FXUS66 KEKA 092202 AFDEKA AREA FORECAST DISCUSSION National Weather Service Eureka CA 302 PM PDT Sun Jun 9 2024 .SYNOPSIS...Isolated thunderstorm possible over the northeastern portion of Trinity County this afternoon. Hot temperatures will rapidly build on Monday with moderate heatrisk for many interior valleys...locally major heatrisk in Lake County, Tuesday and Wednesday. Breezy north to northwesterly winds will return Tuesday and Wednesday, with the strongest gusts over the coastal headlands and exposed ridges. && .DISCUSSION...GOES-West satellite imagery shows a weak upper level trough continuing to eject eastward away from the west coast this afternoon. Temperatures are running 2 to 6 degrees cooler across the interior compared with yesterday's reading. Stratus eroded to the coast and mixed out as northwesterly breezes increase this afternoon to bring a period of sunshine. However, onshore flow will push back inland the stratus later this afternoon and evening. The marine layer is expected to slightly deepen once again tonight into Friday. Some elevated instability has been occurring across the interior portion of the area today, mainly over Trinity County around the Alps and Yolla Bolly. Cumulus has been developing with daytime heating, however most model soundings depict a cap that could inhibit convection over most of our CWA this afternoon. High- resolution guidances remain the primarily activity to the northeastern portion of Trinity County this afternoon into evening. National blend of model indicates there is a 10-15% chances for isolated thunderstorm in the aforementioned area. High pressure will quickly build over the West Coast in the wake of the trough with 850 mb temperatures warming. This will bring a warming trend early this week, with Moderate HeatRisk returning across the interior valleys on Monday and continue through mid week. Interior high temperatures in the mid 90's into low 100s are expected to return across across the warmer locations of Trinity, Lake, interior Mendocino, and northeastern Humboldt. The heat is forecast to peak on Tuesday with locally major heat risk in Lake County. Additionally, a thermal trough is expected to develop near the coast Wednesday. This will promote breezy north-northwesterly winds each afternoon Tuesday and Wednesday over the exposed ridges and coastal headlands, with gusts from 25 to 35 mph at times...locally higher gusts possible over the King Range and Crescent City. NBM probabilities shows a 80% to near 100% for gusts of 40 MPH or more in the King Range, and 45% chances for Crescent City. Another trough in westerly flow will knock down the ridge toward the latter portion of the week; Thursday-Saturday and high temperatures will once again trend down to around seasonal averages. Chance for any rain toward the end of the week or next weekend is quite low, less than 10% near the Oregon border. / ZVS && .AVIATION...A short-lived marine layer has mixed out of KCEC and KACV terminals leading to clear sky and northwesterly, onshore flow through the afternoon with possible gusts as winds flow around a weak thermal trough in the central valley. These onshore winds have the potential to carry sea spray and other aerosols that will create some hazy conditions, possibly bringing down visibilities and leading to some ghost cloud layers registered on METARs. Later tonight however, as a high pressure system approaches out area, model guidance is showing a high possibility (50-70% according to NBM) of the marine stratus layer returning. This layer will actualize as broken to overcast skies overnight into about midday tomorrow morning with locally limited visibilities caused by mist suspended in the air. If and when this low cloud layer forms, it is forecasted to mix out by the afternoon as onshore winds return to the coastal terminals. At KUKI, the story is entirely different. Currently there are clear skies with north winds and gusts reaching up to 20 or so knots. These winds will die off after sunset tonight and calm conditions should prevail. A surge of moisture is forecasted to start creeping up the Russian River valley around this time as well, however that cloud layer is not currently forecasted to make it up to Mendocino Co and should retreat before reaching Cloverdale. DS && .MARINE...Wave heights have been slowly climbing as a moderate long period westerly swell fills into the waters. Seas are further enhanced by gusty northerly winds developing in the outer waters and lee of Cape Mendocino, near or just reaching gale gusts in the southern zones. Steep seas approaching 10 feet and gusty northerlies will persist through Monday, with a brief reprieve expected on Tuesday as the coastal jet shifts slightly offshore and into the southern waters. Winds are forecast to quickly increase late Tuesday into Wednesday, producing widespread gales and steep and hazardous seas, especially in the outer waters. Responsive wave heights approaching 15 feet are possible late Wednesday into Thursday as the gales persist. Inner waters may experience slightly subdued conditions, but waves should still be well within advisory criteria. && .EKA WATCHES/WARNINGS/ADVISORIES... CA... None. NORTHWEST CALIFORNIA COASTAL WATERS... Small Craft Advisory until 3 PM PDT Monday for PZZ450. Small Craft Advisory until 3 AM PDT Tuesday for PZZ455-470. Small Craft Advisory until 3 PM PDT this afternoon for PZZ475. Gale Warning until 9 AM PDT Monday for PZZ475. && $$ Visit us at https://www.weather.gov/eureka Follow us on Facebook and Twitter at: https://www.facebook.com/NWSEureka https://www.twitter.com/NWSEureka For forecast zone information see the forecast zone map online: https://www.weather.gov/images/eka/zonemap.png