka

SYNOPSIS

High pressure continues to build into the area with hot temperatures forecast into early next week. The near coastal and coastal areas may start to see more marine influence over the weekend and into early next week. The hottest temperatures are forecast Monday and Tuesday. Temperatures will begin trending lower mid to late next week.

DISCUSSION

High pressure continues to strengthen across the region. Hot daytimes highs with warmer nights are creating Moderate to Major HeatRisk over the region. The strong Northeast Pacific ridge will amplify and nose in from the west Monday and Tuesday resulting in the hottest temperatures. Much of the interior valleys will see temperatures in the upper 90s to 100. The warmest interior valleys of Humboldt and Trinity County have a chance (60%) and are forecast to exceed 105 Monday and Tuesday. Heat Advisories are out for the interior, and there may be further expansion south into Lake County starting Monday.

A summer southerly stratus surge will work northward around Cape Mendocino overnight and early Sunday morning. The stratus is shallow under the strong ridge, and webcams have already shown dense fog along the Mendocino and far southern Humboldt coast. Once in place along the North Coast, the stratus will become more persistent over at least the next couple of days. This will likely hold temperatures lower along the immediate coast where afternoon scattering does not occur.

The Northeast Pacific ridge will begin breaking down late Tuesday or Wednesday while broader ridging remains in place. Temperatures will enter a lowering trend mid to late next week in response. A weak surge of monsoonal moisture may clip the interior as early as Thursday. This setup would be favorable for elevated thunderstorms should the moisture make it this far west.

AVIATION

A weak disturbance to the south is generating some southerly return flow along to Mendocino coast. Stratus is observed charging up along the Mendocino coast and beginning to breach the corner around Cape Mendocino. Weak northerlies and a secondary southerly eddy along Humboldt and Del Norte will usher in a classic summer southerly stratus surge. Visible satellite reveals strong conformation of the stratus to the coast, implying a shallow layer. Webcams also show very low visibilities around Shelter Cove, confirming fog, potentially dense (1/4SM VIS) is on the way to the remaining coastal terminals through this TAF period. Timing is always problematic, with uncertainty on when it can round the cape, but the latest guidance takes it near or close to ACV near 9Z-11Z, and farther north to CEC 10Z-12Z. The stratus could certainly surge earlier, as is usually the case with these setups.

Once the stratus advances under the strengthening low level inversion, it will likely remain locked in for a bit with smaller windows of afternoon improvement for Sunday and potentially again Monday. Southerly flow through the Russian River Valley will also direct a shallow stratus layer towards UKI through Sunday morning. HRRR soundings saturate the lower levels, and there is a conditional 30% chance for LIFR CIGs Sunday morning at UKI. Surface winds will be light overnight and through Sunday over Northern CA.

MARINE

A weak disturbance to the south is quickly weakening the northerlies and is generating near shore southerly winds. Northerly winds linger slightly longer over outer portions of the northerly waters, keeping larger steep seas in the waters into Sunday. Low clouds and fog, locally dense will be making its way up the coast overnight. Locally dense fog will likely remain over portions of the waters through Sunday and perhaps Monday. Winds will turn gentle by late Sunday morning, other than some accelerated southerlies around Cape Mendocino. Generally light winds are expected Sunday through Monday. Northerlies return late Monday and strengthen through mid next week, with gale conditions likely in portions of the waters. A small around 2 ft long period southerly swell with a period up to 24 seconds will arrive Monday.

FIRE WEATHER

Temperatures will remain hot and dry through early next week. Afternoon relative humidity values have been observed dropping into the low teens to single digits in the warmer interior valleys. A warm thermal belt will keep recoveries poor over the higher ridges. Winds are forecast to remain fairly light and terrain driven. Expect a stronger westerly to northwesterly wind surge Tuesday afternoon. Similar enhanced diurnal winds are likely into mid next week. Temperatures will moderate cooler by middle to late next week. There is a chance for monsoonal moisture to clip the area as early as Thursday. If the moisture does make it this far west, there will be opportunity for elevated thunderstorms. Models have trended slightly more favorable to this solution in recent runs.

COASTAL FLOODING

High astronomical tides are predicted from Saturday, June 13 through Tuesday June 16 for Northwest California. High tides around 8.8 ft will cause coastal flooding around Humboldt Bay, including King Salmon and low- lying roads near Arcata Bottoms. /JJW

EKA WATCHES/WARNINGS/ADVISORIES

CA... Heat Advisory until 10 PM PDT Tuesday for CAZ102-105-116.

Coastal Flood Advisory from 9 PM this evening to midnight PDT tonight for CAZ103.

Heat Advisory from 11 AM Sunday to 10 PM PDT Tuesday for CAZ108-111-117.

Heat Advisory until 10 PM PDT this evening for CAZ113-114- 118>120.

NORTHWEST CALIFORNIA COASTAL WATERS... Coastal Flood Advisory from 9 PM this evening to midnight PDT tonight for PZZ415.

Small Craft Advisory until 3 AM PDT Sunday for PZZ450.

Gale Warning until 9 PM PDT this evening for PZZ470.

Small Craft Advisory until 9 PM PDT this evening for PZZ475.