textproduct: Eureka

KEY MESSAGES

* Hot: Above normal temperatures continue today for the interior with high temperatures in the 90s to around 100.

* Dry lightning: There is a 20 percent chance of thunderstorms mainly in Trinity County this afternoon and evening. Dry lightning and gusty winds will elevate fire risk. There is a 10-15 percent chance of other areas seeing thunder.

* Coastal flooding: Minor coastal flooding around Humboldt Bay possible at the evening high tide through Wednesday night.

SYNOPSIS

Hot temperatures continue across much of the interior today. Isolated dry thunderstorms or showers are possible today in the interior. Slightly cooler temperatures are expected Wednesday through Friday with warming again for the weekend.

DISCUSSION

Monsoonal moisture continues to move into the area early this afternoon and evening. Elevated instability may support a few showers and thunderstorms this afternoon and evening. The highest chances remain in Trinity County for this afternoon, but a few models do show this both farther west and south into Humboldt and Mendocino Counties. Instability is still limited with even the most ambitious models showing 200-400 J/kg at the most. Still, this could be enough for a lightning strikes. "Inverted-V" model soundings along with high PW values nearing 1 inch does support a downburst threat should thunderstorms develop. Strong to near severe wind gusts of 50 mph or higher could follow a thunderstorm. With little to no precipitation expected to reach the ground, erratic, gusty winds could cause fires to spread rapidly. A Red Flag Warning remains in effect this afternoon and evening in Trinity County, northeastern Humboldt County, and southwestern Siskiyou County for this fire threat.

Outside of thunderstorms, high pressure continues to bring hot temperatures to the interior with high temperatures in the 90s to near 100 for most interior valleys. Minor to locally moderate HeatRisk is forecast. A strong marine inversion is in place for the Humboldt and Del Norte coasts, bringing more persistent stratus along the immediate coast. Some brief clearing is possible later this afternoon.

Drier air returns Wednesday as the Pacific Northwest trough moves southwestward. A deeper marine layer is likely to bring interior temperatures down by a few degrees, while bringing more widespread, and possibly persistent, coastal stratus. High pressure returns late week, returning warmer interior temperatures.

Monsoonal moisture returns to the area next Monday through the middle of next week. This will bring additional chances for thunderstorms to the area, though confidence is not high on timing and location at this time. This will need to be watched as it gets closer. /JB

AVIATION

Coastal airports are experiencing a mixed bag of conditions today as the marine layer fluctuates along the coast. At KACV, low ceilings are hovering around 400 feet, though horizontal visibility remains excellent at 10 miles. These low clouds will persist through the afternoon before dropping lower tonight, bringing mist and dense fog that will likely reduce visibilities to a half-mile by early Wednesday morning. Further north at KCEC, thick mist and low ceilings have kept visibilities restricted to around 1 mile today. While a brief afternoon improvement to scattered clouds is expected, low ceilings and dense fog will return by early evening, locking the terminal into LIFR conditions overnight. Meanwhile, inland areas at KUKI will enjoy clear skies and solid VFR thresholds through the entire forecast period. Light afternoon winds will give way to breezy northwesterly winds gusting up to 17 knots late today before becoming calm after sunset.

MARINE

Breezy northerly winds continue, especially in the southern waters in the lee of Cape Mendocino. Localized gale force gusts are likely in the immediate lee of Cape Mendocino. Steep seas of 6 to 8 ft are likely in this expansion fan off the Cape. Elsewhere, winds are expected to be much lighter with peak gusts of 10-20 kts. Seas have subsided outside Cape Mendocino with observed significant wave heights of only 3-5 ft. Thursday night into Friday, the strongest winds to move away from the coast. The outer waters could still see breezy winds with gusts of 20-30 kts, but the inner waters will see much lighter winds. Much milder conditions arrive Saturday night into Sunday. /JB

FIRE WEATHER

For thunderstorm information see general discussion above. Wednesday afternoon, stronger northwest winds are expected in Mendocino, Lake, and eastern Trinity counties. Afternoon RH is expected to be low with teens and 20s expected for much of eastern Lake County and teens in Lake County and Trinity County. These winds and low RHs will elevate fire danger. The upside is these onshore winds will bring more moisture and RH will gradually rise. Winds continue to be breezy Thursday but higher afternoon RHs are expected with 20s and 30s in Mendocino, 20s in Lake County, and teens to 20s to eastern Trinity County. Winds ease Friday, but afternoon RH will also lower back into the teens and 20s. /JB/MKK

COASTAL FLOODING

High astronomical tides and the basin wide warmth in the ocean is creating higher than normal water levels despite light northerly winds. The water levels were close to 0.7 feet over the astronomical tide Monday evening resulting in a high tide of 9.1 feet. This will likely put water levels close to 9 feet again at the North Spit in Humbodlt causing and cause minor flooding again tonight. The tide will begin to diminish Wednesday night/Thursday morning. MKK/EYS

EKA WATCHES/WARNINGS/ADVISORIES

CA... Coastal Flood Advisory from 11 PM this evening to 2 AM PDT Wednesday for CAZ103.

Red Flag Warning until 2 AM PDT Wednesday for CAZ403- 409>412.

NORTHWEST CALIFORNIA COASTAL WATERS... Small Craft Advisory until 3 AM PDT Saturday for PZZ455-475.